Dissertations / Theses on the topic 'Raman thermal'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Raman thermal.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
Abel, Mark Richard. "Thermal Metrology of Polysilicon MEMS using Raman Spectroscopy." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7181.
Full textBonner, Gerald Michael. "Thermal and spectral effects in intracavity Raman lasers." Thesis, University of Strathclyde, 2013. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=22403.
Full textJohnson, Aaron A. "Thermal Processing of Carbon Nanotubes." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1399629659.
Full textKwiecinski, Przemyslaw Mark. "Non contact all optical thermal conductivity measurement utilizing Raman spectroscopy." Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27260.
Full textMalekpour, Hoda. "Optothermal Raman Studies of Thermal Properties of Graphene Based Films." Thesis, University of California, Riverside, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10252873.
Full textEfficient thermal management is becoming a critical issue for development of the next generation of electronics. As the size of electronic devices shrinks, the dissipated power density increases, demanding a better heat removal. The discovery of graphene’s unique electrical and thermal properties stimulated interest of electronic industry to development of graphene based technologies. In this dissertation, I report the results of my investigation of thermal properties of graphene derivatives and their applications in thermal management. The dissertation consists of three parts. In the first part, I investigated thermal conductivity of graphene laminate films deposited on thermally insulating polyethylene terephthalate substrates. Graphene laminate is made of chemically derived graphene and few layer graphene flakes packed in overlapping structure. Two types of graphene laminate were studied: as deposited and compressed. The thermal conductivity of the laminate was found to be in the range from 40 W/mK to 90 W/mK at room temperature. It was established that the average size and the alignment of graphene flakes are parameters dominating the heat conduction. In the second part of this dissertation, I investigated thermal conductivity of chemically reduced freestanding graphene oxide films. It was found that the in-plane thermal conductivity of graphene oxide can be increased significantly using chemical reduction and temperature treatment. Finally, I studied the effect of defects on thermal conductivity of suspended graphene. The knowledge of the thermal conductivity dependence on the concentration of defects can shed light on the strength of the phonon - point defect scattering in two-dimensional materials. The defects were introduced to graphene in a controllable way using the low-energy electron beam irradiation. It was determined that as the defect density increases the thermal conductivity decreases down to about 400 W/mK, and then reveal saturation type behavior. The thermal conductivity dependence on the defect density was analyzed using the Boltzmann transport equation and molecular dynamics simulations. The obtained results are important for understanding phonon transport in two-dimensional systems and for practical applications of graphene in thermal management.
Polam, Anudeep. "Thermal and Draw Induced Crystallinity in Poly-L-Lactic Acid Fibers." Cleveland State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=csu1439843418.
Full textRiedel, Gernot Jurgen. "Time Resolved Raman Thermography : Thermal Dynamics of GaN-based Electronic Devices." Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520665.
Full textHartvigsen, Peter Ward. "Thermal Conductivity and Diffusivity Measurement Assessment for Nuclear Materials Raman Thermometry for Uranium Dioxide and Needle Probe for Molten Salts." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8622.
Full textSobocinski, Raymond Louis 1962. "LASER-INDUCED THERMAL DECAY OF PYRIDINE AND CHLORIDE SURFACE-ENHANCED RAMAN SCATTERING AS A PROBE OF SILVER SURFACE-ACTIVE SITES." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276553.
Full textCoillet, Élodie. "Structural characterization of thin non-crystalline layers for low thermal noise optic." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1132/document.
Full textPredicted in 1916 by Einstein, then detected one hundred year later by the VIRGO and LIGO collaborations, the gravitational waves are a promising tool to observe the universe at scales always bigger. However, to detect a larger number of events, one of the main limitation of the detectors originates in the mirrors coatings thermal noise, thin non-crystalline layers composed of SiO2 and TiO2-doped Ta2O5. The aim of this work is to study the micro-structural origin of the layers thermal noise, by using vibrational spectroscopies, in order to, ultimately, process more efficient materials. Studies show a decrease of the thermal noise when the mirrors are annealed at low temperature. In silica, a structural reorganization happens during the annealing, following the evolution of the thermal noise. Notably, a stress relaxation has been observed. However, in Ta2O5, oxide with a complex structure not much studied, the impact of the annealing seems to be more limited, while the structure crystallizes easily as soon as the temperature increases. To complete our knowledge of this structure, in-situ high pressure measurements were conducted. Finally, the TiO2-doping effect of the Ta2O5 structures was studied
Landström, Anton. "Thermal Stability of Carbon Nanotubes and Role of Intercalation." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-61074.
Full textGhosh, Suchismita. "Thermal conduction in graphene and graphene multilayers." Diss., [Riverside, Calif.] : University of California, Riverside, 2009. http://proquest.umi.com/pqdweb?index=0&did=1957308711&SrchMode=2&sid=2&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1268427434&clientId=48051.
Full textIncludes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 12, 2010). Includes bibliographical references (p. 96-107). Also issued in print.
Russell, Bryn. "Automating the interpretation of thermal paints applied to gas turbine engines using Raman spectroscopy and machine learning." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/automating-the-interpretation-of-thermal-paints-applied-to-gas-turbine-engines-using-raman-spectroscopy-and-machine-learning(c838d0c0-2d3c-4fa6-a158-34ba15db3016).html.
Full textMalcolm, Kirkland D. "Characterization of the thermal properties of chemical vapor deposition grown diamond films for electronics cooling." Thesis, Georgia Institute of Technology, 2016. http://hdl.handle.net/1853/55037.
Full textMauricio, Iglesias Miguel. "Impact of high pressure thermal treatments on food/packaging interactions." Montpellier 2, 2009. http://www.theses.fr/2009MON20225.
Full textThe control of food/packaging interactions is essential to ensure the safety and quality of packed products. In particular, in the framework of the European Project Novel Q (IP6, Novel Processing Methods for the Production and Distribution of High Quality and Safe Foods), the effect of high pressure thermal (HP/T) treatments on food/packaging interactions was assessed in a variety of cases. Migration and scalping were studied for linear low density polyethylene (LLDPE), polylactide (PLA) and a wheat gluten/montmorillonite (WG/MMT) nanocomposite novel biodegradable and nanocomposite materials in food simulating liquids (FSL). Food/packaging interactions were studied after two HP/T treatments intended to perform a pasteurization (800 MPa, 5 min, 40°C) and a sterilization (800 MPa, 5 min, 115°C) treatment, as well as subsequent storage for 10 days. Specific migration of an additive (Uvitex OB) was assessed for LLDPE and PLA, whereas additional tests were carried out for WG/MMT, i. E. Overall migration, protein migration and nanoparticles migration. HP/T treatments did not significantly modify the migration or scalping in the conditions studied except for the release of nanoparticles from WG. Interestingly, the increase in the melting point of LLDPE during HP/T made possible to sterilize it. To date the most frequently used methods in migration assessment are based in time consuming methods based on destruction and quantification. To avoid them, modeling has been recently approved as a method for migration assessment. However, the parameters needed, i. E. Diffusivity (D) and the partition coefficient (K) are seldom available. The use of FTIR and Raman spectroscopy to assess migration behavior and, more importantly, to determine the diffusivity of an additive in LLDPE was successfully carried out allowing a complete characterization of mass transfer
El, Sachat Alexandros. "Characterization of nanostructured materials for thermal conduction and heat transfer control." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/405520.
Full textThe main objective of this thesis is the study of thermal properties of nanostructured materials as a mean to control heat transport. For this purpose thermal measurements with different experimental techniques on length scales covering tens of microns to sub-50 have been performed. Two experimental techniques in particular have been studied and presented in this thesis: (a) the scanning thermal microscopy technique (SThM) and (b) the two-laser Raman thermometry (2LRT). These techniques have been extensively applied to successfully measure thermal properties in various nanomaterials. In particular, two configurations of Si based materials are investigated using 2LRT: (a) Si membranes with thicknesses ranging from to and (b) periodic porous membranes with different lattice parameters and disordered pattern. The results obtained showed that the in-plane thermal conductivity of silicon and its temperature evolution from room temperature to about 1000 can be effectively reduced and tuned by (i) thickness and (ii) periodic patterning (holes). We attribute the reduction of the thermal conductivity to the shortening of the phonon mean free path Λ due to diffuse (incoherent) phonon-boundary scattering. Furthermore, we showed that the temperature dependence of the thermal conductivity of Si membranes in the high temperature range from to is governed by phonons with mean free path smaller than 200 . To investigate thermal transport in supported nanostructures and in smaller length scale, we studied heat transfer between different heated scanning probe sensors and nanomaterials, such as, (i) in-plane epitaxial Si1-xGex alloy nanowires and (ii) self-assembled block copolymer nanostructures, provided high resolution thermal images of sub-50 structures with sub- spatial resolution. The combination of the two experimental techniques was crucial for the thermal characterization of different material systems and the better understanding of fundamental aspects of thermal transport.
Natarajan, Shweta. "Thermal metrology techniques for ultraviolet light emitting diodes." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45891.
Full textBrocero, Guillaume. "Comparaison de méthodes de caractérisation thermique de transistors de puissance hyperfréquence de la filière nitrure de gallium." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC222/document.
Full textAt the moment, AlGaN/GaN HEMTs (High Electron Mobility Transistors) are the most promising for high-power hyperfrequency applications, essentially due to their large carrier density and a high electronic mobility. However, the temperature generating during operational conditions is a crucial parameter to measure, in order to estimate the reliability and durability of components. For these reasons, we compared thermoreflectance and Raman spectroscopy, that are non-destructive and possessing a submicronic spatial resolution. These techniques have already proven their feasibility as thermal characterization methods in both continuous wave and pulsed operational modes. We compare here their adaptability and performance to the conception of a thermal test bench. These methods are known for characterizing specific types of material: metals for thermoreflectance and semiconductors for Raman spectroscopy, leading us to the eventuality to combine them. We compared several results measured by thermoreflectance method with equipment from two different manufacturers that commercialize this technology, so we could highlight some aspects and drawbacks that are note relayed in the literature. With Raman spectroscopy, we identified metrology parameters allowing to realize a thermal measurement setup as reproducible as possible, and we also present an innovative method to probe surface material, especially metals
Rose, Kyle. "Synthesis, Phase Development, and the Mechanism for Negative Thermal Expansion in Aluminum Tungstate." Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1703275/.
