Dissertations / Theses: 'ADI materials'

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CHAKKALAKKAL, JOSEPH JUNIOR. "Design of a weight optimized casted ADI component using topology and shape optimization." Thesis, KTH, Maskin- och processteknologi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-236518.

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Structural Optimization techniques are widely used in product development process in ‘modern industry’ to generate optimal designs with only sufficient material to serve the purpose of the component. In conventional design problems, the design process usually generates overdesigned components with excess material and weight. This will in turn increase the life time cost of machines, both in terms material wastage and expense of usage. The thesis “Design of a weight optimized casted ADI component using topology and shape optimization” deals with redesigning a component from a welded steel plate structure into a castable design for reduced manufacturing cost and weight reduction. The component “Drill Steel Support” mounted in front of the drilling boom of a Face Drilling Machine is redesigned during this work. The main objective of the thesis is to provide an alternative design with lower weight that can be mounted on the existing machine layout without any changes in the mounting interfaces. This thesis report covers in detail procedure followed for attaining the weight reduction of the “Drill Steel Support” and presents the results and methodology which is based on both topology and shape optimization.
Strukturoptimering används ofta i produktutvecklingsprocessen i modern industri för att ta fram optimala konstruktioner med minsta möjliga materialåtgång för komponenten. Konventionella konstruktionsmetoder genererar vanligtvis överdimensionerade komponenter med överflödigt material och vikt. Detta ökar i sin tur livstidskostnaderna för maskiner både i termer av materialavfall och användning. Avhandlingen "Konstruktion av viktoptimerad gjuten ADI-komponent" behandlar omkonstruktionen av en komponent från en svetsad stålplåtstruktur till en gjutbar konstruktion med minskad tillverkningskostnad och vikt. Komponenten “Borrstöd” monterad i framkant av bommen på en ortdrivningsmaskin är omkonstruerad under detta arbete. Huvudsyftet med avhandlingen är ta fram en alternativ konstruktion med lägre vikt och som kan monteras på befintlig maskinlayout utan någon ändring i monteringsgränssnittet. Denna avhandling innehåller en detaljerad beskrivning av förfarandet för att uppnå viktminskningen av "borrstödet" och presenterar resultaten samt metodiken som baseras på både topologi- och parameter- optimering.

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Fulco, Ana Paula Pereira. "Comportamento magn?tico de comp?sitos de matriz polim?rica com adi??o de ferritas." Universidade Federal do Rio Grande do Norte, 2013. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12799.

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Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
Polymer matrix composites offer advantages for many applications due their combination of properties, which includes low density, high specific strength and modulus of elasticity and corrosion resistance. However, the application of non-destructive techniques using magnetic sensors for the evaluation these materials is not possible since the materials are non-magnetizable. Ferrites are materials with excellent magnetic properties, chemical stability and corrosion resistance. Due to these properties, these materials are promising for the development of polymer composites with magnetic properties. In this work, glass fiber / epoxy circular plates were produced with 10 wt% of cobalt or barium ferrite particles. The cobalt ferrite was synthesized by the Pechini method. The commercial barium ferrite was subjected to a milling process to study the effect of particle size on the magnetic properties of the material. The characterization of the ferrites was carried out by x-ray diffraction (XRD), field emission gun scanning electron microscopy (FEG-SEM) and vibrating sample magnetometry (VSM). Circular notches of 1, 5 and 10 mm diameter were introduced in the composite plates using a drill bit for the non-destructive evaluation by the technique of magnetic flux leakage (MFL). The results indicated that the magnetic signals measured in plates with barium ferrite without milling and cobalt ferrite showed good correlation with the presence of notches. The milling process for 12 h and 20 h did not contribute to improve the identification of smaller size notches (1 mm). However, the smaller particle size produced smoother magnetic curves, with fewer discontinuities and improved signal-to-noise ratio. In summary, the results suggest that the proposed approach has great potential for the detection of damage in polymer composites structures
Materiais comp?sitos polim?ricos oferecem vantagens para v?rias aplica??es pela combina??o de propriedades como baixa densidade, elevada resist?ncia mec?nica e m?dulo de elasticidade espec?ficos e resist?ncia a corros?o. Entretanto, por n?o serem magnetiz?veis, esses materiais n?o permitem a utiliza??o de t?cnicas de avalia??o n?o destrutivas que utilizem sensores magn?ticos. Ferritas s?o materiais com excelentes propriedades magn?ticas, estabilidade qu?mica e resist?ncia ? corros?o. Devido a essas propriedades esses materiais s?o promissores para o desenvolvimento de comp?sitos de matriz polim?rica com propriedades magn?ticas. Neste trabalho, discos de comp?sitos de fibra de vidro/ep?xi foram produzidos com adi??o de 10% em massa de part?culas de ferrita de cobalto ou de b?rio. A ferrita de cobalto foi sintetizada pelo m?todo Pechini. A ferrita comercial de b?rio foi submetida a um processo de moagem para se estudar o efeito do tamanho de part?cula nas propriedades magn?ticas do material. A caracteriza??o das ferritas foi realizada pelas t?cnicas de difra??o de raio x (DRX), microscopia eletr?nica de varredura (MEV-FEG) e magnetometria de amostra vibrante (MAV). Entalhes circulares com di?metros de 1, 5 e 10 mm foram introduzidos nos discos de comp?sitos com o aux?lio de uma broca para avalia??o n?o-destrutiva por meio da t?cnica de fuga de fluxo magn?tico (MFL). A abordagem apresentada permitiu identificar todos os entalhes introduzidos nos discos. Os resultados indicaram que os sinais magn?ticos medidos nos discos com a ferrita de b?rio sem moagem e de cobalto apresentaram boa correla??o com a presen?a dos entalhes. O processo de moagem por 12 h e 20 h n?o contribuiu para a melhor identifica??o de entalhes de menor dimens?o (1 mm). Entretanto, o menor tamanho de part?cula permitiu produzir curvas magn?ticas mais suaves, com menos descontinuidades e melhor rela??o sinal-ru?do. Em resumo, os resultados sugerem que a abordagem proposta tem grande potencial para a detec??o de falhas em estruturas de materiais comp?sitos polim?ricos

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Jung, Kyung Young. "Full-wave modeling and analysis of dispersion-engineered materials and plasmon waveguides." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1218503761.

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Martinez, Thomas. "Etude de l'endommagement lors du démasselotage à chaud de bielles en fonte GS ADI moulées forgées." Thesis, Reims, 2016. http://www.theses.fr/2016REIMS002/document.

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Les travaux de cette thèse ont été initiés par la volonté industrielle de lever le verrou technologique du démasselotage à chaud de bielles en fonte GS. Ces bielles sont obtenues par un procédé de fabrication hybride innovant mêlant forgeage et fonderie en moule métallique. Ce procédé exige que le démasselotage soit effectué dans la « chaude de coulée » lorsque la fonte GS est en phase austénitique. La découpe de la fonte dans ces conditions de température fait apparaître des défauts majeurs sur les surfaces découpées préjudiciables à la suite du process. Pour pouvoir répondre à cette problématique, une étude est menée sur la caractérisation du comportement et de l’endommagement de la fonte GS dans les conditions de température du process. Une attention particulière est portée sur l’influence de la microstructure nodulaire sur les mécanismes de la rupture. Afin de se doter d’outils de simulation pour mettre au point le processus de démasselotage à chaud, les paramètres du modèle de comportement et d’endommagement de Gurson-Tvergaard-Needleman appliqués à la fonte GS sont identifiés par méthode inverse. Enfin, un plan d’expérience est déployé sur un démonstrateur de découpe instrumenté afin d’obtenir la configuration optimale des paramètres process pour une découpe sans défaut. Cette dernière étude met en avant la présence d’une transition d’un mode de rupture ductile à fragile lors de l’apparition des défauts de démasselotage
This work was initiated by the technological problematic of hot trimming of nodular cast iron connecting rods. These connecting rods are obtained by an innovative hybrid process that combines forging and metal mold casting. This process requires the trimming to be conducted at high temperatures in the is the austenitic phase of the cast iron. Hot trimming of cast iron brings up major defects on the cut surfaces which are detrimental to the continuing process. To address this problem, a study is conducted on the characterization of the mechanical behavior of nodular cast iron in the process temperature conditions. A particular attention is paid to the influence of the nodular microstructure on the failure mechanisms. To develop simulation tools for nodular cast iron hot trimming, the parameters of Gurson-Tvergaard-Needleman model are identified by inverse method for our material. Finally, a design of experiment is deployed using an instrumented demonstrator to obtain the optimum parameters configuration for a maximized cut surface quality. This latest study highlights the presence of a transition from ductile to brittle mode of failure leading to the hot trimming defects

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Silva, J?nior Jos? Ferreira da. "Comportamento da adi??o do carbeto de ni?bio (nBC) na matriz met?lica do a?o ferr?tico 15kH2mfa." Universidade Federal do Rio Grande do Norte, 2012. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12804.

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Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
The 15Kh2MFA steel is a kind of Cr-Mo-V family steels and can be used in turbines for energy generation, pressure vessels, nuclear reactors or applications where the range of temperature that the material works is between 250 to 450?C. To improve the properties of these steels increasing the service temperature and the thermal stability is add a second particle phase. These particles can be oxides, carbides, nitrites or even solid solution of some chemical elements. On this way, this work aim to study the effect of addition of 3wt% of niobium carbide in the metallic matrix of 15Kh2MFA steel. Powder metallurgy was the route employed to produce this metallic matrix composite. Two different milling conditions were performed. Condition 1: milling of pure 15Kh2MFA steel and condition 2: milling of 15Kh2MFA steel with addition of niobium carbide. A high energy milling was carried out during 5 hours. Then, these two powders were sintered in a vacuum furnace (10-4torr) at 1150 and 1250?C during 60 minutes. After sintering the samples were normalized at 950?C per 3 minutes followed by air cooling to obtain a desired microstructure. Results show that the addition of niobium carbide helps to mill faster the particles during the milling when compared with that steel without carbide. At the sintering, the niobium carbide helps to sinter increasing the density of the samples reaching a maximum density of 7.86g/cm?, better than the melted steel as received that was 7,81g/cm?. In spite this good densification, after normalizing, the niobium carbide don t contributed to increase the microhardness. The best microhardness obtained to the steel with niobium carbide was 156HV and to pure 15Kh2MFA steel was 212HV. It happened due when the niobium carbide is added to the steel a pearlitic structure was formed, and the steel without niobium carbide submitted to the same conditions reached a bainitic structure
O a?o 15Kh2MFA, da fam?lia dos a?os CrMoV, pode ser utilizado em turbinas para gera??o de energia, vasos de press?o, reatores nuclear ou aplica??es, onde o material ? submetido a temperaturas de servi?o entre 250 e 450?C. Uma forma de melhorar as propriedades do a?o, para que ele trabalhe a temperaturas mais altas ou que se torne mais est?vel ? adicionar part?culas de segunda fase na sua matriz. Estas part?culas podem estar na forma de ?xidos, carbetos, nitretos ou at? mesmo em solu??o s?lida quando alguns elementos qu?micos s?o adicionados ao material. Neste contexto, este trabalho objetiva estudar o efeito da adi??o de 3% de carbeto de ni?bio na matriz met?lica do a?o 15Kh2MFA. Para isto a metalurgia do p? foi a rota empregada para a produ??o deste comp?sito de matriz met?lica. Para tal, duas moagens distintas foram realizadas. A primeira com o a?o 15Kh2MFA e a segunda com o a?o 15Kh2MFA com adi??o de 3% de carbeto de ni?bio. A moagem de alta energia foi realizada durante 5 horas. Em seguida, os dois p?s produzidos foram sinterizados em um forno a v?cuo (10-4torr) a temperaturas de 1150?C e 1250?C durante 60 minutos. Ap?s a sinteriza??o as amostras foram submetidas ao tratamento t?rmico de normaliza??o a 950?C. Os resultados mostraram que a adi??o do carbeto de ni?bio ajuda o processo de cominui??o das part?culas, quando comparado com o a?o sem o carbeto de ni?bio. O carbeto de ni?bio tem um papel fundamental na densifica??o das amostras durante a sinteriza??o, levando a densidade 7,86g/cm?, que ? maior do que a densidade do a?o fundido recebido que era de 7,81g/cm?. Apesar desta boa densifica??o, ap?s a normaliza??o, o NbC n?o contribuiu de forma significativa para aumento da dureza, onde a melhor dureza obtida para o a?o com NbC foi de 156HV e para o a?o puro foi de 212HV. Isto se deve ao fato de que, quando o NbC foi adicionado ao a?o, formou-se uma estrutura perl?tica, enquanto que, com o a?o sem adi??o de NbC, submetido as mesmas condi??es, obteve-se uma estrutura bain?tica

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Melo, Maxymme Mendes de. "Formula??o e caracteriza??o de massas de gr?s porcelanato preparadas a partir de mat?rias-primas naturais do Rio Grande do norte e com adi??o de chamote de telhas." Universidade Federal do Rio Grande do Norte, 2006. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15580.

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Traditional ceramics have an important role in the economy of Rio Grande do Norte. The local industries manufacture over 50 million shingles a month, corresponding to 60% of their overall production. As a result of processing flaws, roughly 20% of the production must be discarded, since little or no use has been envisaged for such fired components. Therefore, the use of this kind of residue, especially in the composition of other ceramic materials, comes as an interesting option from the economical and environmental point of view. In this scenario, the objective of the present study was to assess the effect of the addition of fired shingle waste in the composition of porcelainized stoneware tiles. To that end, two porcelainized stoneware tiles compositions were initially prepared. Subsequently, contents from 10 to 30% of roofing tiles chamote were added to each one of them. All raw materials and grog were characterized by FRX, XRD, and thermal analysis. The ceramics were fired using natural gas for 30 min at different temperatures, i.e. 1150, 1200 and 1250?C, and fully characterized. The addition of roofing tiles chamote resulted in composition with superior properties compared to additive-free compositions. Porcelainized stoneware tiles products that fulfill required standards for practical applications were achieved
A ind?stria de cer?mica vermelha ? um dos segmentos de maior import?ncia na economia do Rio Grande do Norte. Nesse setor, o material mais produzido ? a telha, ocupando mais de 60% de todos os artefatos produzidos, com mais de 50 milh?es de pe?as fabricadas por m?s. Sabe-se que devido ? falhas no processamento, o teor de res?duos desse material no RN, pode chegar a um valor de at? 20%, o que significa mais de 10 milh?es de telhas indo diretamente para aterros, visto que estas, depois de queimadas, n?o podem ser reutilizadas no processo de fabrica??o. Desta forma, o uso desse rejeito na produ??o de cer?micas com alto valor agregado, como ? o caso do gr?s porcelanato, se torna uma op??o vi?vel. Do ponto de vista econ?mico essa viabilidade se d?, pelo fato de utilizar-se um rejeito como parte da formula??o. Do ponto de vista ambiental, a viabilidade est? em reduzir o ac?mulo desses rejeitos nos aterros sanit?rios. Desta forma, o presente trabalho tem o objetivo de estudar a influ?ncia da adi??o de descarte de telhas em formula??es de gr?s porcelanatos. Para isso, utilizou-se duas formula??es, adicionando concentra??es de 10, 20 e 30% de chamote para cada uma delas. O Chamote e as mat?rias-primas foram caracterizadas por FRX, DRX, TG, ATD e AG. As queimas foram realizadas em forno a g?s natural com tr?s temperaturas, por 30 minutos de patamar: 1150, 1200 e 1250?C. Ap?s a sinteriza??o os corpos-de-prova foram submetidos a: ensaios f?sicos de RL, AA, PA, MEA, TRF e dilatometria; an?lise mineral?gica por DRX; e microestrutural por MEV. Obteve-se para algumas das formula??es com a adi??o de chamote, propriedades superiores ?s das exigidas por normas para o gr?s porcelanato

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Dragan, Rajnović. "Uticaj mikrostrukture na prelaznu temperaturu ADI materijala." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2015. http://www.cris.uns.ac.rs/record.jsf?recordId=94932&source=NDLTD&language=en.

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U disertaciji je izvršena karakterizacija mikrostrukture i mehaničkih osobinanelegiranog austemperovanogi nodularnog liva (ADI materijala), kao i uticajamikrostrukture na prelaznu temperaturu u intervalu od -196 do +100°C.Utvrđeno je da mehaničke osobine ADI-ja zavise od morfologije ausferitnemikrostrukture i količine zadržanog austenita, tj. parametara austemperovanja.Na osnovu mehaničkih osobina utvrđen je i opseg procesiranja u skladu sastandardima ASTM, ISO i EN. Zaključeno je da prelazna temperatura ADImaterijala zavisi od količine i stabilnosti zadržanog austenita. U višemtemperaturnom opsegu (iznad cca. -25°C) dominantna je količina zadržanogaustenita, dok na nižim temperaturama, stabilnost. Visoka obogaćenostugljenikom, stabilnog zadržanog austenita sprečava stvaranje martenzita naniskim temperaturama, a time i pojavu krtosti kod ADI-ja.
The object of this thesis was to characterize microstructure and mechanical propertiesof the unalloyed ADI material (Austempered Ductile Iron). In addition, the influence ofmicrostructure on the ductile to brittle transition temperature (DBTT) by Charpy impacttest in temperature interval from 196 to +100°C has been studied. The all propertiesobtained depend on the morphology of microstructure and the amount of retainedaustenite, i.e. on the austempering parameters. According to the mechanical propertiesand standard requirements (ASTM, ISO and EN) the processing window has beenproposed, also. It was found that DBTT is influenced by amount and stability of retainedaustenite. In upper temperature range (above cca. 25°C) the most influence factor onDBTT is amount of retained austenite, while at the lower temperatures the stability ismore prominent. Stability of high carbon retained austenite at lower temperaturesprevents transformation to martensite and thus the embrittlement of ADI.

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Rouf, Hasan. "Unconditionally stable finite difference time domain methods for frequency dependent media." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/unconditionally-stable-finite-difference-time-domain-methods-for-frequency-dependent-media(50e4adf1-d1e4-4ad2-ab2d-70188fb8b7b6).html.

