Dissertations / Theses on the topic 'Cementite'
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Nikolussi, Marc. "Cementite in the Fe-N-C system." [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-38396.
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Evteev, Alexander V., Elena V. Levchenko, Irina V. Belova, and Graeme E. Murch. "Molecular dynamics study of carbon diffusion in cementite." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-193325.
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Evteev, Alexander V., Elena V. Levchenko, Irina V. Belova, and Graeme E. Murch. "Molecular dynamics study of carbon diffusion in cementite." Diffusion fundamentals 6 (2007) 15, S. 1-2, 2007. https://ul.qucosa.de/id/qucosa%3A14189.
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Akbay, Taner. "Laser induced reaustenitisation from ferrite/cementite aggregates in steels." Thesis, Imperial College London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410825.
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Farooque, Muhammad. "The study of proeutectoid Widmanstatten cementite in hypereutectoid steels." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314904.
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Kinap, Paulo Eduardo Barros. "Tratamentos térmicos para obtenção de cementita esferoidizada em ferro fundido nodular." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-11072017-145654/.
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O objetivo do presente trabalho, consistiu na obtenção de ferro fundidos nodulares, a serem utilizados na fabricação de eixos, com as seguintes características mecânicas após os tratamentos térmicos adequados: limites de resistência à tração e escoamento mínimos de 700 N/mm2 e 450 N/mm2 respectivamente, alongamento mínimo de 5% e dureza entre 235 à 285 HB. A microestrutura mais adequada à obtenção das características mecânicas desejadas deveria consistir de cementita esferoidizada numa matriz ferrítica, a ser obtida com o tratamento de recozimento ou revenimento de microestruturas previamente perlíticas ou martensíticas, respectivamente. No caso do tratamento de recozimento, as estruturas iniciais consistiram de perlita grossa mais ferrita, presentes no material no estado bruto de fusão, ou, de perlita fina mais ferrita, do material normalizado. Todos os tratamentos térmicos utilizados, dependendo do tempo de tratamento, permitiram a obtenção de cementita esferoidizada. O material normalizado e recozido durante 2 horas a 700ºC, possibilitou a obtenção das propriedades mecânicas desejadas: limites de resistência à tração e de escoamento de 827 N/mm2 e 547 N/mm2 respectivamente, alongamento de 7% e dureza de 277 HB, valores estes, dentro dos limites desejados no presente trabalho. No caso do material temperado e revenido a 700ºC durante 0,5 hora, obteve-se limites de escoamento de 542 N/mm2, alongamento de 6% e dureza de 246 HB. O tratamento de recozimento realizado durante 48 horas, produziu microestrutura quase totalmente ferrítica, com pequenas áreas de agregados de carbonetos. O restante do carbono migrou para os nódulos de grafita secundária ao redor dos mesmos.The purpose of the present work, consisted in obtaining ductile casting iron, that will be used in the shaft production, with de following mechanical properties after the appropriated heat treatments: ultimate tensile strength and yield strength values of 700 N/mm2 and 450 N/mm2 minimum respectively, elongation of 5% minimum and hardness value from 235 to 285 HB. The microstructure more adequated to obtaining the desired mechanical characteristics should consist of spheroidized cementite in a ferritic matrix, to be obtained with the annealing or tempering treatments of microstructures previously pearlitic or martensitic respectively. In the case of the annealing treatment, the initial structures consisted of thick pearlite plus ferrite, wich were in the material in the ascast state, or fine pearlite plus ferrite, of the normalized material. All the used heat treatment, depending on the time of treatment, allowed the obtainment of spheroidized cementite. The material normalized and annealed for 2 hours at 700°C made possible the obtaining of the desired mechanical properties: ultimate tensile strength and yield strength value of 827 N/mm2 and 547 N/mm2 respectively, elongation of 7% and hardness values of 277 HB, values these, in acordance with the aims initially proposed in the present work. In the case of the material quenched and tempered at 700°C for 0,5 hour, it was obtained yield strength values of 542 N/mm2, elongation of 6% and hardness value of 246 HB. The annealing treatment made during 48 hours, produced a microstructure almost totally ferritic, with small areas of aggregated carbides. The remaining of the carbon migrated to the graphite nodules producing secondary graphite around them.
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Nikolussi, Marc [Verfasser]. "Cementite in the Fe-N-C system / vorgelegt von Marc Nikolussi." Stuttgart : Max-Planck-Inst. für Metallforschung, 2008. http://d-nb.info/995395667/34.
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Cowley, S. A. "Aspects of the bainite and proeutectoid cementite transformations in alloy steels." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375221.
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Ibitoye, SA, AA Adeleke, AO Tiamiyu, APL Popoola, and AA Afonja. "Response of cold briquetted IRon (CBI) to high temperatures treatment." Journal of Mining and Metallurgy, 2010. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000467.
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This investigation was carried out to assess the behaviours of Cold Briquetted Iron (CBI) when exposed to increasing temperature changes up to its complete melting. High-temperature behaviours
and melting characteristics of CBI were studied. Ground as-received CBI briquette and those heated to temperatures ranging from 500°C to 1000°C were sieved to maximum of 30 microns diameter size and their room-temperature x-ray diffraction (XRD) measured. CBI was found to contain among others, α-iron, cementite and silica phases. Cementite was found to commence decomposition at 500°C - 600°C and completed by 700°C with conspicuous increase in the concentration of α-iron phase. Only α-iron and silica phases were sustained in CBI at temperatures above 700°C. In an inert
atmosphere, it was discovered that CBI melted over a temperature range of 1527.3°C to 1536.96°C accompanied by an irrecoverable weight loss of 9.6 wt.% of the starting material. It was concluded
that melting CBI would require charging along it appropriate fluxes to take care of the unreduced iron oxide and incorporation into facility for melting CBI an effective deslagging mechanism to
remove unavoidable possible voluminous slag that would be formed.
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Longbottom, Raymond James Materials Science & Engineering Faculty of Science UNSW. "The formation of cementite from hematite and titanomagnetite iron ore and its stability." Awarded by:University of New South Wales. Materials Science and Engineering, 2005. http://handle.unsw.edu.au/1959.4/22023.
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This project examined the reduction and formation of cementite from hematite and titanomagnetite ores and cementite stability. The aim of the project was to develop further understanding of cementite stability under conditions relevant to direct ironmaking and the mechanism of cementite decomposition. The reduction of hematite and ironsand by hydrogen-methane-argon gas mixtures was investigated from 600??C to 1100??C. Iron oxides were reduced by hydrogen to metallic iron, which was carburised by methane to form cementite. The hematite ore was reduced more quickly than the ironsand. Preoxidation of the ironsand accelerated its reduction. Hematite was converted to cementite faster than preoxidised ironsand. The decomposition of cementite formed from hematite was investigated from 500??C to 900??C. This cementite was most stable at temperatures 750-770??C. The decomposition rate increased with decreasing temperature between 750??C and 600??C and with increasing temperature above 770??C. The stability of cementite formed from pre-oxidised titanomagnetite was studied from 300??C to 1100??C. This cementite was most stable in the temperature range 700-900??C. The rate of decomposition of cementite increased with decreasing temperature between 700??C and 400??C and with increasing temperature above 900??C. Cementite formed from ironsand was more stable than cementite formed from hematite
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Kazemi, Mania. "Fundamental Studies Related to Gaseous Reduction of Iron Oxide." Doctoral thesis, KTH, Materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-191021.
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The demands for increasing the efficiency and lowering the environmental effects in iron and steelmaking industries have given rise to interests in application of direct reduction (DR) processes for production of iron by different gases. These advancements require comprehensive models for better control of the process conditions and the product properties. In the present thesis fundamental aspects in reduction of iron oxide were investigated. The experimental studies on reduction of iron oxide pellets were performed under well-controlled conditions in a setup designed for thermogravimetric investigations. The results indicated that the reaction rates by the applied procedure are higher compared to the procedure similar to conventional thermogravimetric analysis (TGA). This difference was caused by the time required for replacing the inert gas by the reaction gases. Reduction by H2-CO mixtures was accompanied by deposition of carbon and formation of cementite. The variations of cementite contents in the industrial iron ore pellets reduced isothermally for different durations, showed that cementite formation starts from the initial stages of reduction. The experimental conditions such as reaction temperature, carbon activity in the reaction gas and reaction time have a large impact on carbide content of the reduced samples. The kinetics of reduction of iron ore powder by H2 and CO gas mixtures with different compositions were studied using a commercial TGA setup. The results showed that the apparent rates of reaction vary linearly with the H2 and CO contents of the gas. Larger amount of H2 resulted in higher reaction rates. The data were employed in the developed reduction model for pellets. The model was based on the mechanism observed in the commercial iron ore pellets reduced by pure hydrogen. The microstructure of reacted pellets showed that reduction of the examined industrial samples is controlled by both chemical reaction and gaseous diffusion. The reduction model was developed by combining computations for the flow and mass transfer in the gas phase, diffusion of gases in the solid phase and chemical reaction at the reaction sites. The modelling and experimental results were in reasonably good agreement. The present model provides a good foundation for a dynamic multi-particle process model. The results highlighted the importance of considering the reduction mechanisms in different types of pellets prior to modelling. Experiments were undertaken to investigate the selective reduction of iron oxide in zinc ferrite. It was observed that gaseous reduction by hydrogen at temperatures up to 873 K is a potential method for reduction of iron oxide to metallic iron, while the zinc oxide remains in the product and losses of metallic zinc are negligible. Using this primary step in the hydrometallurgical processing of EAFD can overcome the difficulties for leaching of zinc ferrite.QC 20160823
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Chen, Chieh-Wen. "The Structural Evolution during Low Temperature Carburization of 17-7 Precipitation Hardened Stainless Steel." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1320086759.