Full textCebik, Jonathan E. "In Situ Raman Spectroscopy of the Nanodiamond-to- Carbon Onion Transformation During Thermal Annealing of Detonation Nanodiamond Powder." Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/7318.
Full textSena, Júnior Diniz Maciel de. "Propriedades Vibracionais e Térmicas do Topiramato Cristalino." reponame:Repositório Institucional da UFC, 2008. http://www.repositorio.ufc.br/handle/riufc/11932.
Full textSubmitted by Edvander Pires (edvanderpires@gmail.com) on 2015-05-04T19:42:01Z No. of bitstreams: 1 2008_tese_dmsenajunior.pdf: 1941905 bytes, checksum: cd866cd3390085e83129c5851eaff4d6 (MD5)
Approved for entry into archive by Edvander Pires(edvanderpires@gmail.com) on 2015-05-07T16:55:19Z (GMT) No. of bitstreams: 1 2008_tese_dmsenajunior.pdf: 1941905 bytes, checksum: cd866cd3390085e83129c5851eaff4d6 (MD5)
Made available in DSpace on 2015-05-07T16:55:19Z (GMT). No. of bitstreams: 1 2008_tese_dmsenajunior.pdf: 1941905 bytes, checksum: cd866cd3390085e83129c5851eaff4d6 (MD5) Previous issue date: 2008
The scientific interest on molecular crystals stems from their great versatility and ease of processing. For pharmaceutically active ingredients, the structure-activity relationship is of major importance. Topiramate, a white and crystalline solid, is a powerful drug efficiently employed to control epilepsy symptoms. The mechanism of action involves a negative modulatory effect on the AMPA/kainate subtypes of glutamate receptors and some types of voltage-gated Na+ and Ca2+ channels, and a positive modulatory effect on some types of GABAA receptors and at least one type of K+ channels in neurons. Despite its pharmacological attributes, the lack of publications regarding its physical-chemical properties in the literature is apparent. In order to fill this gap, a research comprising vibrational spectroscopy techniques (Raman and infrared), thermal analysis (TGA/DTA/DSC), and theoretical calculations, was carried out. With the aid of calculations employing density functional theory (DFT), most of the observed vibrational bands is assigned. Consideration of Raman spectra recorded at temperatures above and below room temperature, as well as under high hydrostatic pressures, indicated maintenance of the orthorhombic crystalline structure under the diverse thermodynamic conditions employed. Thermal analysis, however, showed that, after the melting point, the sample undergoes decomposition in a process comprising three stages, possibly initiated with loss of the sulfamate group by the molecule. This event inspired a theoretical study aimed at promoting the sulfamate group bond breakage in a controlled way by employing a laser instead of heat. This was accomplished by quantum dynamics simulations which showed that, by using a set of ultrashort pulses in the infrared region, it is possible to reach levels close to 70 % dissociation in less than 3 ps.
O interesse científico pelos cristais moleculares resulta da facilidade de processamento destes materiais, e de sua grande versatilidade. No caso de drogas, a relação entre estrutura e atividade é de suma importância. Topiramato, um sólido branco e cristalino, é um fármaco utilizado com bastante eficiência para controlar os sintomas da epilepsia. O mecanismo de ação envolve um efeito modulatório negativo nos receptores de glutamato do subtipo AMPA/kainato e alguns tipos de canais de Na+ e Ca2+ voltagem-dependentes, bem como um efeito modulatório positivo em alguns tipos de receptores GABAA e pelo menos um tipo de canal de K+ nos neurônios. A despeito de suas qualidades farmacológicas, a escassez de trabalhos relacionados às suas propriedades físico-químicas na literatura é evidente. Para ajudar a preencher esta lacuna, uma investigação envolvendo técnicas de espectroscopia vibracional (Raman e infravermelho), análises térmicas (TGA/DTA/DSC), e cálculos teóricos, foi realizada. Com a ajuda de cálculos empregando a teoria do funcional de densidade (DFT), a atribuição da maioria das bandas vibracionais observadas foi realizada. A observação dos espectros Raman obtidos em temperaturas acima e abaixo da ambiente, bem como sob altas pressões hidrostáticas, indicou que a estrutura cristalina ortorrômbica é mantida nas diferentes condições termodinâmicas empregadas. A análise térmica, entretanto, mostrou que, após a fusão, o material sofre decomposição em um processo que envolve três etapas, possivelmente iniciado com a perda do grupo sulfamato pela molécula. Este fato motivou um estudo teórico a fim de modelar a quebra da ligação do sulfamato de maneira controlada, utilizando um laser em lugar de calor. Isto foi realizado com simulações de dinâmica quântica, que mostraram que, através da utilização de uma combinação de pulsos ultracurtos na região do infravermelho, é possível atingir níveis próximos a 70% de dissociação em menos de 3 ps.
Osterhout, Jeffrey T. "Diversity of Microfossils and Preservation of Thermally Altered Stromatolites from Anomalous Precambrian Paleoenvironments." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1470753351.
Full textTran, Thi Hong Van. "Investigation into the thermal dehydroxylation and decomposition of hydroxylapatite during atmospheric plasma spraying." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2009. http://nbn-resolving.de/urn:nbn:de:swb:105-3432055.
Full textZhang, Nana. "Crescimento e propriedades vibracionais de cristais a base de óxidos." reponame:Repositório Institucional da UFC, 2012. http://www.repositorio.ufc.br/handle/riufc/13623.
Full textSubmitted by Edvander Pires (edvanderpires@gmail.com) on 2015-10-20T18:59:42Z No. of bitstreams: 1 2012_tese_nzhang.pdf: 4710011 bytes, checksum: 716fc88d4757851465337af57bbae3e8 (MD5)
Approved for entry into archive by Edvander Pires(edvanderpires@gmail.com) on 2015-10-20T20:23:57Z (GMT) No. of bitstreams: 1 2012_tese_nzhang.pdf: 4710011 bytes, checksum: 716fc88d4757851465337af57bbae3e8 (MD5)
Made available in DSpace on 2015-10-20T20:23:57Z (GMT). No. of bitstreams: 1 2012_tese_nzhang.pdf: 4710011 bytes, checksum: 716fc88d4757851465337af57bbae3e8 (MD5) Previous issue date: 2012
In this work we used different experimental techniques to study four different series of inorganic oxide crystals, namely: (i) congruent lithium isotope niobate (C7LN), (ii) rare-earth doped mixed vanadates ((Nd,Yb):YxGd1-x(VO4)); (iii) alkali metal doped and pure calcium barium niobates (CaxBa1-xNb2O6); and (iv) potassium tantalite niobate (KTa1-xNbxO3). Below we describe the studies performed for each class. (i) For further investigation on the defect structure of lithium niobate crystals (LiNbO3 – hereafter LN) using the neutron scattering technique, a congruent lithium isotope niobate crystal (C7LN) was grown by the Czochralski method from a 48.4% 7Li melt. The X-ray powder diffraction (XRPD) results show that the as-grown crystal is a single-phased (R3c) LN. We observed 4A1(TO)+7E(TO) Raman modes. The crystal composition (Li mol%) determined from UV absorption edge and Raman measurements is 47.47% and 47.34%, respectively. The specific heat (Cp), thermal diffusion coefficients (λa , λc), thermal conductivities (κa , κc) and the average thermal expansion coefficients (a , c) were determined. The effect of Li vacancy content is analyzed by comparing the results with those obtained for near stoichiometric lithium isotope niobate (NS7LN) and congruent natural lithium niobate (CLN) crystals. The values of all thermal parameters of C7LN are smaller than those of NS7LN and CLN, which may be related to either the difference of vacancy content or isotope substitution. (ii) The room temperature phonon modes of the isostructural (Nd,Yb):YxGd1-x(VO4) laser crystals were determined using the Raman scattering technique, and the observed wavenumbers follow the overall mode distribution expected for REVO4 (RE = rare earth) compounds with the tetragonal zircon structure, . They were assigned according to the group theory in terms of the internal modes of the VO4 tetrahedron and the external modes of the YxGd1-x(VO4) lattice. No appreciable changes in the phonon wavenumbers were observed for Yb:GdVO4 (Yb = 0.008, 0.015, 0.020, 0.025, and 0.035), indicating that the force fields in the GdVO4 lattice are not strongly altered by Yb doping at the Gd site. However, most of the phonon wavenumbers in the systems (Nd,Yb):YxGd1-x(VO4) shifts upwards (one-phonon-like behavior) when Y replaces Gd. (iii) The room temperature phonon modes of both the alkali metal doped and pure CaxBa1-xNb2O6 (hereafter CBNx) crystals were determined using the Raman scattering technique. Owing to the intrinsic disorder of the tetragonal lattice we observed few and broad bands. The wavenumber of the internal modes observed shifts upwards when the volume of the unit cell increases. This blue shift is likely to be related to the shortening of the Nb-O band length of the NbO6 octahedrons. The Curie temperatures of the ferroelectric to paraelectric phase transition for all the CBN-like crystals were obtained from DSC measurements. The Raman spectra of CBN32 in the temperature range from 300 to 568 K were recorded in order to investigate and verify the ferroelectric phase transformation. The lower-temperature (25-260 K) dependent Raman spectra of CBN32 were also recorded, and the results show that it may exhibit a phase transition at 75-100 K. (iv) Single crystals of potassium tantalite niobate, KTa1-xNbxO3 (KTNx, x = 0.45, 0.50, and 0.55), were synthesized by the top-seeded solution growth method. The Raman scattering technique is used to investigate the sequence of phase transitions undergone by KTNx crystals. Special attention is given to the changes which characterize the orthorhombic-to-rhombohedral phase transition.