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The efficiency of the conventional, explicit finite difference time domain (FDTD)method is constrained by the upper limit on the temporal discretization, imposed by the Courant–Friedrich–Lewy (CFL) stability condition. Therefore, there is a growing interest in overcoming this limitation by employing unconditionally stable FDTD methods for which time-step and space-step can be independently chosen. Unconditionally stable Crank Nicolson method has not been widely used in time domain electromagnetics despite its high accuracy and low anisotropy. There has been no work on the Crank Nicolson FDTD (CN–FDTD) method for frequency dependent medium. In this thesis a new three-dimensional frequency dependent CN–FDTD (FD–CN–FDTD) method is proposed. Frequency dependency of single–pole Debye materials is incorporated into the CN–FDTD method by means of an auxiliary differential formulation. In order to provide a convenient and straightforward algorithm, Mur’s first-order absorbing boundary conditions are used in the FD–CN–FDTD method. Numerical tests validate and confirm that the FD–CN–FDTD method is unconditionally stable beyond the CFL limit. The proposed method yields a sparse system of linear equations which can be solved by direct or iterative methods, but numerical experiments demonstrate that for large problems of practical importance iterative solvers are to be used. The FD–CN–FDTD sparse matrix is diagonally dominant when the time-stepis near the CFL limit but the diagonal dominance of the matrix deteriorates with the increase of the time-step, making the solution time longer. Selection of the matrix solver to handle the FD–CN–FDTD sparse system is crucial to fully harness the advantages of using larger time-step, because the computational costs associated with the solver must be kept as low as possible. Two best–known iterative solvers, Bi-Conjugate Gradient Stabilised (BiCGStab) and Generalised Minimal Residual (GMRES), are extensively studied in terms of the number of iteration requirements for convergence, CPU time and memory requirements. BiCGStab outperforms GMRES in every aspect. Many of these findings do not match with the existing literature on frequency–independent CN–FDTD method and the possible reasons for this are pointed out. The proposed method is coded in Fortran and major implementation techniques of the serial code as well as its parallel implementation in Open Multi-Processing (OpenMP) are presented. As an application, a simulation model of the human body is developed in the FD–CN–FDTD method and numerical simulation of the electromagnetic wave propagation inside the human head is shown. Finally, this thesis presents a new method modifying the frequency dependent alternating direction implicit FDTD (FD–ADI–FDTD) method. Although the ADI–FDTD method provides a computationally affordable approximation of the CN–FDTD method, it exhibits a loss of accuracy with respect to the CN-FDTD method which may become severe for some practical applications. The modified FD–ADI–FDTD method can improve the accuracy of the normal FD–ADI–FDTD method without significantly increasing the computational costs.

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Silva, Yankel Bruno Fontes. "Estudo da zirc?nia refor?ado com alumina." Universidade Federal do Rio Grande do Norte, 2008. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12685.

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Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
Ceramics materials have good properties including chemical stability, high hardness and wear resistance. Moreover, due to its fragility, can suffer failure under relatively low levels of tension. Actually zirconia is the material of choice in metal free dental prostheses used in dentistry due its inertia in physiological environment, good bending strength, hardness and fracture toughness. The alumina and mixed tungsten and titanium carbides additions, acting as reinforcement elements in the zirconia matrix, have as their main objective the improvement of mechanical properties of this material. In this work, samples of zirconia, zirconia with 30% wt of alumina and zirconia with 30% wt mixed carbides were analyzed. The samples were sintered by uniaxial hot pressing on 30 MPa pressure, for 1 hour in an argon atmosphere. They were physically characterized by porosity and density measurements, and mechanically by 3-points bending strength and Vickers microhardness. The X-ray diffraction was used for the phase identifications and microstructure was examined by scanning electron microscopy (SEM). The addition of mixed carbides as reinforcement elements in zirconia matrix provides improvements in all properties analyzed in this work. The alumina addition has dropped the zirconia strength, although it caused improvement in other properties
Materiais cer?micos apresentam boas propriedades incluindo estabilidade qu?mica, elevada dureza e resist?ncia ao desgaste. Por outro lado, devido a sua fragilidade, podem sofrer falha sob n?veis de tens?es relativamente baixos. A zirc?nia ? hoje o material de escolha em odontologia para o uso em pr?teses dentais do tipo metal free por ser inerte em meio fisiol?gico, apresentar boa resist?ncia ? flex?o, dureza e tenacidade ? fratura. A adi??o da alumina e dos carbetos mistos de tungst?nio e tit?nio ,atuando como elementos de refor?o na matriz de zirc?nia, t?m como principal objetivo o aperfei?oamento das propriedades mec?nicas deste material. No presente trabalho, foram analisadas amostras de: zirc?nia, zirc?nia com 30% em peso de alumina e zirc?nia com 30% em peso de carbetos mistos. Os corpos de prova foram sinterizados por prensagem a quente uniaxial, sobre press?o de 30 MPa, durante 1 hora em atmosfera de arg?nio. Os mesmos foram caracterizados fisicamente por meio de medidas de porosidade e de densidade, e mecanicamente por resist?ncia a flex?o em 3 pontos e microdureza Vickers. A difra??o de raios X foi utilizada para a identifica??o das fases presentes e a microestrutura foi analisada por microscopia eletr?nica de varredura (MEV). A adi??o dos carbetos mistos como elemento de refor?o da matriz de zirc?nia ocasionou uma melhoria em todas as propriedades analisadas neste trabalho. A adi??o da alumina proporcionou uma queda na resist?ncia mec?nica da zirc?nia, apesar de ter ocasionado melhora nas demais propriedades

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Souza, Bruno Vaz de. "Desenvolvimento de ferro fundido austemperado (ADI) em banho de zinco-alumínio." Pontifícia Universidade Católica do Rio Grande do Sul, 2015. http://hdl.handle.net/10923/7475.

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This work presents the influence of the heat treatment parameters of austempering carried out in a zinc aluminum bath on the mechanical properties of a ductile cast iron (ADI). Samples were extracted from as-cast standard blocks for the austempering heat treatment. The material was heated to 900°C for 60 minutes for austenitization and cooled in a zinc-aluminum bath, to a temperature of 400°C, for 30 minutes, 60 minutes and 90 minutes. The samples were analyzed by optical microscopy, scanning electron microscopy, and mechanical tests (Brinell hardness, Micro Vickers hardness, Izod Impact Test and Tensile Test). The results, comparing the mechanical properties and microstructural characteristics in all cycles, present results compatible with the two stages of the material process window, confirming the effectiveness of the zinc-aluminum bath in getting the ADI.
O presente trabalho apresenta a influência da variação de parâmetros do tratamento térmico de austêmpera realizado usando um banho de zinco fundido, e os efeitos nas propriedades mecânicas do ferro fundido austemperado (ADI). Corpos de prova foram extraídos de blocos fundidos padronizados para aplicação dos tratamentos térmicos de austêmpera. O material foi aquecido a 900oC durante 60 minutos para austenitização, e então resfriado em um banho de zinco-alumínio fundido a 400oC por 30 minutos, 60 minutos e 90 minutos. Os corpos de prova foram analisados por microscopia óptica, microscopia eletrônica de varredura e ensaios mecânicos (dureza Brinnell, microdureza Vickers, testes de Impacto Charpy e Resistência à Tração). Os resultados, comparadas as propriedades mecânicas e características microestruturais em todos os ciclos, apresentam resultados compatíveis com os dois estágios previstos pela janela de processo do material, confirmando a efetividade do banho de Zinco-Alumínio na obtenção do ADI.

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Paim, Martina Fernandes. "Avalia??o da adi??o de montmorilonita organofilizada a adesivos baseados em borracha natural." Pontif?cia Universidade Cat?lica do Rio Grande do Sul, 2016. http://tede2.pucrs.br/tede2/handle/tede/6938.

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Adhesives, by definition, are substances capable of maintaining two materials together from the union of their surfaces. Due to the expansion of applications and variety of materials, adhesives are becoming important in several industrial fields requiring bonding reliability. Improvements in adhesives of natural rubber (NR) were achieved by adding a low level in the solid phase of organically modified montimorillonite (OMMT). The clay addition effect in elastomeric compounds was analyzed through the open time of adhesives, viscosity in rheoviscometer, curing behavior process by differential scanning calorimetry (DSC) and contact angle. Improvements in viscosity, open time and contact angle was observed in adhesives with nanoclay. The results group of these tests show that the improvement of the adhesive was more noticeable at a 4% OMMT adhesive due the lower contact angle and consequently better spreading. The curing behavior process showed no changes with OMMT incorporation.
Os adesivos, por defini??o, s?o subst?ncias capazes de manter dois materiais unidos a partir da uni?o de suas superf?cies. Devido ? expans?o de aplica??es e variedade de materiais, os adesivos v?m se tornando importantes em v?rios ramos industriais exigindo confiabilidade de colagem. Melhorias em adesivos de borracha natural (NR) foram obtidas pela adi??o em fase s?lida de um baixo teor de nanopart?cula natural, a montmorilonita organicamente modificada (OMMT). O efeito da adi??o de argila no composto elastom?rico foi analisado atrav?s de ensaios de tempo em aberto, viscosidade em reoviscos?metro, processo de cura por calorimetria explorat?ria diferencial (DSC) e ?ngulo de contato. O adesivo com nanocarga apresentou melhorias na viscosidade, tempo em aberto e ?ngulo de contato. O conjunto de resultados destes ensaios demonstram que a melhoria mais percept?vel foi do adesivo com teor de 4% em massa devido ao menor ?ngulo de contato e consequentemente melhor espalhamento. O comportamento no processo de cura n?o apresentou mudan?as com a incorpora??o de OMMT.

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Souza, Bruno Vaz de. "Desenvolvimento de ferro fundido austemperado (ADI) em banho de zinco-alum?nio." Pontif?cia Universidade Cat?lica do Rio Grande do Sul, 2015. http://tede2.pucrs.br/tede2/handle/tede/6220.

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This work presents the influence of the heat treatment parameters of austempering carried out in a zinc aluminum bath on the mechanical properties of a ductile cast iron (ADI). Samples were extracted from as-cast standard blocks for the austempering heat treatment. The material was heated to 900?C for 60 minutes for austenitization and cooled in a zinc-aluminum bath, to a temperature of 400?C, for 30 minutes, 60 minutes and 90 minutes. The samples were analyzed by optical microscopy, scanning electron microscopy, and mechanical tests (Brinell hardness, Micro Vickers hardness, Izod Impact Test and Tensile Test). The results, comparing the mechanical properties and microstructural characteristics in all cycles, present results compatible with the two stages of the material process window, confirming the effectiveness of the zinc-aluminum bath in getting the ADI.
O presente trabalho apresenta a influ?ncia da varia??o de par?metros do tratamento t?rmico de aust?mpera realizado usando um banho de zinco fundido, e os efeitos nas propriedades mec?nicas do ferro fundido austemperado (ADI). Corpos de prova foram extra?dos de blocos fundidos padronizados para aplica??o dos tratamentos t?rmicos de aust?mpera. O material foi aquecido a 900oC durante 60 minutos para austenitiza??o, e ent?o resfriado em um banho de zinco-alum?nio fundido a 400oC por 30 minutos, 60 minutos e 90 minutos. Os corpos de prova foram analisados por microscopia ?ptica, microscopia eletr?nica de varredura e ensaios mec?nicos (dureza Brinnell, microdureza Vickers, testes de Impacto Charpy e Resist?ncia ? Tra??o). Os resultados, comparadas as propriedades mec?nicas e caracter?sticas microestruturais em todos os ciclos, apresentam resultados compat?veis com os dois est?gios previstos pela janela de processo do material, confirmando a efetividade do banho de Zinco-Alum?nio na obten??o do ADI.

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Balzer, Marcos Estevam. "Determinação da janela de processo de austêmpera de um ADI sem adição de elementos de liga através de ensaios mecânicos e metalográficos." Florianópolis, SC, 2003. http://repositorio.ufsc.br/xmlui/handle/123456789/84983.

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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Ciência e Engenharia de Materiais.
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O presente trabalho teve como principal objetivo a determinação da janela de

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Pereira, Maur?cio Rodrigues. "Estudo da adi??o de argila expandida na formula??o de concretos leves." Universidade Federal do Rio Grande do Norte, 2008. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12669.

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Lightweight concrete has been the subject of several studies towards the development of new building materials. Emphasis has been given on the particle size effect and nature of aggregates used as raw materials. The present study includes an analysis of the materials that make this kind of concrete, analyzes of mechanical properties such as compressive and tensile strength, in addition to assessments of the interface concrete aggregate/matrix interface, porosity and absorption profile of chloride ions in lightweight concrete based on expanded clay. The experiments were carried out by molding cylindrical samples 100 mm in diameter and 200 mm in height. The dosage experiments were performed without additives or with the addition of minerals: (T1) 1: 2.01: 1.10: 0.78 (T2) 1: 2.00: 1.32 : 0.62 - (T3) 1 :1.93 :1.54: 0.47 (cement : sand : expanded clay 0500 : expanded clay 1506).The water to cement ratio was set to 0.43. Expanded clay minerals with different average particle sizes were used, i.e., 9.5 mm/0500 and 19 mm/1506. The larger aggregate was coated by a glassy layer, yielding lower water absorption characteristics to the concrete. The results showed that the use of light expanded clay aggregates is a technically interesting solution to the production of lightweight concrete for construction applications
Considerando-se as tend?ncias de novos materiais na Constru??o Civil, o concreto leve tem sido objeto de v?rios trabalhos, com ?nfase na granulometria e suas mat?rias primas. Incluem-se neste estudo a altera??o de tra?os e dos materiais que comp?em esse concreto, analisando altera??es nas propriedades mec?nicas como resist?ncia ? compress?o e tra??o por compress?o diametral, al?m da interface agregado/matriz, porosidade e perfil de absor??o de ?ons cloreto no concreto leve ? base de argila expandida. Os experimentos foram realizados atrav?s de moldagem de corpos de prova cil?ndricos, com 100 mm de di?metro e 200 mm de altura. A dosagem experimental foi efetuada sem aditivos ou adi??es minerais, nos tra?os unit?rios em massa: (T1) 1 : 2,01 : 1,10 : 0,78 (T2) 1 : 2,00 : 1,32 : 0,62 - (T3) 1 : 1,93 : 1,54 : 0,47 (cimento : areia : argila expandida 0500 : argila expandida 1506); fixando-se a rela??o ?gua/cimento em 0,43. Para tanto, utilizou-se como agregado gra?do uma argila expandida, nas gradua??es 9,5 mm/0500 e 19 mm/1506. A argila de gradua??o maior era revestida com uma camada vitrificada, o que propiciou menor absor??o de ?gua pelo concreto. Os resultados mostraram que a utiliza??o da argila expandida como agregado leve ? uma solu??o tecnicamente vi?vel na produ??o de concreto leve para Constru??o Civil.

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Castillo, Gambino Trinidad, Rodríguez Omar Díaz, Donayre Rosalba María García, Campos Rosangel Paola Príncipe, and Torres Ricardo Antonio Vizcardo. "Asesoría y comercio internacional - ACI." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2018. http://hdl.handle.net/10757/624854.

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"ACI - Asesoría en Comercio Internacional" es una idea de negocio que consiste en brindar a todas las empresas relacionadas con los negocios internacionales y aduanas, la actualización de todos sus colaboradores en aspectos técnicos acerca de los cambios y/o actualizaciones publicadas en las Normas Legales, encargándose de la lectura e interpretación de la parte técnico-legal y comunicada hacia ustedes mediante un video instructivo y una plataforma web. Los videos estarán en lenguaje sencillo, fácil de entender a cargo de profesionales en derecho aduanero y docentes en esta materia.
“ACI- International Commerce Advisors”, is a business plan that consist in giving all related companies with international businesses and customs brokerage, the up to date of all their workers about technical aspects and changes that are published into the Legal Norms of the official daily called El Peruano. Being in charge of an appropriate reading and interpretation of the legal & technical side, given toward you through a simple instructive video in a web platform. These videos are made in a simple language, easy to understand, given by professionals in customs law and educational in this matter.
Trabajo de investigación

