Over the past decade, environmental concerns and safety regulation have led to increasing demand for vehicles with higher passenger safety and fuel economy. This has spurred intensive research on advanced high strength steels (AHSS). The quench and partitioning (Q&P) heat treatment is a novel approach that has led to development of one group of third generation AHSS alloys. In recent years most of the studies on the Q&P process were dedicated to the effect of the heat treatment parameters on microstructural evolution and mechanical properties. However, micromechanical deformation behavior of constituent phases and damage evolution in Q&P steels are not fully understood. In this study, damage micromechanisms in a commercial QP980 were investigated with the aid of in-situ tensile tests under a scanning electron microscope (SEM) followed by local strain mapping using microscopic digital image correlation (µ-DIC) analysis so as to quantify the microstructural deformation of constituent phases. Nano-hardness measurements were conducted to correlate the amount of plastic deformation of each phases to its strength. Ex-situ tensile tests coupled with electron back scattered diffraction (EBSD) and X-ray diffraction (XRD) were conducted to study the influence of transformation induced plasticity (TRIP) of the retained austenite phase on microstructural damage and deformation. It was found that average local true strain in ferrite was approximately two times and three times greater than that of martensite and blocky retained austenite respectively, which was with the good agreement with nano-hardness measurements showing that retained austenite blocks was three times and two times harder than martensite and ferrite respectively. Damage in both ferrite and martensite starts at the same total strain; however, damage growth is faster in martensite leading to the formation of large cavities. The average local true strain ratio of ferrite to martensite decreases after total true strains higher than 0.1 and the reduction is more pronounced in regions with higher martensite volume fraction. EBSD results showed that at total true strain of 0.07 some of the retained austenite blocks located at the ferrite and martensite interfaces were almost fully transformed to martensite. According to XRD results at the point of necking 57% of retained austenite transformed to martensite. There is evidence of brittle cracking of large blocky retained austenite in regions with strain localization starting at relatively low strains but appear to have little impact on the final failure process. The good deformation ability of QP980 is attributed primarily to co-deformation of ferrite and martensite and secondarily to the TRIP effect. / Thesis / Master of Applied Science (MASc)

No presente trabalho foram estudados alguns efeitos causados pelo jateamento por granalhas no aço Cr-Si-V, processo que tem por objetivo aumentar a resistência à fadiga. Para este estudo a variação de parâmetros no processo são ferramentas para melhor compreender os mecanismos que influenciam esta propriedade. Os parâmetros utilizados neste trabalho foram a variação da granalha e o pré tensionamento das amostras aplicados em lâminas utilizadas em feixe de molas automobilísticas de aço de liga cromo silício vanádio (SAE 9254+V). Inicialmente foi realizada a avaliação do perfil de tensão residual, efetuada por difração de raios-x pelo método do sen2 ao longo da espessura na região onde a tensão é compressiva. Nos resultados nota-se um efeito anômalo em relação ao perfil característico da distribuição de tensão residual com a perda de compressão nas camadas iniciais em relação à superfície jateada. Com o uso da microscopia eletrônica de varredura foi observado a região afetada pelo jateamento por granalhas notando que as regiões plasticamente deformadas se encontram nas mesmas regiões onde ocorre a diminuição da tensão residual compressiva. O perfil obtido pela difração de raios-x fornece as informações necessárias com o propósito de conjugar os efeitos que a microtensão (microdeformação) influenciam na macrotensão (tensão residual). Esta relação foi comprovada pela sobreposição dos resultados encontrados na distribuição da microdeformação da rede cristalina com a tensão residual ao longo da espessura na região plasticamente deformada. Os resultados dos perfis das difrações de raios-x mostraram a existência de anisotropia de tensões entre os planos, geradas por defeitos de empilhamento e pela densidade de discordâncias. Assim sendo, para