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Dias, Joachim Octave Valentin. "The first high-strength bainitic steel designed for hydrogen embrittlement resistance." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/273831.
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The phenomenon of hydrogen embrittlement in steel has been known for over 150 years. Hydrogen-resistant alloys have been developed to mitigate this effect and three types of alloys with optimised structures have been enhanced over the years: nickel alloys, stainless steels, and quenched and tempered martensitic low alloy steels. Nevertheless, those alloys are limited in terms of strength and ductility. The aim of the work presented in this thesis was to design bainitic alloys with hydrogen embrittlement resistance, and with a better combination of strength and ductility than conventional alloys. In the novel alloys, two microstructural features were produced to mitigate the damaging effects of hydrogen: 1. A percolating austenite structure, in which hydrogen diffusion is orders of magnitude lower than in bainitic ferrite. This feature was introduced to impede the ingress of hydrogen through the structure. 2. Iron carbide traps, which can form at the bainite transformation temperature. This feature was introduced to trap diffusible hydrogen and prevent it from causing damage. The alloys, designed with the aid of computer models and phase transformation theory, contained a volume fraction of retained austenite above its percolation threshold, theorised as 0.1, which was proven to form an effcient barrier to hydrogen ingress. The effective diffusivity of hydrogen, measured using an electrochemical permeation technique, was shown to decrease with increasing austenite fraction up to the percolation threshold. It was seen to plateau for austenite fractions comprised between 0.1 and 0.18, and to decrease further for fractions above 0.18. The compositions of the alloys were precisely selected to allow for iron carbides to precipitate during the bainitic transformation reaction. Until the present work, only alloy carbides V4C3, TiC and NbC had been reported to strongly trap hydrogen. The literature was very inconsistent regarding the trapping ability of cementite, with reported trap binding energies ranging from 11 to 66 kJ mol−1. The carbides produced in the alloys were identified as cementite. The cementite fraction was measured to be 0.001 ± 0.0001 for one of the designed alloys, which is the lowest ever reported carbide fraction in steel measured using a simple X-ray diffraction technique. Experimental thermal desorption spectroscopy data were used to determine the binding energy of hydrogen to cementite to be 37.5 kJ mol−1, suggesting that cementite is not a strong hydrogen trap. Further tests performed after room temperature hydrogen degassing displayed insignifcant amount of trapped hydrogen, thus confrming the reversible nature of cementite traps. The comparison of two successive transients using the electrochemical permeation technique confirmed that result. The influence of the heat treatments on the microstructures and on the mechanical properties of the designed alloys was extensively studied. The novel alloys met all the set requirements, and successfully outperformed conventional alloys in terms of strength and ductility. They did not meet the NACE TM0316-2016 standard requirement for operation in hydrogen-rich environments, likely owing to the inadequate trapping ability of cementite. Future work should focus on exploring the possible use of alternative carbides for hydrogen trapping in bainitic structures.
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Wang, Yunning. "Etude et modélisation de l'effet du revenu sur les évolutions des microstructures, du comportement thermomécanique et des contraintes résiduelles de trempe." Thesis, Vandoeuvre-les-Nancy, INPL, 2006. http://www.theses.fr/2006INPL047N/document.
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La relaxation des contraintes résiduelles de trempe au cours du revenu dépend fortement des évolutions des microstructures et du comportement thermomécanique. Ainsi, la prévision de l’évolution des contraintes résiduelles nécessite le couplage entre les calculs des champs de température, des transformations de phases, des contraintes et des déformations au cours du traitement. Dans ce travail, nous avons développé un modèle métallurgique pour décrire les cinétiques de précipitation au cour du revenu : la germination, la croissance et la coalescence (ou dissolution) du carbure epsilon et de la cémentite. Ce modèle permet de calculer les évolutions de la composition chimique de la matrice, du type, des distributions de taille des précipités lors du revenu de la martensite d’aciers faiblement alliés. Dans une deuxième étape, nous avons développé un modèle thermomécanique permettant de prédire l’évolution de la contrainte d’écoulement de la martensite revenue, basé sur les évolutions des paramètres microstructuraux obtenus par le modèle métallurgique. Le modèle thermomécanique prend en compte les différents mécanismes de durcissement (durcissement par solution solide, durcissement par les précipités et durcissement par dislocations), et l’effet de la température de déformation. Une validation expérimentale de ces modèles a été menée dans le cas de l’acier 80MnCr5 en s’appuyant sur des résultas obtenus par microscopie électronique à transmission et dilatométrie thermomécanique. Les modèles métallurgique et thermomécanique ont finalement été introduits dans le logiciel de calcul par éléments finis ZeBuLoN pour simuler l’évolution des contraintes internes lors de la trempe et du revenu. Une première analyse de la relaxation des contraintes au cours du revenu a été effectuéeThe relaxation of the residual stress during the tempering process is strongly related to the evolutions of the microstructure and thermomechanical properties. Thus, the simulation of the evolution of residual stresses requests the coupling of the temperature field, the phase transformations and the stress and strain evolutions all along the process. In this work, firstly, a metallurgical model has been developed to describe the tempering kinetics: nucleation, growth (or dissolution) and coarsening of the epsilon carbide and the cementite. This model allows to predict the evolutions of the matrix composition, the type, size and distribution of the precipitates during the tempering of martensite for low and middle alloyed steels. Secondly, based on the microstructure parameters calculated by the metallurgical model, a thermomechanical model has been also developed to predict the evolution of the flow stress of tempered martensite. The thermomechanical model not only takes into account the different hardening mechanisms (solution hardening, precipitate hardening and the dislocation hardening), but also the effect of deformation temperature. An experimental validation of the two models has been performed for a 80MnCr5 steel using the results obtained by electron transmission microscopy and thermomechanical dilatometry. Finally, the metallurgical model and the thermomechanical model have been implemented into the finite element calculation software ZeBuLoN to simulate the evolution of internal stress during the quenching and tempering process. A first analysis of the stress relaxation during tempering has been performed
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Vancostenoble, Alix. "Etude des mécanismes de corrosion sous contrainte d'aciers ferrito-perlitiques en milieu aqueux confiné contenant du CO2 dissous." Thesis, Saint-Etienne, EMSE, 2015. http://www.theses.fr/2015EMSE0772.
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L’objectif de ce travail est d’améliorer la compréhension des phénomènes de Corrosion Sous Contrainte (CSC) susceptibles d’être rencontrés sur les fils d’armures des conduites flexibles, faits d’aciers ferrito-perlitiques. Dans l’annulaire des conduites flexibles, l’environnement chimique des aciers est constitué d’une « eau de mer » confinée et saturée en CO2. Celui-ci favorise la formation d’une couche protectrice de sidérite qui semble avoir un effet déterminant sur la vitesse de corrosion de l’acier. Les conditions de service entrainant des fluctuations de l’environnement ou des contraintes appliquées s’ajoutant à des contraintes résiduelles peuvent provoquer la rupture des conditions d’équilibre entre l’acier et son environnement protecteur, et amorcer ainsi la CSC.Les paramètres microstructuraux et mécaniques qui gouvernent l’amorçage et la propagation de fissures par CSC dans les aciers ferrito-perlitiques dans un milieu confiné simulé sont identifiés au moyen d’essais de traction lente menés sous différents potentiels électrochimiques sur des éprouvettes lisses et micro-entaillées. La phase d’amorçage met en jeu des effets de synergie entre la localisation de la plasticité et la dissolution de l’acier. Cependant, des effets de l’hydrogène doivent être pris en compte dans la propagation des fissures. L’hydrogène, au travers d’interactions hydrogène/plasticité, entraine l’avancée des fissures. Il a été également démontré que l’emploi de microstructures particulières peut favoriser ou retarder les effets de l’hydrogène sans pour autant affecter la limite d’élasticité de la même manièreIn confined solutions containing dissolved CO2, ferrito-pearlitic steels can suffer Stress Corrosion Cracking (SCC). We could find such situations in the annulus of flexible pipes. In these conditions, a protective corrosion product, the siderite FeCO3, is formed on the steel surface decreasing the corrosion rate. In service, environment fluctuation (such as pH, potential…) and/or an addition of applied stress can disturb the balance between the steel and this protective film, causing the fracture of the latter and leading to SCC.The objective is to understand the mechanism of SCC in such environments and to identify the parameters controlling the initiation and the propagation of cracks. Slow strain rate tensile tests in confined solution are carried out on smooth and notched specimens to study crack initiation and propagation. Crack initiation is controlled by synergistic effects between localized plasticity and the dissolution processes. However, hydrogen effects must be considered to explain crack propagation. Through hydrogen/plasticity interactions, hydrogen ingress leads to crack propagation. It is also demonstrated that the design and use of specific microstructures may promote or delay hydrogen effects, without affecting the yield strength in the same manner. Finally, the influence of a torsional pre-strain on the susceptibility to Environmentally-Assisted Cracking of a cold-worked ferrito-pearlitic steel is studied
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Smith, Bjorn Nicholas. "Improved acetabular cementing techniques." Thesis, Queensland University of Technology, 2007. https://eprints.qut.edu.au/16560/1/Bjorn_N._Smith_Thesis.pdf.