Neste trabalho usamos diferentes técnicas experimentais para estudar quatro séries de cristais inorgânicos a base de óxidos, a saber: (i) niobato de lítio isotópico (C7LN), (ii) vanadatos mistos de terra-raras dopados com terra-raras ((Nd,Yb):YxGd1-x(VO4)), (iii) niobato de bário e cálcio puro e dopado com metais alcalinos, e (iv) niobato-tantalato de potássio. A seguir descrevemos os estudos realizados para cada série. (i) Para futuras investigações acerca da estrutura de defeitos em cristais de niobato de lítio (LN) utilizando a técnica de espalhamento de nêutrons, crescemos cristais de niobato de lítio isotópico (C7LN). Das medidas de raios x determinamos que a estrutura cristalina é R3c. Das medidas de espalhamento Raman, observamos 4A1+7E modos de vibração. A concentração de Li (em mol %) foi determinada a partir das medidas de absorção no ultravioleta (47.47%) e do espectro de vibração (47.34%). Obtivemos ainda os valores para o calor específico, os coeficientes de difusão térmica, as condutividades térmicas e os coeficientes de expansão térmica médios. O efeito das vacâncias de Li no composto C7LN foi investigado a partir da comparação com os compostos niobato de lítio aproximadamente estequiométrico isotópico (NS7LN) e niobato de lítio natural (CLN). Observamos que os valores dos parâmetros térmicos do C7LN são menores do que aqueles apresentados pelos compostos NS7LN e CLN. Isto ocorre ou devido aos defeitos ou a substituição isotópica de Li. (ii) Analisamos o espectro de fônons dos compostos (Nd,Yb):YxGd1-x(VO4) que são utilizados como meios ativos em lasers de estado sólido. Observamos que os espectros obtidos seguem a distribuição de fônons esperada para os compostos REVO4 com estrutura tetragonal, D4h19. A designação dos modos de vibração foi estabelecida de acordo com a previsão da Teoria de Grupos, em termos dos modos internos e externos da rede. Não observamos nenhuma modificação no espectro de fônons dos compostos Yb:GdVO4 (Yb = 0.008, 0.015, 0.020, 0.025 e 0.035), indicando assim que a rede GdVO4 não é afetada pela inclusão de íons de Yb. Entretanto, observamos que a frequência da maioria dos fônons nos sistemas (Nd,Yb:YxGd1-xVO4) Y aumenta com o aumento da concentração de Y. (iii) Analisamos espectro de fônons a temperatura ambiente dos compostos CBN puros e dopado com metais alcalinos. Devido a desordem intrínseca da rede tetragonal, observamos menos modos do que os previstos pela Teoria de Grupos. Observamos também que a frequência dos modos internos aumenta quando o volume da célula unitária aumenta. Este aumento está provavelmente relacionado a diminuição das distâncias interatômicas entre os átomos do octaedro NbO6. A partir de medidas térmicas, determinamos a temperatura de transição de fase dos compostos investigados. As transições de fase para o composto CBN32 foram também investigadas através da técnica de espalhamento Raman. (iv) A sequência de transições de fases exibidas pelos compostos de niobato-tantalato de potássio (KTNx, x = 0.45, 0.50 e 0.55), foram estudadas através da técnica de espalhamento Raman. Aumentando a temperatura, a sequência de transições de fase é a seguinte: romboédrica-ortorrômbica-tetragonal-cúbica. Discutimos quais as alterações que surgem nos espectros Raman que devem ser associadas às transições consideradas. Em especial, discutimos a transição romboédrica-ortorrômbica.
Kim, Samuel H. "Addressing thermal and environmental reliability in GaN based high electron mobility transistors." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52244.
Full textBudhavaram, Naresh Kumar. "Facile protein and amino acid substitution reactions and their characterization using thermal, mechanical and optical techniques." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/40340.
Full textPh. D.
Do, Tuyet-Trinh. "Thermal degradation of polyvinyl chloride blends / by Tuyet-Trinh Do." Thesis, Queensland University of Technology, 2000.
Find full textDidenko, Stanislav. "Artificially induced anisotropy of thermal conductivity in 2D Si phononic membranes." Thesis, Lille, 2019. http://www.theses.fr/2019LIL1I048.
Full textThis thesis work is devoted to the development of practical mechanisms for the heat guiding in silicon low-dimensional nanostructures. The motivation comes from both the field of IC thermal management and emerging technology of Si-based thermoelectric devices, where directional heat guiding can play an important role. A series of micrometre-sized thermal characterisation platforms was designed and fabricated. The objective is to study experimentally the feasibility of artificially-induced in-plane anisotropy of effective thermal conductivity (κ) in Si nanopatterned membranes. By the combined use of micro Raman Thermometry, Rigorous Coupled Wave Analysis and Finite Element Modelling (FEM) it was possible to measure the thermal gradient, membrane conductance and determine effective thermal conductivities. This experiment confirms the possibility to induce artificially high anisotropy of κ in Si phononic membranes. Finally, purposefully designed parameterized FEM model demonstrated the possible implementation of the induced anisotropic effects in the area of IC thermal-management
Simões, Rebeca Delatore [UNESP]. "Estudo das propriedades físicas de blendas de PVDF/Látex visando aplicação como biomaterial." Universidade Estadual Paulista (UNESP), 2005. http://hdl.handle.net/11449/88469.
Full textCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
O principal objetivo deste trabalho de mestrado foi a obtenção e caracterização estrutural de um material com propriedades físico-químicas compatíveis com aquelas requeridas por um biomaterial. Filmes contendo diferentes volumes de látex de borracha natural em uma massa fixa de poli(fluoreto de vinilideno) (PVDF), na forma de pó foram fabricados por compressão/aquecimento de uma mistura de ambos os materiais sem o uso de qualquer solvente. Este é um fator importante considerando o uso destes filmes no futuro próximo como biomateriais em diferentes aplicações (indução do crescimento do tecido ósseo, por exemplo), uma vez que os solventes convencionais usados para dissolver o PVDF têm se mostrado tóxicos ao organismo humano. Os filmes foram submetidos a um tratamento via descarga corona de forma que amostras com e sem tal tratamento foram caracterizadas através das técnicas de espectroscopia vibracional via espalhamento Raman e absorção no infravermelho (FTIR), análise térmica via termogravimetria (TG), calorimetria exploratória diferencial (DSC) e análise dinâmico-mecânica (DMA) e microscopias ótica e eletrônica (MEV). As medidas termomecânicas mostraram que os filmes obtidos possuem características mecânicas similares àquelas encontradas no osso humano e boa estabilidade térmica considerando-se a aplicação desejada. As medidas via espectroscopia vibracional indicaram que o PVDF e o látex não interagem quimicamente, compondo uma blenda polimérica. Além disto, os resultados obtidos via micro-Raman mostraram que o aumento da quantidade de látex na blenda permite uma melhor dispersão deste látex na matriz de PVDF quando da produção dos filmes...
The main goal of this work was to obtain and characterize structurally a material with physical-chemical properties compatible with those required for a biomaterial. Films containing different volumes of latex of natural rubber in a fixed mass of poly (vinylidene fluoride) (PVDF) powder were fabricated by compressing/annealing a mixture of both materials without using any solvent. This is an important issue having in mind to use these films in the future as biomaterials in different applications (growing of the bone tissue, for instance) once the solvents used to dissolve the PVDF are toxic to human being. The films were submitted to a corona discharge treatment in a way that samples with and without such treatment were characterized using micro-Raman scattering and Fourier transform infrared absorption (FTIR) spectroscopies, thermo-mechanical techniques using thermogravimetry (TG), differential scanning calorimetry (DSC) and dynamical-mechanical analysis (DMA) and optical and scanning electron microscopies (SEM). The thermo-mechanical measurements revealed that the films present mechanical properties close to that found for the human bone and high thermal stability considering the desired applications. The vibrational spectroscopies showed that the latex and PVDF do not interact chemically leading to the formation of a polymeric blend. Besides, the results recorded using the micro-Raman technique revealed that the higher the amount of latex in the blend, the better the miscibility between both materials. In terms of morphology, the blend surface is formed by two domains: one is rougher and contains the latex well dispersed into the PVDF matrix while the other is smoother and contains both materials as well but in a less homogeneous dispersion. However, as the volume of latex is increased from 0.3 to 1.0 mL, the smoother domains become rarer to be found... (Complete abstract, click electronic address below)
Junior, Virgilio Tattini. "Efeito da liofilização sobre a estrutura e mudanças de fase da albumina bovina modificada por reação com metoxi-polietilenoglicol." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/9/9134/tde-19092006-194927/.
Full textPEG conjugation masks the proteins surface and increases the molecular size of the polypeptide, thus reducing its renal ultrafiltration, preventing the approach of antibodies or antigen processing cells and reducing the degradation by proteolytic enzymes. The PEG conveys to molecules its physico-chemical properties and therefore modifies also biodistribution and solubility of peptide and non-peptide drugs. This property opens new techniques in biocatalysis and in pharmaceutical technology where many insoluble drugs are solubilized by PEG conjugation and thus more easily administered. Aqueous protein solutions are readily denatured (often irreversibly) by numerous stresses arising in solution, e.g., heating, agitation, freezing, pH changes, and exposure to interfaces or denaturants, usually resulting in lost of clinical efficacy and increase the risk of adverse side effects. Even if its physical stability is maintained, a protein can be degraded by chemical reactions (e.g., hydrolysis and deamidation), many of which are mediated by water. The practical solution to the protein stability dilemma is to remove the water. Lyophilization is most commonly used to prepare dehydrated proteins, which, theorecally, should have the desired long-term stability at ambient temperatures. The protein used in this study was the bovine serum albumin (BSA), largely studied in the biochemical field. Through Raman spectroscopy associated with thermal analysis using DSC, Colorimetric analysis and the determination of water content It was observed that the fast freezing (30 °C/min.) favored the maintenance of the conformational structure in the protein after lyophilization, however increased the primary drying in seven hours with regard to the slow freezing (2,5 °C/min.). After the modification of bovine serum albumin with methoxy-PEG it was observed that the BSA-PEG (1:0,25) showed a lower degree of structural alterations and consequently a lower variation on the physical-chemical characteristics, moreover optimized the conditions during the lyophilization process and storage of the protein when it was compared to BSA-PEG (1:0,5).