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Figueiredo, Lucas Ricardo Fernandes. "Propriedades adesivas de pol?meros biodegrad?veis derivados do glicerol com adi??o de nanowhiskers de celulose." PROGRAMA DE P?S-GRADUA??O EM CI?NCIA E ENGENHARIA DE MATERIAIS, 2017. https://repositorio.ufrn.br/jspui/handle/123456789/25053.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)
?Adesivos verdes? t?m despertado grande interesse cient?fico e tecnol?gico como alternativa aos produtos comerciais convencionais, que em geral, liberam subst?ncias t?xicas e levam um longo per?odo de tempo para degradar. Entretanto, as propriedades mec?nicas limitadas e a r?pida degrada??o de alguns pol?meros biodegrad?veis limitam seu uso na maioria das aplica??es pr?ticas. No presente trabalho, comp?sitos foram preparados usando pol?meros biodegrad?veis e nanowhiskers de celulose (NWC) visando sua utiliza??o como adesivos para madeira. O objetivo da pesquisa foi estudar o efeito da adi??o dos nanowhiskers de celulose (NWC) nas propriedades mec?nicas e na degrada??o dos pol?meros. Os pol?meros biodegrad?veis sintetizados por policondensa??o ? base de glicerol e ?cidos foram poli (adipato de glicerol) - PGA, poli (maleato de glicerol) - PGM, poli (citrato de glicerol) - PGC, poli (ftalato de glicerol) - PGPh, poli (succinato de glicerol) PGSu e poli (sebacato de glicerol) - PGS. Al?m desses, copol?meros poli (glicerol succinato-co-maleato) - PGMSu, poli (glicerol succinato-co-adipato) - PGASu e poli (glicerol adipato-co-maleato) - PGMA foram tamb?m sintetizados. Nanowhiskers de celulose (NWC) foram adicionados aos pol?meros para avalia??o dos seus efeitos na melhoria das propriedades mec?nicas e no controle da taxa de degrada??o. Os materiais foram produzidos com a adi??o de 0, 5, 10 e 20% em peso de NWC. Os pol?meros puros e os comp?sitos foram analisados por Calorimetria Diferencial de Varredura (DSC), An?lise termogravim?trica (TGA), difra??o de Raios X (DRX) e espectroscopia Infravermelho por transformada de Fourier (FTIR). Juntas adesivas foram produzidas em corpos de prova de pinus (Pinus elliottii) e angelim (Vatairea heteroptera Ducke) e submetidas a degrada??o por envelhecimento acelerado e testes de cisalhamento sob tra??o. Juntas coladas produzidas com adesivos ? base de acetato de polivinila - PVAc e cianoacrilato foram tamb?m testadas, nas mesmas condi??es, para fins de compara??o. As an?lises t?rmicas indicaram que a maioria dos pol?meros biodegrad?veis ? base de glicerol testados s?o est?veis at? aproximadamente 260?C e a adi??o de NWC aumentou a estabilidade t?rmica (Tonset) de alguns pol?meros em 26?C at? 48?C, enquanto outros n?o foram afetados. As an?lises de superf?cie de fratura por microscopia eletr?nica de varredura (MEV) ap?s os testes de cisalhamento sugerem redu??o de ductilidade com a incorpora??o de NWC ao adesivo. As medidas de ades?o indicaram que os adesivos verdes desenvolvidos a partir de pol?meros de glicerol com 10 e 20% em peso de NWC apresentaram resist?ncia ao cisalhamento superior ao adesivo comercial ? base de PVAc. Os melhores resultados e resist?ncia ao cisalhamento foram obtidos para PGASu com 20% em peso de NWC (2,57 ? 0,36 MPa) e PGM com 20% em peso de NWC (2,33 ? 0,43 MPa), enquanto que a resist?ncia ao cisalhamento do acetato de polivinila - PVAc foi de 1,58 ? 0,18 MPa. O envelhecimento resultou em maior resist?ncia ao cisalhamento de alguns adesivos. A melhoria mais significativa foi obtida para PGMA com 20% em peso de NWC, que atingiu (3,89 ? 0,74 MPa) ap?s 250 h de envelhecimento, portanto, maior que a resist?ncia ao cisalhamento do cianoacrilato (3,12 ? 0,53 MPa). Em ?ltima an?lise, os resultados apresentados neste trabalho sugerem que a adi??o de nanowhiskers de celulose (NWC) ? uma abordagem vi?vel para ajustar as propriedades mec?nicas e degrada??o dos pol?meros biodegrad?veis.
?Green adhesives? are of great scientific and technological interest as an alternative to conventional commercial products, which often release toxic substances and take long time to degrade. However, the poor mechanical properties and fast degradation of some biodegradable polymers limit their use in most practical applications. In the present work, novel biodegradable composites were prepared using biodegradable polymers and cellulose nanowhiskers (CNW) for their use as wood adhesives. The goal of the investigation was to study the effect of the addition of CNW on the mechanical properties and degradation of the polymers. The biodegradable polymers synthesized by polycondensation based on glycerol and acids were poly(glycerol adipate) - PGA, poly(glycerol maleate) - PGM, poly(glycerol citrate) - PGC, poly(glycerol phthalate) - PGPh, poly(glycerol succinate) - PGSu and poly(glycerol sebacate) - PGS. In addition, the copolymers synthesized were poly(glycerol succinate-co-maleate) - PGMSu, poly(glycerol succinate-co-adipate) ? PGASu and poly(glycerol adipate-co-maleate) ? PGMA. Cellulose nanowhiskers (CNW) were added to the polymers as an approach for improving the mechanical properties and controlling the degradation rate. Composites were produced with the addition of 0, 5, 10 and 20 wt.% of CNW. The neat polymers and composites were analyzed by Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). Adhesively bonded joints were produced in test specimens of slash pine (Pinus elliottii) and angelim (Vatairea heteroptera Ducke) and subjected to accelerated aging and tested under shear by tensile loading. Bonded joints produced with polyvinyl acetate - PVAc and cyanoacrylate based adhesives were also tested under the same conditions for comparison purposes. Thermal analyses indicated that most of the biodegradable glycerol-based polymers tested are stable up to about 260?C and the addition of CNW increased the thermal stability (Tonset) of some polymers by 26?C up to 48?C, while others were not affected. Analyses of the fracture surfaces after the shear tests by Scanning Electron Microscopy (SEM) suggest less ductile fracture with the incorporation of CNW to the adhesive. The shear strengths of the green adhesives developed from glycerol with 10 and 20 wt.% CNW were greater than that of the commercial PVAc based adhesive. The best results of shear strengths were obtained for PGASu 20 wt.% CNW (2.57 ? 0.36 MPa) and PGM 20 wt.% CNW (2.33? 0.43 MPa), while the shear strength for polyvinyl acetate - PVAc was 1.58 ? 0.18 MPa. Aging improved the shear strength of some adhesives. The best result was obtained for PGMA 20 wt.% CNW, which reached (3.89 ? 0.74 MPa) after 250h of aging, thus greater than the shear strength of cyanoacrylate (3.12 ? 0.53 MPa). Ultimately, the results presented in this work suggest that the addition of cellulose nanowhiskers (CNW) is a viable approach to tailor mechanical properties and degradation of biodegradable polymers.

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Menezes, Roberta Ara?jo Cavalcante de. "Estudo do efeito da adi??o de zirc?nia na microestrutura e propriedades do a?o EUROFER sinterizado." PROGRAMA DE P?S-GRADUA??O EM CI?NCIA E ENGENHARIA DE MATERIAIS, 2016. https://repositorio.ufrn.br/jspui/handle/123456789/22251.

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Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq)
Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)
O a?o EUROFER ? uma liga que foi desenvolvida para aplica??o em reator nuclear, apresentando propriedades mec?nicas compat?veis com essa utiliza??o, desde que, a temperatura de servi?o n?o ultrapasse 550?C, devido a sua baixa resist?ncia a flu?ncia. Visando melhorar as propriedades mec?nicas do EUROFER, estudos est?o sendo desenvolvidos adicionando ?tria, e o com isso tem-se um comp?sito com uma maior temperatura de trabalho, de aproximadamente 650?C. Dentro desse contexto, neste trabalho, estudou-se o efeito da adi??o de zirc?nia e da atmosfera de sinteriza??o na microestrutura e propriedades mec?nicas do a?o EUROFER processado atrav?s das etapas da metalurgia do p?. Inicialmente, foram adicionados 5%, em peso, de zirc?nia ao a?o, e realizada a moagem de alta energia em um moinho planet?rio por 5 horas com velocidade de 400rpm. Em seguida, os p?s particulados foram recozidos em forno resistivo a v?cuo a temperatura de 950?C por 30 minutos para uma melhor compacta??o. Os p?s de EUROFER puro e de EUROFER com 5% de zirc?nia mo?dos forma compactados a frio sob uma press?o uniaxial de a??o dupla com carga de 700 MPa, em uma matriz met?lica de cavidade cil?ndrica de 5 mm de di?metro. Os compactados a verde foram sinterizados em forno resistivo a v?cuo e em forno resistivo com fluxo de arg?nio a uma temperatura de 1300?C por 60 minutos com taxa de aquecimento de 10?C/min. Os p?s de partidas e os p?s mo?ods foram caracterizados por: distribui??o do tamanho de part?culas, fluoresc?ncia de raio-X (FRX), difra??o de raio-X (DRX) com refinamento, microscopia eletr?nica de varredura (MEV) e espectroscopia de energia dispersiva (EDS). E, as amostras sinterizadas foram caracterizadas por difra??o de raio-X (DRX), microscopia ?ptica (MO), microscopia eletr?nica de varredura (MEV) e espectroscopia de energia dispersiva (EDS); e, tamb?m, analisadas por ensaios de densidade, dilatometria e microdureza. Foi observado que a microestrutura inicial do EUROFER n?o se manteve durante o processamento do material, e, com isso, as suas propriedades mec?nicas apresentaram varia??es. Dessa forma, os resultados de microdureza obtidos para as amostras com adi??o de zirc?nia (fluxo de arg?nio 253,4HV e v?cuo 119,35HV), foram maiores que os de a?o puro sinterizados (fluxo de arg?nio 119,25HV e v?cuo 84,65HV). E, al?m disso, as amostras sinterizadas no forno resistivo com fluxo de arg?nio apresentaram valores de microdureza superiores as das amostras sinterizadas em forno resistivo a v?cuo.
The EUROFER is an alloy steel developed for application in nuclear reactor, with mechanical properties compatible with such a use, since the operating temperature does not exceed 550?C due to its low creep resistance. In order to improve the mechanical properties of EUROFER, studies have been developed by adding yttria, producing a composite with higher working temperature of approximately 650?C. In this work, we studied the effect of adding zirconia and sintering atmosphere on microstructure and mechanical properties of EUROFER steel processed through the steps of powder metallurgy. Initially, wt % zirconia was added to steel and high energy ball milling was performed in a planetary milling for 5 hours at 400rpm. Then the particles were annealed in a resistance vacuum furnace at 950?C for 30 minutes for better compression. The pure EUROFER powder and EUROFER with 5 wt% zirconia cold compacted under a uniaxial double-acting pressure of 700 MPa in a cylindrical metal matrix with a cavity of 5 mm in diameter. The green samples were sintered in resistance vacuum furnace and resistance furnace with argon flow at 1300 ?C for 60 minutes with a heating rate of 10 ?C / min. Primary and milled powders were characterized by particle size distribution analysis, X-ray fluorescence (XRF), X-ray diffraction (XRD) with refinement, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). And the sintered samples were characterized by X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS); and also analyzed by density measurement, dilatometry behavior and microhardness. It was observed that the initial microstructure of EUROFER did not maintain during processing of the material, and, therefore, its mechanical properties presented variations. Thus, the results of microhardness obtained for samples with zirconia (argon flow 253,4 HV and vacuum 119,35 HV) were higher than those of sintered pure steel (argon flow and vacuum 119,25HV 84,65HV) . Thus, the results of microhardness obtained for samples with added zirconia (argon flow and vacuum 253,4HV 119,35HV) were higher than those of sintered pure steel (argon flow 119,25 HV and vacuum 84,65 HV). Besides, the samples sintered in the resistance furnace under argon flow had higher hardness than samples sintered in vacuum resistance furnace.

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Oliveira, Arthur Gabriel Ferreira de. "Estudo da influ?ncia da adi??o de n?quel em alumina pela rota da metalurgia do p?" Universidade Federal do Rio Grande do Norte, 2015. http://repositorio.ufrn.br/handle/123456789/21025.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)
Os materiais cer?micos a base de alumina t?m sido bastante utilizados em componentes estruturais principalmente pelo fato de possuir propriedades como alta dureza, in?rcia qu?mica e boa resist?ncia ao desgaste, entretanto, sua baixa tenacidade ? um fator que compromete seu uso em diversas outras aplica??es, tendo a adi??o de n?quel como uma poss?vel solu??o para este problema, nesse contexto, esse trabalho tem como objetivo estudar a adi??o de n?quel em alumina utilizando a rota da metalurgia do p?. O percentual de n?quel adicionado variou em 2, 4 e 6% p e para cada composi??o foi realizada moagem de alta energia em moinho planet?rio por 2, 4, 9 e 16h. Posteriormente as amostras foram compactadas a 300 MPa e sinterizadas em forno ? v?cuo a 1400?C por 2h. As amostras foram caracterizadas quanto as propriedades f?sicas e mec?nicas observando-se no geral uma melhora na sinterabilidade com o aumento do tempo de moagem e teor de n?quel, com diminui??o e homogeneiza??o da porosidade e aumento da dureza, al?m de densidades acima de 80% da te?rica, observou-se tamb?m uma disparidade no tempo de moagem de 4 horas, onde se alcan?ou os maiores valores de dureza (2% de n?quel), de 1068,7 +/- 32,6 HV e densidade cerca de 99% da te?rica
Ceramic materials alumina basis have been widely used in structural components, mainly because owning properties such as high hardness, chemical inertness and good wear resistance, however, the low toughness is a factor that compromises its use in many other applications, featuring the addition of nickel as a possible solution to this problem, in this context, this work aims to study the addition of nickel alumina using the route of powder metallurgy processing of the material. The percentage of nickel were added 2, 4 and 6 wt%; and each composition to high energy milling in a planetary mill was performed for 2, 4, 9 and 16h. Subsequently, the samples were compacted at 300 MPa and sintered in a vacuum oven at 1400?C for 2h. The samples were characterized as the physical and mechanical properties, observing, in general, an improvement in sinterability of the material with increasing grinding time and nickel content, and mixing with a decrease of porosity and increase of hardness, density values above 80% of theoretical were obtained. The milling time of 4 hours and addition of 2% nickel, particularly if achieved higher hardness (HV 1068.7 +/- 32.6) and density of about 99% theoretical density.

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Cesero, Leonardo de. "Influ?ncia da adi??o de nanopart?culas de s?lica nas propriedades mec?nicas de gessos odontol?gicos." Pontif?cia Universidade Cat?lica do Rio Grande do Sul, 2017. http://tede2.pucrs.br/tede2/handle/tede/7904.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES
Conselho Nacional de Pesquisa e Desenvolvimento Cient?fico e Tecnol?gico - CNPq
The current applications of nanotechnology in dentistry include adhesive systems and composite resins, but they are still quite limited in dental materials. Dental stone is a widely used material, and the incorporation of silica nanoparticles is still unexplored. The purpose of this study is to evaluate the behavior of the mechanical properties of dental stones with the addition of silica nanoparticles at different concentrations. A total of 180 samples were prepared, 90 for each dental stone (Durone and Fuji Rock). For the control group (CG), no silica particles were added, while test group 1 (TG1) had silica nanoparticles added to 1% by weight, and test group 2 (TG2) had silica nanoparticles added to 5% by weight. The roughness, diametral tensile strength (DTS) and compressive strength were measured 24 hours after the start of spatulation. The mean roughness values for Durone were CG= 0,55, TG1= 0,36 and TG2= 0,28 ?m and for Fuji Rock were CG= 0,47, TG1= 0,31 and TG2= 0,35 ?m. The mean DTS values for Durone were CG= 6,03, TG1= 5,17 and TG2= 5,02 MPa and for Fuji Rock were CG= 6,41, TG1= 5,23 and TG2= 4,56 MPa. The mean compressive strength values for Durone were CG= 35,44, TG1= 32,70 and TG2= 32,44 MPa and for Fuji Rock were CG= 42,97, TG1= 31,22 and TG2= 29,86 MPa. Surface roughness was statistically lower for the Durone and Fuji Rock stones (p< 0,001) when silica nanoparticles were added. For DTS and compressive strength, the addition of silica nanoparticles did not lead to statistically better results when compared to the control groups (p> 0,05).
A nanotecnologia na Odontologia est? presente nos sistemas adesivos e nas resinas compostas, sendo sua aplica??o ainda bastante limitada nos materiais dent?rios. O gesso odontol?gico ? um material amplamente utilizado e a incorpora??o de nanopart?culas de s?lica ? desconhecida. O objetivo do estudo ? avaliar o comportamento das propriedades mec?nicas dos gessos odontol?gicos a partir da adi??o de nanopart?culas de s?lica em diferentes concentra??es. Foram confeccionadas 180 amostras, sendo 90 para cada gesso (Durone e Fuji Rock). No grupo controle (GC) n?o foram adicionadas part?culas, no grupo teste 1 (GT1) foram adicionadas 1% em peso e o grupo teste 2 (GT2) recebeu 5% em peso de nanopart?culas de s?lica. Os testes de rugosidade, tra??o diametral (DTS) e compress?o foram realizados ap?s 24 horas do in?cio da espatula??o. Os valores m?dios de rugosidade para o Durone foram de GC= 0,55, GT1= 0,36 e GT2= 0,28 ?m e para o Fuji Rock foram de GC= 0,47, GT1= 0,31 e GT2= 0,35 ?m. Para DTS foram de GC= 6,03, GT1= 5,17 e GT2= 5,02 MPa para o Durone e para o Fuji Rock foram de GC= 6,41, GT1= 5,23 e GT2= 4,56 MPa. Para compress?o foram de GC= 35,44, GT1= 32,70 e GT2= 32,44 MPa para o Durone e para o Fuji Rock foram de GC= 42,97, GT1= 31,22 e GT2= 29,86 MPa. Houve uma menor rugosidade superficial estatisticamente para os gessos Durone e Fuji Rock (p< 0,001) quando adicionadas nanopart?culas de s?lica. Para a DTS e compress?o n?o houve estatisticamente resultados melhores quando adicionadas nanopart?culas de s?lica em compara??o aos grupos controles (p> 0,05).

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Pamenius, Madeleine Jansson. "Rubber impression materials, a mechanical approach an investigation of material properties and their application in computer simulation of dimensional stability /." Stockholm : Division of Dental Materials and Technology, Dept. of Clinical Oral Sciences, School of Dentistry, Karolinska Institutet, 1994. http://catalog.hathitrust.org/api/volumes/oclc/30989203.html.

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R?go, Jos? K?io Max Alves do. "Efeito da adi??o dos azocorantes DR73 e DB79 nas propriedades do poli(metacrilato de metila)." Universidade Federal do Rio Grande do Norte, 2012. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12743.

