Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph. D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 10, 2007) Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 141-148).

Made available in DSpace on 2014-06-11T19:23:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-06-20Bitstream added on 2014-06-13T18:09:40Z : No. of bitstreams: 1 souza_ae_me_bauru.pdf: 2026557 bytes, checksum: 7c154df4043c97f750918f33c97e250f (MD5) / Foi estudada a influência de cinza de bagaço de cana e rocha sedimentar, adicionadas a um material argiloso, durante o processo de sinterização. O material argiloso e os aditivos foram caracterizados utilizando Difratometria de Raio X, Espectrometria de flurescência de Raio X e Análise Térmica. As amostras de cinza e rocha foram moídas, peneiradas a 0,088 mm e 0,125 mm, respectivamente, e incorporadas nos teores de 0, 20, 40, 60 e 80% em massa ao material argiloso. Foram preparados corpos de prova, prensados uniaxialmente a 19 Mpa, para cada corpo de prova, em uma prensa manual. As peças foram sinterizadas nas temperaturas de 500, 800, 900, 1000, 1100 e 1200º C, usando um forno tipo mufla e, posteriormente, submetidos a análise difratométrica e a ensaios físicos e mecânicos de absorção de água, retração linear de queima, massa específica aparente, perda de massa ao fogo, porosidade aparente e módulo de ruptura à flexão. A difratometria de raios X mostrou que a cinza é composta de material cristalino, predominantemente quartzo; a rocha sedimentar apresentou, além de quartzo, argilominerais micáceos e o material argiloso teve como fase principal a caulinita, contendo ainda hidróxido de alumínio e óxidos de ferro em menores concentrações. A análise química mostrou que, além do silício, a cinza e a rocha sedimentar apresentaram concentrações de óxidos de alumínio, potássio, cálcio, ferro e magnésio, enquanto que no material, os óxidos de silício, alumínio, ferro e titânio foram predominantes. As análises térmicas das diferentes misturas mostraram algumas reações que indicam transformação (inversão do quartzo), decomposição (perda de hidróxidos) e formação de fase (mulita) durante o aquecimento das amostras. Difração de raios X sustentou as hipóteses levantadas nos termograms das amostras... / The influence of sugar cane bagasse ash and sedimentary rock, added to clay material, in the sintering process was studied. The clay material and the additives were characterized by X-ray diffraction, X-ray spectroscopy and thermal analysis. The ash and rock samples were triturated, sieved to 0.088 mm and 0.125 mm, respectively, and incorporated at 0, 20, 40, 60, and 80% in the clay material. Prismatic probes were prepared, each pressed at 19 Mpa in a manual press. The pieces were sintered at 500, 800, 900, 1000, 1100 ans 1200ºC, and then characterized by X-ray diffraction and tests for water absorption, linear shrinkage, apparent specific mass, loss on ignition, apparent porosity and flexural strength. X-ray diffraction showed that the ash was composed of crystalline material, predominantly quartz; the sedimentary rock contained, besides quartz, mica; and the main phase of the clay material was kaolinite, but also contained aluminum hydroxide and iron oxides in lower concentrations. Chemical analysis showed that, besides silicon, the ash and the sedimentary rock also contained concentrations of oxides of aluminum, potassium, calcium, iron and magnesium, while in the clay material, silicon oxide, aluminum, iron and titanium were predominant. Thermal analyses of the different of the mixtures showed some reactions that indicated transformation (inversion of the quartz), decomposition (loss of hydroxides) and phase formation (mullite) during the heating of the samples. X-ray diffraction supported the findings in the thermal analysis of the analyzed samples. The tests showed that both the ash and sedimentary rock worsened the mechanical properties of the clay material, although they contributed to the improvement of other attributes. The presence of quartz in the ash and rock hindered the formation of the mullite phase formed during the sintering process... (Complete abstract click electronic acess below)

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No description available.

Metal carbides have attracted much attention over the past several years due to their unique qualities. The purpose of this research is to develop a cermet that demonstrates desired properties of nano-size titanium carbide (TiC) and copper-nickel (Cu-Ni) metals. In this study stoichiometric, nano-size TiC was synthesized through a patented carbothermal synthesis process (U.S. Patent No.: 5,417,952). The resulting TiC was sintered with varying copper (12.5-37.5wt %) and nickel (12.5-25wt %) contents. Hardness, fracture toughness, and microscopy studies were performed. Average hardness ranging between 325-1292 HV were found, with copper content showing a strongly negative correlation with hardness. Fracture toughness values were found to be between 4.85-14.36 Mpa*m^.5; TiC content had a nearly linear, negative correlation with fracture toughness. Samples with high copper to nickel ratios showed poor homogeneity and wetting.