obter os valores das microtensões devem ser considerados os fatores das constantes elásticas (conforme o módulo das direções) e dos planos cristalográficos. O método aplicado foi o Williamson-Hall modificado. Além deste método outros também foram utilizados, tais como: método de Warren-Averbach e o método Single Line, este aplicando a série de Fourier, porém, ao observar os resultados, nota-se a diferença entre os valores obtidos nas deformações, tanto aos métodos quanto aos planos cristalográficos, porém a ênfase deste trabalho foi dada às características dos perfis da distribuição e não aos valores absolutos. Somando a isto, foi proporcionado o estudo da distribuição do tamanho médio de cristalito ao longo da espessura no perfil das difrações de raios-x e os resultados mostraram que esta distribuição varia de forma inversa a microdeformação. A relação entre o tamanho médio de cristalito e a variação das distâncias interplanares corresponde diretamente a alterações das densidades de discordâncias ocorridas no material que por sua vez estão ligadas às microdeformações da rede cristalina. Como complemento ao trabalho foram analisados o fator de concentração de tensão e ensaios de fadiga do material. O fator de concentração de tensão não variou conforme a utilização das granalhas S330 e S390, ambas sendo aplicadas no mesmo regime de jateamento. Os ensaios de fadiga indicaram que o pré tensionamento aumenta a vida útil nas tensões cíclicas do material estudado. / In the present work, some effects caused by jateamento por granalhas on Cr-Si-V steel have been studied, a process that aims to increase fatigue resistance. For this study the variation of parameters in the process are tools to better understand the mechanisms that influence this property. The parameters used in this work were the variation of the grit and the pre-tensioning of the samples applied in leafs used in automotive springs of chrome silicon vanadium alloy steel (SAE 9254 + V). Initially the evaluation of the residual stress profile was performed by x-ray diffraction using the sen2 method along the thickness in the region where the stress is compressive. The results show an anomalous effect in relation to the characteristic profile of the residual stress distribution with the decrease of compression in the initial layers in relation to the blasted surface. With the use of scanning electron microscopy, the region affected by grit blasting was observed, noting that the plastically deformed regions are located in the same regions where the compressive residual stress decrease. The profile obtained by X-ray diffraction provides necessary information with the aim of combining the effects of microstress (microstrain) on macrostress (residual stress). This relationship was confirmed by the overlap of the results found in the distribution of the microstrain of the crystalline lattice with the residual stress along the thickness in the plastically deformed region. The results of the x-ray diffraction tests show an existence of tensile anisotropy between the planes generated by stacking faults and the dislocations density. Therefore, to obtain the values of the microstress must be considered the factors of the elastic constants and the crystallographic planes. The method applied was the modified Williamson-Hall. Beyound this method, others were also used, such as: Warren-Averbach method and the Single Line method, this applying the Fourier series, however, when observing the results, we can notice the difference between the values obtained in the deformations, however, the emphasis of this work was on the characteristics of the distribution profiles and not on the absolute values. In addition, the study of the distribution of the mean crystallite size along the thickness of the X-ray diffraction profile was provided and the results showed that this distribution varies inversely with microstrain. The relationship between the mean crystallite size and the variation of the interplanar distances corresponds directly to changes in the densities of dislocations occurring in the material, which in turn are linked to the microstrain of the crystalline lattice. As a complement to the work, the stress concentration factor and fatigue tests of the material were analyzed. The stress concentration factor did not change according to the use of the S330 and S390 grit, both being applied in the same blasting regime. Fatigue tests indicated that pretensioning increases the useful life of the cyclic stresses of the material studied.