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The most common cause for revision total hip replacement surgey is aseptic loosening of the acetabular component. This thesis explores the effect of three techniques to improve the depth and quality of cemented acetabular component fixation in primary total hip replacement. This may have beneficial effects on the longevity of cemented acetabular components and reduce the rate of revision surgery for aseptic loosening.
Aims: 1. Determine the effect of the rim cutter on cement pressure during cup insertion. 2. Examine the effect of the rim cutter on cement penetration distance. 3. Evaluate the effect of bone grafting of the acetabular notch. 4. Determine the effect of iliac suction during cement pressurisation. 5. Compare the behaviour of bone cement with Play Dough.
Materials and Methods: 1. Sawbones hemi pelvis models were fitted with pressure transducers at the rim and apex of the acetabulum. Peak pressure was measured upon insertion of cups with different flange sizes and when the acetabulum was prepared with the rim cutter. 2. Foam cavities were used to measure the depth of cement penetration when the same cups and rim cutter were used. 3. Hemi pelvis models were modified to simulate bone grafting of the acetabular notch. Again, pressure sensors were mounted at the apex and rim of the acetabulum. Intra-acetabular cement pressure was compared with native acetabulae. 4. A back bleeding model of the acetabulum was fitted with a suction catheter. The effect on cement penetration into cancellous bone was measured compared with no suction. 5. Play Dough pressurisation and penetration into hemi pelvises and foam was compared to bone cement.
Results: 1. Significant increase in peak apex and rim pressures when flanged cup inserted into an acetabulum prepared with the rim cutter compared with both flanged and unflanged cups alone. 2. Significant increase in cement penetration at the rim of the acetabulum when rim cutter used and flanged cup inserted when compared with flanged and unflanged cups alone. 3. Significant increase in intra-acetabular pressure when cement pressurised in presence of simulated acetabular notch bone grafting compared with normal acetabulae. 4. Significant increase in cement penetration distance when suction used compared with no suction. 5. Significant differences in the flow characteristics between bone cement and Play Dough.
Conclusion: The authors recommend preparation of the acetabular rim with the rim cutter and bone grafting of the acetabular notch to improve the depth and uniformity of the cement mantle in cemented primary THA. Play Dough at room temperature is not a suitable substitute for bone cement in in-vitro cementing studies.
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Smith, Bjorn Nicholas. "Improved acetabular cementing techniques." Queensland University of Technology, 2007. http://eprints.qut.edu.au/16560/.
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The most common cause for revision total hip replacement surgey is aseptic loosening of the acetabular component. This thesis explores the effect of three techniques to improve the depth and quality of cemented acetabular component fixation in primary total hip replacement. This may have beneficial effects on the longevity of cemented acetabular components and reduce the rate of revision surgery for aseptic loosening. Aims: 1. Determine the effect of the rim cutter on cement pressure during cup insertion. 2. Examine the effect of the rim cutter on cement penetration distance. 3. Evaluate the effect of bone grafting of the acetabular notch. 4. Determine the effect of iliac suction during cement pressurisation. 5. Compare the behaviour of bone cement with Play Dough. Materials and Methods: 1. Sawbones hemi pelvis models were fitted with pressure transducers at the rim and apex of the acetabulum. Peak pressure was measured upon insertion of cups with different flange sizes and when the acetabulum was prepared with the rim cutter. 2. Foam cavities were used to measure the depth of cement penetration when the same cups and rim cutter were used. 3. Hemi pelvis models were modified to simulate bone grafting of the acetabular notch. Again, pressure sensors were mounted at the apex and rim of the acetabulum. Intra-acetabular cement pressure was compared with native acetabulae. 4. A back bleeding model of the acetabulum was fitted with a suction catheter. The effect on cement penetration into cancellous bone was measured compared with no suction. 5. Play Dough pressurisation and penetration into hemi pelvises and foam was compared to bone cement. Results: 1. Significant increase in peak apex and rim pressures when flanged cup inserted into an acetabulum prepared with the rim cutter compared with both flanged and unflanged cups alone. 2. Significant increase in cement penetration at the rim of the acetabulum when rim cutter used and flanged cup inserted when compared with flanged and unflanged cups alone. 3. Significant increase in intra-acetabular pressure when cement pressurised in presence of simulated acetabular notch bone grafting compared with normal acetabulae. 4. Significant increase in cement penetration distance when suction used compared with no suction. 5. Significant differences in the flow characteristics between bone cement and Play Dough. Conclusion: The authors recommend preparation of the acetabular rim with the rim cutter and bone grafting of the acetabular notch to improve the depth and uniformity of the cement mantle in cemented primary THA. Play Dough at room temperature is not a suitable substitute for bone cement in in-vitro cementing studies.
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Hantcherli, Muriel. "Influence d’éléments d’addition sur les transformations de la martensite revenue dans les aciers faiblement alliés." Thesis, Saint-Etienne, EMSE, 2010. http://www.theses.fr/2010EMSE0570/document.
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L’objectif de ce travail est d’optimiser la résistance au revenu d’un acier martensitique à 0,6% de carbone, faiblement allié en Cr, V, et Si/Al. Une série d’alliage modèle ternaire de haute pureté (Fe-C-X, X=Cr, V, Si, Al) a été élaborée à l’EMSE par fusion en creuset froid.. L’étude du comportement des alliages a été réalisée au moyen d’une caractérisation fine de la précipitation (Diffraction RX, MEB-FEG, MET) complétée par des mesures dilatométriques. Le comportement des alliages modèles a été comparé à celui de l’alliage industriel. Le vanadium est responsable de deux effets : (i) les carbures de vanadium bloquent la croissance des grains au cours de l’austénitisation ; (ii) le vanadium dissous permet la précipitation d’une cémentite (V,Cr,Fe)3C à l’origine d’un pic de durcissement secondaire pour un revenu vers 550°C. Le silicium a un effet particulier : il stabilise la matrice martensitique et retarde la précipitation de la cémentite vers des températures de revenu plus élevées, augmentant ainsi la résistance au revenu. Cependant, le silicium se révèle nocif pour le procédé industriel de mise en forme utilisé. Deux nouveaux alliages ont alors été élaborés pour chercher un élément de substitution à l’aluminium : un alliage ou le silicium est remplacé par l’aluminium, et un alliage ou le silicium est absent. L’aluminium reste neutre dans l’alliage mais l’étude de ces deux nuances a permis de mettre en évidence la possibilité d’utiliser une nuance ne contenant pas de silicium mais présentant une résistance au revenu comparable a celle de la nuance industrielle, du fait de la présence conjointe du chrome et du vanadiumThe purpose of this work is to optimise the strength of a tempered martensitic medium C steel, containing low-level of Cr, V and Si/Al. A series of high purity "model" ternary alloys (Fe-C–X, X=Cr, V, Si, Al) was prepared (EMSE) by the cold crucible method. The initial structures of quenched alloys were optimised through appropriate austenitizing conditions. Analysis of alloys behaviour on tempering was performed through carbide precipitation characterisation (X-ray diffraction, SEM and TEM), completed by hardness and dilatometric measurements. The behaviour of "model" alloys was compared to that of the industrial material.Vanadium addition is responsible for two effects: (i) vanadium carbides lock the grain growth during the austenitizing; (ii) dissolved vanadium promotes the precipitation of (V,Cr)3C, that is at the origin of a secondary hardening peak near 550°C. Silicon addition has an interesting effect, as it stabilises the martensitic matrix and increases the temperature of cementite precipitation. Therefore, a high value of hardness is conserved up to high tempering temperatures.Unfortunately, because of some noxious properties, the industrial process in concern excludes the presence of Si. That’s why two new model alloys have been prepared and tested, in which the silicon addition (i) was absent, or (ii) replaced by Al.Aluminium has been shown to be "neuter" vs tempering behaviour. Moreover, the interesting effect of secondary hardening (550°C) has been observed in both Si-free steels, showing that alloying with only Cr and V can be enough to get the expected behaviour of the studied steel
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Babic, Marijan. "Role of Interfacial Chemistry on Wettability and Carbon Dioxide Corrosion of Mild Steels." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1483543296145156.