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Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
Currently new polymeric materials have been developed to replace other of traditionally materials classes. The use of dyes allows to expand and to diversify the applications in the polymeric materials development. In this work the behavior and ability of azo dyes Disperse Blue 79 (DB79) and Disperse Red 73 (DR73) on poly(methyl methacrylate) (PMMA) were studied. Two types of mixtures were used in the production of masterbatches: 1) rheometer 2) solution. Processing by extrusion-blow molding of PMMA was carried out in order to evaluate the applications of polymeric films. Thermal analysis were performed by thermogravimetry to evaluate polymer and azo dyes thermal stability. Colorimetric analysis were obtained through monitoring the spectral variations associated with sys/trans/anti azo dyes isomerization process Colorimetric data were treated and evaluated in accordance to the color system RGB and CIEL*ab, by monitoring the color change as function of time. Mechanical properties, characterized by tensile tests, were evaluated and correlated with the presence and content of azo dyes in the samples. Analyses by scanning electronic microscopy (SEM) were performed on the surfaces of samples to check the azo dye dispersion after the mixing process. It was concluded that the production of PMMA/azo dyes is possible and feasible, and the mixtures produced had synergy of properties for use in various applications
Atualmente novos materiais polim?ricos v?m sendo desenvolvidos, visando substituir outras classes de materiais tradicionalmente empregados. O uso de corantes possibilita ampliar e diversificar as possibilidades de aplica??es no desenvolvimento desses novos materiais. Neste trabalho foi estudado o comportamento e a capacidade de tingimento dos azocorantes: Azul Disperso 79 (DB79) e o Vermelho Disperso 73 (DR73), em uma matriz de poli(metacrilato de metila) (PMMA). Duas formas de misturas foram utilizadas na produ??o dos concentrados: na primeira, em re?metro de torque e na segunda, em solu??o. O processamento por extrus?o-sopro do PMMA foi realizado neste trabalho com intuito de avaliar suas aplica??es na forma de filmes polim?ricos. An?lises t?rmicas foram realizadas por termogravimetria para avaliar a estabilidade t?rmica dos pol?meros e dos azocorantes. An?lises por colorimetria foram obtidas por meio do acompanhamento das mudan?as espectrais associadas ao processo de isomeriza??o cis/trans/anti dos azocorantes. Os dados de colorimetria foram tratados e avaliados segundo o sistema de cores RGB e CIEL*ab, por meio do acompanhamento da mudan?a de colora??o em fun??o do tempo. As propriedades mec?nicas, caracterizadas por meio de ensaios de tra??o uniaxial, foram avaliadas e correlacionadas com a presen?a e quantidade de azocorantes na constitui??o das amostras. An?lises por microscopia eletr?nica de varredura (MEV) foram realizadas nas superf?cies das amostras para verificar a dispers?o dos corantes no final do processo de mistura. Verificou-se que a produ??o de PMMA/azocorantes ? poss?vel e vi?vel e as misturas produzidas apresentaram sinergia de propriedades para utiliza??o em diversas aplica??es

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Oliveira, Gerl?nea Silva de. "Estudo e caracteriza??o de comp?sitos de metal duro com adi??o de Ni (WC-Ni)." PROGRAMA DE P?S-GRADUA??O EM CI?NCIA E ENGENHARIA DE MATERIAIS, 2016. https://repositorio.ufrn.br/jspui/handle/123456789/22250.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)
O n?quel tem sido bastante utilizado, em estudos, como substituto do cobalto no metal duro - WC-Co, devido apresentar maior resist?ncia ? corros?o e ? oxida??o, al?m das propriedades mec?nicas e de aspectos econ?micos. Atualmente, carbetos e metais s?o adicionados ao metal duro, para aumentar a sinterabilidade do material, e, consequentemente, as suas propriedades de dureza e tenacidade. Neste trabalho, foram estudados os efeitos da varia??o percentual de Ni e dos par?metros de sinteriza??o (temperaturas de sinteriza??o e isotermas) nas propriedades do sinterizado WC-Ni. Os produtos sinterizados foram obtidos atrav?s das etapas de processamento da metalurgia do p?, no qual p?s de carbeto de tungst?nio ? WC com adi??o de 5 e 15%p. de N?quel ? Ni foram mo?dos em um moinho planet?rio de alta energia durante 8 horas. Em seguida, os p?s particulados foram compactados em uma prensa uniaxial sob carga de 300 Mpa numa matriz cil?ndrica de 5 mm de di?metro. A sinteriza??o dos compactados a verde foi realizada nas temperaturas de 1350 ?C e 1450?C, com isotermas de 30 e 90 minutos, no dilat?metro; e, na temperatura de 1350? C, com isotermas de 30 e 90 minutos, em forno ? v?cuo. Os p?s de partida (WC e Ni) e os mo?dos foram caracterizados por difra??o de raios ? X (DRX), microscopia eletr?nica de varredura (MEV) e espectroscopia de energia dispersiva (EDS); e as amostras sinterizadas foram caracterizadas por MEV, EDS e medidas de microdureza. Os valores de microdureza Vickers foram maiores para as amostras de WC-5%p.Ni sinterizadas a 1450?C, com isotermas de 30 e 90 minutos no dilat?metro (1078,6 HV e 1246,1 HV, respectivemente). No forno a v?cuo, o melhor resultado de microdureza, tamb?m, foi para as amostras WC-5%p.Ni sinterizadas a 1350?C com isoterma de 30 e 90 minutos (849,6 HV e 914,7 HV, respectivemente). As amostras de WC-5%p.Ni sinterizadas no forno a v?cuo a 1350?C com isotermas de 30 e 90 minutos mostraram maiores valores de microdureza comparados aos das amostras WC-5%pNi sinterizadas no dilat?metro a 1350?C com isoterma de 30 e 90 minutos.
Nickel has been widely used as a substitute for cobalt in WC-Co hardmetal studies due to greater corrosion and oxidation resistance as well as mechanical properties and economic aspect. Currently, carbides and metals are added to hard metal in order to increase the sinterability of the material, and consequently their hardness and toughness. In this study, the effects of different amount of Ni and sintering parameters (sintering temperatures and holding time) on properties of sintered WC-Ni were studied. The sintered products were obtained via powder metallurgy processing steps, in which powders of tungsten carbide (WC) with 5 and 15 wt% Nickel (Ni) were milled in a planetary high energy ball milling for 8 hours. Then, the particulate powders were compacted into a cylindrical die with 5 mm in diameter under a uniaxial load of 300 MPa. Sintering of the green samples was carried out at 1350 and 1450?C with holding time of 30 and 90 minutes, in resistance furnace and at 1350? C, with 30 and 90 minutes holding time in vacuum furnace. Starting (WC and Ni) and milled powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Sintered samples were also characterized by SEM, EDS and microhardness measurements. Hardness results were higher for WC-5 wt% Ni sintered in the resistance furnace at 1450 ? C with 30 and 90 minutes holding time (1078.6 and 1246.1 Hv respectively). WC-5wt% Ni Samples sintered in vacuum furnace at 1350 ?C with 30 to 90 minutes holding time obtained a higher microhardness compared to ones sintered in the resistance furnace at 1350 ?C with holding time of 30 and 90 minutes.

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Azevedo, Heytor Vitor Souza Bezerra de. "Efeito da adi??o de WC e Co na sinteriza??o e propriedades mec?nicas da alumina." Universidade Federal do Rio Grande do Norte, 2016. http://repositorio.ufrn.br/handle/123456789/21026.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)
Comp?sitos ? base de alumina (Al2O3), carbeto de tungst?nio (WC) e cobalto (Co) apresentam propriedades espec?ficas como baixa densidade, alta resist?ncia ? oxida??o, alto ponto de fus?o e elevada in?rcia qu?mica. Esse comp?sito revela ser um material promissor para ser aplicado em diversos campos da engenharia. Este trabalho tem como objetivo avaliar algumas propriedades mec?nicas durante a confec??o e, ap?s a sinteriza??o do comp?sito (Al2O3 - WC - Co). P?s comp?sitos com a composi??o de 80%.p de Al2O3, 18%.p de WC e 2%.p de Co foram processados pela rota de moagem de alta energia (MAE), em moinho planet?rio por 50 horas, bem como por mistura manual em um recipiente de vidro, seguindo a mesma propor??o em peso. Amostras foram coletadas (2, 10, 20, 30, 40 e 50 horas) durante o processo de moagem. Em seguida, os p?s foram prensados no formato de amostra circular com di?metro de 5 mm em uma prensa uniaxial com press?es de 200 e 400 MPa. A sinteriza??o ocorreu de duas maneiras: a primeira sinteriza??o via fase s?lida foi realizada ? 1300 ?C e ? 1126 ?C durante 1h com taxa de aquecimento de 10?C/min em forno resistivo sob atmosfera de arg?nio as press?es de compacta??o utilizadas foram de 200 e 400 MPa, a segunda sinteriza??o foi realizada em dilat?metro via fase s?lida ? 1300 ?C com press?o de compacta??o de 200 MPa, tamb?m foi realizada em dilat?metro outra sinteriza??o, desta vez por fase l?quida ? 1550 ?C com press?es de compacta??o de 200 e 400 MPa, obedecendo os mesmos par?metros utilizados no forno resistivo. As mat?rias-primas foram caracterizadas por difra??o de raios X - (DRX), fluoresc?ncia de raios X - (FRX), microscopia eletr?nica de varredura (MEV), espectroscopia por dispers?o de energia (EDS) e particulometria a laser. As amostras sinterizadas foram submetidas a ensaios de microdureza. Os resultados mostraram que a moagem de alta energia atingiu os objetivos quanto ao tamanho de part?cula e a densifica??o do comp?sito. Entretanto, a microdureza n?o alcan?ou resultados significativos, isso ? um ind?cio que o comp?sito possui baixa tenacidade ? fratura.
Composites based on alumina (Al2O3), tungsten carbide (WC) and cobalt (Co) exhibit specific properties such as low density, high oxidation resistance, high melting point and high chemical inertia. That composite shows to be a promising material for application in various fields of engineering. In this work, the mechanical properties of the composite (Al2O3 ? WC ? Co), particularly density and hardness, were evaluated according to the effects of the variables of powder processing parameters, green compact and sintered. Powder composites with the composition of 80 wt% Al2O3, 18 wt% WC and 2 wt% Co were processed by high energy ball milling in a planetary mill for 50 hours as well as mixed by manual mixing in a glass vessel with the same proportion. Samples were collected (2, 10, 20, 30, 40 and 50 hours) during the milling process. Then, the powders were compacted in a cylindrical die with 5 mm in diameter in a uniaxial press with pressures of 200 and 400 MPa. The sintering was in two stages: first, the solid phase sintering was performed at 1126 and 1300 ?C for 1 hour with a heating rate of 10 ?C/min in a resistive furnace under argon atmosphere for green samples compacted in 200 and 400 MPa; the second sintering was performed on dilatometer in solid phase at 1300 ?C for green sample compacted in 200 MPa, another sintering also was performed on dilatometer, this time in liquid phase at 1550 ?C for green samples compacted in 200 and 400 MPa, with the same parameters used in resistive furnace. The raw materials were characterized by X ? ray diffraction (XRD), X ? ray fluorescence (XRF), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and laser particlemeter. The sintered samples were subjected to microhardness testing. The results showed that high energy milling achieved to the objectives regarding the particle size and the dispersion of composite phases. However, the hardness did not achieve to significant results, this is an indication that the composite has low fracture toughness.

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Gonçalves, Rene Francisco Boschi. "Termocinética de combustão de materiais energéticos (ADN, AP e H2) aplicados na indústria aeroespacial." Instituto Tecnológico de Aeronáutica, 2009. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=831.

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Os materiais energéticos têm sido utilizados ao longo dos tempos em aplicações civis e militares. De forma concomitante, estudos foram direcionados focando os mecanismos de combustão desses materiais, incluindo seu comportamento cinético e termodinâmico durante a queima. O objetivo do presente trabalho foi estudar de forma sistemática os mecanismos de decomposição térmica da dinitramida de amônio (ADN), perclorato de amônio (AP), isolado e formulado como propelente sólido compósito, além do hidrogênio, por meio de simulação computacional. Foram levados em conta todos os parâmetros cinéticos e termodinâmicos para a realização destas simulações. Além disso, foi realizada a determinação dos parâmetros de Arrhenius para as reações elementares que envolvem o mecanismo global de decomposição térmica do hidrogênio por métodos de química quântica molecular. O comportamento da combustão da ADN para o caso do grão propelente sólido instalado na câmara de combustão de um motor-foguete convencional foi comparado ao comportamento quando em sistema aberto, nas condições ambiente. O livre fornecimento de oxigênio no sistema aberto acarreta um aumento significativo na velocidade das reações elementares do mecanismo global. A decomposição térmica do AP foi simulada nas condições de queima do grão instalado na câmara de combustão de um motor-foguete, de forma isolada ou formulado no "binder" de polibutadieno líquido hidroxilado (PBLH). Os resultados mostraram que a pressão do meio é um fator crítico na queima do AP isolado, enquanto para o AP formulado com PBLH, a variação no comportamento de queima em função da pressão pode ser desconsiderada. Por meio de métodos de química quântica molecular, foram determinados os parâmetros cinéticos e termodinâmicos das reações elementares do mecanismo de combustão do hidrogênio. Estes resultados foram comparados com os obtidos experimentalmente por meio de simulação de queima em um reator em regime transiente. Notou-se que mudanças no valor absoluto da energia de ativação acarretaram variações significativas no comportamento global da decomposição térmica do material.

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Sanabio, Robson Guimar?es. "An?lise experimental de danos em pist?es de motor ? gasolina operando com adi??o de g?s hidr?xi." Universidade Federal do Rio Grande do Norte, 2015. http://repositorio.ufrn.br/handle/123456789/20221.

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A adi??o de hidrog?nio gasoso como fonte alternativa de combust?vel vem sendo largamente utilizada. Hoje em dia, v?rias experi?ncias est?o em andamento para a utiliza??o de geradores de hidrog?nio (eletrolisadores) por demanda em ve?culos automotores. Em todos os an?ncios desses produtos seus fabricantes afirmam que este procedimento fornece uma redu??o de consumo de combust?vel, reduz os n?veis de emiss?o de gases t?xicos pela descarga e melhora a vida ?til do motor. A presente pesquisa faz uma an?lise da estrutura f?sica de pe?as de motores que utilizam eletrolisadores por demanda. Para isto, foi montado um sistema estacion?rio com um motogerador de energia el?trica, monocil?ndrico, e adaptados dois eletrolisadores um de c?lula seca e outro de c?lula molhada. Nas etapas de observa??o, foram feitas an?lises de consumo em quatro faixas de carga de trabalhos e observado o pist?o do motor, que foi cortado e analisado por microscopia ?tica (MO), Microscopia Eletr?nica de Varredura e de Energia Dispersiva (MEV-EDS), Microscopia Confocal e Difra??o de Raios - X (DRX), no sistema estacion?rio, em cada etapa. Os resultados mostraram uma redu??o consider?vel no consumo de combust?vel e uma corros?o acentuada no pist?o original de f?brica, feito de liga alum?nio-sil?cio. Como barreira ? corros?o foi feita uma nitreta??o por plasma na cabe?a do pist?o, que se mostrou resistente ao ataque pelo hidrog?nio, embora tenha apresentado evid?ncias de tamb?m ter sido atacada. Concluiu-se que os eletrolisadores automotivos podem ser uma boa op??o em termos de consumo e redu??o de emiss?es de gases t?xicos, por?m o material das c?maras de combust?o dos ve?culos devem ser preparados para este fim.
The addition of hydrogen gas as an alternative fuel source has been widely used, as well reported in scientific literature. Today, several experiments are underway for the use of hydrogen generators (electrolysers) demand for motor vehicles. In all these products their ads manufacturers claim that this provides a reduction of fuel consumption, reduces the emission levels of toxic gas by the discharge and improves engine life. This research analyzes the physical structure of engine components using electrolysis on demand. To this end, a stationary system was fitted with a power generator of electricity, drum roller and adapted two electrolyzers: a dry cell and wet cell other. In steps observation were consumption analyzes in four work load ranges and observing the piston engine, which has been cut and analyzed by Optical Microscopy (OM), Scanning Electron Microscopy and Dispersive Energy (SEM-EDS), X ? Ray Diffraction (XRD) and Confocal Microscopy, the stationary system in each step. The results showed a considerable reduction in fuel consumption and a high corrosion in the original factory piston constituted of aluminum-silicon alloy. As corrosion barrier was made a plasma nitriding in the piston head, which proved resistant to attack by hydrogen, although it has presented evidence also, of having been attacked. It is concluded that the automotive electrolysers can be a good choice in terms of consumption and reducing toxic gas emissions, but the material of the combustion chambers of vehicles must be prepared for this purpose.

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26

Santos, Osvaldo Cruz. "Formula??o de bloco intertravado cer?mico com adi??o de res?duos urbanos e industriais." Universidade Federal do Rio Grande do Norte, 2013. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12832.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
The production of waste from urban and industrial activities is one of the factors of environmental contamination and has aroused attention of the scientific community, in the sense of its reuse. On the other hand, the city of Salvador/Ba, with approximately 262 channels, responsible for storm water runoff, produces every year, by the intervention of cleaning and clearing channels, a significant volume of sediments (dredged mud), and thus an appropriate methodology for their final destination. This study aims to assess the influence of incorporation of these tailings in arrays of clay for production of interlocked block ceramic, also known as ceramic paver. All the raw materials from the metropolitan region of Salvador (RMS) were characterized by x-ray fluorescence, x-ray diffraction, thermal analysis (TG and TDA), particle size analysis and dilatometry. With the use of statistical experimental planning technique, ternary diagram was defined in the study region and the analyzed formulations. The specimens were prepared with dimensions of 60x20x5mm?, by uniaxial pressing of 30 MPa and after sintering at temperatures of 900?, 1000? and 1100?C the technological properties were evaluated: linear shrinkage, water absorption, apparent porosity, apparent specifies mass, flexural rupture and module. For the uniaxial compression strength used cylindrical probe body with ? 50 mm. The standard mass (MP) was prepared with 90% by weight of clay and 10% by weight of Channel sediment (SCP), not being verified significant variations in the properties of the final product. With the incorporation of 10% by weight of manganese residue (PFM) and 10% by weight of the Ceramic waste (RCB) in the mass default, in addition to adjusting the plasticity due to less waste clay content, provided increased linear firing shrinkage, due the significant concentration of K2O, forming liquid phase at low temperature, contributing to decreased porosity and mechanical resistance, being 92,5 MPa maximum compressive strength verified. After extract test leachate and soluble, the piece containing 10% of the PFM, was classified as non-hazardous and inert material according to NBR10004/04 ABNT. The results showed the feasibility on using waste, SCP, RCB and PFM clay mass, at temperatures above 900?C, paver ceramic production, according to the specifications of the technical standards, so that to exceed the 10% of the PFM, it becomes imperative to conduct studies of environmental impacts
A produ??o de res?duos provenientes das atividades urbanas e industriais ? um dos fatores de contamina??o ambiental e tem despertado aten??o da comunidade cientifica, no sentido do seu reaproveitamento. Por outro lado, a cidade do Salvador/Ba, com aproximadamente 262 canais, respons?veis pelo escoamento de ?guas pluviais, produz todo ano, pela necessidade de interven??o de limpeza e desobstru??o de canais, um volume significativo de sedimentos (lama dragada), impondo dessa forma uma metodologia adequada para sua destina??o final. Este trabalho tem como objetivo avaliar a influ?ncia da incorpora??o desses rejeitos em matrizes de argila para produ??o de bloco intertravado cer?mico, tamb?m conhecido como paver cer?mico. Todas as mat?rias primas oriundas da Regi?o Metropolitana de Salvador (RMS) foram caracterizadas por fluoresc?ncia de raios -X, difra??o de raios -X, analise t?rmica (TG e TDA), analise granulom?trica e dilatometria. Com a utiliza??o da t?cnica estat?stica de planejamento experimental, foi definida em diagrama tern?rio a regi?o de estudo e as formula??es analisadas. Foram preparados os corpos de prova com dimens?es de 60x20x5mm3, por prensagem uniaxial de 30 MPa e, ap?s sinteriza??o nas temperaturas de 900?, 1000? e 1100?C, as propriedades tecnol?gicas avaliadas foram: retra??o linear, absor??o de ?gua, porosidade aparente, massa especifica aparente, m?dulo de ruptura ? flex?o. Para a resist?ncia ? compress?o uniaxial utilizou-se o corpo de prova cil?ndrico com ? de 50mm. A massa padr?o (MP) foi preparada com 90% em peso de argila e 10% em peso do sedimento de canais (SCP), n?o sendo verificadas varia??es significativas nas propriedades do produto final. Com a incorpora??o de 10% em peso do res?duo de mangan?s (PFM) e 10% em peso do rejeito cer?mico (RCB) na massa padr?o, al?m do ajuste da plasticidade, em fun??o de menor teor de argilominerais dos res?duos, proporcionou aumento da retra??o linear de queima, devido a significativa concentra??o de K2O, formando fase liquida em baixa temperatura, contribuindo para diminui??o da porosidade e aumento da resist?ncia mec?nica, sendo 92,5 MPa a m?xima resist?ncia ? compress?o verificada. Ap?s teste do extrato lixiviado e solubilizado, a pe?a contendo 10% do PFM, foi classificada como material n?o perigoso e inerte segundo NBR10004/04 da ABNT. Os resultados mostraram viabilidade na utiliza??o dos res?duos SCP, RCB e PFM em massa argilosa, em temperaturas acima de 900?C, para produ??o de bloco intertravado, paver cer?mico, de acordo com as especifica??es das normas t?cnicas, de forma que, para teores superiores a 10% do PFM, torna-se imperativo a realiza??o de estudos de impactos ambientais