No presente trabalho foram estudados alguns efeitos causados pelo jateamento por granalhas no aço Cr-Si-V, processo que tem por objetivo aumentar a resistência à fadiga. Para este estudo a variação de parâmetros no processo são ferramentas para melhor compreender os mecanismos que influenciam esta propriedade. Os parâmetros utilizados neste trabalho foram a variação da granalha e o pré tensionamento das amostras aplicados em lâminas utilizadas em feixe de molas automobilísticas de aço de liga cromo silício vanádio (SAE 9254+V). Inicialmente foi realizada a avaliação do perfil de tensão residual, efetuada por difração de raios-x pelo método do sen2 ao longo da espessura na região onde a tensão é compressiva. Nos resultados nota-se um efeito anômalo em relação ao perfil característico da distribuição de tensão residual com a perda de compressão nas camadas iniciais em relação à superfície jateada. Com o uso da microscopia eletrônica de varredura foi observado a região afetada pelo jateamento por granalhas notando que as regiões plasticamente deformadas se encontram nas mesmas regiões onde ocorre a diminuição da tensão residual compressiva. O perfil obtido pela difração de raios-x fornece as informações necessárias com o propósito de conjugar os efeitos que a microtensão (microdeformação) influenciam na macrotensão (tensão residual). Esta relação foi comprovada pela sobreposição dos resultados encontrados na distribuição da microdeformação da rede cristalina com a tensão residual ao longo da espessura na região plasticamente deformada. Os resultados dos perfis das difrações de raios-x mostraram a existência de anisotropia de tensões entre os planos, geradas por defeitos de empilhamento e pela densidade de discordâncias. Assim sendo, para obter os valores das microtensões devem ser considerados os fatores das constantes elásticas (conforme o módulo das direções) e dos planos cristalográficos. O método aplicado foi o Williamson-Hall modificado. Além deste método outros também foram utilizados, tais como: método de Warren-Averbach e o método Single Line, este aplicando a série de Fourier, porém, ao observar os resultados, nota-se a diferença entre os valores obtidos nas deformações, tanto aos métodos quanto aos planos cristalográficos, porém a ênfase deste trabalho foi dada às características dos perfis da distribuição e não aos valores absolutos. Somando a isto, foi proporcionado o estudo da distribuição do tamanho médio de cristalito ao longo da espessura no perfil das difrações de raios-x e os resultados mostraram que esta distribuição varia de forma inversa a microdeformação. A relação entre o tamanho médio de cristalito e a variação das distâncias interplanares corresponde diretamente a alterações das densidades de discordâncias ocorridas no material que por sua vez estão ligadas às microdeformações da rede cristalina. Como complemento ao trabalho foram analisados o fator de concentração de tensão e ensaios de fadiga do material. O fator de concentração de tensão não variou conforme a utilização das granalhas S330 e S390, ambas sendo aplicadas no mesmo regime de jateamento. Os ensaios de fadiga indicaram que o pré tensionamento aumenta a vida útil nas tensões cíclicas do material estudado. / In the present work, some effects caused by jateamento por granalhas on Cr-Si-V steel have been studied, a process that aims to increase fatigue resistance. For this study the variation of parameters in the process are tools to better understand the mechanisms that influence this property. The parameters used in this work were the variation of the grit and the pre-tensioning of the samples applied in leafs used in automotive springs of chrome silicon vanadium alloy steel (SAE 9254 + V). Initially the evaluation of the residual stress profile was performed by x-ray diffraction using the sen2 method along the thickness in the region where the stress is compressive. The results show an anomalous effect in relation to the characteristic profile of the residual stress distribution with the decrease of compression in the initial layers in relation to the blasted surface. With the use of scanning electron microscopy, the region affected by grit blasting was observed, noting that the plastically deformed regions are located in the same regions where the compressive residual stress decrease. The profile obtained by X-ray diffraction provides necessary information with the aim of combining the effects of microstress (microstrain) on macrostress (residual stress). This relationship was confirmed by the overlap of the results found in the distribution of the microstrain of the crystalline lattice with the residual stress along the thickness in the plastically deformed region. The results of the x-ray diffraction tests show an existence of tensile anisotropy between the planes generated by stacking faults and the dislocations density. Therefore, to obtain the values of the microstress must be considered the factors of the elastic constants and the crystallographic planes. The method applied was the modified Williamson-Hall. Beyound this method, others were also used, such as: Warren-Averbach method and the Single Line method, this applying the Fourier series, however, when observing the results, we can notice the difference between the values obtained in the deformations, however, the emphasis of this work was on the characteristics of the distribution profiles and not on the absolute values. In addition, the study of the distribution of the mean crystallite size along the thickness of the X-ray diffraction profile was provided and the results showed that this distribution varies inversely with microstrain. The relationship between the mean crystallite size and the variation of the interplanar distances corresponds directly to changes in the densities of dislocations occurring in the material, which in turn are linked to the microstrain of the crystalline lattice. As a complement to the work, the stress concentration factor and fatigue tests of the material were analyzed. The stress concentration factor did not change according to the use of the S330 and S390 grit, both being applied in the same blasting regime. Fatigue tests indicated that pretensioning increases the useful life of the cyclic stresses of the material studied.