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Eid, Cynthia Joseph. "Synthèse et caractérisation de nouvelles nanostructures à base d’oxyde et de carbure de Fe." Thesis, Lyon 1, 2010. http://www.theses.fr/2010LYO10172/document.
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Comme les propriétés physiques d'un matériau à l’échelle nanométrique sont largement dépendantes de la taille et de la forme des nanostructures, il est inutile de synthétiser de nouvelles compositions et morphologies. L’étude avancée de leur structure par les techniques de caractérisation usuelles (MET, MEB, DRX, Raman…) permettra de collecter toutes les informations nécessaires à la compréhension de leurs propriétés physiques (magnétiques, optiques, électriques). Dans ce manuscrit, nous décrirons plusieurs approches d’élaboration de nanostructures 0D, 1D et 2D multifonctionnelles afin de mieux connaître les paramètres qui contrôlent leur composition chimique et leur structure. De plus, ce travail de recherche a abouti à la synthèse de nouveaux matériaux à base d’oxyde et de carbure de fer. Des nanofibres magnétiques ayant des morphologies originales « Ruban » et « tube » ont été élaborées par la technique d’électrospinning en modifiant plusieurs paramètres expérimentaux : concentration de la solution, atmosphères de traitement thermique, température de recuit… De plus, des couches minces guidantes dopées par des nanostructures magnétiques ont été préparées par la technique dip-coating. Nous avons mené une étude complexe et détaillée sur les propriétés structurales de ces matériaux afin de définir les paramètres expérimentaux qui permettront d’obtenir des nano objets de bonne qualité. Dans un but ultime, nous souhaiterons explorer les possibilités d’application de ces matériaux qui présentent à la fois des caractéristiques électriques et magnétiquesThe physical properties of a nanomaterial strongly depend on the size and the shape of the nanostructure. As a consequence, it is interesting to elaborate new materials with different compositions and morphologies. The advanced study on the structure using common characterization techniques (TEM, MEB, XRD, Raman…) allows us to collect all the important information on their physical properties (magnetic, optical and electrical properties). In this thesis, we describe multiple ways to elaborate multifunctional nanostructures with 0D, 1D and 2D in order to study the parameters that control their chemical composition and structure. Besides, this research lead to the elaboration of new nanomaterials based on the oxide and the carbide forms of iron. Magnetic nanofibers with different morphologies (belts, tubes) were prepared using the electrospinning technique while controlling several experimental parameters : solution concentration, pyrolysis atmosphere, thermal treatment temperature… Moreover, thin layers doped with magnetic nanostructures were deposited on a pyrex substrate using the dip-coating technique. A full and detailed study on their structural properties was performed in order to reach the experimental parameters that allow us to obtain high quality products. Finally, we wish to explore the possible applications of these materials that present interesting electrical and magnetic characteristics
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Loke, Maphole Emelly. "Standard protocols for restoring heritage cementing materials." Thesis, Cape Peninsula University of Technology, 2020. http://hdl.handle.net/20.500.11838/3050.
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Thesis (MEng (Civil Engineering))--Cape Peninsula University of Technology, 2020The history of the South African construction industry dates as far back as the seventeenth century, with structures such as the Castle of Good Hope, cathedrals, museums and memorials, among many others. Heritage structures represent the history of a country and its development. These structures do not only elaborate on the history, but also embody unique designs and materials used for their construction. This makes historic structures physically distinct from modern constructions. However, heritage structures often show critical signs of deterioration, which threaten their existence thereof. In attempts to rescue these national treasures, the use of Portland cement has been a common practice, but there are problems with using such modern materials. The application of incompatible materials is said to accelerate the deterioration and endanger the authenticity of these monuments. This practice is a result of a misunderstanding of the original material behaviour and has been responsible for the failure of many restoration projects. For developing countries, South Africa in particular, this approach has undoubtedly impacted negatively on the economy, as repeated repairs are necessary. Characterisation of the original cementing materials is the key to compatible restoration of heritage buildings. The research describes the development of an integrated protocol to establish the properties of the original heritage cementing materials. The key objective for the study was to investigate and standardise an analytical procedure whose primary purpose is the identification of major and minor components of heritage cementing materials and binder-to-aggregate ratio, which would be useful for production of repair materials. The results obtained from the experimental investigation into the physical, chemical and mineralogical properties of the original materials from the Castle of Good Hope and Robben Island are presented in this study. The experimental results were analysed for their ability to provide useful data at minimal costs. After that, a standard protocol was developed, incorporating the procedure for sampling as well as preparation of the sample, material analysis and documentation. The standard protocol includes the cohesion test, visual investigation and titration test for analysis of the salts and metal oxides present in the materials. These tests provide relevant data for the search of replica repair materials. The standard protocol will be useful for local heritage authorities, as it could be incorporated into the conservation management plans prior to restoration works. This will ensure compatible and sustainable restoration of historic buildings, not only in South Africa, but around the world. The heritage materials for the two oldest buildings in the Western Cape were made of hydraulic lime-based mortars, seashells, and uniform and well-graded sand. Less than 5% of the materials showed no traces of a binder. The restored areas were restored with cement-based materials. The affordable standard methodology for characterising original heritage cementing materials involved the sample collection that represents the majority of the building, sample preparation, detailed visual investigation and cohesion test, as well as hydraulicity and cementation indices analysis to determine the type of binder. These tests were concluded to be convenient, easy to conduct and cost-effective.
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Santhapur, Naveen Misra Anil. "Properties of sand-self cementing fly ash mixtures." Diss., UMK access, 2007.
Find full textAbstract:
Thesis (M.S.)--School of Computing and Engineering. University of Missouri--Kansas City, 2007."A thesis in civil engineering." Typescript. Advisor: Anil Misra. Vita. Title from "catalog record" of the print edition Description based on contents viewed May 23, 2008. Includes bibliographical references (leaves 32-34). Online version of the print edition.
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Carrasco-Teja, Mariana. "Primary cementing of a highly deviated oil well." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/17466.
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In this thesis we study laminar displacement flows of one fluid by another in a horizontal annulus. The study comes from the primary cementing of highly deviated oil and gas wells. Highly deviated wells are those in which part of the well bore is nearly horizontal. Primary cementing is a critical process in the construction of a
well. The objective is to provide zonal isolation, i.e., a hydraulic seal between the well and the surrounding rock. This is essential to protect the environment and increase the productivity of the well. Therefore, an understanding of the process is indispensable. We model primary cementing displacement flows using a Hele-Shaw approach, and provide simple scientific tools to improve the design of cementing
jobs.
The contribution of the thesis comes in three parts. Firstly, we analyse the displacement of one viscoplastic fluid by another in a near-horizontal eccentric annulus with a fixed inner pipe. We present examples that illustrate the differences between vertical and horizontal displacements. We then derive a 1D lubrication model which
gives analytical conditions that predict when the flow will stratify, according to the fluid properties and the annulus geometry. Secondly, we derive a 2D displacement model for Newtonian fluids which includes rotation and reciprocation of the inner cylinder. This is a common practice in the industry and not well understood. Using an asymptotic approach, we find steady-state traveling wave solutions for nearly-
flat interfaces. Then we use numerical simulations to understand the flow dynamics for more elongated interfaces. In particular, we show that casing rotation can lead to local instabilities and mixing, which can shorten the length of the interface. Finally, we generalise this moving casing model to viscoplastic fluids. Using a lubrication-
type model we explore the effects of casing motion, again deriving conditions for there to be steady solutions.
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Alp, Baris. "Utilization Of Ggbfs Blended Cement Pastes In Well Cementing." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614683/index.pdf.
Full textAbstract:
In well cementing, the cement slurry is exposed to the conditions far different than those of ordinary Portland cement (PC) used in construction. After placement, hardened cement paste should preserve integrity and provide zonal isolation through the life of the well. American Petroleum Institute (API) Class G cement is the most common cement type used in various well conditions. Class G cement has a high degree of sulfate resistance which makes it more stable than PC when subjected to the compulsive well conditions. Ground granulated blast furnace slag (GGBFS) blended cement has a long history of use in the construction industry, but is not extensively used in well cementing applications.
This study presents an experimental program to investigate the applicability of CEM I and GGBFS blended cement pastes in the well cementing industry. Class G cement and blends of CEM I and GGBFS with the proportions (80:20), (60:40), (40:60) and (20:80) are prepared with same water/cement ratio (0.44) as restricted for Class G cement in API Specification 10A to be tested. The cement pastes are cured for ages of 1 day, 7 days and 28 days at 80
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El-Baghdadi, Ahmed. "Carbon dioxide activated steel slag as a cementing material." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107748.