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27

Moraes, Martimiano Krusciel de. "Efeito da adi??o de nanopart?culas pozol?nicas nas propriedades e estrutura da pasta de cimento classe G em meios ricos em CO2." Pontif?cia Universidade Cat?lica do Rio Grande do Sul, 2016. http://tede2.pucrs.br/tede2/handle/tede/7078.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES
Funda??o de Amparo ? Pesquisa do Estado do Rio Grande do Sul (FAPERGS)
Carbon capture and storage in geological formations is a promising technology to mitigate emissions of the main greenhouse gas, CO2. However, its application involves maintaining the integrity of the materials used in the injection wells to prevent leakage of CO2. On the other hand, advances in nanotechnology research have contributed to improve the performance of cementitious materials. In this context, this work investigate the influence of the incorporation of clay (organomodified montmorillonite- OMMT) and silica nanoparticles in the class G cement paste used in the completion and abandonment of oil wells in two reaction media, wet supercritical CO2 and water saturated with CO2, at high pressure (15 MPa) and high temperature (90 ?C) for 7, 21 and 56 days. The techniques of field emission gun scanning electron microscopy (FEG/SEM), X ray diffraction (XRD), Vickers hardness and compressive strength were used to evaluate the effect of degradation on the structure and mechanical properties of the cement paste. In general, the inclusion of nanoparticles promoted an increase in chemically altered layer, with the exception of adding 0.5% OMMT, which can be an indication that there is an adequate amount of nanoparticles that can produce an increasing on the resistance to chemical degradation in the presence of CO2. However, in general, the results indicate an improvement on mechanical properties with the addition of nanoparticles, compared with the cement paste without addiction of nanoparticles. Among all types and concentrations of nanoparticles studied, the best results in terms of density and resistance to degradation by CO2 was obtained for the content of 0.5% OMMT.
A captura e armazenamento de carbono em forma??es geol?gicas ? uma tecnologia promissora para mitiga??o das emiss?es do principal g?s de efeito estufa, o CO2. Entretanto, sua aplica??o envolve manter a integridade por longos per?odos de tempo dos materiais empregados nos po?os de inje??o para evitar vazamento de CO2. Por outro lado, o avan?o nas pesquisas em nanotecnologia tem contribu?do para a melhoria do desempenho de materiais ciment?cios. Neste contexto, este trabalho investiga a influ?ncia da incorpora??o de nanopart?culas de argila (montmorilonita organof?lica- OMMT) e s?lica nas propriedades da pasta de cimento classe G empregada na completa??o e abandono de po?os de petr?leo, em dois meios reacionais, CO2 supercr?tico ?mido e ?gua saturada com CO2, a alta press?o (15 MPa) e temperatura (90 ?C), durante 7, 21 e 56 dias. As t?cnicas de microscopia eletr?nica de varredura por emiss?o de campo (FEG/MEV), difra??o de raios X (DRX), microdureza Vickers e resist?ncia ? compress?o foram utilizadas para avaliar o efeito da degrada??o na estrutura e propriedades mec?nicas da pasta de cimento. De modo geral, a inclus?o de nanopart?culas promoveu um aumento da camada alterada quimicamente, com exce??o da adi??o de 0,5% de OMMT, o que ? um indicativo de que h? um teor adequado de nanopart?culas que pode aumentar a resist?ncia ? degrada??o qu?mica em presen?a de CO2. Contudo, de um modo geral, observou-se uma melhora nas propriedades mec?nicas com a adi??o de nanopart?culas, se comparado com a pasta de cimento padr?o. Dentre os tipos e teores de nanopart?culas testados, os melhores resultados em termos de densidade da pasta endurecida e resist?ncia ? degrada??o por CO2 foram obtidos para o teor de 0,5% de OMMT.

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28

Tagg, Woo Chiat, and n/a. "Novel fluorescent organometallic materials." University of Otago. Department of Chemistry, 2009. http://adt.otago.ac.nz./public/adt-NZDU20090430.133100.

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This thesis describes the synthesis and properties of some extended donor-acceptor dyads with the donor being a ferrocenyl moiety and a fluorescent naphthalimide group as the acceptor. Two series of extended ferrocenyl-naphthalimide dyads were prepared in reasonable yield depending on the synthetic route. The first are a series of three ferrocenyl-CH=CH-spacer-C[triple bond]C-naphthalimide dyads in which the spacers are phenyl, biphenyl and anthryl and the second are a series of three ferrocenyl-C[triple bond]C-spacer-C[triple bond]C-naphthalimide dyads in which the spacers are 2,2� -bithiophene, 2,5-dimethoxybenzene and tetrafluorobenzene groups. The molecular structures of some compounds have been determined by X-ray diffraction although with many challenges because of the extensive [pi]-[pi] stacking of molecules that leads to ready aggregation in the solid state, particularly for the ferrocenyl-CH=CH-spacer-C[triple bond]C-naphthalimide dyads, in which the naphthalimide bears a methyl head group. In order to reduce the [pi]-[pi] stacking effect between the molecules and also to produce chiral molecules for the potential nonlinear optical applications, a chiral α-methylbenzylamine was introduced as the head group of naphthalimide for the ferrocenyl-C[triple bond]C-spacer-C[triple bond]C-naphthalimide dyads. The resulting comounds successfully gave crystals of sufficient quality for X-ray structural investigation. While the oxidative electrochemistry of the ferrocenyl compound in the two series of dyads was largely predictable (E� ~ 0.55 V for ferrocenyl-CH=CH- and ~ 0.72 V for ferrocenyl-C[triple bond]C-), the presence of spacers in the dyads appeared to afford stability to the reduced naphthalimide species. This was exhibited by the appearance of chemically reversible one-electron reduction processes for each of the compounds investigated. Similar unusual chemical reversibility was also shown by the spacer-C[triple bond]C-naphthalimide precursor systems. For the ferrocenyl-CH=CH-spacer-C[triple bond]C-naphthalimide dyads, the oxidation and reduction potentials closely resembled those of the simple ferrocenyl-CH=CH-spacer systems. This suggested that augmentation of the simple ferrocenyl-CH=CH-phenyl, -biphenyl and -anthryl systems with an alkyne linked naphthalimide unit showed little influence on the oxidation of the ferrocenyl moiety or the reduction of the naphthalimide unit. However, for the ferrocenyl-C[triple bond]C-spacer-C[triple bond]C-naphthalimide dyads, the oxidation and reduction potentials are influenced by the inductive effects of the spacers. While an anodic shift was observed for the dyad with the electron-withdrawing spacer tetrafluorobenzene, a cathodic shift was displayed for the dyads with the electron-donating spacers 2,2�-bithiophene and 2,5-dimethoxybenzene compared to that in the simple ferrocenyl-C[triple bond]C-naphthalimide system. The spectroscopic properties of the ferrocenyl-CH=CH-spacer-C[triple bond]C-naphthalimide dyads showed that interpolation of the aromatic spacers does not interfere with the internal charge separation. Oxidation of the ferrocenyl moiety resulted in bleaching of the metal-to-ligand charge transfer band at ~ 500 nm and the growth of a new band in the near infrared region at ~ 1000 nm. This new band can be assigned to a ligand-to-metal charge transfer transition, where the ferrocenium now acts as an acceptor to the naphthalimide donor. For the ferrocenyl-C[triple bond]C-spacer-C[triple bond]C-naphthalimide dyads, the spectroscopic properties showed that the mutually electron-withdrawing tetrafluorobenzene and naphthalimide units had little interaction despite their connection by a conductive alkyne link. In contrast, the dyads containing the electron-donating 2,2�-bithiophene and 2,5-dimethoxybenzene showed some degree of interaction between the spacer and the naphthalimide fragments. This was evidenced by the appearance of a broad absorption band in the range 410 - 440 nm, which is associated with an orbital that is delocalised between the spacer and the naphthalimide fragments. Again, the roles of donor and acceptor were reversed on oxidation of the ferrocenyl moiety. This resulted in the growth of a new near infrared band at ~750 mn for the dyad containing the tetrafluorobenzene spacer and at ~ 1000 nm for the dyads with 2,2�-bithiophene and 2,5 -dimethoxybenzene spacers. The ferrocenyl unit went from being a net donor to ferrocenium, which was acting as an acceptor, with the tetrafluorobenzene spacer adopting the donor role more reluctantly than the delocalised 2,2�-bithiophene-C[triple bond]C-naphthalimide and 2,5-dimethoxybenzene-C[triple bond]C-naphthalimide moieties. 1,3,5-Tri- and 1,2,4,5-tetra-substituted benzene cores were also used as spacers for the preparation of extended arrays of ferrocenyl-naphthalimide dyads. Utilisation of the 1,3,5 -tri-substituted benzene core enabled the core to be embellished in three directions, resulting in Y-motif extended arrays containing either one ferrocenyl unit [(ethenylferrocenyl)-C₆H₃-(C[triple bond]C-C₆H₅)₂] or one naphthalimide moiety [(4-piperidino-N-propargyl-naphthalimide)-C₆H₃-(Br)₂]. With the 1,2,4,5-tetra-substituted benzene core, the extension of the core was possible in four directions and gave extended arrays in an X-motif. Again, these systems contained either ferrocenyl units [bis(alkoxyferrocenyl)-C₆H₂-(C[triple bond]C-C₆H₅)₂] or naphthalimide moieties [(tetrakis-naphthalimide)-C₆H₂]. Attempts to incorporate both ferrocenyl and naphthalimide fragments into the X- or Y-motif extended arrays were unsuccessful. By adding C₂Co₂(CO)₆dppm across the triple bonds of two of the four alkyne groups in the X-motif naphthalimide system [(tetrakis-naphthalimide)-C₆H₂], it was possible to incorporate two oxidisable C₂Co₂(CO)₄dppm cluster units into the molecule. The electrochemistry of the resulting system showed two discrete oxidation processes, suggesting the possibility of some interaction between the dicobalt cluster redox centres.

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29

Dultra, Eduardo Jorge Vidal. "Adi??o de subprodutos da cinza da casca de caf? (coffea canephora) em massa cer?mica para porcelanato." Universidade Federal do Rio Grande do Norte, 2013. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12834.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
To produce porcelain tiles fluxing agents are used in order to obtain a liquid phase during firing. This liquid phase fills the pores decreasing porosity, water absorption and contributes to material densification. In the porcelain tiles industry, feldspar is the main flux material used, with quantities ranging between 35 and 50%. Studies focus on the discovery of materials with flux characteristics that can reduce the consumption of feldspar by porcelain tiles industry. In this context, the coffee husk ashes, a residue obtained when coffee husks are burned to produce heat for the dryers during the processing of the green fruit, have as main chemical constituents potassium, calcium and magnesium, giving them characteristics of fluxing material. Brazil is the largest coffee producer in the world and is responsible for over 30% of the world s production. In this work a physical treatment of coffee husk ash was carried out in order to eliminate the organic matter and, after this, two by-products were obtained: residual wastes R1 and R2. Both residues were added separately as single fluxes and also in association with feldspar in mixtures with raw materials collected in a porcelain industry located in Dias d ?vila-Ba. The addition of these residues aimed to contribute to the reduction of the consumption of feldspar in the production of porcelain tiles. Specimens were produced with dimensions of 60 mm x 20 mm x 6 mm in an uniaxial die with compacting pressure of 45 MPa. The samples were heated to a temperature of 1200 ?C, for 8 minutes. Tests were performed to characterize the raw materials by XRF, XRD, particle size analysis, DTA and TGA and, additionally, the results of the physical properties of water absorption, apparent porosity, linear shrinkage, density, dilatometry, flexural strength and SEM of sintered body were analyzed. Additions of less than 8% of the residue R1 contributed to the decrease of porosity, but the mechanical strength of the samples was not satisfactory. Additions of 5% the R2 residue contributed significantly to decrease the water absorption and apparent porosity, and also to increase the mechanical strength. Samples with addition of feldspar associated with the R2 residue, in proportions of 6.7% of R2 and 6.7% of feldspar, led to results of water absorption of 0.12% and mechanical strength of 46 MPa, having parameters normalized to the manufacture of porcelain stoneware tiles
Na fabrica??o de porcelanatos s?o utilizados fundentes com a finalidade de obter fase l?quida durante a queima que, por sua vez, preenche os poros diminuindo a porosidade, a absor??o de ?gua, e contribui para a densifica??o do material. Na ind?stria de porcelanatos o feldspato ? o principal material fundente utilizado, com percentuais que variam entre 35 e 50% em massa. Pesquisas s?o direcionadas para a descoberta de materiais com caracter?sticas fundentes que possam diminuir o consumo de feldspato. Nesse contexto, a cinza da casca de caf?, res?duo obtido quando cascas de caf? s?o queimadas a fim de produzir calor para os secadores mec?nicos durante o beneficiamento do fruto, possuem como principais elementos o pot?ssio, c?lcio e magn?sio, conferindo-lhe caracter?sticas de material fundente. O Brasil ? o maior produtor de caf? do mundo, respons?vel por mais de 30% da produ??o mundial. Nesse trabalho, foi realizado um tratamento f?sico na cinza de caf? com a finalidade de eliminar parte do material carbonizado e, ap?s este, foram obtidos dois subprodutos: res?duo R1 e res?duo R2. Ambos os res?duos foram adicionados, separadamente, como ?nicos fundentes, e tamb?m associados ao feldspato, em massas com mat?rias primas coletadas em uma f?brica de porcelanatos localizada no munic?pio de Dias d ?vila-Ba. A adi??o desses res?duos teve o objetivo de verificar a possibilidade de reduzir o consumo de feldspato na produ??o de porcelanatos. Foram confeccionados corpos de prova com dimens?es de 60 mm x 20 mm x 6 mm em matriz uniaxial, com press?o de compacta??o de 45 MPa. Os corpos de prova foram sinterizados na temperatura de 1200 ?C com patamar de 8 minutos. Foram realizados ensaios para caracteriza??o das mat?riasprimas por FRX, DRX, AG, ATD e ATG, e analisados os resultados das propriedades f?sicas de absor??o de ?gua, porosidade aparente, retra??o linear, MEA, an?lise dilatom?trica, resist?ncia ? flex?o e MEV do corpo sinterizado. A adi??o de at? 8% do res?duo R1 contribuiu para a diminui??o da porosidade aparente, por?m a resist?ncia mec?nica das amostras n?o foi satisfat?ria. A adi??o de 5% de res?duo R2 contribuiu significativamente para diminuir absor??o de ?gua e porosidade aparente, e tamb?m, para o aumento da resist?ncia mec?nica ? flex?o. As amostras com adi??o do res?duo R2 associado ao feldspato, nas propor??es de 6,7% de R2 e 6,7% de feldspato, obtiveram resultados de absor??o de ?gua de 0,12% e resist?ncia mec?nica ? flex?o de 46 MPa, atendendo aos par?metros normalizados para fabrica??o de porcelanatos

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Melo, Guilherme F?bio de. "Concreto celular polim?rico: influ?ncia na adi??o de res?duo de poli?ster insaturado termofixo." Universidade Federal do Rio Grande do Norte, 2009. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12726.

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Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
This work addresses the production of lightweight concrete building elements, such as plates, prefabricated slabs for pre-molded and panels of fencing, presenting a singular concrete: the Lightweight Concrete, with special properties such low density and good strength, by means of the joint use of industrial waste of thermosetting unsaturated polyesters and biodegradable foaming agent, named Polymeric Lightweight Concrete. This study covered various features of the materials used in the composition of the Polymeric Lightweight Concrete, using a planning of factorial design 23, aiming at studying of the strength, production, dosage processes, characterization of mechanical properties and microstructural analysis of the transition zone between the light artificial aggregate and the matrix of cement. The results of the mechanical strength tests were analyzed using a computational statistics tool (Statistica software) to understand the behavior and obtain the ideal quantity of each material used in the formula of the Polymeric Lightweight Concrete. The definition of the ideal formula has the purpose of obtaining a material with the lowest possible dry density and resistance to compression in accordance with NBR 12.646/92 (≥ 2.5 MPa after 28 days). In the microstructural characterization by scanning electron microscopy it was observed an influence of the materials in the process of cement hydration, showing good interaction between the wrinkled face of the residue of unsaturated polyesters thermosetting and putty and, consequently, the final strength. The attaining of an ideal formula, given the Brazilian standards, the experimental results obtained in the characterization and comparison of these results with conventional materials, confirmed that the developed Polymeric Lightweight Concrete is suitable for the production of building elements that are advantageous for construction
Neste trabalho ? abordada a aplica??o da tecnologia dos concretos leves ? produ??o de elementos construtivos, tais como placas pr?-fabricadas para lajes pr?-moldadas, pain?is de veda??o e pe?as pr?-moldadas, e ao desenvolvimento de um concreto celular com propriedades especiais de baixa densidade e boa resist?ncia mec?nica, em fun??o da utiliza??o conjunta de res?duo industrial de poli?ster insaturado termofixo (PIT) e espuma biodegrad?vel incorporadora de ar, denominado de Concreto Celular Polim?rico (CCP) . O estudo abrangeu diferentes tra?os dos materiais empregados na composi??o do CCP, sendo utilizado um planejamento fatorial 23, para an?lises dos processos de dosagem e produ??o, caracteriza??o das propriedades mec?nicas, bem como an?lises microestruturais da zona de transi??o entre o agregado artificial leve (PIT) e a matriz de cimento. Os resultados dos testes de resist?ncia mec?nica foram analisados utilizando-se uma ferramenta computacional de estat?stica (Statistica Software) para compreens?o do comportamento e obten??o da concentra??o ideal de cada material utilizado na formula??o do CCP. A defini??o da f?rmula ideal teve como finalidade a obten??o de um material com a menor densidade a seco poss?vel e resist?ncia ? compress?o que atendesse ? norma NBR 12.646/92 (≥ 2,5 MPa aos 28 dias). Na caracteriza??o microestrutural por microscopia eletr?nica de varredura, observou-se a influ?ncia dos materiais no processo de hidrata??o do cimento, onde constatou-se boa intera??o entre o res?duo de PIT, cuja face ? enrugada, e a pasta de cimento. A obten??o da formula??o de um novo material que atende ? norma brasileira, os resultados experimentais obtidos nas caracteriza??es e compara??o desses resultados com materiais convencionais, comprovaram que o Concreto Celular Polim?rico desenvolvido ? adequado ? produ??o de elementos construtivos que apresentam vantagens quando aplicados ? constru??o civil

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He, Wendy Weiyu, and wendy he@deakin edu au. "The mechanical behaviour of irregular fibre materials." Deakin University. School of Engineering and Technology, 2002. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20061208.081806.