Zhang, Nana. "Crescimento e propriedades vibracionais de cristais a base de Ãxidos." Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=7241.
Full textNeste trabalho usamos diferentes tÃcnicas experimentais para estudar quatro sÃries de cristais inorgÃnicos a base de Ãxidos, a saber: (i) niobato de lÃtio isotÃpico (C7LN), (ii) vanadatos mistos de terra-raras dopados com terra-raras ((Nd,Yb):YxGd1-x(VO4)), (iii) niobato de bÃrio e cÃlcio puro e dopado com metais alcalinos, e (iv) niobato-tantalato de potÃssio. A seguir descrevemos os estudos realizados para cada sÃrie. (i) Para futuras investigaÃÃes acerca da estrutura de defeitos em cristais de niobato de lÃtio (LN) utilizando a tÃcnica de espalhamento de nÃutrons, crescemos cristais de niobato de lÃtio isotÃpico (C7LN). Das medidas de raios x determinamos que a estrutura cristalina à R3c. Das medidas de espalhamento Raman, observamos 4A1+7E modos de vibraÃÃo. A concentraÃÃo de Li (em mol %) foi determinada a partir das medidas de absorÃÃo no ultravioleta (47.47%) e do espectro de vibraÃÃo (47.34%). Obtivemos ainda os valores para o calor especÃfico, os coeficientes de difusÃo tÃrmica, as condutividades tÃrmicas e os coeficientes de expansÃo tÃrmica mÃdios. O efeito das vacÃncias de Li no composto C7LN foi investigado a partir da comparaÃÃo com os compostos niobato de lÃtio aproximadamente estequiomÃtrico isotÃpico (NS7LN) e niobato de lÃtio natural (CLN). Observamos que os valores dos parÃmetros tÃrmicos do C7LN sÃo menores do que aqueles apresentados pelos compostos NS7LN e CLN. Isto ocorre ou devido aos defeitos ou a substituiÃÃo isotÃpica de Li. (ii) Analisamos o espectro de fÃnons dos compostos (Nd,Yb):YxGd1-x(VO4) que sÃo utilizados como meios ativos em lasers de estado sÃlido. Observamos que os espectros obtidos seguem a distribuiÃÃo de fÃnons esperada para os compostos REVO4 com estrutura tetragonal, D4h19. A designaÃÃo dos modos de vibraÃÃo foi estabelecida de acordo com a previsÃo da Teoria de Grupos, em termos dos modos internos e externos da rede. NÃo observamos nenhuma modificaÃÃo no espectro de fÃnons dos compostos Yb:GdVO4 (Yb = 0.008, 0.015, 0.020, 0.025 e 0.035), indicando assim que a rede GdVO4 nÃo à afetada pela inclusÃo de Ãons de Yb. Entretanto, observamos que a frequÃncia da maioria dos fÃnons nos sistemas (Nd,Yb:YxGd1-xVO4) Y aumenta com o aumento da concentraÃÃo de Y. (iii) Analisamos espectro de fÃnons a temperatura ambiente dos compostos CBN puros e dopado com metais alcalinos. Devido a desordem intrÃnseca da rede tetragonal, observamos menos modos do que os previstos pela Teoria de Grupos. Observamos tambÃm que a frequÃncia dos modos internos aumenta quando o volume da cÃlula unitÃria aumenta. Este aumento està provavelmente relacionado a diminuiÃÃo das distÃncias interatÃmicas entre os Ãtomos do octaedro NbO6. A partir de medidas tÃrmicas, determinamos a temperatura de transiÃÃo de fase dos compostos investigados. As transiÃÃes de fase para o composto CBN32 foram tambÃm investigadas atravÃs da tÃcnica de espalhamento Raman. (iv) A sequÃncia de transiÃÃes de fases exibidas pelos compostos de niobato-tantalato de potÃssio (KTNx, x = 0.45, 0.50 e 0.55), foram estudadas atravÃs da tÃcnica de espalhamento Raman. Aumentando a temperatura, a sequÃncia de transiÃÃes de fase à a seguinte: romboÃdrica-ortorrÃmbica-tetragonal-cÃbica. Discutimos quais as alteraÃÃes que surgem nos espectros Raman que devem ser associadas Ãs transiÃÃes consideradas. Em especial, discutimos a transiÃÃo romboÃdrica-ortorrÃmbica.
In this work we used different experimental techniques to study four different series of inorganic oxide crystals, namely: (i) congruent lithium isotope niobate (C7LN), (ii) rare-earth doped mixed vanadates ((Nd,Yb):YxGd1-x(VO4)); (iii) alkali metal doped and pure calcium barium niobates (CaxBa1-xNb2O6); and (iv) potassium tantalite niobate (KTa1-xNbxO3). Below we describe the studies performed for each class. (i) For further investigation on the defect structure of lithium niobate crystals (LiNbO3 â hereafter LN) using the neutron scattering technique, a congruent lithium isotope niobate crystal (C7LN) was grown by the Czochralski method from a 48.4% 7Li melt. The X-ray powder diffraction (XRPD) results show that the as-grown crystal is a single-phased (R3c) LN. We observed 4A1(TO)+7E(TO) Raman modes. The crystal composition (Li mol%) determined from UV absorption edge and Raman measurements is 47.47% and 47.34%, respectively. The specific heat (Cp), thermal diffusion coefficients (λa , λc), thermal conductivities (κa , κc) and the average thermal expansion coefficients (a , c) were determined. The effect of Li vacancy content is analyzed by comparing the results with those obtained for near stoichiometric lithium isotope niobate (NS7LN) and congruent natural lithium niobate (CLN) crystals. The values of all thermal parameters of C7LN are smaller than those of NS7LN and CLN, which may be related to either the difference of vacancy content or isotope substitution. (ii) The room temperature phonon modes of the isostructural (Nd,Yb):YxGd1-x(VO4) laser crystals were determined using the Raman scattering technique, and the observed wavenumbers follow the overall mode distribution expected for REVO4 (RE = rare earth) compounds with the tetragonal zircon structure, . They were assigned according to the group theory in terms of the internal modes of the VO4 tetrahedron and the external modes of the YxGd1-x(VO4) lattice. No appreciable changes in the phonon wavenumbers were observed for Yb:GdVO4 (Yb = 0.008, 0.015, 0.020, 0.025, and 0.035), indicating that the force fields in the GdVO4 lattice are not strongly altered by Yb doping at the Gd site. However, most of the phonon wavenumbers in the systems (Nd,Yb):YxGd1-x(VO4) shifts upwards (one-phonon-like behavior) when Y replaces Gd. (iii) The room temperature phonon modes of both the alkali metal doped and pure CaxBa1-xNb2O6 (hereafter CBNx) crystals were determined using the Raman scattering technique. Owing to the intrinsic disorder of the tetragonal lattice we observed few and broad bands. The wavenumber of the internal modes observed shifts upwards when the volume of the unit cell increases. This blue shift is likely to be related to the shortening of the Nb-O band length of the NbO6 octahedrons. The Curie temperatures of the ferroelectric to paraelectric phase transition for all the CBN-like crystals were obtained from DSC measurements. The Raman spectra of CBN32 in the temperature range from 300 to 568 K were recorded in order to investigate and verify the ferroelectric phase transformation. The lower-temperature (25-260 K) dependent Raman spectra of CBN32 were also recorded, and the results show that it may exhibit a phase transition at 75-100 K. (iv) Single crystals of potassium tantalite niobate, KTa1-xNbxO3 (KTNx, x = 0.45, 0.50, and 0.55), were synthesized by the top-seeded solution growth method. The Raman scattering technique is used to investigate the sequence of phase transitions undergone by KTNx crystals. Special attention is given to the changes which characterize the orthorhombic-to-rhombohedral phase transition.
Brown, Matthew Thomas. "Caracterização petrológica e química dos carvões utilizados em usinas termelétricas brasileiras e as cinzas geradas no processo de combustão." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/38631.
Full textIn this study feed coal, bottom ash and fly ash from coal-burning power plants located in southern Brazil (Candiota (RS), Charqueadas (RS), São Jerônimo (RS) and Jorge Lacerda (SC)) were collected in intervals of three to four months over a period of one a period of one year and analyzed by petrological and chemical methods. Analyses on the feed coal samples included the following: petrological (vitrinite reflectance and maceral analysis) chemical (proximate and ultimate analyses, determination of calorific values) and mineralogical (X-ray diffraction and Raman micro-spectrometry). Analyses on bottom and fly ash samples included X-ray diffraction, total carbon (TC) and petrological methods.The petrological analyses showed that the coals from Rio Grande do Sul have a rank of: subbituminous, while the coal from Jorge Lacerda is composed of a blend of coals with ran levels that ranged from subbituminous to meta-anthracite, with a predominance of high volatile bituminous coal. The maceral analysis showed that vitrinite and inertinite were the dominate maceral groups in the coals. The coal blends from Jorge Lacerda were composed of different vitrinite populations and also included peat and petroleum coke. The proximate analysis showed that the coals have high ash content, with average values of: 49.0% wt. for Candiota, 47.6% wt. for Charqueadas, 38.9% wt. for São Jerônimo and 40.5 for Jorge Lacerda. The ultimate analysis showed average sulfur values of: 1.4% wt. for Candiota, 0.9% wt. for Charqueadas, 0.7% wt. for São Jerônimo and 2.0% wt. for Jorge Lacerda. The average calorific values were: 2928 cal/g for Candiota, 3156 cal/g for Charqueadas, 3834 cal/g for São Jerônimo and 4510 cal/g for Jorge Lacerda. The mineral matter consisted of mainly quartz and kaolinite, as determined by X-ray diffraction. The mineral matter of the bottom ash and fly ash, as determined by X-ray diffraction, consisted predominately of quartz and mullite. The average values of the TC in the bottom ash and fly ash was determined to be: 0,66 wt.% and 0,35 wt.% for Candiota, 10,11 wt.% and 1,17 wt.% for Charqueadas, 16,97 wt.% and 9,34 wt.% for São Jerônimo and 2,47 wt.% and 0,99 wt.% for Jorge Lacerda respectively. The mineral matter of the ash samples consisted mostly of glass and spinel spheres. Crassisphere and crassinetworks, derived from vitrinite, were common char particles observed in the ash samples, as well as mixed dense and solid/fusinoid, particles derived from inertinite macerals. Ash samples from São Jerônimo contained several unburnt coal particles, while samples from Jorge Lacerda contained solid particles derived from petroleum coke.Raman spectrometry was used to characterize the coal samples in this study, with respect to the different maceral groups and changes in coal rank. The Raman spectra of vitrinite and inertinite were similar with the exception that vitrinite had higher D- peak wave numbers and the G-peaks were wider. The spectrum obtained for liptinites consisted of a high background florescence, without significant peaks. With increasing coal rank, the widths of the G and D-peaks become smaller.