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Steel slag is a major by-product of the steel industry, with a production of nearly 300 kg for every tonne of steel produced. It has been conventionally used as an aggregate in road base construction, but this use has been limited due to the high free lime content, which causes volume expansion problems. This thesis explores the feasibility of using CO2 activation to eliminate free lime and develop strength for a steel slag-based building product. The CO2 activated steel slag has the potential to be used as cementing material to replace Ordinary Portland Cement (OPC) and to sequester carbon dioxide through activation. The technology can show numerous technical and environmental benefits, while minimizing the embodied energy in the final products.Compressive strength and carbon uptake of compacts made of KOBM1, KOBM2, ladle and GGBF slag were evaluated in comparison with counterpart OPC compacts. KOBM slag showed the greatest potential, with compressive strength and carbon uptake values comparable to OPC. The microstructural change of carbon dioxide activated KOBM slag was assessed in detail by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Its durability was also measured by the means of an accelerated water softening test. The wallboard made of KOBM slag bonded with sawdust was fabricated, and its mechanical performance was found to be competitive to commercial cement-based wall-boards. The research demonstrates that certain types of steel slags can be successfully activated by carbon dioxide in the production of commercial products to replace OPC.Le laitier d'acier est un important coproduit de l'industrie de l'acier ayant une production près de 300 kilogrammes pour chaque tonne d'acier produite. Il est traditionnellement utilisé pour la construction d'infrastructure routière, étant ajouté comme additif dans le ciment et les agrégats. Cependant la forte présence de chaux libre dans les résidus de métallurgie cause une expansion de volume lors de son utilisation comme matériau de construction, ce qui limite son application dans l'industrie.Cette thèse explore la possibilité d'éliminer la chaux libre par l'activation de la réaction chimique du CO2 ainsi développer la résistance pour un produit de construction à base de laitier d'acier. L'activation du dyoxide de carbone présent dans le laitier d'acier a le potentiel d'être utilisé comme matériau cimentière au lieu du ciment Portland ordinaire en plus de séquestrer le CO2 grâce à son activation. Cette technologie peut démontrer de nombreux avantages techniques et environnementaux, tout en minimisant l'énergie intrinsèque des produits finaux.Des essais pour quatre différents types de scories compactes, formées à partir de KOBM1, KOBM2, et de scories de GGBF ont été realisés afin de tester leur capacité d'absorption de carbone et leur résistance à la compression. Les résultats ont été comparés avec des spécimens homologues produits avec du ciment Portland ordinaire. Le changement microstructurel du laitier KOBM avec CO2 activé a été évalué en détail par diffraction des rayons X, TGA et SEM. Sa durabilité, par un essai de résistance à l'eau a également été mesurée. Des plaques de plâtre à base de laitier d'acier KOBM liés avec de la sciure de bois ont été fabriquées, leur performance mécanique s'est avérée tout à fait comparable à celle des plaque de plâtres en ciment offertes sur le marché. Finalement, la recherche conclut que l'activation du dioxyde de carbone de certains produits commerciaux, faits à base de laitier d'acier, peuvent être utilisés et permette l'emploi du laitier d'acier pour remplacer le ciment Portland ordinaire dans certains produits commerciaux.
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Chorell, Hugo. "Cementing the Future - A Closer Look at FDI and Growth." Thesis, Uppsala University, Department of Economics, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9217.
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Tanzania is one of the world’s poorest countries. But it has a lot to offer and in recent years both tourists and companies have realised this. This thesis focuses on the companies and takes a closer look at the growth performance and the inflow of Foreign Direct Investments (FDI) to Tanzania. By presenting a case on the cement industry in Tanzania the thesis also provide some insight in the mechanisms of FDI on a more practical level. The findings conclude that the FDI and growth have both increased extensively since the 1990’s, but I refrain from comments on the causality of this relationship. The economic reforms that the country underwent in the 1990’s are thought to have played a key role in the development of the country. From the case presented we draw the conclusion that a FDI can affect the value chain as well as the whole country in numerous ways.
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Sundström, Gema, and Guha Kashyap. "CEMenting Growth : Customer Experience Management as a driver of Growth." Thesis, Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-31490.
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Purpose: The purpose of this study is the purpose of this study is to gain a more in-depth understanding of customer experience management and how it enables growth within an organization. Background: Customer Experience Management has been described as a process where the entire experience of a customer with a product/service and a company is strategically managed. It has been highlighted as a key area for organisations to focus on, yet, CEM is continuously being researched both by researchers and business practitioners as there is still a vague understanding on the topic. Nonetheless, CEM has been displayed as a successful process, however, very little research has gone into showing that it could enable organizational growth.
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Topoliński, Szymon. "Badanie wytrzymałości kompozytów grunt organiczny-spoiwo cementowe formowanych metodą mieszania." Rozprawa doktorska, Uniwersytet Technologiczno-Przyrodniczy w Bydgoszczy, 2014. http://dlibra.utp.edu.pl/Content/626.
Full textAbstract:
Praca opisuje wzmacnianie słabonośnych podłoży zbudowanych z gruntów organicznych. Głównym celem badań była ocena praktycznej skuteczności stosowania cementu do wzmacniania gruntów słabonoścnych o różnej zawartości substancji organicznej
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BUOSO, Alessandra. "La piezoresistività dei compositi cementizi rinforzati con nanotubi in carbonio." Doctoral thesis, Università degli studi di Bergamo, 2013. http://hdl.handle.net/10446/28962.
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Carbon nanotubes (CNT) are based on one or more sheets of graphite rolled up into a tube. Adding carbon nanotubes, the electrical resistivity of cementitious composites changes by varying the stress conditions. Variation in the electric resistivity can be ascribed to the increase in the number of contact points of CNTs by increasing loading: the higher the compressive stress, the higher the contact points, the lower the resistivity. This particular CNT behaviour can be used to evaluate the level of stress in reinforced concrete structures, to monitor the traffic flow, to weigh vehicles, to control the entrance in restricted areas, to switch on electrical or heating equipments. In the present work data on rheological and mechanical properties, electrical resistivity and pressure-sensitive behaviour under cyclic compressive loading of cement composites containing multi-walled carbon nanotubes (MWNT) are presented. Results show that carbon nanotubes improve the flexural and compressive strength of cementitious composites only if they are efficiently dispersed. In fact, in order to form a conductive network and enhance the piezoresistive properties of cementitious mixtures, Carbon NanoTubes (CNTs) were dispersed in the cement matrix by two different methods: only by sonication and by a surfactant (LAS) in an aqueous solution. At the end of the mixing procedure, a defoamer (tributyl phosphate) was added in order to decrease the air bubble in MWNT filled cement-based composites created by the surfactant. Moreover, the addition of CNTs leads to a notable decrease in volume electrical resistivity and enhances the pressure sensitivity of the cementitious mixtures. Experimental results show that the electrochemical impedance changes synchronously with the compressive stress levels for all the specimens. Moreover, the piezoresistive response is better for cement composites and increases adding more CNTs percentage.
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LORENZI, Sergio (ORCID:0000-0002-1337-7590). "Corrosione-erosione dell'acciaio a contatto con conglomerati cementizi allo stato fresco." Doctoral thesis, Università degli studi di Bergamo, 2010. http://hdl.handle.net/10446/611.
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Farris, Stephen Robert. "The effect of admixtures on the hydration of oilwell cement." Thesis, Keele University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325862.
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Bell, Gillian M. M. "Cement reactions in hydrothermal conditions." Thesis, University of Aberdeen, 1989. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU497149.
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Fundamental processes of cement hydration were studied at elevated temperatures, between 100 and 200oC at saturated steam pressure, using hydrothermal curing. Initial investigations centred on treatments on Ca3SiO5 and -Ca_2SiO_4, synthesised in the laboratory, having compositions similar to those which occur in cement clinker. Their reaction products, either separately or with blending agents such as quartz or silicic acid, were identified by x-ray diffraction. Further characterisation data were obtained for tobermorite, xonotlite, hillebrandite, gyrolite, truscottite, kilchoanite, calciochondrodite, -dicalcium silicate hydrate and tricalcium silicate hydrate using scanning electron microscopy, infrared spectroscopy and nuclear magnetic resonance spectroscopy. The current postulated structures of hillebrandite and tricalcium silicate hydrate were reassessed. The factors affecting compressive strength development of cement pastes were reviewed. Theoretical volume changes were calculated for the formation of hydrothermal calciumsilicate hydrates. These may be a useful aid in assessing the suitability of a particular phase and estimating the likely consequences of phase changes on strength. The nature of the silica source affects the type of products obtained. A more detailed study of the reaction between Ca3SiO5 and various blending agents was undertaken in order to correlate between formulation, mineralogy after hydrothermal treatment, compressive strength and porosity. Actual cement blends were studied using a typical class G oilwell cement and various blending agents. In short term tests the mineralogy and compressive strength were determined with varying compositions and temperatures. It is hoped that this information will be an aid in predicting optimum compositions by correlating properties with the nature of the materials and their chemistry. Class J cement hydration and class G cement blends were also studied by infrared and nuclear magnetic resonance spectroscopy.