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This work investigates the effect of fibre irregularities on the mechanical behaviour of the irregular fibres using the finite element method (FEM). The first part of this work examines that the effect of fibre dimensional irregularities on the linear and non-linear tensile behaviour of the fibres, using a two-dimensional (2D) finite element models. In the linear simulation, a concept of method Youngs modulus is introduced. The method Youngs modulus, breaking load and breaking extension are affected by the magnitude and frequency of diameter variation in the fibre specimen. Fibre dimensional variation and the gauge length effect are also simulated. In the non-linear analysis, some additional information is obtained on changes in the yield and post-yield regions, which are clearly shown in the load-extension curves. Further investigation is focused on the flexural buckling behaviour of fibres with dimensional irregularities. A three-dimensional (3D) finite element model is used to simulate the buckling deformation of dimensionally irregular fibres, and the critical buckling load of the simulated fibre is calculated. Two parameters, the effective length and the average diameter within the effective length of an irregular fibre, are considered to be the key factors that influence the buckling behaviour of the fibre. An important aspect of this work is the calculation of the effective length of an irregular fibre specimen during buckling. This method has not been reported before. The third part of this work is on the combined tensile and torsional behaviour of fibres with dimensional irregularities, using a three-dimensional (3D) finite element model. Two types of fibres, polyester and wool, are simulated with sine waves of different level (magnitude) and frequency at different twist levels. For the polyester fibre, experiment verification of the simulation results has been carried out, and the results indicate the FE model is well acceptable for the simulation. The final part of this work examines the combined effect of dimensional and structural irregularities on the fibre tensile behaviour. Three-dimensional (3D) finite element models are used to simulate the cracks (transverse, longitudinal, combined transverse and longitudinal cracks) and cavities distributed in uniform fibres and fibres with 30% level of diameter variation, respectively. One of important conclusions is that under the simulated conditions, the dimensional irregularity of fibre influences the tensile behaviour of fibres more than the fibre structural irregularity. The fibre dimensional irregularity affects not only the values of the breaking load and breaking extension, but also the shape of load-extension curves. However, the fibre structural irregularity simulated in the study appears to have little effect on the shape of the load-extension curves. In addition, the effect of crack or cavity size, type and distribution on fibre tensile properties is also investigated.

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R?go, Vilson Ribamar. "Estudo do efeito da adi??o da esc?ria de aciaria no processamento e propriedades finais de telhas cer?micas." Universidade Federal do Rio Grande do Norte, 2010. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12772.

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This research presents an overview of the addition steelwork dust of ceramic shingles in order to contribute to the utilization use of such residue. The ceramic industry perspective in the Brazilian State of Piau? is quite promising. Unlike other productive sectors, the ceramic industry uses basically natural raw materials. Its final products are, in short, the result of transforming clay compounds. These raw materials are composed primarily of aluminum oxide, silicon, iron, sodium, magnesium, end calcium, among others. It was verified that steelwork dust is composed primarily of these same oxides, so that its incorporation in to structural ceramics is a very reasonable idea. Both clay and steelwork powder were characterized by AG, XRF, XRD, TGA and DTA. In addition, steelwork dust samples containing (0%, 5%, 10%, 15%, 20% and 25%) were extruded and burned at 800?C, 850?C, 900?C and 950?C. Then t echnological tests of linear shrinkage, water uptake, apparent porosity, apparent density and flexural strengthwere carried at. The results showed the possibility of using steelwork powder in ceramic shingles until 15% significant improvement in physical and mechanical properties. This behavior shows the possibility of burning at temperatures lower than 850?C, thus promoting a product final cost reduction
Neste trabalho ? estudado o efeito da adi??o da esc?ria de aciaria em massas cer?micas para ind?strias de cer?mica vermelha, visando contribuir com o aproveitamento desses rejeitos. Foi feito uma avalia??o da sua adi??o ? massa cer?mica para produ??o de telhas. O panorama da ind?stria cer?mica no estado do Piau? ? bastante promissor. Diferente de outros setores produtivos, o setor cer?mico utiliza, basicamente, mat?rias-primas naturais. O seu produto final ?, em suma, o resultado da transforma??o de compostos argilominerais. Essas mat?rias-primas s?o compostas, basicamente, de ?xidos de alum?nio, sil?cio, ferro, s?dio, magn?sio, c?lcio, dentre outros. Verificou-se que a esc?ria de aciaria ? composta principalmente por esses mesmos ?xidos, de forma que sua incorpora??o ? massa de cer?mica estrutural ? uma ideia absolutamente razo?vel. Foram caracterizadas as mat?rias-primas argila e esc?ria de aciaria por AG, FRX, DRX, TGA e DTA. Tamb?m foram conformados por extrus?o e queimados nas temperaturas de 800?C, 850 ?C, 900?C e 950?C corpos-deprova com 0%, 5%, 10%, 15%, 20% e 25% de teor de esc?ria de aciaria. Em seguida, foram realizados ensaios tecnol?gicos de retra??o linear, absor??o de ?gua, porosidade aparente, massa espec?fica aparente e resist?ncia mec?nica ? flex?o. Os resultados mostraram a possibilidade de se utilizar at? 15% de esc?ria de aciaria na massa cer?mica para telhas. At? essa dosagem, melhorias consider?veis nas caracter?sticas f?sicas e mec?nicas avaliadas foram observadas. O estudo tamb?m mostrou a possibilidade de queima em temperaturas mais baixas que 850?C, promovendo, assim, uma redu??o dos custos finais do produto

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Nascimento, Allana Azevedo do. "Adi??o de poli(etileno-co-?cido-metacr?lico) (EMAA) como agente de auto-reparo em comp?sitos carbono-ep?xi." PROGRAMA DE P?S-GRADUA??O EM CI?NCIA E ENGENHARIA DE MATERIAIS, 2017. https://repositorio.ufrn.br/jspui/handle/123456789/24726.

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As t?cnicas de auto-reparo em resinas ep?xi v?m sendo desenvolvidas buscando aumentar a vida ?til e reduzir os custos associados ? manuten??o desses materiais durante o servi?o. A adi??o de termopl?sticos ? matriz termofixa produzindo resinas repar?veis aparece como t?cnica de reparo promissora. Neste trabalho, o termopl?stico poli (etileno-co-?cido-metacr?lico) (EMAA) foi adicionado no plano m?dio de laminados comp?sitos carbono-ep?xi para fabrica??o de um sistema de reparo. Foram fabricadas placas com 5%, 10% e 15% de EMAA em massa de resina do prepreg. Ensaios de resist?ncia ao cisalhamento interlaminar (ILSS), an?lise din?mico mec?nica (DMA), espectroscopia de infravermelho por transformada de Fourier (FTIR), microscopia eletr?nica de varredura (MEV) e microscopia eletr?nica de varredura com fonte de emiss?o de campo (MEV-FEG) foram conduzidos para avaliar o efeito da adi??o desse termopl?stico ao comp?sito e seu comportamento antes e ap?s o reparo. As amostras reparadas n?o apresentaram aumento na resist?ncia ao cisalhamento interlaminar (ILSS) ap?s o reparo. Entretanto, para maiores porcentagens de EMAA, houve redu??o dessa propriedade, al?m de redu??o de m?dulo de elasticidade e da temperatura de transi??o v?trea (Tg), em rela??o aos valores apresentados pelo comp?sito puro. Imagens de MEV confirmaram a forte ades?o entre o EMAA e a resina ep?xi, formando uma camada adesiva que impediu a forma??o de delamina??es no plano m?dio do laminado.
Self-healing techniques in epoxy resins have been developed to improve the durability and reduce costs associated with repairs of these materials during service. The addition of thermoplastics into the thermoset matrix producing mendable resins appears as a promising self-healing technique. In this study, poly(ethylene-co-methacrylic acid) (EMAA) was added in the mid-plane of carbon fiber-epoxy composites laminates to produce a self-healing system. Plates were manufactured with addition of 5%, 10% and 15% of EMAA as related to the resin weight of prepreg. Interlaminar shear strength test (ILSS), dynamic mechanical analysis (DMA), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and field-emission gun scanning electron microcopy (FEG-SEM) were employed in order to evaluate the effect of the addition of the thermoplastic to the composite and its behavior before and after a healing cycle. The healed samples did not show an increase in interlaminar shear strength (ILSS) after healing. However, for higher percentages of EMAA there was a reduction of this property, besides a reduction of Young?s modulus and glass transition temperature (Tg), in relation to the values presented by the unmodified composite. SEM images confirmed the strong adhesion between EMAA and epoxy resin, which produced an adhesive layer that prevented delamination in the mid-plane of the laminate.

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Souza, C?cero Leonardo Pereira de. "Influ?ncia do aporte t?rmico e da adi??o de filmes de alum?nio e PVC em eletrodos revestidos E7018." PROGRAMA DE P?S-GRADUA??O EM CI?NCIA E ENGENHARIA DE MATERIAIS, 2017. https://repositorio.ufrn.br/jspui/handle/123456789/24727.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)
A soldagem a arco el?trico por eletrodo revestido (SMAW) ? uma das mais antigas t?cnicas de soldagem e a primeira a ser utilizada industrialmente em grande escala. Durante o s?culo XX a soldagem SMAW foi a mais usada como t?cnica de uni?o permanente de metais, sendo at? hoje, mesmo com coexist?ncia de diversas outras t?cnicas, uma das que possuem maior utiliza??o no mercado brasileiro. Nesse tipo de soldagem uma das maiores preocupa??es ? o cuidado no armazenamento do eletrodo, pois o mesmo n?o pode ficar exposto a atmosfera ambiente, j? que absorveria umidade, que ? danoso para a qualidade da solda. A umidade introduz na zona fundida o hidrog?nio que pode levar ao surgimento de trincas a frio. A solu??o normalmente usada ? a da ressecagem em temperaturas at? 450? C, acompanhada de armazenamento em estufas, pr?tica que gera custos adicionais para um projeto de fabrica??o. Nesse contexto o presente trabalho teve a inten??o de caracterizar a zona fundida de soldas feitas com eletrodos revestidos E7018 encobertos com filmes de alum?nio e PVC, aplicados com o intuito de resguarda-los contra a umidade ambiente, diminuindo custos e tempo com secagem, tamb?m variando o valor de aporte t?rmico utilizado durante a soldagem. Essa atual investiga??o d? continuidade ? pesquisa recente sobre a influ?ncia de tais filmes protetores na composi??o e, em especial, na microestrutura do metal de solda depositado, onde a quantifica??o dos constituintes e caracteriza??o microestrutural ocorreu atrav?s de um software para avalia??o de imagens. No presente caso, com a utiliza??o de um microsc?pio com emiss?o de campo, MEV-FEG, foram obtidas imagens com elevado contraste, que permitiram um levantamento detalhado dos tipos de constituintes presentes, assim como uma an?lise mais precisa de sua morfologia. Em particular foi poss?vel avaliar quantitativamente o efeito dos filmes protetores no tamanho de gr?o e na raz?o de aspecto do microconstituinte AF (ferrita acicular). Com base numa revis?o da literatura ? apresentada uma an?lise cr?tica acerca dos par?metros que tiveram maior relev?ncia na forma??o da microestrutura final e nas propriedades mec?nicas obtidas. Os resultados conduziram a constata??o de que para maiores valores de aporte t?rmico a microestrutura, em especial a ferrita acicular, tende a ser mais grosseira. Com a utiliza??o dos revestimentos de PVC e tinta de alum?nio obteve-se uma leve diminui??o nessa granulometria, j? que a microestrutura apresentou-se mais refinada do que com os eletrodos de refer?ncia (E7018 puro e BRH4R).
The shield metal arc welding (SMAW) is one of the oldest welding processes and the first one to be used in large industrial scale. During the XX century the SMAW was the most applied process for metal joining, remaining until nowadays as one of the most used in the Brazilian market. In this kind of welding one of the biggest problems is to avoid the hydrogen induced cold cracking, what imposes rigid requirements in the storing of the weld consumables. In order to avoid the humidity absorption, the consumables must be dried out in special ovens at temperatures in the order of 450 C, what implies in additional and higher manufacturing costs. In this context a recent research suggested modifications in coating of electrodes providing an alternative for execution of welding with low hydrogen electrode AWS E7018 without having to dry it, The welds were developed with basic coated electrodes (hygroscopic) externally painted with aluminum spray paint for high temperatures or wrapped with thin plastic films (PVC) and aluminum foil films. The induced metallurgical changes in the deposited metal, associated with the addition of new materials to the electrode coating, were investigated, wereby the microconstituents in the fusion zone were quantified using a software for image analysis. In the actual work, with the use of a field emission microscope, MEV-FEG, high contrast images could be obtained, this allowed a detailed characterization of the various microconstituents and a more precise description of their morphology. In special it was possible to evaluate the influence of the protective films in the grain size and aspect ratio of the microconstituent AF (acicular ferrite). On base of a literature review a critical analysis is presented, that embraces the effect of the more relevant parameters on the final microstructure and resulting mechanical properties. The results showed that for higher values of heat input the microstructure, especially the acicular ferrite, tends to be coarser. With the use of PVC coatings and aluminum paint, a slight reduction was achieved in this granulometry, since the microstructure was more refined than with reference electrodes (E7018 pure and BRH4R).

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Lau, Desmond, and desmond lau@rmit edu au. "Characterisation of Novel Carbonaceous Materials Synthesised Using Plasmas." RMIT University. Applied Sciences, 2009. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20091119.102551.

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Novel carbon materials such as carbon onions, nanotubes and amorphous carbon (a-C) are technologically important due to their useful properties. Normally synthesised using plasmas, their growth mechanisms are not yet fully understood. For example, the growth mechanism of the high density phase of a-C, tetrahedral amorphous carbon (ta-C), has been a subject of debate ever since its discovery. The growth mechanism of carbon nanostructures such as carbon onions and nanotubes is also not well known. The aim of this thesis is two-fold. Firstly, to provide insight into the growth of carbon films, in particular, the driving force behind the formation of diamond-like bonding in a-C which leads to ta-C. Secondly, to investigate the growth of carbon onions and other sp2 bonded carbon nanostructures such as nanotubes. To achieve the first aim, carbon thin films were deposited using cathodic arc deposition at a range of ion energies, substrate temperatures and Ar background gas pressures. These films were characterised using electron microscopy techniques to examine their microstructure, density and sp3 content. It was found that the formation of the ta-C is due to a stress-induced transition whereby a critical stress of 6.5±1.5 GPa is needed to change the phase of the film from highly sp2 to highly sp3. Within this region, a preferentially oriented phase with graphitic sheets aligned perpendicular to the substrate surface was found. By investigating the role of elevated temperatures, the ion energy-temperature

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Wang, Caiyun. "Cathodic materials for nickel-metal hydride batteries." Access electronically, 2003. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20041217.140721/index.html.

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Ferreira, Narayanna Marques. "Adi??o de nanopart?culas de Ti em matriz de Fe atrav?s da deposi??o por magnetron sputtering." Universidade Federal do Rio Grande do Norte, 2011. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12725.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
Microalloyed steels constitute a specific class of steel with low amount of carbon and microalloying elements such as Vanadium (V), Niobium (Nb) and Titanium (Ti). The development and application of microalloyed steels and steels in general are limited to the handling of powders with particles of submicron or nanometer dimensions. Therefore, this work presents an alternative in order to construction of microalloyed steels utilizing the deposition by magnetron sputtering technique as a microalloying element addiction in which Ti nanoparticles are dispersed in an iron matrix. The advantage of that technique in relation to the conventional metallurgical processes is the possibility of uniformly disperse the microalloying elements in the iron matrix. It was carried out deposition of Ti onto Fe powder in high CH4, H2, Ar plasma atmosphere, with two deposition times. After the deposition, the iron powder with nanoparticles of Ti dispersed distributed, were compacted and sintered at 1120 ? C in resistive furnace. Characterization techniques utilized in the samples of powder before and after deposition of Ti were Granulometry, Scanning Electron Microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (DRX). In the case of sintered samples, it was carried out characterization by SEM and Vickers Microhardness assays. The results show which the deposition technique by magnetron sputtering is practicable in the dispersion of particles in iron matrix. The EDX microanalysis detected higher percentages of Ti when the deposition were carried out with the inert gas and when the deposition process was carried out with reactive gas. The presence of titanium in iron matrix was also evidenced by the results of X-ray diffraction peaks that showed shifts in the network matrix. Given these results it can be said that the technique of magnetron sputtering deposition is feasible in the dispersion of nanoparticles of iron matrix in Ti.
Os a?os microligados constituem uma classe espec?fica de a?o com baixos teores de carbono e elementos microligantes, como: van?dio (V), ni?bio (Nb) e tit?nio (Ti). O desenvolvimento e aplica??o dos a?os microligados, e de a?os em geral, est?o limitados ? manipula??o dos p?s com part?culas de dimens?es submicrom?tricas ou mesmo nanom?tricas. Mediante isto, este trabalho apresenta uma t?cnica alternativa para a fabrica??o de a?os microligado empregando a deposi??o por magnetron sputtering, como fonte de adi??o de elemento microligante na forma de nanopart?culas de tit?nio dispersa em matriz de ferro. A vantagem dessa t?cnica em rela??o aos processos metal?rgicos convencionais ? a possibilidade de dispersar uniformemente o elemento microligante na matriz de ferro. Foram realizadas deposi??es de Ti sobre p? de ferro em atmosfera de CH4, H2, Ar, com dois tempos de deposi??o diferentes. Ap?s as deposi??es, o p? de ferro com nanopart?culas de Ti dispersamente distribu?das, foram compactados e sinterizados a 1120?C em forno resistivo. As t?cnicas de caracteriza??o utilizadas nas amostras de p? de ferro antes e ap?s a deposi??o de Ti foram granulometria, microscopia eletr?nica de varredura (MEV), energia dispersiva de raios X (EDX) e difra??o de raios X (DRX). Para as amostras sinterizadas utilizou-se a caracteriza??o por microscopia eletr?nica de varredura (MEV) e ensaio de microdureza Vickers. A microan?lise por EDX detectou percentuais maiores de Ti para as deposi??es em atmosfera de g?s inerte em rela??o ?s deposi??es em atmosfera de g?s reativo. A presen?a de tit?nio na matriz de ferro tamb?m foi evidenciada pelos resultados da difra??o de raios-X que apresentaram deslocamentos nos picos da rede da matriz. Diante desses resultados pode-se afirmar que a t?cnica de deposi??o por magnetron sputtering ? vi?vel na dispers?o de nanopart?culas de Ti em matriz de ferro.