Souza, Nelson Luis Gonçalves Dias de. "Estudo da degradação de polímeros e blendas aplicados à bovinocultura." Universidade Federal de Juiz de Fora, 2015. https://repositorio.ufjf.br/jspui/handle/ufjf/316.
Full textApproved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-01-25T15:51:16Z (GMT) No. of bitstreams: 1 nelsonluisgoncalvesdiasdesouza.pdf: 6400467 bytes, checksum: f13622d122292f1c2363e10cf9d7b85f (MD5)
Made available in DSpace on 2016-01-25T15:51:16Z (GMT). No. of bitstreams: 1 nelsonluisgoncalvesdiasdesouza.pdf: 6400467 bytes, checksum: f13622d122292f1c2363e10cf9d7b85f (MD5) Previous issue date: 2015-05-18
CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Os polímeros constituem um grupo particular de macromoléculas (moléculas de alto peso molecular constituídas por grandes cadeias de átomos) caracterizado pela repetição de um ou mais grupos atômicos (monômero), que são responsáveis pela formação da cadeia polimérica e, consequentemente, suas características físico-químicas. Suas propriedades derivam principalmente das interações que ocorrem entre os elementos da sua macroestrutura (interações intramoleculares) ou com outros compostos (interações intermoleculares). As blendas poliméricas são formadas a partir da mistura de dois ou mais polímeros com o intuito de obter um novo material com propriedades diferentes dos polímeros que os originaram. A produção de blendas é uma maneira simples e barata de se obter novos materiais poliméricos, pois não há a necessidade de realizar sínteses. No estudo de uma blenda polimérica dois fatores devem ser avaliados: a miscibilidade e a compatibilidade, sendo a preparação e o estudo das blendas uma parte importante da ciência dos polímeros. Apesar das blendas já serem amplamente usadas e estudadas, os efeitos da mistura de polímeros nos processos de estabilização e degradação não são compreendidos. Os polímeros podem ser divididos em diversas classes sendo uma delas relacionada com os polímeros biodegradáveis que fazem parte de um campo emergente de pesquisa. Um grande número de polímeros biodegradáveis tem sido sintetizado recentemente, e alguns microrganismos e enzimas são capazes de degradá-los. Assim nesse trabalho estudou-se num primeiro momento a compatibilidade de miscibilidade de blendas poliméricas envolvendo mistura de polímeros não biodegradáveis e biodegradáveis, através da utilização de técnicas espectroscópicas (infravermelho e Raman) e análises térmicas (TG e DSC). Em seguida a degradação desses polímeros foi realizada estudando sua estabilidade ao serem submetidos a ação de enzimas proteolíticas do rúmen (análise por Raman e infravermelho) e ao serem submetidos a degradação no solo, que nesse caso além das análises vibracionais estudou-se a perda da massa desses matérias ao decorrer do tempo. Por fim o estudo da toxicidade celular de algumas blendas foram realizados a fim de avaliar a possibilidade de sua aplicação em medicina veterinária.
The polymers are a particular group of macromolecules (high molecular weight molecules formed by long chains of atoms) characterized by the repetition of one or more atomic groups (monomer), which are responsible for the formation of the polymeric chain and consequently its physicochemical characteristics chemical. Its properties are principally derived from interactions among the elements of its macrostructure (intramolecular interactions) or other compounds (intermolecular interactions). The polymer blends are formed from a mixture of two or more polymers in order to obtain a new material with different properties of the polymers originated. The production of polymer blends is a simple and inexpensive way to obtain new polymeric materials, since there is no need to perform syntheses. In the study of a polymer blend two factors must be evaluated, the miscibility and compatibility the study of a polymer blend two factors must be evaluated, the miscibility and compatibility, and the preparation and study of the blends are an important part of polymer science. Although the blends are already widely used and studied the effects of polymer mixture in the degradation and stabilization processes are not understood. The polymers can be divided into several classes including biodegradable polymers that are part of an emerging field research; a great many biodegradable polymers have been synthesized recently and some microorganisms and enzymes are capable of degrading them. Thus this work we studied at first compatibility miscibility of polymer blends involving mixing of non-biodegradable and biodegradable polymers, using spectroscopic techniques (infrared and Raman) and thermal analysis (TG and DSC). Then the degradation of these polymers was carried out by studying their stability when subjected to the action of proteolytic enzymes in the rúmen (by Raman and infrared analysis) and undergoing degradation in the soil, in this case in addition to analysis by Raman and infrared spectroscopy it is study loss of mass of the material over time. In order to study the cellular toxicity of some blends were conducted to evaluate the possibility of its application in veterinary medicine.
Gonçalves, Anderson. "ESTUDO DA DEPENDÊNCIA COMPOSICIONAL COM AS PROPRIEDADES TÉRMICAS E ESPECTROSCÓPICAS DO SISTEMA TeO2-Li2O-BaO." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2016. http://tede2.uepg.br/jspui/handle/prefix/855.
Full textFundação Araucária de Apoio ao Desenvolvimento Científico e Tecnológico do Paraná
In this work were studied the tellurite glasses of the glass system (100-x-y)TeO2-yLi2O-xBaO obtained by melt quenching method and characterized by techniques X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Raman Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), UV-Vis Spectroscopy, linear refractive index and density measurements. The results of DRX measurements allowed classifying the samples with a standard characteristic diffraction amorphous structures. The DSC results show that the samples located close to the center of the glass-forming region have the highest values for the thermal stability, these being greater than 100 °C. Results of Raman spectroscopy show that there is a decrease in the connectivity of the network glass formed and of the TeO4 units with decreasing amount of tellurium. The units of TeO3+1 show an increase while for TeO3 units there is not a well defined behavior. The FTIR results show a decrease in TeO4 units and increase in TeO3 units with decreasing amount of tellurium. The Band Gap (Eg) energy values obtained are in agreement with those found in the literature for tellurite glasses. The results also indicate that electronic transitions that occur are of the type permitted indirect, still being observed an increase in Eg values as tellurium replaced. The structural changes create Non Bridging Oxygen (NBO), but the connection between the NBO and Te atoms is weak, which do not influence in Eg behavior. This influence starts to be strong above a certain value of BaO content (which depends on the Li2O content). While these values to the energy band gap increase, the values of the linear refractive index decreases, agreeing with what is presented in the literature. For polarizability ion oxide, only the samples with 5% Li2O shows behavior consistent with what is reported in the literature, inversely proportional to the Band Gap values and proportional to the refractive index.
Neste trabalho foram estudados os vidros teluretos do sistema vítreo (100-x-y)TeO2-yLi2O-xBaO obtidos pelo método de melt quenching e caracterizados pelas técnicas de Difração de Raios X (DRX), Calorimetria Diferencial de Varredura (DSC), Espectroscopia Raman, Espectroscopia no Infravermelho por Transformada de Fourier (FTIR), Espectroscopia UV-Vis, medidas de índice de refração linear e densidade. Os resultados das medidas de DRX permitiram classificar as amostras que apresentavam um padrão de difração característico de estruturas amorfas. Os resultados de DSC mostraram que as amostras localizadas próximas ao centro da região de formação vítrea apresentaram os maiores valores para a estabilidade térmica, sendo estes maiores que 100 °C. Os resultados de espectroscopia Raman mostraram que ocorre uma diminuição na conectividade da rede vítrea formada e das unidades de TeO4 com a diminuição da quantidade de telúrio. As unidades de TeO3+1 apresentaram um aumento, enquanto que para as unidades de TeO3 não há um comportamento bem definido. Os resultados de FTIR mostraram uma diminuição nas unidades de TeO4 e um aumento nas unidades de TeO3 com a diminuição da quantidade de telúrio. Os valores de energia de Band Gap (Eg) obtidos estão de acordo com os encontrados na literatura para vidros teluretos. Os resultados também indicam que as transições eletrônicas que ocorrem são do tipo permitida indireta, sendo observado ainda um aumento nos valores de Eg à medida que o telúrio é substituído. As modificações estruturais que ocorreram criam oxigênios não ligados (NBO – non-bridging-oxygen), mas os mesmos são fracamente conectados aos átomos de Te, não influenciando tanto nos valores de Eg até certa quantidade de BaO (que depende da quantidade de Li2O). Enquanto estes valores para a energia de Band Gap aumentam, os valores para o índice de refração linear diminuem, concordando com o que é apresentado pela literatura. Para a polarizabilidade do íon óxido, apenas as amostras com 5% de Li2O apresentaram comportamento coerente com o que é reportado na literatura, sendo inversamente proporcional ao Band Gap e proporcional ao índice de refração.
Junior, João de Araújo. "Estudo da degradação parcial de filmes de blendas de poli(tereftalato de butileno-co-adipato de butileno) e poli(ácido láctico) no processo de compostagem doméstica." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-10112016-101541/.