This dissertation discusses the synthesis, processing, and characterization of titanium carbide (TiC) and titanium diboride (TiB2) based materials for structural and electronic application. A series of TiB2 and TiC-TiB2 powders was prepared through a novel carbon coated precursors method. Reaction process, phase evolution, and microstructures were analyzed and characterized. The synthesized powders have the advantages of fine particle size (nano to submicron grade, 100nm to 800nm), high purity (low levels of contaminations such as free carbon and oxygen), loose agglomeration, and high surface area (~2.5 m2/g to 7.2 m2/g). Using the synthesized powders, three categories of composites were prepared: (1) TiB2-TiC-Ni composites with improved mechanical properties for structural applications; (2) TiB2-TiNiFeCrCoAl high-entropy alloy (HEA) composites with enhanced hardness and toughness for structural application; (3) TiC-Ti3Al based composites with good electrical and oxidation properties as the interconnect in solid oxide fuel cell. The author focuses on the sintering mechanism, microstructure and interface, reactions, and properties characterizations of above three types of composites. Correlations of processing-microstructures-properties are discussed and established based on scientific observation.

Made available in DSpace on 2015-09-17T15:24:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-01-09. Added 1 bitstream(s) on 2015-09-17T15:46:54Z : No. of bitstreams: 1 000843246.pdf: 1851895 bytes, checksum: 017cb6322b609052302e82e247cff99c (MD5) / O objetivo deste trabalho foi avaliar o efeito do método de sinterização, convencional e por meio de energia micro-ondas, sobre as características microestruturais e propriedades mecânicas de cerâmicas à base de zircônia Y-TZP. A hipótese nula foi que a sinterização realizada por forno de micro-ondas não influencia na resistência à flexão biaxial de discos Y-TZP, tanto dos discos envelhecidos por meio de uma cicladora termomecânica, quanto nos grupos não-ciclados. Cem amostras em forma de discos de cerâmica VIPI Block Zirconn (12 x 1,2 mm) foram usinados de acordo com as normas ISO 6872 para o ensaio de flexão biaxial e foram separados em grupos de acordo com o método de sinterização e de envelhecimento termomecânico: Grupo I: Sinterização convencional e sem ciclagem mecânica; Grupo II: Sinterização convencional + ciclagem termomecânica; Grupo III: Sinterização em micro-ondas e sem ciclagem termomecânica; Grupo IV: Sinterização em micro-ondas + ciclagem termomecânica. Os corpos de prova foram submetidos à flexão biaxial após a sinterização para os grupos não ciclados e após a ciclagem para os grupos os quais foram submetidos ao envelhecimento (1.200.000 ciclos, carga de 45 N e frequência de 2,8 Hz, biaxial, imersos em água 37 °C). Foi realizada análise qualitativa das amostras por meio de um microscópio eletrônico de varredura e difração de raios-X em oito amostras (n = 2) para todos os grupos. Para a análise estatística foi utilizado o módulo Weibull (m), sendo que não houve diferença significativa quando comparado à ciclagem, porém houve quando comparado o método. O mesmo ocorreu quando foi aplicada a análise de variância (α = 5%). Conclui-se que o protocolo de sinterização praticado neste estudo não teve sucesso na sinterização da zircônia odontológica, e o termociclagem não afeta as características microestruturais e mecânicas da Y-TZP / The objective of this study was to evaluate the impact of the sintering method, conventional and through microwave energy on the microstructural characteristics and mechanical properties of ceramics based on Y- TZP zirconia. The null hypothesis is that sintering is carried out by microwave oven has no effect on the biaxial flexural strength Y- TZP disc, both discs aged by means of a thermo cycler, and in the non- cycled groups. One hundred samples in the form of VIPI Block Zirconn ceramic discs (12 x 1.2 mm) were machined in accordance with ISO 6872 standards for biaxial bending test and were divided into groups according to the method of sintering and thermomechanical aging: Group I: conventional and without mechanical cycling sintering ; Group II : conventional + thermomechanical cycling sintering ; Group III: microwave sintering and without thermomechanical cycling ; Group IV: in microwave sintering + thermomechanical cycling . The specimens were subjected to biaxial bending after sintering for non-cycled groups and after cycling for groups which were submitted to aging ( 1,200,000 cycles, 45 N load and frequency of 2.8 Hz, biaxial, immersed in water 37 °C). Qualitative analysis was performed on samples using a scanning electron microscope and X-ray diffraction samples in eight samples(n = 2) for all groups. For statistical analysis the Weibull modulus (m) was used, and there was no significant difference when compared to cycling, but there was compared the method. The same happened when the analysis of variance (α = 5%) was applied. It follows that sintering protocol performed in this study had no success in dental zirconia sintering and thermal cycling does not affect the microstructure and mechanical properties of Y- TZP