Dissertations / Theses on the topic 'Mg-Al-O'

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Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
The Layered Double Hydroxides has become extremely promising materials due to its range of applications, easily obtained in the laboratory and reusability after calcination, so the knowledge regarding their properties is of utmost importance. In this study were synthesized layered double hydroxides of two systems, Mg-Al and Zn-Al, and such materials were analyzed with X-ray diffraction and, from these data, we determined the volume density, planar atomic density, size crystallite, lattice parameters, interplanar spacing and interlayer space available. Such materials were also subjected to thermogravimetric analysis reasons for heating 5, 10, 20 and 25 ? C / min to determine kinetic parameters for the formation of metaphases HTD and HTB based on theoretical models Ozawa, Flynn-Wall Starink and Model Free Kinetics. In addition, the layered double hydroxides synthesized in this working ratios were calcined heating 2.5 ? C / min and 20 ? C / min, and tested for adsorption of nitrate anion in aqueous solution batch system at time intervals 5 min, 15 min, 30 min, 1h, 2h and 4h. Such calcined materials were also subjected to exposure to the atmosphere and at intervals of 1 week, 2 weeks and 1 month were analyzed by infrared spectroscopy to study the kinetics of regeneration determining structural called "memory effect"
Os Hidr?xidos Duplos Lamelares tem se tornado materiais extremamente promissores devido a sua gama de aplica??es, f?cil obten??o em laborat?rio e a possibilidade de reutiliza??o ap?s calcina??o, portanto o conhecimento referente ? suas propriedades ? de extrema relev?ncia. Neste estudo foram sintetizados hidr?xidos duplos lamelares de dois sistemas, Mg-Al e Zn-Al, e tais materiais foram submetidos a an?lise com difra??o de raios X e, a partir de tais dados, foram determinados a densidade volum?trica, densidade at?mica planar, tamanho do cristalito, par?metros de rede cristalina, dist?ncia interplanar e espa?o interlamelar dispon?vel. Tais materiais tamb?m foram submetidos ? an?lise termogravim?trica em raz?es de aquecimento de 5, 10, 20 e 25 ?C/min para determina??o de par?metros cin?ticos durante a forma??o das metafases HTD e HTB com base nos modelos te?ricos de Ozawa, Flynn-Wall, Starink e Model Free Kinetics. Al?m disso, os hidr?xidos duplos lamelares sintetizados neste trabalhado foram calcinados em raz?es de aquecimento de 2,5 ?C/min e 20 ?C/min e submetidos a ensaios de adsor??o de ?nion nitrato em solu??o aquosa em sistema de batelada em intervalos de tempo de 5 min, 15 min, 30 min, 1h, 2h e 4h. Tais materiais calcinados tamb?m foram submetidos ? exposi??o com a atmosfera e em intervalos de tempo de 1 semana e 2 semanas foram analisados atrav?s de difra??o de raios X para estudo determina??o da cin?tica de regenera??o estrutural denominada efeito mem?ria