Full textIn this study, blends of the synthetic polyester poly(butylene adipate-cotherephtalate) - PBAT - and the natural one poly(lactic acid) - PLA - used as biodegradable plastic shopping bags were studied. Samples of these materials were weighed and buried in simulated soil for four months to simulate domestic composting. These samples were then studied by Differential Scanning Calorimetry (DSC), Thermogravimetry (TG, including a comparative non-isothermal Kinetic Analysis with PE shopping bags containing prodegradation agents), Transformed Fourier Raman Vibrational Spectroscopy (FT-Raman), Wide Angle X-Ray Diffraction (WAXD) and Gel Permeation Chromatography (GPC). It was observed that even though there was no significant mass loss in the period of the ageing when using conventional home composting, important structural changes were detected in the samples, such as the reduction of activation energies (Ea) for the thermal decomposition processes, the reduction of intensity of the peak associated with the stretching of the carbonyl present in both polyesters and also a dramatic decrease in molecular weights. In parallel, the acceleration of the biodegradation process with vermicomposting was investigated, with very promising results, including the total disintegration of the samples when submitted to a previous treatment of sun light exposure.
Baldez, Thays Silva. "Estudo estrutural, térmico e vibracional do crista de Bis (L-alaninato) de Níquel (II) di-hidratado." Universidade Federal do Maranhão, 2016. http://tedebc.ufma.br:8080/jspui/handle/tede/1344.
Full textMade available in DSpace on 2017-05-05T20:04:11Z (GMT). No. of bitstreams: 1 ThaysSilvaBaldez.pdf: 2095828 bytes, checksum: 9de3dacfb0850842d669bc07ee7407eb (MD5) Previous issue date: 2016-07-06
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Amino acids complex of transition metals has increasingly attracted the interest of researchers due to their wide range of physical properties for understanding metal-amino acid interactions. In this work [Bis(L-Alaninato)Diaqua] Nickel(II) Dihydrate [Ni(C3H6O2N)2(H2O)2.2H2O] crystals were obtained by slow evaporation method using 0,1 mol/L of NiCl2.6H2O, 0,2 mol/L of L-alanine and NaOH. Rietveld refinement of X-ray data confirmed the structure. The structural properties of these crystals were studied by X-ray diffraction (XRD) in the temperature range from 25 to 150 °C. Thermal analysis experiments were performed by TG/DTA between 25 and 500 °C, and by DSC between 25 and 250 °C. The results obtained by TG/DTA indicate the loss of water molecules by [Bis(L-Alaninato)Diaqua] Nickel(II) Dihydrate crystals at temperatures of 64 and 117 °C, which was also confirmed by the results obtained by DSC. The X-ray diffraction pattern show new peaks, in temperatures around 55 and 110 ° C, indicating to loss of water by crystals. The transformation is irreversible because the diffraction pattern obtained after the sample return to the room temperature differs from that obtained before heating of the sample. The vibrational properties were analyzed by Raman spectroscopy between 25 and 185 °C. The Raman spectroscopy measurements as a function of the temperature show the loss of water molecules. The spectra at high temperatures resemble the spectrum at room temperature, showing that the crystal undergoes phase transformation, but probably do not change the crystal symmetry.
Aminoácidos complexados com metais de transição têm atraído cada vez mais o interesse de pesquisadores devido à grande variedade de propriedades físicas que eles apresentam para o entendimento das interações metal-aminoácido. Neste trabalho, cristais de Bis(L-alaninato) de Níquel (II) di-hidratado [Ni(C3H6O2N)2(H2O)2.2H2O] foram obtidos por meio da evaporação lenta do solvente de uma solução saturada contendo 0,1 mol/L de NiCl2.6H2O, 0,2 mol/L de L-alanina e NaOH. Após a obtenção da amostra, a confirmação da estrutura deu-se por refinamento de Rietveld. As propriedades estruturais desses cristais foram estudadas por medidas de difração de raios-X em função da temperatura na faixa de 25 a 150 °C. Experimentos de análise térmica foram realizados por TG/DTA entre 25 e 500 °C e por DSC entre 25 e 250 °C. Os resultados obtidos por TG/DTA evidenciam a saída das moléculas de água do cristal de Bis(L-alaninato) de Níquel (II) di-hidratado nas temperaturas de 64,51 e 117,25 °C, que também foi confirmada pelos resultados obtidos por DSC. O padrão de difração de raios-X mostrou desaparecimento e o surgimento de novos picos no difratograma, para temperaturas próximas a 55 °C e 110 °C, indicando a saída de água do cristal. Essa transformação é irreversível, pois o padrão de difração obtido após a amostra retornar à temperatura ambiente difere significativamente daquele obtido antes do aquecimento. As propriedades vibracionais foram analisadas por Espectroscopia Raman entre 25 e 185 °C. As medidas dos espectros Raman em função da temperatura evidenciam a saída das moléculas de água. O espectro à alta temperatura se assemelha ao espectro à temperatura ambiente, mostrando que o cristal sofre transformação de fase, mas provavelmente permanece com a mesma simetria cristalina.
Hubert, Sébastien. "Transitions de phases solides induites par un procédé de compression directe : application à la caféine et à la carbamazépine." Phd thesis, Université Claude Bernard - Lyon I, 2012. http://tel.archives-ouvertes.fr/tel-00903563.
Full textPereira, Adriano Bezerra. "Caracterização estrutural e térmica de cristais de L-Arginina•HClxHBr1-x." Universidade Federal do Maranhão, 2016. http://tedebc.ufma.br:8080/jspui/handle/tede/1341.
Full textMade available in DSpace on 2017-05-05T19:27:14Z (GMT). No. of bitstreams: 1 AdrianoPereira.pdf: 4552452 bytes, checksum: c5dc1a24e3fc6e843a7a494ecc39cb39 (MD5) Previous issue date: 2016-07-29
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ)
Fundação de Amparo à Pesquisa e ao Desenvolvimento Científico e Tecnológico do Maranhão (FAPEMA)
Materials consisting of amino acids are of great interest in the application in nonlinear optical (NLO) and are being studied more carefully because they have properties better than the potassium dihydrogen phosphate (KDP), the material most commonly used for Second Generation Harmonic (SHG). In this work, the crystals of L-arginine hydrobromidric monohydrate (LAHBr) and L-arginine hydrochloridric monohydrate (LAHCl) were grown at room temperature (25° C) by the method of slow evaporation of solvent. Were also synthesized hydrochlorobromidric L-arginine monohydrate crystals (LAHClBr) from the mixture of the compounds in equimolar proportions 1:3, 1:1 and 3:1. These five crystals were characterized by the techniques of X-Ray Fluorescence (XRF), Diffraction X-Ray (XRD), Raman Spectroscopy, Thermogravimetry (TG), Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC). The chemical composition of the single crystal was analyzed by X-ray Fluorescence (XRF) and compositions obtained were: C6H14N4O2•HCL0.14BR0.86•H2O (LAHCl0,14Br0,86), C6H14N4 O2•HCL0.42BR0.58•H2O (LAHCl0,42Br0,58), e C6H14N4O2•HCL0.63BR0.37•H2O (LAHCl0,63Br0,37). The structural parameters of the crystals were characterized by X-ray diffraction (XRD) in association with the Rietveld refinement. The all samples crystallize with the monoclinic structure (space group P21) and the unit cell volume of LAHClxBr1-x series decreases with increasing concentration of chlorine in the composition of the samples. The vibrational modes were observed by Raman Spectroscopy. The Raman spectrum experiments have shown that bands associated with lattice modes undergo blue shifts as the concentration of chorine ion is increased in addition to complement the results obtained by XRD technique. The thermal analysis of TG, DTA and DSC showed that the crystals analyzed show a decrease in temperature of the characteristic exothermic phase transition event, as well as increasing in the melting temperature of the material, with increasing chlorine concentration. The crystals LAHBr, LAHClBr and LAHCl to lose water of hydration suffer phase transformation goes to anhydrous phase without change in structure (monoclinic-monoclinic) and present structural phase transition around 150 oC.
Materiais constituídos por aminoácidos são de grande interesse na aplicação em óptica nãolinear (NLO) e estão sendo estudados com maior atenção por apresentarem propriedades melhores do que o material mais utilizado para Geração de Segundo Harmônico (SHG); dihidrogenofosfato de potássio (KDP). Neste trabalho os monocristais de L-arginina hidrobromídrica monohidratada (LAHBr) e L-arginina hidroclorídrica monohidratada (LAHCl) foram crescidos à temperatura ambiente (25°C), pelo método de evaporação lenta do solvente. Também foram sintetizados cristais de L-arginina hidroclorobromídrica monohidratada (LAHClBr), a partir da mistura dos dois compostos, nas proporções molares 1:3, 1:1 e 3:1. Esses cinco cristais foram caracterizados pelas técnicas de Fluorescência de raios-X (FRX), Difração de raios-X (DRX), Espectroscopia Raman, Termogravimetria (TG), Análise Diferencial Térmica (DTA) e Calorimetria Exploratória Diferencial (DSC). A composição química dos monocristais foi analisada por FRX e as composições são: C6H14N4O2•HCL0.14BR0.86•H2O (LAHCl0,14Br0,86), C6H14N4O2•HCL0.42BR0.58•H2O (LAHCl0,42Br0,58), e H14N4O2•HCL0.63BR0.37•H2O (LAHCl0,63Br0,37), para as amostras de LAHClBr 1:3, LAHClBr 1:1 e LAHClBr 3:1, respectivamente. Os parâmetros estruturais dos cristais foram caracterizados por DRX em associação com o refinamento de Rietveld, onde observamos que todas as amostras se cristalizam com a estrutura monoclínica (grupo espacial P21) e que o volume da célula unitária da série LAHClxBr1-x diminue com o aumento da concentração de Cloro na composição das amostras. Os modos vibracionais foram observados por Espectroscopia Raman. Os espectros Raman mostraram que as bandas associadas aos modos de rede sofreram blue shifts com o aumento da concentração de Cl, além de complementar os resultados obtidos pela técnica de DRX. As análises térmicas de TG, DTA e DSC mostraram que os cristais analisados apresentaram uma diminuição de temperatura do evento exotérmico característico de transição de fase com o aumento da concentração de Cl, bem como, aumento da temperatura em que ocorre a fusão do material. Os cristais de LAHBr, LAHClBr e LAHCl ao perderem água de hidratação sofrem transformação de fase indo para a fase anidra sem mudança na estrutura cristalina monoclínicamonoclínica) e apresentam uma transição de fase estrutural em torno de 150 oC.