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Namnabat, Soha, Kyung-Jo Kim, Adam Jones, Roland Himmelhuber, Christopher T. DeRose, Douglas C. Trotter, Andrew L. Starbuck, Andrew Pomerene, Anthony L. Lentine, and Robert A. Norwood. "Athermal silicon optical add-drop multiplexers based on thermo-optic coefficient tuning of sol-gel material." OPTICAL SOC AMER, 2017. http://hdl.handle.net/10150/625995.

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Silicon photonics has gained interest for its potential to provide higher efficiency, bandwidth and reduced power consumption compared to electrical interconnects in datacenters and high performance computing environments. However, it is well known that silicon photonic devices suffer from temperature fluctuations due to silicon's high thermo-optic coefficient and therefore, temperature control in many applications is required. Here we present an athermal optical add-drop multiplexer fabricated from ring resonators. We used a sol-gel inorganic-organic hybrid material as an alternative to previously used materials such as polymers and titanium dioxide. In this work we studied the thermal curing parameters of the sol-gel and their effect on thermal wavelength shift of the rings. With this method, we were able to demonstrate a thermal shift down to -6.8 pm/% for transverse electric (TE) polarization in ring resonators with waveguide widths of 325 nm when the sol-gel was cured at 130 % for 10.5 hours. We also achieved thermal shifts below 1 pm/% for transverse magnetic (TM) polarization in the C band under different curing conditions. Curing time compared to curing temperature shows to be the most important factor to control sol-gel's thermo-optic value in order to obtain an athermal device in a wide temperature range. (C) 2017 Optical Society of America

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Fernandes, Maria Roseane de Pontes. "Comp?sitos de matriz met?lica ? base n?quel com adi??o de TaC e NbC produzidos via metalurgia do p?" Universidade Federal do Rio Grande do Norte, 2014. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12857.

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Carbide reinforced metallic alloys potentially improve some important mechanical properties required for the overall use of important engineering materials such as steel and nickel. Nevertheless, improved performance is achieved not only by composition enhancement but also by adequate processing techniques, such as novel sintering methods in the case of powder metallurgy. The method minimizes energy losses in addition to providing uniform heating during sintering. Thus, the general objective of this study was to evaluate the density, hardness, flexural strength, dilatometric behavior and to analyze the microstructure of metal matrix composites based nickel with addition of carbides of tantalum and / or niobium when sintered in a conventional furnace and Plasma assisted debinding and sintering (PADS). Initially, were defineds best parameters of granulation, screening and mixing procedure. After, mixtures of carbonyl Ni and 5%, 10% and 15 wt.% NbC and TaC were prepared in a Y-type mixer under wet conditions during 60 minutes. The mixtures were then dried and granulated using 1.5 wt. % paraffin diluted in hexane. Granulates were cold pressed under 600 MPa. Paraffin was then removed from the pressed pellets during a pre-sintering process carried out in a tubular furnace at 500 ?C during 30 min. The heating rate was 3 ?C/min. The pellets were then sintered using either a plasma assisted reactor or a conventional resistive tubular furnace. For both methods, the heating rate was set to 8 ?C/min up to 1150 ?C. The holding time was 60 minutes. The microstructure of the sintered samples was evaluated by SEM. Brinell hardness tests were also carried out. The results revealed that higher density and higher hardness values were observed in the plasma-assisted sintered samples. Hardness increased with the concentration of carbides in the Ni-matrix. The flexural strength also increased by adding the carbides. The decline was larger for the sample with addition of 5% 5% TaC and NbC. In general, compositions containing added carbide 10% showed less porous and more uniform distribution of carbides in the nickel matrix microstructural appearance. Thus, both added carbide and plasma sintering improved density, hardness, flexural strength and microstructural appearance of the composites
Ligas met?licas refor?adas por carbetos melhoram potencialmente algumas propriedades mec?nicas necess?rias para a utiliza??o de importantes materiais de engenharia, tais como o a?o e o n?quel. No entanto, o desempenho ? conseguido n?o apenas pela melhoria de composi??o, mas tamb?m por t?cnicas de processamento adequadas, tais como, novos m?todos de sinteriza??o, no caso da metalurgia do p?. Desta forma, o objetivo do presente trabalho foi avaliar a dureza, resist?ncia ? flex?o, comportamento dilatom?trico e analisar a microestrutura de comp?sitos de matriz met?lica base n?quel com adi??o de carbetos de t?ntalo e/ou ni?bio quando sinterizados em forno tubular convencional e Plasma assisted debinding sintering (PADS). Os carbetos (5%, 10% e 15% em massa) foram misturados ao p? de n?quel carbonila via ?mido com aux?lio do misturador Y adaptado durante 1h. Ap?s secagem, as misturas foram submetidas ao processo denominado de granula??o em tambor. Utilizou-se 1,5% de parafina (% massa) dilu?da em hexano. Os p?s granulados foram compactados a frio utilizando press?o de 600 MPa. Antes da sinteriza??o a uma taxa de 8 ?C/min com patamar 1h na temperatura de 1150?C tanto em forno tubular quanto em reator PADS, as amostras foram pr?-sinterizadas em forno tubular para extra??o da parafina a uma taxa de 3 ?C/min com patamar 30 min em 500 ?C. A dureza avaliada foi a Brinell e a an?lise microestrutural por MEV. Os resultados mostraram que as amostras sinterizadas assistidas por plasma apresentaram dureza superior ?quelas sinterizadas em forno convencional. As imagens por MEV comprovaram esses maiores valores de durezas, uma vez que a matriz apresentou-se mais densificada. Com rela??o ? adi??o dos carbetos, a dureza aumentou com o aumento da concentra??o dos mesmos. A resist?ncia ? flex?o tamb?m aumentou ao adicionar os carbetos. A retra??o foi maior para a amostra com adi??o de 5% de TaC e 5% NbC. De maneira geral, as composi??es com adi??o de 10% de carbetos apresentaram um aspecto microestrutural menos poroso e com uma distribui??o mais uniforme dos mesmos na matriz de n?quel. Assim, tanto a adi??o de carbetos quanto a sinteriza??o com aux?lio do plasma melhoraram a dureza e o aspecto microestrutural dos comp?sitos

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Oliveira, José Irineu Sampaio de. "Síntese e caracterização do oxidante ADN (dinitramida de amônio), usado em propelentes para aplicação aeroespacial." Instituto Tecnológico de Aeronáutica, 2014. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=2941.

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Dinitramida de amônio (ADN) é um oxidante utilizado em propelentes de foguetes. Para a obtenção de ADN, foram utilizados, nesse estudo, como materiais de partida, sulfamato de amônio e ácido sulfâmico, em rotas de síntese, com diferentes condições. A proporção de reagentes e os métodos de purificação foram testados, e as amostras resultantes foram analisadas por espectroscopia na região do infravermelho médio (MIR). Para a síntese em que sulfamato de amônio foi utilizado como reagente de partida, as amostras foram, também, analisadas por espectroscopia na região do infravermelho próximo (NIR). Para as amostras cristalizadas, foram realizadas análises por calorimetria exploratória diferencial (DSC), para determinar seu ponto de fusão e valor de entalpia, durante seu processo de decomposição, além da obtenção de sua micrografia por microscopia eletrônica de varredura (SEM). Podem ser destacados, nesse estudo, os seguintes resultados: a) a síntese de ADN, utilizando-se o sulfamato de amônio como material de partida e nitração com HNO3/H2SO4, mostrou-se mais promissora, sendo esse produto obtido, pela primeira vez em nosso país; b) foi necessário o desenvolvimento de metodologia específica, nos laboratórios do IAE, para a obtenção e purificação do ADN sintetizado, constituindo uma contribuição do estudo na área de síntese deste oxidante para propelentes; c) o ADN obtido foi caracterizado, não somente por MIR mas também por NIR, que apresenta um número menor de estudos na literatura; d) as análises DSC e SEM mostraram boa concordância com os dados encontrados na literatura. A possibilidade de interação entre o sistema à base do polímero de azoteto de glicidila e da dinitramida de amônio (GAP/ADN) foi também avaliada, por FT-IR, nas regiões MIR e NIR. O sistema GAP e perclorato de amônio (GAP/AP), com oxidante mais usual, foi analisado por MIR. Maiores alterações espectrométricas foram observadas para o sistema GAP/ADN. Foi observado um alargamento de bandas para ambos os sistemas na região entre 3100-3500 cm-1, sugerindo interações entre os grupos OH do GAP e NH4+ do ADN ou AP. A diminuição da intensidade da banda do grupo N3 do GAP e o aumento de intensidade do nitroílo (NO2+) do ADN também foram notados, sugerindo interação entre esses grupos, no sistema GAP/ADN. Na tentativa de extrair o material usado no microencapsulamento do ADN utilizado como referência, foi feito um tratamento com tolueno. As análises FT-IR UATR/ATR/PAS da superfície do ADN referência mostraram que, basicamente, possa existir um composto orgânico éster e/ou amínico, aromático, heterocíclico e/ou contendo hidroxila.

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Pinto, Erica Natasche de Medeiros Gurgel. "Adi??o de res?duo cer?mico em pastas geopolim?ricas para cimenta??o de po?os de petr?leo." Universidade Federal do Rio Grande do Norte, 2011. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12790.

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The development of activities the of oil and gas sector have promoted the search for suitable materials for cementing oil wells. In the state of the Rio Grande do Norte, the integrity of the cement sheath tends to be impaired during steam injection, a procedure necessary to increase oil recovery in reservoirs with low-viscosity oil. The geopolymer is a material that can be used as alternative cement, since it has been used in the production of fire-resistant components, building structures, and for the control of toxic or radioactive residues. Geopolymers result from condensation polymer alkali aluminosilicates and silicates resulting three-dimensional polymeric structures. They are produced in a manner different from that of Portland cement, which is made an activating solution that is mixed with geopolymer precursor. Among the few works studied allowed us to conclude that the pastes prepared with metakaolin as precursor showed better performance of its properties. Several studies show the addition of waste clay as a means of reducing cost and improving end of the folder properties. On this basis, the goal is to study the influence of the addition of ceramic waste in geopolymer paste. To develop the study of rheology tests were carried out, filtered, thickening time, compressive strength, free water, specific gravity and permeability, according to the American Pretoleum Institute (API). The results for all formulations studied show that the folders have high mechanical strength to a light paste; low filtrate volume, absence of free water, very low permeability, slurry, consistent with a light paste, and thickening time low that can be corrected with the use of a retardant handle. For morphological characterization, microstructural, physical, chemical and thermal tests were carried out by XRD, MEV, DTA, TG, FTIR. In the trial of XRD, it was found that geopolymer is an amorphous material, with a peak of crystalline kaolinite. In tests of TG / DTA, revealed the presence of a significant event, which represents the mass loss related to water, and also observed the reduction of weight loss by increasing the concentration of ceramic waste. In the trial of MEV, we found a uniform matrix without the presence of other phases. In the trial of FT-IR, we observed the presence of the band related to water. From all results it was determined that the optimum concentration range of use is between 2.5 and 5% of waste ceramic
O desenvolvimento das atividades do setor de petr?leo e g?s tem promovido a busca de materiais mais adequados para cimenta??o de po?os de petr?leo. No estado do RN, a integridade da bainha cimentante tende a ser prejudicada durante a inje??o de vapor, procedimento necess?rio para aumentar a recupera??o do petr?leo em reservat?rios com ?leo de alta viscosidade. O geopol?mero ? um material que pode ser utilizado como cimento alternativo, uma vez que vem sendo empregado na produ??o de componentes resistentes ao fogo, na constru??o de estruturas, e para o controle de res?duos t?xicos ou radioativos. Geopol?meros resultam da condensa??o polim?rica de aluminosilicatos e silicatos alcalinos originando estruturas polim?ricas tridimensionais. S?o produzidos de uma maneira distinta daquela do cimento Portland, onde ? feita uma solu??o ativadora que ? misturada ao precurssor geopolim?rico. Dentre os trabalhos estudados, alguns permitiram-nos concluir que as pastas preparadas com metacaulim como precursor apresentaram melhor desempenho de suas propriedades. V?rios estudos apresentam a adi??o de res?duos argilosos como forma de redu??o do custo final e melhoria das propriedades da pasta. Com base nisso, o objetivo do trabalho ? estudar a influ?ncia da adi??o de rejeito cer?mico em pastas geopolim?ricas. Para o desenvolvimento do estudo foram realizados testes de reologia, filtrado, tempo de espessamento, resist?ncia ? compress?o, ?gua livre, peso espec?fico e permeabilidade, de acordo com o American Pretoleum Institute (API). Os resultados encontrados para todas as formula??es demonstram que as pastas estudadas apresentam resist?ncia mec?nica elevada para uma pasta leve; volume de filtrado baixo; aus?ncia de ?gua livre; permeabilidade muito baixa; pasta flu?da, coerente com uma pasta leve; e tempo de espessamento baixo, que pode ser corrigido com a utiliza??o de um retardador de pega. Para caracteriza??o morfol?gica, microestrutural, f?sico-qu?mica, qu?mica e t?rmica, foram realizadas caracteriza??es por DRX, MEV, DTA, TG, FT-IR. No ensaio de DRX, verificou-se que o geopol?mero ? um material amorfo, com um pico cristalino de caulinita. Nos testes de TG/DTA, foi observado a presen?a de um evento significativo, que representa a perda de massa referente a ?gua, sendo observado tamb?m a redu??o da perda de massa com o aumento da concentra??o de rejeito cer?mico. No ensaio de MEV, encontrou-se uma matriz uniforme e nos espectros de FT-IR, observou-se a presen?a da banda referente ? ?gua. A partir de todos os resultados foi poss?vel determinar que a faixa de concentra??o ?tima de rejeito cer?mico para uso em pastas geopolim?ricas ? entre 2,5 e 5 %

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Machado, Tercio Graciano. "Estudo da adi??o de res?duo de scheelita em matriz cer?mica: formula??o, propriedades f?sicas e microestrutura." Universidade Federal do Rio Grande do Norte, 2012. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12813.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
Extractivism mineral is considered an activity highly degrading, due to the large volume of material that he moves in the form of ore and residues. The vast majority of mining companies do not show any technology or economically viable application that will allow the recycling of mineral residue, these being launched in areas receiving located the "open skies" degrade the environment. In Rio Grande do Norte to the production of ceramic red restricts their activities to the production of products such as: solid bricks, ceramic blocks, tiles, among others. Seeking to unite experiences and technical information that favor sustainable development, with important benefits to the construction sector and civil society in general, the present work studies the incorporation of the residue of scheelite in ceramic matrix kaolinitic, coming from the municipality of Boa Sa?de - RN, in percentage of 5 %, 10 %, 20 %, 30% 40% and 50 %, by evaluating its microstructure, physical properties and formulation. The raw materials were characterized through the trials of X ray fluorescence, Diffraction of X rays, Differential Thermal Analysis and Termogravimetric Analysis. The samples were formed and fired at temperatures of 850o, 900o, 1000o, 1050o, 1100o, 1150o and 1200 oC, with isotherm of 1 hour and heating rate of 10 oC/min. Assays were performed technological of loss to fire, Water Absorption, Apparent Porosity, Apparent Density, Mass Loss in Fire and Bending Resistance; in addition to the Scanning Electron Microscopy, analyzing their physical and mechanical properties. The use of residue of scheelite in ceramic mass kaolinitic provided a final product with technological properties that meet the technical standards for the production of bricks and roofing tiles, with the percentage of 20% of waste that showed the best results
O extrativismo mineral ? considerado uma atividade altamente degradante, devido ao grande volume de material que ele movimenta em forma de min?rio e res?duo. A grande maioria das empresas mineradoras n?o apresenta nenhuma tecnologia ou aplica??o economicamente vi?vel que permitam a reciclagem do res?duo mineral, sendo estes lan?ados em ?reas de recebimento localizadas a c?u aberto , degradando o meio ambiente. No Rio Grande do Norte a produ??o de cer?mica vermelha restringe suas atividades ? produ??o de produtos como: tijolos maci?os, blocos cer?micos, telhas, dentre outros. Buscando unir experi?ncias e informa??es t?cnicas que favore?am o desenvolvimento sustent?vel, com importantes benef?cios ao setor da Constru??o Civil e ? sociedade em geral, o presente trabalho estuda a incorpora??o do res?duo de scheelita em matriz cer?mica caulin?tica, proveniente do munic?pio de Boa Sa?de RN, em percentuais de 5%, 10%, 20%, 30% 40% e 50%, avaliando sua microestrutura, propriedades f?sicas e formula??o. As mat?rias-primas foram caracterizadas atrav?s dos ensaios de Fluoresc?ncia de raios X, Difra??o de raios X, An?lise T?rmica Diferencial e An?lise Termogravim?trica. Os corpos de prova foram conformados e queimados nas temperaturas de 850o, 900o, 1000o, 1050o, 1100o, 1150o e 1200 oC, com isoterma de 1 hora e taxa de aquecimento de 10 oC/min. Foram realizados os ensaios tecnol?gicos de Perda ao Fogo, Absor??o de ?gua, Porosidade Aparente, Massa Espec?fica Aparente e Tens?o de Ruptura ? Flex?o; al?m da Microscopia Eletr?nica de Varredura, analisando-se suas propriedades f?sicas e mec?nicas. A utiliza??o de res?duo de scheelita em massa cer?mica caulin?tica propiciou um produto final com propriedades tecnol?gicas que atendem as normas t?cnicas para produ??o de blocos e telhas cer?micas, sendo que o percentual de 20% de res?duo apresentou os melhores resultados