This research work presents the first comprehensive study on nanocrystalline materials produced in bulk quantities using a novel continuous electrodeposition process. A series of nanocrystalline Ni and Ni-Fe alloy continuous foils were produced and an intensive investigation into their structure and various properties was carried out. High-resolution transmission electron microscopy (HR-TEM) revealed the presence of local strain at high and low angle, and twin boundaries. The cause for these local strains was explained based on the interpretation of non-equilibrium grain boundary structures that result when conditions of compatibility are not satisfied. HR-TEM also revealed the presence of twin faults of the growth type, or “growth faults”, which increased in density with the addition of Fe. This observation was found to be consistent with a corresponding increase in the growth fault probabilities determined quantitatively using X-ray diffraction (XRD) pattern analysis. Hardness and Young’s modulus were measured by nanoindentation. Hardness followed the regular Hall-Petch behaviour down to a grain size of 20 nm after which an inverse trend was observed. Young’s modulus was slightly reduced at grain sizes less than 20 nm and found to be affected by texture. Microstrain based on XRD line broadening was measured for these materials and found to increase primarily with a decrease in grain size or an increase in intercrystal defect density (i.e., grain boundaries and triple junctions). This microstrain is associated with the local strains observed at grain boundaries in the HR-TEM image analysis. A contribution to microstrain from the presence of growth faults in the nanocrystalline Ni-Fe alloys was also noted. The macrostresses for these materials were determined from strain measurements using a two-dimensional XRD technique. At grain sizes less than 20 nm, there was a sharp increase in compressive macrostresses which was also owed to the corresponding increase in intercrystal defects or interfaces in the solid.

This research work presents the first comprehensive study on nanocrystalline materials produced in bulk quantities using a novel continuous electrodeposition process. A series of nanocrystalline Ni and Ni-Fe alloy continuous foils were produced and an intensive investigation into their structure and various properties was carried out. High-resolution transmission electron microscopy (HR-TEM) revealed the presence of local strain at high and low angle, and twin boundaries. The cause for these local strains was explained based on the interpretation of non-equilibrium grain boundary structures that result when conditions of compatibility are not satisfied. HR-TEM also revealed the presence of twin faults of the growth type, or “growth faults”, which increased in density with the addition of Fe. This observation was found to be consistent with a corresponding increase in the growth fault probabilities determined quantitatively using X-ray diffraction (XRD) pattern analysis. Hardness and Young’s modulus were measured by nanoindentation. Hardness followed the regular Hall-Petch behaviour down to a grain size of 20 nm after which an inverse trend was observed. Young’s modulus was slightly reduced at grain sizes less than 20 nm and found to be affected by texture. Microstrain based on XRD line broadening was measured for these materials and found to increase primarily with a decrease in grain size or an increase in intercrystal defect density (i.e., grain boundaries and triple junctions). This microstrain is associated with the local strains observed at grain boundaries in the HR-TEM image analysis. A contribution to microstrain from the presence of growth faults in the nanocrystalline Ni-Fe alloys was also noted. The macrostresses for these materials were determined from strain measurements using a two-dimensional XRD technique. At grain sizes less than 20 nm, there was a sharp increase in compressive macrostresses which was also owed to the corresponding increase in intercrystal defects or interfaces in the solid.