Delchini, Sylvain. "Etude tectono-thermique d'un segment orogénique varisque à histoire géologique complexe : analyse structurale, géochronologique et thermique du massif des Jebilet, de l'extension à la compression." Thesis, Orléans, 2018. http://www.theses.fr/2018ORLE2003/document.
Full textThis thesis presents the reconstruction of the tectono-thermal history of the Paleozoic Jebilet massif (Morocco), from its pre-orogenic evolution at the Upper Devonian-Lower Carboniferous to its structuration during the variscan-alleghanian orogeny at the Upper Carboniferous-Lower Permian. To address this issue, this work is organized around two approaches: (1) one metrological applied to the Raman Spectroscopy of Carbonaceous Matterial (RSCM) and (2) the other integrating a structural and geochronological study and a thermicity analysis.The metrological approach allowed to validate the applicability of the RSCM geothermometer (1) in a context of polyphase metamorphism, (2) for carbonate rocks and skarns of Jebilet and (3) to propose a new parameter Raman RSA allowing to better specify temperatures above 500°C and extend the applicability of the method to maximum temperatures of up to 700°C.From the integrated approach, three tectono-thermal episodes were highlighted. The first episode D₀, corresponds to an extensive tectonic allowing the opening of the Jebilet basin at the Upper Devonian-Lower Carboniferous. This opening is accompanied by a HT thermal anomaly as shown by the important bimodal and granodioritic magmatic activity dated between 358 ± 7 Ma and 336 ± 4 Ma and the TRSCM higher than 500°C recorded by the rocks. During Upper Carboniferous, the compressive phase structuring the Jebilet massif begins with the emplacement of superficial nappes (D₁), followed by the variscan major phase (D2). Structural analysis showed a gradual evolution of D₂ deformation regime from coaxial compression to dextral transpression consistent with WNW-ESE to NW-SE horizontal shortening. D₂ is associated with two thermal events, the first is syn-tectonic with TRSCM between 300 and 400°C, and the second is syn- to post-tectonic with TRSCM between 600 and 660°C.This tectono-thermal context would be the expression of geodynamic processes involving from the Upper Devonian a delamination of the Rheic lithosphere by "slab break-off" or "slab roll-back" which would induce (1) the rise of hot asthenospheric current, and (2) the clockwise rotation of Gondwana and its gradual amalgamation with Laurussia structuring the variscan-alleghanian belt during the Upper Carboniferous-Lower Permian
Fall, Andras. "Application of fluid inclusions in geological thermometry." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/30265.
Full textPh. D.
Carvalho, Elaine Aparecida. "Estudo das propriedades térmicas e ópticas de materiais nanoestruturados." Universidade Federal de Juiz de Fora (UFJF), 2013. https://repositorio.ufjf.br/jspui/handle/ufjf/4891.
Full textApproved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-06-26T18:10:31Z (GMT) No. of bitstreams: 1 elaineaparecidacarvalho.pdf: 7755814 bytes, checksum: b31278b6963ad259e85e174cf59c5391 (MD5)
Made available in DSpace on 2017-06-26T18:10:31Z (GMT). No. of bitstreams: 1 elaineaparecidacarvalho.pdf: 7755814 bytes, checksum: b31278b6963ad259e85e174cf59c5391 (MD5) Previous issue date: 2013-03-18
CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Neste trabalho, três diferentes materiais (vidros, filmes finos e nanofluidos) foram analisados com o objetivo de verificar mudanças nas propriedades térmicas e ópticas devido a presença de nanopartículas de metais nobres. Nos vidros e filmes, o crescimento de nanopartículas foi induzido através do tratamento térmico das amostras enquanto que nos nanofluidos, a nucleação das nanopartículas foi obtida através de um procedimento químico de uma única etapa. A formação das nanopartículas metálicas nestes materiais foi confirmada pelas imagens de microscopia eletrônica e pelo pico de plasmon superficial presente nos espectros de absorção. Espectros Raman foram obtidos com a finalidade de verificar se ocorreu alguma mudança estrutural. Medidas de lente térmica foram realizadas em todas as amostras, fornecendo os valores da difusividade térmica. As matrizes vítreas estudadas foram germanato (Ge02 - PbO) e telurito (Te02 - PbO-Ge02), dopadas com nanopartículas de prata e com os íons terras raras Érbio, Ytérbio e Túlio na forma trivalente. Foi verificado que ocorreu um aumento de 20 % e 8 % na difusividade térmica dos vidros germanatos e teluritos, respectivamente, devido a adição de nanopartículas de prata e que o tratamento térmico provocou a quebra de anéis de tetraedros formados nos vidros germanato. Os filmes finos contendo nanopartículas de ouro e prata foram crescidos em um substrato através da técnica de co-sputtering utilizando a matriz vítrea de germanato (Ge02 - PbO) como alvo. Os resultados indicam a formação de estruturas diferentes daquelas detectadas no vidro, além de apresentar mudanças no comportamento térmico em relação a matriz vítrea. Nos nanofluidos de ouro e prata foram observados um aumento de 20% e 16%, respectivamente, na difusividade térmica em relação a difusividade térmica água pura.
In this work, three different materials (glasses, thin films and nanofluids) were analysed to check the changes in their thermal and optical properties due to the presence of noble metal nanoparticles. In the glasses and films, the nucleation of nanoparticles was induced by thermal treatment of the samples while in the nanofluids the nanoparticles were obtained through one-step chemical reaction. The presence of metallic nanoparticles was confirmed by electron microscopy images and by surface plasmon peaks detected via absorption technique in the ultraviolet and visible region of the electromagnetic spectrum. In addition, Raman spectra were obtained to check structural changes. Thermal lens measurements were performed in all samples to obtain the respective thermal diffusivity. Studied vitreous system were germanate (Ge02 - PbO) and tellurite (Te02 - PbO-Ge02) doped with silver nanoparticles, rare earth ions, erbium, thulium and ytterbium in the trivalent form. It was found an increase of 20% and 8% in the thermal diffusivity of germanate and tellurite glasses, respectively, due to the addition of silver nanoparticles. It also verified that the thermal treatment has caused the break of Ge04 tetrahedra rings. Thin films containing gold and silver nanoparticles were grown by the co-sputtering technique using the germanate vitreous matriz (Ge02 - PbO) as target. Raman results show structural differences between thin films and the corresponding glasses. This was reflected in a different thermal behavior. In gold and silver nanofluids were observed an increase of 20% and 16% in the thermal diffusivity in comparison with the thermal diffusivity of pure water, respectively.
Simões, Rebeca Delatore. "Estudo das propriedades físicas de blendas de PVDF/Látex visando aplicação como biomaterial /." Presidente Prudente, 2005. http://hdl.handle.net/11449/88469.
Full textBanca: Neri Alves
Banca: Osvaldo Novais de Oliveira Júnior
O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp
Resumo: O principal objetivo deste trabalho de mestrado foi a obtenção e caracterização estrutural de um material com propriedades físico-químicas compatíveis com aquelas requeridas por um biomaterial. Filmes contendo diferentes volumes de látex de borracha natural em uma massa fixa de poli(fluoreto de vinilideno) (PVDF), na forma de pó foram fabricados por compressão/aquecimento de uma mistura de ambos os materiais sem o uso de qualquer solvente. Este é um fator importante considerando o uso destes filmes no futuro próximo como biomateriais em diferentes aplicações (indução do crescimento do tecido ósseo, por exemplo), uma vez que os solventes convencionais usados para dissolver o PVDF têm se mostrado tóxicos ao organismo humano. Os filmes foram submetidos a um tratamento via descarga corona de forma que amostras com e sem tal tratamento foram caracterizadas através das técnicas de espectroscopia vibracional via espalhamento Raman e absorção no infravermelho (FTIR), análise térmica via termogravimetria (TG), calorimetria exploratória diferencial (DSC) e análise dinâmico-mecânica (DMA) e microscopias ótica e eletrônica (MEV). As medidas termomecânicas mostraram que os filmes obtidos possuem características mecânicas similares àquelas encontradas no osso humano e boa estabilidade térmica considerando-se a aplicação desejada. As medidas via espectroscopia vibracional indicaram que o PVDF e o látex não interagem quimicamente, compondo uma blenda polimérica. Além disto, os resultados obtidos via micro-Raman mostraram que o aumento da quantidade de látex na blenda permite uma melhor dispersão deste látex na matriz de PVDF quando da produção dos filmes... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The main goal of this work was to obtain and characterize structurally a material with physical-chemical properties compatible with those required for a biomaterial. Films containing different volumes of latex of natural rubber in a fixed mass of poly (vinylidene fluoride) (PVDF) powder were fabricated by compressing/annealing a mixture of both materials without using any solvent. This is an important issue having in mind to use these films in the future as biomaterials in different applications (growing of the bone tissue, for instance) once the solvents used to dissolve the PVDF are toxic to human being. The films were submitted to a corona discharge treatment in a way that samples with and without such treatment were characterized using micro-Raman scattering and Fourier transform infrared absorption (FTIR) spectroscopies, thermo-mechanical techniques using thermogravimetry (TG), differential scanning calorimetry (DSC) and dynamical-mechanical analysis (DMA) and optical and scanning electron microscopies (SEM). The thermo-mechanical measurements revealed that the films present mechanical properties close to that found for the human bone and high thermal stability considering the desired applications. The vibrational spectroscopies showed that the latex and PVDF do not interact chemically leading to the formation of a polymeric blend. Besides, the results recorded using the micro-Raman technique revealed that the higher the amount of latex in the blend, the better the miscibility between both materials. In terms of morphology, the blend surface is formed by two domains: one is rougher and contains the latex well dispersed into the PVDF matrix while the other is smoother and contains both materials as well but in a less homogeneous dispersion. However, as the volume of latex is increased from 0.3 to 1.0 mL, the smoother domains become rarer to be found... (Complete abstract, click electronic address below)
Mestre
Возний, Андрій Андрійович, Андрей Андреевич Возный, Andrii Andriiovych Voznyi, Володимир Володимирович Косяк, Владимир Владимирович Косяк, Volodymyr Volodymyrovych Kosiak, Олександр Олександрович Подопригора, et al. "Термічно-індукований фазовий перехід у плівках SnxSy." Thesis, Інститут фізики напівпровідників імені В.Є. Лашкарьова, 2017. http://essuir.sumdu.edu.ua/handle/123456789/65520.