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43

Santos, Alessandra Agna Ara?jo dos. "Estudo da sinteriza??o de carbeto de tungst?nio utilizando ligantes alternativos 316L e FeNi com adi??o de cromo." PROGRAMA DE P?S-GRADUA??O EM CI?NCIA E ENGENHARIA DE MATERIAIS, 2017. https://repositorio.ufrn.br/jspui/handle/123456789/24639.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)
Metal duro do tipo WC-Co ? utilizado na usinagem, perfura??o e ou fabrica??o de ferramentas de corte. Atualmente, 70% das ferramentas de corte s?o carbetos do tipo WCligante. Em n?meros de produ??o, aproximadamente 40,000 MT de ferramentas ? base de WC foram produzidas mundialmente desde 2011. Hoje, mais de 90% da produ??o de todo o metal duro, do tipo WC-ligante, utiliza o cobalto como ligante principal. A superioridade do cobalto em rela??o a outros ligantes est? ligada a v?rios fatores, sendo o principal a largura da janela de carbono no diagrama de fase. As pesquisas por ligantes alternativos que possam vir a substituir ao menos de forma parcial o cobalto s?o de extrema import?ncia, devido: ? escassez e pre?o do cobalto e principalmente pelo sistema WC-Co ser carcinog?nico. O objetivo da referida tese de doutorado foi analisar a viabilidade do uso dos ligantes alternativos 316L e FeNi com adi??o de cromo no WC. Ambos os sistemas WC-316L (teores de ligante de 5, 7 e 20%) e WC-20%FeNi com adi??o de cromo (em 5, 10 e 20%) foram processados pela rota de metalurgia do p?, seguindo as etapas: prepara??o das misturas, moagem (1h, 24h), compacta??o uniaxial (200 MPa) e sinteriza??o a v?cuo (1400oC/1h). As caracteriza??es realizadas em todas as amostras sinterizadas foram: microsc?pia ?tica e eletr?nica, difra??o de raios x, satura??o magn?tica e coercitividade, dureza, ataque qu?mico eletrol?tico. Foi realizado c?lculos das sec??es verticais dos diagramas de fase para o sistema WC-FeNi com adi??o de cromo. Os resultados obtidos e discutidos demonstram que o ligante 316L n?o ? uma alternativa viav?l em metal duro devido conter elevado teor de cromo. O ligante alternativo 316L quando sinterizado com carbeto de tungst?nio sempre precipitar? fase eta, fato que inviabiliza sua aplica??o como ligante alternativo em WC. Para o ligante FeNi com adi??o de cromo, os resultados demonstram que o m?ximo teor de cromo que pode estar contido em solu??o em WC, de forma que n?o haja precipita??o de carbeto de cromo ? de aproximadamente 4%. A adi??o de cromo acima de 4% em solu??o, leva ? precipita??o de carbetos complexos de cromo, e ainda reduz drasticamente a janela de carbono do comp?sito.
Hard metal WC-Co is used in the machining, drilling and or manufacturing of cutting tools. Currently, 70% of the cutting tools are WC-binder carbides. In production numbers, approximately 40,000 MT of WC-binder tools have been produced worldwide since 2011. Today, more than 90% of all WC-binder production uses cobalt as the main binder. The superiority of cobalt over other binders is linked to several factors, the main being the width of the carbon window in the phase diagram. The search for alternative binders that may at least partially replace cobalt is of extreme importance due to the scarcity and price of cobalt and especially the WC-Co system being carcinogenic. The goal of this doctoral thesis was to analyze the feasibility of using alternatives binders 316L stainless steel and FeNiCr alloy, in tungsten carbide. Both system WC-316L (5, 7 and 20% of binder contents) and WC-20%FeNi with addition of chromium (in 5, 10 and 20% in solution) were processed by powder metallurgy route following the steps: preparation of the mixtures, milling (1h, 24h), compaction uniaxial (200MPa) and vacuum sintering (1400oC/1h). The all samples were characterized by optical and electron microscopy, xray diffraction, magnetic saturation and coercivity, hardness and electrolytic etching. The calculation of vertical sections of the phase diagrams for the system WC-FeNiCr was made. The results obtained and discussed demonstrate that the binder 316L, is not a viable alternative in hard metal because it contains high chromium content. The binder 316L when sintered with tungsten carbide will always precipitate eta phase, which makes its application as an alternative binder in WC impossible. For the binder FeNiCr, the results demonstrate that the maximum content of chromium that may be contained in solution in tungsten carbide that there is no precipitation of chromium carbide is approximately 4%. The addition of chromium above 4% in solution leads to the precipitation of chromium complex carbides, and further drastically reduces the carbon window of the composite.

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Lima, Flank Melo de. "Avalia??o do comportamento reol?gico de pastas de cimento para po?os de petr?leo com adi??o de plastificantes." Universidade Federal do Rio Grande do Norte, 2006. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12838.

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The isolation of adjacent zones encountered during oilwell drilling is carried out by Portland-based cement slurries. The slurries are pumped into the annular positions between the well and the casing. Their rheological behavior is a very important component for the cementing process. Nowadays, several alternative materials are used in oilwell cementing, with goal the modification and the improvement of their properties, mainly the increase of the fluidity. And this can be reached by using plasticizers additives able to account for different oilwell conditions, yielding compatible cement slurries and allowing enough time for the complete cementing operation. If the rheological properties of the slurry are properly characterized, the load loss and flow regime can be correctly predicted. However, this experimental characterization is difficult. Rheological models capable of describing the cement slurry behavior must be capable of predicting the slurry cement deformation within reasonable accuracy. The aim of this study was to characterize rheologically the slurries prepared with a especial class of Portland cement, water and plasticizers based on lignosulfonate, melamine and polycarboxylate at temperatures varying from 27?C to 72?C. The tests were carried out according to the practical recommendations of the API RP 10B guidelines. The results revealed a great efficiency and the dispersive power of the polycarboxylate, for all temperatures tested. This additive promoted high fluidity of the slurries, with no sedimentation. High lignosulfonate and melamine concentrations did not reduce the rheological parameters (plastic viscosity and yield stress) of the slurries. It was verified that these additives were not compatible with the type of cement used. The evaluated rheological models were capable of describing the behavior of the slurries only within concentration and temperature ranges specific for each type of additive
Pastas de cimento do tipo Portland s?o usadas para isolamento de po?os de petr?leo. Esse procedimento ? realizado por meio do bombeio da pasta no espa?o anular entre o po?o e a coluna de revestimento, de modo a se obter fixa??o e veda??o eficiente e permanente. Para isso o comportamento reol?gico da pasta de cimento ? um componente de extrema import?ncia para o processo de cimenta??o. Atualmente, diversos materiais alternativos s?o utilizados em pastas para cimenta??o, objetivando a modifica??o e a melhoria de suas propriedades, principalmente no que diz respeito ao aumento de fluidez. Isso pode ser alcan?ado por meio da utiliza??o de novos aditivos do tipo plastificantes, capazes de suportar as diversas condi??es de po?os, promovendo ?s pastas propriedades compat?veis ?s condi??es encontradas, permitindo, ainda, um tempo suficiente de trabalhabilidade para a completa execu??o do servi?o de cimenta??o. Assim, se as propriedades reol?gicas da pasta s?o bem caracterizadas, a perda de carga e o regime de fluxo podem ser prognosticados corretamente. Contudo, essa caracteriza??o ? dif?cil do ponto de vista experimental. Modelos reol?gicas capazes de descrever o que ocorre, dever?o ser capazes de predizer a deforma??o da pasta de cimento com razo?vel exatid?o. Portanto, a finalidade deste trabalho foi o estudo e a caracteriza??o reol?gica de pastas constitu?das de cimento Portland classe especial, ?gua e aditivos do tipo plastificante, a base de lignossulfonato, melamina e policarboxilato, em temperaturas na faixa de 27?C a 72?C. Os testes foram realizados de acordo com as recomenda??es pr?ticas da norma API RP 10B. Os resultados dos ensaios demonstraram a grande efici?ncia e o poder dispersivo do policarboxilato, para todas as temperaturas estudadas. O aditivo promoveu uma alta fluidez, sem efeitos de sedimenta??o. O aumento das concentra??es de lignossulfonato e melamina n?o reduziu os par?metros reol?gicos (viscosidade pl?stica e limite de escoamento). Tamb?m foi verificado que esses aditivos n?o foram compat?veis com o tipo de cimento utilizado. Por fim, os modelos reol?gicos avaliados foram capazes de descrever o comportamento das pastas apenas para faixas de temperatura e concentra??o de cada tipo de aditivo

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Medeiros, Leonardo Coutinho de. "Adi??o de cascalho de perfura??o da bacia potiguar em argilas para uso em materiais cer?micos: influ?ncia da concentra??o e temperatura de queima." Universidade Federal do Rio Grande do Norte, 2010. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12692.

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Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
One of waste produced on large scale during the well drilling is the gravel drilling. There are techniques for the treatment of the same, but there isn t consensus on what are the best in terms of economic and environmental. One alternative for disposal of this waste and objective of this paper is the incorporation and immobilization of gravel clay matrix to assess their technological properties. The Raw Materials used were characterized by the following techniques: Chemical Analysis by X-ray fluorescence (XRF), mineralogical analysis by X-ray Diffraction (XRD), Grain Size Analysis (FA) and Thermal Analysis by Thermogravimetry (TG) and thermodiferential (DTA). After characterizing, samples were formulated in the following percentages: 0, 5, 10, 15, 25, 50, 75, 100% (weight) of gravel drilling, then the pieces were pressed, dried (110 ? C) and sintered at temperatures of 850, 950 and 1050 ? C. After sintering, samples were tested for water absorption, linear shrinkage, flexural strength, porosity, density, XRD and test color. The results concluded that the incorporation of gravel drilling is a viable possibility for solid masonry bricks and ceramic blocks manufacture at concentrations and firing temperature described here. Residue incorporation reduces an environmental problem, the cost of raw materials for manufacture of ceramic products
Um dos res?duos produzidos em grande escala durante a perfura??o de po?os de petr?leo ? o cascalho de perfura??o. Existem t?cnicas para seu tratamento, mas n?o existe um consenso sobre quais s?o as melhores do ponto de vista econ?mico e ambiental. Uma das alternativas de destina??o final deste res?duo e objetivo de estudo deste trabalho ? a incorpora??o e imobiliza??o do cascalho em matrizes argilosas para avaliar as suas propriedades tecnol?gicas. As Mat?rias-Primas utilizadas foram caracterizadas pelas seguintes t?cnicas: An?lise Qu?mica por Fluoresc?ncia de raios-X (FRX); An?lise Mineral?gica por Difra??o de raios-X (DRX); An?lise Granulom?trica (AG) e An?lise T?rmica por Termogravimetria (TG) e Termodiferencial (DTA). Ap?s a caracteriza??o, as amostras foram formuladas nas seguintes porcentagens: 0, 5, 10, 15, 25, 50, 75, 100% em peso de cascalho de perfura??o, em seguida as pe?as foram prensadas, secas (110 ?C) e sinterizadas nas temperaturas de 850, 950 e 1050 ?C. Ap?s a sinteriza??o, as amostras foram submetidas a ensaios de Absor??o de ?gua, Retra??o Linear de Queima, Tens?o de Ruptura ? Flex?o, Porosidade Aparente, Massa Espec?fica Aparente, DRX e Ensaio de Cor. Os resultados obtidos conclu?ram que a incorpora??o de cascalho de perfura??o ? uma possibilidade vi?vel para a fabrica??o de tijolos maci?os de alvenaria e blocos cer?micos em determinadas concentra??es e temperaturas de queima descrita neste trabalho. A incorpora??o deste res?duo al?m de amenizar um problema ambiental, reduz os custos com mat?rias-primas para fabrica??o de produtos cer?micos

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46

Yao, Yueping Jane. "Carbon based anode materials for lithium-ion batteries." Access electronically, 2003. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20050111.120602/index.html.

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Lao, Zhuo Jin. "Metal oxides as electrode materials for electrochemical capacitors." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060726.101327/index.html.

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Ng, See How. "Nanostructured materials for electrodes in lithium-ion batteries." Access electronically, 2007. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20080313.142752/index.html.

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Palma, Aldemiro Jos? Rocha. "Adi??o de chamote de velas de igni??o inserv?veis na obten??o de cer?mica branca a base de alumina." Universidade Federal do Rio Grande do Norte, 2010. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15614.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
This work presents research into the addition of chamotte obtained from the ceramic isolator of unusable spark plugs in formulations of material mixes for standard white ceramic material with aluminum oxide bases. After the physical chemical characterization of the primary materials, standard clay and the chamotte, three mixtures were prepared with concentrations of 10, 20 and 30% chamotte by weight in relation to the standard clay. The test samples underwent heating at a rate of 30 0C/min to levels that included 100o , 200o , 300o, 400o, 500o e 600 0C and also we submitted to three distinct burn temperatures: 1450o, 1500o e 1550 0C, remaining at these temperatures for 2 hour periods. After sintering, the physical and microstructural properties of the different test samples were measured and analyzed. The results show that the materials obtained present good technical properties and that the chamotte can be reutilized as an additive in the production of white ceramic material with an aluminum oxide base
Neste trabalho estudou-se a influ?ncia da adi??o de chamote obtido do isolador cer?mico de velas de igni??o inserv?veis na formula??o de massas de cer?mica branca a base de alumina. Ap?s caracteriza??o f?sico-qu?mica das mat?rias-primas, argila-padr?o e chamote, foram preparadas tr?s formula??es de concentra??es 10, 20 e 30% em peso de chamote em rela??o ? argila-padr?o. Os corpos-de-prova foram submetidos ao aquecimento numa taxa de 30 0C/min em patamares de 100? , 200? , 300? , 400? , 500? e 600 0C e queimados em tr?s temperaturas distintas a 1450? , 1500? e 1550 0C, permanecendo 2 horas na temperatura de patamar. Ap?s as sinteriza??es, as propriedades f?sicas e a evolu??o microestrutural de fases dos corpos-de-prova foram mensuradas e discutidas. Os resultados mostraram que os materiais obtidos apresentam boas propriedades e que o chamote pode ser reaproveitado como aditivo na produ??o de cer?micas brancas a base de alumina

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au, minakshi@murdoch edu, and Manickam Minakshi Sundaram. "Electrochemistry of Cathode Materials in Aqueous Lithium Hydroxide Electrolyte." Murdoch University, 2006. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20061210.143803.

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Electrochemical behavior of electrolytic manganese dioxide (EMD), chemically prepared battery grade manganese dioxide (BGM), titanium dioxide (TiO2), lithium iron phosphate (LiFePO4) and lithium manganese phosphate (LiMnPO4) in aqueous lithium hydroxide electrolyte has been investigated. These materials are commonly used as cathodes in non-aqueous electrolyte lithium batteries. The main aim of the work was to determine how the electroreduction/oxidation behavior of these materials in aqueous LiOH compares with that reported in the literature in non-aqueous electrolytes in connection with lithium batteries. An objective was to establish whether these materials could also be used to develop other battery systems using aqueous LiOH as electrolyte. The electrochemical characteristics of the above materials were investigated by subjecting them to slow scan cyclic voltammetry and determining the charge/discharge characteristics of Zn/cathode material-aqueous LiOH batteries. The products of electroreduction/oxidation were characterized by physical techniques using X-ray diffraction (XRD), scanning electron micrography (SEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), Thermogravimetric analysis (TG) and infra-red spectrometry (IR). The reduction of ã-MnO2 (EMD) in aqueous lithium hydroxide electrolyte is found to result in intercalation of Li+ into the host structure of ã-MnO2. The process was found to be reversible for many cycles. This is similar to what is known to occur for ã-MnO2 in non-aqueous electrolytes. The mechanism, however, differs from that for reduction/oxidation of ã-MnO2 in aqueous potassium hydroxide electrolyte. KOH electrolyte is used in the state-of-art aqueous alkaline Zn/MnO2 batteries. Alkaline batteries based on aqueous KOH as the electrolyte rely upon a mechanism other than K+ intercalation into MnO2. This mechanism is not reversible. This is explained in terms of the relative ionic sizes of Li+ and K+. The lithium-intercalated MnO2 lattice is stable because Li+ and Mn4+ are of approximately the same size and hence Li+ is accommodated nicely into the host lattice of MnO2. The K+ ion which has almost double the size of Li+ cannot be appropriately accommodated into the host structure and hence the K+ -intercalated MnO2 phase is not stable. Chemically prepared battery grade MnO2 (BGM) is found to undergo electroreduction/oxidation in aqueous LiOH via the same Li+ intercalation mechanism as for the EMD. While the Zn/BGM- aqueous LiOH cell discharges at a voltage higher than that for the Zn/EMD- aqueous LiOH cell under similar conditions, the rechargeability and the material utilization of the BGM cell is poorer. The cathodic behavior of TiO2 (anatase phase) in the presence of aqueous LiOH is not reversible. In addition to LiTiO2, Ti2O3 is also formed. The discharge voltage of the Zn/TiO2- aqueous LiOH cell and material utilization of the TiO2 as cathode are very low. Hence TiO2 is not suitable for use in any aqueous LiOH electrolyte battery. LiFePO4 (olivine-type structure) as a cathode undergoes electrooxidation in aqueous LiOH forming FePO4. However the subsequent reduction forms not only the original LiFePO4 but also Fe3O4. Thus the process is not completely reversible and hence LiFePO4 is not a suitable material for use as a cathode in aqueous battery systems. LiMnPO4 (olivine-type structure) undergoes reversible electrooxidation in aqueous LiOH forming MnPO4. The charge/discharge voltage profile of the Zn/MnPO4-aqueous LiOH cell, its coulombic efficiency and rechargeability are comparable to that of the cell using ã-MnO2. EMD and LiMnPO4 both have the potential for use in rechargeable batteries using aqueous LiOH as the electrolyte. Recommendations for further developmental work for such batteries are made.

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