A small-scale adiabatic calorimeter has been constructed as part of a larger project to study nano-particles and to facilitate specific heat measurements on samples where it is difficult to obtain enough material to run on the current large-scale adiabatic apparatus. This calorimeter is designed to measure sample sizes of less than 0.8 cc over a temperature range from 13 K to 350 K. Specific heat results on copper, sapphire, and benzoic acid show the accuracy of the measurements to be better than ±0.4% for temperatures higher than 50 K. The reproducibility of these measurements is generally better than ±0.25%. Experimental specific heat data was collected on this new apparatus for synthetic akaganeite, β-FeOOH, for samples with varying degrees of hydration. Our results yield values for Δ_0^298.15S°m of 79.94 ±0.20 J•K^-1•mol^-1 and 85.33 ±0.021 J•K^-1•mol^-1 for samples of β-FeOOH0.551H2O and β-FeOOH0.652H2O, respectively. From this data, we were able to determine the standard molar entropy for bare β-FeOOH, as Δ_0^298.15S°m = 53.8 ±3.3 J•K^-1•mol^-1, based on subtractions of the estimated contribution of water from the hydrated species. Additionally, the specific heats of α-uranium, titanium diboride, and lithium flouride have been measured on a low-temperature, semi-adiabatic calorimeter down to 0.5 K. For the α-uranium, the specific heat of a polycrystalline sample was compared to that of a single crystal, and it was found that there was a significant difference in the specific heats, which has been attributed to microstrain in the polycrystal. The third law entropy for the polycrystal at 298.15 K, Δ_0^298.15S°m, calculated from these heat capacities is 50.21 ±0.1 J•K^-1•mol^-1, which is good in agreement with previously published values of polycrystal samples. For the single crystal Δ_0^298.15S°m, calculated using the thermodynamic microstrain model, is 49.02 ±0.2 J•K^-1•mol^-1. The low-temperature specific heats of titanium diboride and lithium fluoride have been measured from 0.5 K to 30 K as part of a larger project in the construction of a neutron spectrometer. For this application, the measured specific heats were used to extrapolate the specific heats down to 0.1 K with lattice, electronic, and Schottky equations for the respective samples. The resultant specific heat values at 0.1 K for TiB2 and 6LiF are 4.08E-4 ±0.27E-4 J•K^-1•mol^-1 and 9.19E-9 ±0.15E-9 J•K^-1•mol^-1, respectively.

No description available.

Made available in DSpace on 2017-07-21T19:25:47Z (GMT). No. of bitstreams: 1 Luis Valerio Prandel.pdf: 10631150 bytes, checksum: 0e039282f135a5275af84e3d9bd6d4ee (MD5) Previous issue date: 2015-03-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The soil is a complex and heterogeneous medium containing solid, liquid, gases and several organisms. Its solid phase is composed of minerals that present well defined and highly organized chemical composition. Tropical climate soils, classified as hardsetting, are kaolinitic and present low nutrient and organic matter amounts. Nowadays, there is no consensus about these soils hardsetting characteristics. The characterization of physical and chemical properties of these horizons and their granulometric fractions enables the physical, chemical and mineralogical investigation of five hardsetting soils in this study. Spectroscopic and microscopic techniques, thermal analysis and X-ray diffraction with the Rietveld Method were employed. The RM-XRD made possible to quantify and estimate crystallite average size and mineral micro-deformations. Part of these results was associated to Kaolinite, Halloysite, and Goethite isomorphic substitution. The quantitative XRF analyses revealed the content of chemical elements in the soils under study with higher accuracy. The thermal analysis techniques showed that Kaolinite of weathered soils is susceptible to dehydroxylation at lower temperatures. SEM micrographs revealed the particle typical shapes and these results were confirmed through the AFM that estimated the number of crystallites and the average number of kaolinite layers in the clay fraction. Most of the particles observed through microscopic techniques were ascribed to the Kaolinite, and their micromorphological characteristics could be compared to crystallite size and microdeformations obtained through the RM-XRD. Therefore, based on the results of spectroscopic, microscopic, thermal analyses and X-ray diffraction with Rietveld Method, it was possible to understand the several degrees of