Full textHerraiz, Michael. "Graphène et fluorographène par exfoliation de graphite fluoré : applications électrochimiques et propriétés de surface." Thesis, Université Clermont Auvergne (2017-2020), 2018. http://www.theses.fr/2018CLFAC094/document.
Full textIts electronic conductivity or its optical transparency are unequaled physicochemicalproperties of graphene which explain the increased number of exfoliation methods based ongraphitic precursors to obtain this material. To overcome the use of a graphite/graphene oxidecharacterized by a poorly controlled surface chemistry, graphite fluorides, with variablecrystallinity and also fluorine concentration, were prepared by fluorination of graphite under puremolecular fluorine atmosphere after optimization of the process parameters. The obtainedprecursors, whether by dynamic or static fluorination, were characterized : X-Ray diffraction, FTIRand Raman spectroscopies for the structure, and their texture probed by Scanning andTransmission Electron Microscopy. After that, three methods of exfoliation were developed, basedon different mechanisms: i) a thermal shock, already known but decomposition mechanisms wererefined in this study, ii) an exfoliation within liquid medium by pulsed electrochemical treatment,using for the first time a fluorinated graphite for the synthesis of few-layered fluorinated grapheneand finally iii) an unconventional method, based on the interaction between femtosecond laser andhighly fluorinated graphite to induce mechanisms like controlled reduction, and especially for thisstudy exfoliation of the matrix. These methods have permit to highlight the interest of fluorine inthe current race for the synthesis of graphene, and have shown the production of graphenematerials, having an interesting fluorinated residual functionalization for some applications
Khalifa, Muftah. "Parameters Controlling Distribution of Diagenetic Alterations within Fluvial and Shallow Marine Sandstone Reservoirs : Evidence from the Libyan Basins." Doctoral thesis, Uppsala universitet, Mineralogi, petrologi och tektonik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-284581.
Full textErrata: Felaktigt disputationsdatum på spikbladet.
CRUZ, Nayara da Silva. "Síntese e caracterização do cristal de B-Alaninato de Níquel (II)." Universidade Federal do Maranhão, 2017. https://tedebc.ufma.br/jspui/handle/tede/tede/1938.
Full textMade available in DSpace on 2017-09-21T17:25:16Z (GMT). No. of bitstreams: 1 NayaraCruz.pdf: 2821867 bytes, checksum: 4cc762016119d71d331457a53080cac3 (MD5) Previous issue date: 2017-07-14
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The crystals based in Amino acid have been studied recently, mainly due to their useful properties for electronic, non-linear optical and magnetic applications. One of most used amino acids are β-alanine, whose complexes with nickel were studied in the 1990s. However, there are no studies on the thermal and structural stability of this material. In order to better investigate β-alanine complexes with metal ions, this work presents the structural and thermal study of nickel (II) β-alaninate crystal. The crystals were grown by slow evaporation of the solvent. The crystals grew after a period of 30 days. The techniques used for the characterization of the sample were: X-Ray Diffraction (XRD) along with the refinement by the Rietveld method, Raman spectroscopy at room temperature and with temperature variation, Fourier Transform Infrared Spectroscopy (FTIR) and Thermal Analysis By Differential Exploratory Calorimetry (DSC). The XRD data showed that the crystals grown were the desired ones, presenting the same triclinic structure and spatial group P1. The DSC results showed events corresponding to water loss followed by phase transformation and subsequent melting at approximately 138 ° C. The results obtained by Raman Spectroscopy at room temperature and with temperature variation showed 32 spectral bands for the crystal, of which 5 are referring to the network modes or external modes. Raman spectroscopy confirmed the observed phase transformation on the DSC curve due to the loss of the water molecule. As the temperature increases, the bands shift to the number of smaller waves. For the results obtained at temperatures above 137 ° C the appearance of spectral bands was not observed, indicating that the crystal was melted as observed in the DSC curve. The results of X-ray diffraction as a function of temperature showed that, as the temperature increases, the peaks shift to smaller angles and that the process is non-reversible, characteristic of a phase transformation. For the FITR data we have that most bands have a high spectral absorption showing a total of 26 bands. The present result shows that the crystal is thermally stable up to 110 ° C and can be used for application below this temperature.
Cristais à base de aminoácidos têm sido estudados recentemente, principalmente devido à suas propriedades úteis para aplicações eletrônicas, óptica não linear e magnéticas. Dentre os aminoácidos mais utilizados há a β-alanina, cujos complexos com níquel foram estudados na década de noventa. Contudo, não há estudos da estabilidade térmica e estrutural desse material. No intuito de investigar melhor complexos de β-alanina com íons metálicos, este trabalho apresenta o estudo estrutural e térmico do cristal de β- alaninato de níquel (II). Os cristais foram crescidos por meio do método de evaporação lenta do solvente. Os cristais cresceram após um período de 30 dias. As técnicas utilizadas para a caracterização da amostra foram: Difração de Raios X (DRX) juntamente com o refinamento pelo método de Rietveld, Espectroscopia Raman em temperatura ambiente e com variação de temperatura, Espectroscopia no Infravermelho com Transformada de Fourier (FTIR) e Análise Térmica pela técnica de Calorimetria Exploratória Diferencial (DSC). Os dados de DRX comprovaram que os cristais crescidos eram os desejados, apresentando a mesma estrutura triclínica e grupo espacial P1. Os resultados de DSC mostraram eventos que correspondem à perda de água seguida da transformação de fase e posterior fusão em aproximadamente 138°C. Os resultados obtidos por Espectroscopia Raman à temperatura ambiente e com variação de temperatura apresentaram 32 bandas espectrais para o cristal, das quais cinco são referentes aos modos de rede ou modos externos. A espectroscopia Raman confirmou a transformação de fase observada na curva de DSC, devido à perda da molécula de agua. À medida que a temperatura aumenta, ocorreu o deslocamento das bandas para número de ondas menores. Para os resultados obtidos em temperaturas superiores a 137°C não se observou o aparecimento de bandas espectrais, indicando que o cristal sofreu fusão conforme observado na curva de DSC. Os resultados de Difração de Raios X em função da temperatura mostraram que, à medida que ocorre o aumento da temperatura ocorre o deslocamento dos picos para ângulos menores e que o processo é não reversível, característica de uma transformação de fase. Para os dados de FITR, a maioria das bandas apresentam uma alta absorção espectral mostrando um total de 26 bandas. O presente resultado mostra que o cristal é termicamente estável até 110°C podendo ser utilizado para aplicação abaixo dessa temperatura.
Massoud, Mouhannad. "Experimental characterization of heat transfer in nanostructured silicon-based materials." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI063/document.
Full textThis PhD thesis deals with the experimental characterization of heat transfer at the nanoscale in materials compatible with microelectronic processes. Two characterization techniques are applied to two different systems, irradiated mesoporous silicon and suspended silicon membranes. The first characterization technique is micro-Raman thermometry. The laser power heats up the exposed sample. The determination of the thermal conductivity requires the modeling of the heat source using finite element simulations. The modeling of the heat source relies on different parameters that should be carefully determined. The second characterization technique is Scanning Thermal Microscopy (SThM), an Atomic Force Microscopy (AFM)-based technique. Operated in its active mode, the AFM probe is replaced by a resistive Wollaston probe that is heated by Joule heating. Used in AFM contact mode, this technique allows a local thermal excitation of the studied material. The determination of the thermal conductivity requires the analysis of the thermal response of the probe using calibration samples and modeling when dealing with complicated geometries. The effect of the tip position on heat transfer between the tip and the sample is studied. A new method decoupling the heat transfer between the tip and the sample, at the contact and through air, is proposed for determining the thermal conductivity of complicated geometries. The results obtained from the two techniques on irradiated mesoporous silicon samples using heavy ions in the electronic regime are in good agreement. They show a degradation of the thermal conductivity of mesoporous silicon due to the increase in the amorphous phase while increasing the ion fluence. The results obtained on suspended silicon membrane strips show a decrease in the thermal conductivity of more than 50 % in comparison to bulk silicon. When perforated into a phononic structure of sub-100 nm period, the membrane thermal conductivity is about one order of magnitude lower than the bulk. A chapter introducing a promising silicon-based material for the evidence of phonon coherence concludes the manuscript
Lišková, Zuzana. "Aplikace SPM při studiu a modifikaci ultratenkých vrstev Pt, Co a graphenu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228669.
Full textAli, Muhammad. "RAMAN CHARACTERIZATION OF STRUCTURAL PROPERTIES OF THERMALLY MODIFIED NANOGRAPHITE." Thesis, Umeå universitet, Institutionen för fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-108425.
Full textIbrahim, Mohamed Asim Yousif. "Co-processing of drugs and co-crystal formers and its effect on pharmaceutical dosage-form performance : co-crystallization of urea/2-methoxybenzamide, caffeine/malonic acid, caffeine/oxalic acid and theophylline/malonic acid systems : solid-state characterization including imaging, thermal, X-ray and Raman spectroscopic techniques with subsequent evaluation of tableting behaviour." Thesis, University of Bradford, 2008. http://hdl.handle.net/10454/12760.
Full text