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Riderelli, Luca. "Applicazione di cementi fotocatalitici nelle opere di ingegneria civile." Doctoral thesis, Università Politecnica delle Marche, 2013. http://hdl.handle.net/11566/242558.
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Nell’ambito della realizzazione di opere di ingegneria civile, quali edifici, reti
stradali in un contesto di tessuto connettivo urbano e non, l’impiego di cementi
fotocatalitici si colloca nel contesto attuale in cui è necessario coniugare
esigenze di valorizzazione del patrimonio esistente e di nuova edificazione con
le problematiche derivanti dall’inquinamento e di durabilità anche estetica.
Attraverso il processo fotocatalitico si è in grado di ridurre le concentrazioni di
inquinanti fotochimici in aria, mantenere le superfici pulite, bianche nonché
attive nella cattura e nello smaltimento di composti sotto forma di sali dilavati.
Di qui la scelta di abbinare alle consuete caratteristiche di impiego di un
cemento tradizionale le proprietà derivanti dal processo ossidativo
fotocatalitico, nel sincretistico approccio dell’impiego di cementi additivati con
TiO2.
Le possibili applicazioni comprendono numerose opere di ingegneria civile. Le
realizzazioni su cui si è indagato hanno coinvolto la messa a punto, dapprima, di
miscele di calcestruzzo drenante con cemento fotocatalitico, con aggregati
naturali e/o riciclati, per pavimentazioni stradali e la realizzazione di provini per
lo studio in laboratorio di fotocatalisi. Si è quindi proceduto a studiare
applicazioni in campo prova di calcestruzzo drenante e calcestruzzo drenante
fotocatalitico, di materiali fotocatalitici, tra cui un rasante e pitture, per
l’applicazione su superfici in ambiente outdoor ed indoor, quali su pareti di una
galleria stradale, di prodotti fotocatalitici per la applicazione a freddo su
pavimentazione, in particolare, di tipo autostradale.
Per quanto concerne la messa a punto delle miscele, il calcestruzzo drenante è
stato oggetto di studio in laboratorio calcestruzzi per il raggiungimento di
adeguate proprietà meccaniche ed idrauliche di permeabilità, nonché sono
state analizzate le proprietà in termini di abbattimento di inquinanti organici ed
inorganici, attraverso prove in modalità plug-flow, seguendo la attuale
normativa italiana aggiungendo tuttavia prove realizzate in modalità batch,
proponendo un modello per la caratterizzazione dei materiali e dei campioni
provenienti da opere realizzate con cementi fotocatalitici attraverso parametri
cinetici e di adsorbimento. Sono stati condotti studi sull’analisi per immagini,
approfondendo le indagini tramite scansioni in 2D e 3D, dimostrandone l’utilità
di impiego.
Relativamente agli studi su grande scala, sono state progettate e verificate
metodologie di lavoro atte a monitorare, isolare, indagare i parametri ritenuti
fondamentali nello studio di applicazioni di questo tipo. Si presentano i risultati
di realizzazioni e monitoraggio relativi ad una pavimentazione realizzata in
calcestruzzo drenante fotocatalitico, rivestimenti per gallerie, applicazione di
prodotti su pavimentazione autostradale.In civil engineering works, such as realization of new buildings and road networks, the application of photocatalytic cement is functional to the aesthetic conservation and to the abatement of pollutant concentrations, both for existent constructions and for new ones. Photocatalytic process allows to reduce concentrations in air of photochemical pollutants and to keep the surface white and clear. Also, it is capable to capture and dispose of compounds as innocuous salts. For these reasons, taking into account the joint of oxidative photocatalytic process and traditional cement turns to be useful in application of cement with the admixture of TiO2. A wide and significant contribution can be given to the environmental aspects among sustainable constructions. On the one hand, pervious concrete mix design and photocatalytic pervious concrete, mortars and paints specimens were tested in laboratory in order to evaluate the mechanical characteristics and photocatalytic activity. Pervious concrete pavements were studied for the realization as road infrastructures, also replacing natural aggregate with recycled ones. On the other hand, pervious concrete and photocatalytic pervious concrete were tested on field. Their activity and capability to drain water were verified. An experimental research was carried out inside a highway tunnel painted with photocatalytic coatings: paints and a coat. Photocatalytic coatings and grout were applied to highway road surface, on field. Environmental properties of photocatalytic pervious concrete were tested considering the abatement of organic and inorganic compounds in plug-flow tests, as recommended by Italian regulations. Batch tests and a related model are proposed for the characterization of photocatalytic materials by kinetic and adsorption parameters. Analyses on images, 3D and 2D scans were run. Their results are extremely useful for evaluating materials’ surfaces, referring to the high specific surfaces and corresponding depollution performances of this concrete. Finally, monitoring systems were designed and verified in order to study and evaluate the proper parameters which are considered to be the ones that control applications on field. Results from applications and monitoring systems of a photocatalytic concrete pavement, a tunnel and a highway pavement are showed.
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Lamontagne, Aude. "Etude des mécanismes physiques responsables des évolutions microstructurales des aciers perlitiques au cours du tréfilage et du vieillissement post-tréfilage." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0109/document.
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Les câbles métalliques utilisés pour le renforcement des pneumatiques sont obtenus par assemblage de fils fins produits par tréfilage d’un fil d’acier perlitique à teneur en carbone proche de la composition eutectoïde. La mise en forme par tréfilage a pour but, d’une part de donner au fil son diamètre final et, d’autre part de l’écrouir et lui conférer une très haute résistance mécanique (3500 MPa environ pour des fils de diamètre de 200 µm environ). L’objectif actuel est de porter cette résistance à un niveau proche de 5000 MPa afin d’abaisser la quantité d’acier de renfort et de diminuer ainsi le poids et le coût des pneumatiques. Toutefois l’obtention de fils à ultra-haute résistance (5000 MPa) se voit confronter à deux obstacles majeurs. En effet, le renforcement de l’acier au cours de l’étape de tréfilage engendre des évolutions microstructurales et mécaniques très importantes qui provoquent l’apparition d’une fragilisation des fils. Ce phénomène est considéré comme le seuil de tréfilabilité au-delà duquel le fil ne peut plus être renforcé par écrouissage. Au-delà de cette fragilisation prématurée du fil, un phénomène de vieillissement post-tréfilage provoque lui aussi une évolution de la microstructure et une perte de la ductilité au cours du temps à température ambiante ou encore suite à des traitements thermiques basse température (< 200°C). Cette instabilité des fils dans le temps peut être fortement pénalisante pour leur mise en assemblage en vue d’obtenir les renforts métalliques puisqu’elle est responsable de nombreuses ruptures des fils. L’objectif de ce travail de thèse a consisté alors à contribuer à la définition des évolutions microstructurales, à l’origine des variations des propriétés mécaniques qui apparaissent au cours de l’écrouissage et du vieillissement post-tréfilage. Pour cela, une approche expérimentale originale reposant sur l’utilisation combinée de plusieurs techniques de caractérisation globales et indirectes (pouvoir thermoélectrique, résistivité électrique, spectroscopie mécanique, calorimétrie…), couplée à des analyses en sonde atomique tomographique et à des essais de traction, a été mise en place dans l’idée de fournir un faisceau d’éléments permettant de proposer un scénario pour interpréter les différentes évolutions microstructurales en question. Il a ainsi pu être mis en évidence que l’étape de tréfilage provoquait la dissolution de la cémentite induisant la sursaturation de la ferrite en carbone. Cette microstructure fortement hors équilibre suite à la déformation, revient alors à un état thermodynamiquement plus stable au cours du vieillissement post-tréfilage à travers trois mécanismes différents : la ségrégation des atomes de carbone sur les défauts microstructuraux et la précipitation de carbures intermédiaires métastables suivie de leur transformation en cémentiteSteelcords are produced by assembling cold-drawn pearlitic steel wires with a composition close to the eutectoid one. The cold-drawing step has two goals: it provides the final shape of the wire and its very high mechanical resistance (about 3500 MPa for wires with a diameter of 200 µm). Nowadays, the industrial target aims at achieving a mechanical resistance of about 5000 MPa in order to lower the quantity of steelcord introduced into tires so decreasing their weight and their cost. However, there are two major obstacles to obtaining these ultra-high strength wires. Indeed, the steel reinforcement during cold-drawing induces significant microstructural and mechanical evolutions, which embrittle the wires. This phenomenon is considered as the limit of drawability beyond which wires cannot be plastically deformed anymore. In addition to that, post-drawing ageing can also induce a microstructural evolution and a loss of ductility due to storage at room temperature or during heat treatments at low temperatures (< 200°C). This instability of the wires microstructure can be very damaging for the assembly step leading to wire breakage. The aim of this work was to contribute to the assessment of the microstructural evolution responsible for the variations of mechanical properties that appear during drawing and post-drawing ageing. To achieve this goal, an original experimental approach combining global and indirect characterization techniques (thermoelectric power, electrical resistivity, mechanical spectroscopy, calorimetry…) with Atom Probe Tomography analyses has been set up in order to provide a range of evidences that converge towards a unique scenario to interpret the different microstructural evolution. It was thus shown that cold-drawing leads to cementite dissolution inducing over saturation of ferrite in carbon atoms. This non-equilibrium microstructure tends to return to a more stable state during post-drawing ageing through three different ageing mechanisms: the segregation of carbon atoms on microstructural defects, the precipitation of secondary carbides and their transformation in cementite
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Patel, Sachin Misra Anil. "Cold in-place recycling of asphalt pavement with self-cementing fly ash." Diss., UMK access, 2006.