crystallinity of minerals which are part of the granulometric fractions of hardsetting horizons in kaolinitic soils. / O solo é um meio complexo e heterogênio de sólidos, líquidos, gases e diversos organismos. A fase sólida é composta de minerais que apresentam composição química definida e altamente ordenada. Solos de clima tropical, classificados como coesos são cauliníticos e apresentam baixa quantidade de nutrientes e matéria orgânica. Atualmente não se chegou a um consenso sobre o caráter coeso desses solos. A caracterização das propriedades físicas e químicas desses horizontes e de suas frações granulométricas possibilita uma investigação física, química e mineralógica de cinco solos coesos de estudo desse trabalho. Para isso foram utilizadas técnicas espectroscópicas, microscópicas, de análises térmicas e Difração de raios X com método de Rietveld. Com os resultados de MR-DRX foi possível quantificar, estimar o tamanho médio de cristalitos e microdeformações dos minerais. Parte desses resultados foram associados com a substituição isomórfica na Caulinita, Haloisita e Goethita. As análises de FRX quantitativas revelaram maior acurácia o teor de elementos químicos nos solos estudados. As técnicas de análises térmicas mostraram que as Caulinitas de solos intemperizados são susceptíveis a desidroxilação a menores temperaturas. Micrografias por MEV revelaram os formatos típicos de partículas e esses resultados foram confirmados por meio da AFM que estimou a quantidade de cristalitos e o número médio de empilhamento das camadas de Caulinita na fração argila. A maior parte das partículas observadas nas técnicas microscópicas foi atribuída a Caulinita, sendo que suas características micromorfológicas puderam ser comparadas com tamanho de cristalitos e microdeformações obtidos pelo MRDRX. Assim, com base nos resultados das análises espectroscópicas, microscópicas, térmicas e de difração de raios X pelo método de Rietveld foi possível compreender os diversos graus de cristalinidade dos minerais que compõem as frações granulométricas de horizontes coesos de solos cauliníticos.

Submitted by Angela Maria de Oliveira (amolivei@uepg.br) on 2018-04-26T13:22:22Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Marcel Tadshi Izumi.pdf: 4222698 bytes, checksum: e7c749993223b983b4e37d54985610de (MD5) / Made available in DSpace on 2018-04-26T13:22:22Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Marcel Tadshi Izumi.pdf: 4222698 bytes, checksum: e7c749993223b983b4e37d54985610de (MD5) Previous issue date: 2018-02-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Três metais CFC comercialmente puros (alumínio, cobre e prata) foram deformados por ensaios de tração uniaxial e caracterizados por difração de raios X in situ, utilizando uma fonte síncrotron, em temperatura ambiente (293K) e criogênica (77K). A supressão parcial da recuperação dinâmica decorrente do processamento criogênico permite melhorias nas propriedades mecânicas, tais como ductilidade e resistência. Esta supressão resulta em um aumento na densidade de defeitos internos dos metais durante a deformação, promovendo um refino microestrutural e aumento da microdeformação. O refino microestrutural é manifestado pela evolução de dimples na superfície de fratura e pela redução do tamanho médio de cristalitos. Todos os metais apresentaram maior resistência mecânica em temperaturas criogênicas, entretanto somente o cobre e a prata apresentaram aumento de ductilidade. Esse comportamento é atribuído à menor energia de defeito de empilhamento destes metais em comparação com o alumínio. / Three FCC commercially pure metals (aluminum, copper and silver) were deformed by uniaxial tensile tests and were characterized by in situ X-ray diffraction, using a synchrotron source, at room (293K) and cryogenic (77K) temperatures. The partial suppression of dynamic recovery due to cryogenic processing allows an improvement in mechanical properties, such as ductility and strength. This suppression results in an increase in the internal defects density of metals during the strain, promoting microstructural refining and increase of microstrain. The microstructural refinement is manifested by dimples evolution on the fracture surface and reduction of average crystallite size. All metals present higher mechanical strength at cryogenic temperature, nevertheless the ductility only was increased in copper and silver. This behavior is attributed to lower stacking fault energy of these metals in comparison with aluminum.

Made available in DSpace on 2014-12-17T14:07:00Z (GMT). No. of bitstreams: 1 AlexsandraCC.pdf: 2480283 bytes, checksum: 5ee60db44e31addafb5e193c9292f73e (MD5) Previous issue date: 2008-12-10 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The cerium oxide has a high potential for use in removing pollutants after combustion, removal of organic matter in waste water and the fuel-cell technology. The nickel oxide is an attractive material due to its excellent chemical stability and their optical properties, electrical and magnetic. In this work, CeO2-NiO- systems on molars reasons 1:1(I), 1:2(II) e 1:3(III) metal-citric acid were synthesized using the Pechini method. We used techniques of TG / DTG and ATD to monitor the degradation process of organic matter to the formation of the oxide. By thermogravimetric analysis and applying the dynamic method proposed by Coats-Redfern, it was possible to study the reactions of thermal decomposition in order to propose the possible mechanism by which the reaction takes place, as well as the determination of kinetic parameters as activation energy, Ea, pre-exponential factor and parameters of activation. It was observed that both variables exert a significant influence on the formation of complex polymeric precursor. The model that best fitted the experimental data in the dynamic mode was R3, which consists of nuclear growth, which formed the nuclei grow to a continuous reaction interface, it proposes a spherical symmetry (order 2 / 3). The values of enthalpy of activation of the system showed that the reaction in the state of transition is exothermic. The variables of composition, together with the variable temperature of calcination were studied by different techniques such as XRD, IV and SEM. Also a study was conducted microstructure by the Rietveld method, the calculation routine was developed to run the package program FullProf Suite, and analyzed by pseudo-Voigt function. It was found that the molar ratio of variable metal-citric acid in the system CeO2-NiO (I), (II), (III) has strong influence on the microstructural properties, size of crystallites and microstrain network, and can be used to control these properties / O ?xido de c?rio tem um alto potencial em uso para remo??o de p?s poluentes de combust?o, remo??o de mat?rias org?nicas de ?guas residuais e na tecnologia de c?lulas a combust?vel. O ?xido de n?quel ? um material atraente devido a sua excelente estabilidade qu?mica, bem como suas propriedades ?pticas, el?tricas e magn?ticas. Neste trabalho, sistemas de CeO2-NiO nas raz?es molares 1:1(I), 1:2(II) e 1:3(III) metal-?cido c?trico foram sintetizados utilizando o m?todo Pechini. Foram utilizadas t?cnicas de TG / DTG e DTA para monitorar o processo de degrada??o da mat?ria org?nica at? a forma??o do ?xido. Atrav?s da an?lise termogravim?trica e aplicando-se o m?todo din?mico proposto por Coats-Redfern, foi poss?vel realizar estudos das rea??es de decomposi??o t?rmica com o intuito de propor o poss?vel mecanismo pelo qual a rea??o se processa, como tamb?m, a determina??o de par?metros cin?ticos como energia de ativa??o, Ea, fator pr?-exponencial e par?metros termodin?micos de ativa??o. Foi observado que ambas as vari?veis exercem grande influ?ncia na forma??o do complexo polim?rico precursor. O modelo que melhor ajustou-se aos dados experimentais no modo din?mico foi o R3, que consiste de crescimento nuclear, onde, os n?cleos formados crescem at? atingirem uma interface de rea??o cont?nua, este, prop?e uma simetria esf?rica (ordem 2/3). Os valores de entalpia de ativa??o do sistema evidenciaram que a rea??o no estado de transi??o ? exot?rmica. As vari?veis de composi??o, juntamente com a vari?vel temperatura de calcina??o foram estudadas por diferentes t?cnicas, tais como: DRX, IV e MEV. Tamb?m foi realizado um estudo microestrutural pelo m?todo de Rietveld, cuja rotina de c?lculo foi desenvolvida para ser executada no pacote do programa Fullprof Su?te, e analisada pela fun??o pseudo-Voigt. Verificou-se que a vari?vel raz?o molar metal-?cido c?trico no sistema CeO2-NiO (I),(II),(III) tem forte influ?ncia nas propriedades microestruturais, tamanho de cristalito e microdeforma??o de rede, e podem ser usados para controlar estas propriedades