Find full textAbstract:
Thesis (M.S.)--School of Computing and Engineering. University of Missouri--Kansas City, 2006."A thesis in civil engineering." Typescript. Advisor: Anil Misra. Vita. Title from "catalog record" of the print edition Description based on contents viewed Nov. 1, 2007. Includes bibliographical references (leaves 49-58). Online version of the print edition.
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Peerzada, Farrahnaz. "Effect of surface preparation on bond strength of resin luting cementsto dentine." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B41712377.
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García-Torra, Mª Dolors. "Apropiacions socials d’un espai funerari arquitecturitzat. El cas del Cementiri Nou d’Igualada." Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/671870.
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És cert que un cop produït el traspàs, els morts canvien de domicili i van a parar a dominis invisibles o al no res. Però també requereixen algun tipus de presència entre els mortals en el seu mateix mon físic. A la ciutat d’Igualada, actualment, aquesta necessitat és coberta per dos cementiris que representen dues modalitats ben diferents de cementiri urbà. Per una banda, compta amb un cementiri vuitcentista, d’estil neoclàssic –el Cementiri Vell– i per l’altra, amb un cementiri contemporani –Cementiri Nou–, projectat per dos arquitectes de renom internacional, Enric Miralles i Carme Pinós. A falta de lloc en el vell recinte funerari, no hi ha cap altra alternativa que inhumar en el Cementiri Nou, cosa que no convenç a un nombre important d’usuaris. Per ells, portar a terme les pràctiques post mortem en un indret de disseny, com és la nova edificació funerària, els suposa estar utilitzant un cementiri projectat per uns arquitectes a partir d’un espai essencialment representat o concebut, aliè al seu entorn i a les apropiacions socials a les que se suposa que ha de servir. Essent el resultat un espai arquitectònic de nova generació, el cementiri no compta amb els codis de significats simbòlics forjats per la tradició funerària que fa que no sigui un espai reconegut i apte com a lloc de repòs etern. Per això, els seus usuaris porten accions de contínua revalorització per tal de rehabilitar el valor d’ús de l’espai i la seva significació com a obra.Once deceased, the dead switch address and end up inhabiting ethereal domains. Yet we also require that they take some kind of presence in the physical world of the living. In the town of Igualada, this need is covered two very different cemeteries. One of them is a 19th-century, neoclassical-style cemetery—the Cementiri Vell (Old Cemetery)—the other one is the Cementiri Nou (New Cementery), a contemporary cementery projected by two renowned architects, Enric Miralles and Carme Pinós. Due to lack of space in the Old Cemetery, new burials must necessarily take place in the New Cemetery, an option that many residents dislike. For them, engaging in post mortem funerary practices in a design space such as the newer facility involves using a cemetery projected as a conceived space, alien to their environment and to the social appropriations that it should allow. Being a new-generation architectural space, the codes of symbolic meanings forged by the funerary tradition are absent in the New Cemetery, which therefore stands as a space that is not recognized as apt for eternal rest. For this reason, its users carry out a continuous task of revalorization aimed at rehabilitating the use value of this space and its signification as an oeuvre.
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Adeoye, Adedapo B. "Improving the Viscoelastic Properties of Cement for Oil and Gas Well Cementing Operations." Thesis, University of Louisiana at Lafayette, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10002480.
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The importance of cement integrity in the downhole well cannot be over looked. Cement designed for a particular well may not work for another well. As a result, there is a need to design well cement based on appropriate well conditions in order to achieve good integrity during the life time of the well. This research focused on micro-annulus and crack problems associated with downhole well cements. Waste tires have contributed to environmental problems.
Waste tires can be crushed into small particles and used for construction purposes. This is seen as a promising avenue to get rid of the waste tires. This research focused on the possibility of adding tire rubber particles to well cement to reduce the effect of micro-annuli and cracks in well cement. Tire rubber particles of 4 different sizes were used in this research, which was then divided into two parts. The first part dealt with rheology and compressive strength of concretes. These parameters were used to select cement designs with optimum value for subsequent tests. The other part included permeability and creep tests. Permeability measured the amount of water the concrete materials could yield while the creep test measured strain developed when concrete specimen was subjected to a constant stress for 30 minutes and the amount of strain recovered when the concrete specimen was unloaded for another 30 minutes. Creep compliance was done to measure the rate at which strain was developing, which is a function of time under constant stress.
Concrete containing the largest rubber particle size had good amount of strain recovery after unloading while concrete samples containing the smallest rubber particle size had the lowest amount of strain recovery.
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Femiano, Alessandra. "Sviluppo di cementi ossei bioattivi e bio-riassorbibili per vertebroplastica rigenerativa." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/4681/.
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Upadhyaya, Sushant Misra Anil. "Cold in place recycling of asphalt pavement with self cementing fly ash laboratory studies /." Diss., UMK access, 2004.
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Thesis (M.S.)--School of Computing and Engineering. University of Missouri--Kansas City, 2004."A thesis in civil engineering." Typescript. Advisor: Anil Misra. Vita. Title from "catalog record" of the print edition Description based on contents viewed Feb. 28, 2006. Includes bibliographical references (leaves 70-76 ). Online version of the print edition.
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Rieder, Clemens M. "Cementing solidarity in EU health care law : the role of rights and the ECJ." Thesis, University of Reading, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.559258.
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In a series of cases over the last 10 years or so the Court of Justice of the European Union (EU) has begun to link health care with the principle of free movement of services. In this way health care, a traditional prerogative of the nation state, has become a focal point ofEU integration. One distinctive aspect of public national health care systems is that they are based on solidarity. Therefore any discussion of EU health care also needs to address the rather elusive concept of solidarity. A core question to be discussed in this context is whether it is accurate to assume that the nation state is the largest entity in which robust forms of solidarity are possible. The legal framework, in particular rights, whilst having an important role to play in this discussion can only provide a starting point in the analysis of this question. This thesis argues that the Court has applied consequentialism in its case law which made it easier for Member States to accept the supranational involvement in the sensitive area of health care. It will seek to tease out what might be regarded as Pareto and utilitarian influenced reasoning in the Court's case law which so far has been a crucial factor in developing EU health care law. A consequence of this approach is that it is primarily focused on national solidarity as the basis of EU health care. An alternative conceptual proposition would be deontology. The thesis discusses possible implications of such an approach; one being that supranational solidarity would become more prevalent in EU health care. Therefore it is necessary to study the relationship between the normatively desirable, and the factually possible ('ought' implies 'can'). In answering this question the thesis analyses whether we fmd different motivational factors between the national and the supranationallevel which may serve as an explanation for the fact that so far, the nation state seems to be the biggest entity in terms of robust solidarity.
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Ognibene, Giacomo. "Studio di una miscela in misto cementato con aggregati riciclati da C&D." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/6540/.
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La ricerca, presentata in questa tesi di laurea, si pone quale obiettivo, quello di studiare le possibilità di impiego di materiali provenienti da attività da C&D, in sostituzione degli inerti vergini di cava, nella confezione dei misti cementati per strati di base e fondazioni stradali. Lo studio è stato condotto per conto della CEA (Cooperativa Edile Appennino S.c.a.r.l.) la quale ha fornito il materiale riciclato in due diverse curve granulometriche 0/20 e 0/30. Tutte le prove sono state eseguite presso il Laboratorio di Strade della Facoltà di Ingegneria dell’Università degli Studi di Bologna.
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Casadio, Laura. "Caratterizzazione fisica, chimica e strutturale di cementi biomedici a componente multi-minerale." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/4318/.
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Lind, Fredrik. "Polymerkoncentrationens inverkan på härdresultatet av seghärdningsstål." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-65989.
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Ovako Sweden AB i Hällefors har vid seghärdning av stål problem med sprickor. Studier visar på att tillsatser av polymer i kylvattnet ger ett långsammare och jämnare kylförlopp, vilket minskar risken för sprickor. För att fastställa vilken mängd polymer som är lämplig att tillsätta i kylvattnet vid härdning av deras låglegerade segment av seghärdat stål, så har undersökningar utförs på två stålsorter. Skillnaden i härdresultat mellan de olika testade koncentrationsnivåerna var små, men vid högre polymerkoncentration så fördelades hårdheten något jämnare genom hela tvärsnittet.Ovako Sweden AB have problems with cracks during the process of hardening of steel. Studies show that the additives of polymer in the cooling water gives a slower and more even cooling process, which reduce the risk of crack onset. To decide the amount of polymer that is suitable to put in the cooling water at the hardening of their low-alloy steel segment of quenched and tempered steel, so studies have been conducted on two types of steel. The difference in hardening results between different tested concentration levels were small, but at higher polymer concentration the hardness was distributed slightly more evenly throughout the cross section.
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Mourad, Firas. "The Effect of Temperature on Different Resin Cements Used for Cementing a Milled Titanium Bar." Thesis, The University of Alabama at Birmingham, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10683963.
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Purpose: To investigate the effect of acrylic processing on push-out strength of Ti copings luted to Milled Ti frameworks using differing resin cements.
Materials and Methods: The experimental design consisted of three groups of 30 specimens each. Three different luting cements were utilized (One for each group), Panavia V5 Dual Cure Kuraray, Multilink Dual Cure Hybrid Ivoclar-Vivadent, and RelyX Unicem-2 self-adhesive 3M. The experimental model consists of trans-mucosal Titanium Coping, Abutment analog, Milled Ti hollow cylinder (9.0mm-OD) represents the milled Ti bar. The Abutment copings were luted to milled-Ti cylinders using the 3 dental cements and an alignment jig to assure repeatability used during cementation. Waxing then acrylic processed by two protocols (Fast and Conventional) for two groups (not the control) were completed. Processed specimens were finished, polished, and stored in distilled H2O at 24 °C for 24 hours prior to testing. Push-out strengths were measured (N/mm2), with Instron 5565 mechanical testing system, crosshead speed 1 mm/min. Failure mode was evaluated by high-magnification light microscopy and SEM. Significance determined by ANOVA and Tukey’s post hoc test (p < 0.05).
Results: Two-way ANOVA shows no significant interaction (p = 0.45 > 0.05) between the two variables, processing technique and the cement. Only the cement is significantly different. So, the cement is not affected by the process and vise-versa. One-way ANOVA shows no significant differences in push-out strength within the same cement groups. However, it has found a difference among the groups (P < 0.0001). Tukey’s post hoc test found significant differences among the cements groups (p < 0.05).
Conclusion: Within the limitations of this in-vitro study, no differences in cement push-out strength were found between acrylic processing methods, but differed by cement type.
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Holder, Terrence Bernard. "The determination of chloride threshold concentrations using different supplementary cementing materials in steel-reinforced concrete." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0003/MQ45588.pdf.
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Malekmohammadi, Sardar. "An experimental study of two multi-fluid flows of interest to the oilfield cementing industry." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/11566.
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In this work two multi-fluid flows are studied. In the first project, displacement flows in an eccentric annulus were studied experimentally. Displacement flows occur in the oil and gas industry during well construction when drilling mud is displaced by a cement slurry. To remove mud effectively, it is important to design the fluid rheology so that a steady displacement front can be achieved when displacing along an eccentric annulus. In our research, we have investigated the effects of viscosity, density and eccentricity of inner pipe on the interface dynamics. An experimental matrix is devised in a manner to capture the boundary between steady and unsteady displacements for specific pairs of fluids, and to compare against previously published models.
Reasonable qualitative agreement was achieved however a systematic discrepancy was observed due to the presence of secondary flows and dispersion in the experiments. These effects have not been studied carefully so far and more sophisticated models are needed to predict this type of flow. In the second project, slumping flows of two non-Newtonian fluids in
horizontal closed pipes were studied. This type of flow occurs during the abandonment of horizontal oil and gas wells, when sealing the well through the setting of cement plugs. We have studied the effects of changes in density difference and of small deviations from a perfectly horizontal inclination.
The effects of these parameters on the slump length versus time were analyzed. Comparison of numerical and experimental results shows broadly similar trends, but with some qualitative differences also observed, possibly due to interfacial effects
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Chamberlain-Creangă, Rebecca A. "Cementing modernisation : transnational markets, language and labour tension in a Post-Soviet factory in Moldova." Thesis, London School of Economics and Political Science (University of London), 2011. http://etheses.lse.ac.uk/274/.
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The aim of my thesis is to investigate workers’ reactions to transnational market reform in a Soviet-era factory in the Republic of Moldova. The thesis finds that there are varying, blurred responses of contestation and consent to market modernisation in the context of one factory, the Rezina Cement Plant of Egrafal Group Ltd., one of Moldova’s first major European transnational-corporate (TNC) private enterprises. Language plays a critical role in workers’ responses, since language is important to Egrafal Ltd.’s goal of market integration and capitalist labour reform. However, corporate language expectations frequently clash with the language that was previously embedded in Moldova’s industrial workscape. As a result, the thesis argues that workers adopt, resist or modify factory reforms through what I call linguistic styles or situational performative modes linked with ideas of modernity, markets and mutuality. The thesis goes on to argue that employees’ spatial status location in the plant, irrespective of job skill and income, corresponds to employees’ differing linguistic modalities and differing tendencies towards protest and accommodation in response to factory restructuring. Workers in the top strata of the factory’s Administration Building speak multiple languages, long for cosmopolitan lifestyles and benefit from high integration into corporate-market structures. Many achieved job mobility in the plant since socialism and now accommodate to capitalism and corporate styles through linguistic codeswitching. The middle strata of ethno-linguistic minorities in Administration’s laboratory and the lower strata on the shop floor lack corporate-backed linguistic capital and are on the fringe of modernisation; both are highly job insecure and protest capitalist change by way of what appears to be traditional language usage, but is in fact a contemporary response to liberal-economic change. This finding leads the study to conclude that workers’ fragmented linguistic-based reactions to market reform do not entail real protectionist collectivism, as Polanyi would have envisioned (Polanyi 1944, 150), nor enduring moral-economic protest along the lines of E.P. Thompson (1971). This is for the very reason of workers’ competing modernist longings and job insecurity – alienating workers from each other whilst drawing them back to local ties – which effectively keeps workers in perpetual oscillation between markets and mutuality.
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Vayssade, Anne-Laure. "Flows of Herschel-Bulkley fluids in confined environments : applications to the cementing of oil wells." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066214/document.
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En 2010, la plus grande catastrophe de l’histoire de l’industrie pétrolière s’est produite dans le golfe du Mexique avec l’explosion du puit de pétrole Macondo. Les causes de l’accident sont connues : la couche de ciment dans l’espace annulaire du puit qui est supposée empêcher les fuites, a cédé. Ces fuites sont dues à la présence de boue (la boue est utilisée lors du forage du puit avant sa cimentation) dans l’annulaire dégradant la prise du ciment. Nous utilisons la microfluidique afin d’étudier la question des films de boue qui restent sur les parois de l’annulaire. Le ciment et la boue sont modélisés par des suspensions de microgel qui ont des propriétés rhéologiques similaires. Des nombres sans dimension comparables entre la microfluidique et la situation réelle permettent d’extraire de cette étude des informations pertinentes pour l’industrie pétrolière. Nous menons des expériences de déplacements de suspensions de microgel par d’autres fluides et nous mesurons l’évolution de l’épaisseur du film laissé derrière l’interface en fonction du temps et de la vitesse de l’interface. Nous testons différentes géométries dans lesquelles les propriétés de surface sont modifiées afin d’empêcher ou de permettre le glissement des fluides dans le système. Nous montrons que le glissement est un paramètre crucial de l’expérience. De plus, nous avons aussi étudié l’écoulement de fluides de Herschel-Bulkley en systèmes confinés. Cette étude a mis en évidence un nouvel effet associé à une longueur caractéristique qui n’avait pas encore été mentionnée dans la littérature. Cette étude fondamentale révèle la richesse de la dynamique des fluides de Herschel-BulkleyIn 2010, in the Gulf of Mexico, the blow out of the Macondo well was the largest accident in the history of the petroleum industry. It appeared clearly that the cement sheath in the annular gap of the well that is supposed to hinder leakages failed. Leakages are due to the presence of mud (the mud is used during the well fabrication) in the annular gap that damage cement hardening. We use the microfluidic tool to address the question of the mud film left in the annular gap during the cementing process. The cement and the mud will be modelled by microgel suspensions, which turn out to have similar rheological characteristics. Important dimensionless numbers can be made comparable so that useful information can be extracted from studies performed in microfluidic environments. We perform experiments in which we displace microgel suspensions by another fluid. We image the film left behind the finger and we observe its evolution over time and as a function of the front velocity. Various geometries are tested in which the walls chemistry are tuned to allow or prevent slippage. We show that slippage is a crucial parameter of the experiments. Additionally to this approach, we have also performed a study on the flow of Herschel-Bulkley fluids in confined systems. This study revealed a novel effect associated to a characteristic length that has not been reported before. This fundamental study reveals the richness of Herschel-Bulkley flow dynamics
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Cirasole, Adriano. "Studio finalizzato alla caratterizzazione meccanica in situ di conglomerati cementizi additivati con PFU (Pneumatici Fine Uso)." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amslaurea.unibo.it/2317/.
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