Дисертація на здобуття наукового ступеня доктора технічних наук зі спеціальності 05.17.11 – технологія тугоплавких неметалічних матеріалів. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2015 р. Дисертацію присвячено створенню теоретичних основ технології тугоплавких неформованих матеріалів з високою міцністю, вогнетривкістю та стійкістю до дії агресивних середовищ на основі алюмінатів і хромітів лужноземельних елементів за рахунок цілеспрямованого формування фазового складу та структури клінкеру, цементного каменю і бетону. Систематизовано базу термодинамічних даних; на основі встановлених фазових рівноваг уточнено та досліджено субсолідусну будову потрійних та чотирикомпонентних підсистем багатокомпонентної системи (Mg, Ca, Sr, Ba)O – Al₂O₃ – Cr₂O₃ та встановлено їх подібність, яка полягає у співіснуванні алюмінатів з хромітом лужноземельного елементу та з периклазом, що обумовлює стабільні технологічні параметри твердофазного синтезу вогнетривких алюмохромітних в'яжучих матеріалів та бетонів на основі їх композицій. Встановлено особливості протікання процесів фазоутворення та гідратації алюмохромітних цементів, визначено механізми структуроутворення клінкерів та цементного каменю. Розроблено склади високоміцних, вогнетривких алюмохромітних цементів та бетонів на їх основі, визначено їх основні фізико-механічні та технічні властивості. Розроблено ресурсо- та енергозберігаючу технологію отримання алюмохромітних цементів з використанням відходів хімічної галузі промисловості. Неформовані матеріали, розроблені з використанням алюмохромітних цементів було апробовано в промислових та напівпромислових умовах з позитивним результатом, а результати досліджень впроваджені у практику навчального процесу.
Thesis for the doctor of technical sciences degree in specialty 05.17.11 – Technology of refractory nonmetallic materials. – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2015. The thesis is dedicated to the creation of theoretical foundations of refractory unshaped materials development on the base of aluminates and chromites of alkaline-earth elements with high strength, fire resistance and resistance to aggressive environments due to directed formation of clinker structure, cement stone and concrete. Thermodynamic database has been systematized; subsolidus structure of ternary and quarternary subsystems of the multicomponent (Mg, Ca, Sr, Ba)O – Al₂O₃ – Cr₂O₃ system has been clarified and researched, their geometrical-topological similarity has been established, which consists in co-existence of aluminate with chromite of alkaline-earth element and with periclase that determines stable conditions of synthesis of refractory aluminochromite binding materials and concretes on the base of their compositions. Aspects of the process of phase formation and hydration of aluminochromite cements established, mechanisms of structure formation of clinkers and cement stone have been determined. Compositions of refractory high-strength and resistant to aggressive environments aluminochromite cements and concretes on their base have been developed, their main physico-mechanical and technical characteristics have been determined. Resource and energy saving technology of preparation of aluminochromite cements with the use of chemical industry wastes has been developed. Unshaped materials developed with the use of aluminochromite cements have been approved in industrial and semi-industrial conditions with positive results, and the results have been incorporated into the practice of academic process.

циальности 05.17.11 – технология тугоплавких неметаллических материалов. – Национальный технический университет "Харьковский политехнический институт", Харьков, 2015 г. Диссертационная работа посвящена решению научно-практической проблемы создания теоретических основ технологии тугоплавких неформованных материалов с высокой прочностью, огнеупорностью и стойкостью к воздействию агрессивных сред на основе алюминатов и хромитов щелочноземельных элементов за счет целенаправленного формирования фазового состава и структуры клинкера, цементного камня и бетона. Систематизирована база термодинамических данных соединений, входящих в состав многокомпонентной системы (Mg, Ca, Sr, Ba)O – Al₂O₃ – Cr₂O₃, на основе установленных фазовых равновесий исследовано субсолидусное строение ее трех- и четырехкомпонентных подсистем и установлено их подобие, заключающееся в сосуществовании алюминатов с хромитом щелочноземельного элемента и с периклазом, что обусловливает устойчивые технологические параметры твердофазного синтеза высокопрочных, огнеупорных алюмохромитных вяжущих материалов и бетонов на их основе. На основании данных регрессионного анализа и результатов физико-механических испытаний оптимизированы составы алюмохромитных цементов и установлено соответствие их характеристик требованиям нормативной документации: нормальная густота цементного теста 23 – 29 %; сроки схватывания: начало – от 40 мин до 2 час, конец – от 55 мин до 4 час 15 мин; предел прочности при сжатии в возрасте 28 суток твердения 57 – 75 МПа; предел прочности при изгибе в возрасте 28 суток твердения 6,2 – 6,8 МПа, огнеупорность – 1700 – 1900 °С. Исследованы особенности протекания процессов фазообразования клинкеров алюмохромитных цементов и установлено, что в начальный период протекания процесса фазообразования скорость реакций лимитируется химическим взаимодействием компонентов сырьевой смеси на границе раздела фаз и только после образования непрерывного слоя продуктов твердофазных реакций скорость процесса определяется диффузией компонентов в реакционную зону. Последовательность образования фаз (монохромит – моноалюминат – трехосновный хромит – трехосновный алюминат) подтверждена рентгенофазовыми исследованиями, термодинамическими расчетами и расчетами энергии кристаллической решетки, что обусловливает формирование дефектной структуры алюмохромитных клинкеров. Исследованы клинкеры алюмохромитных цементов и установлено, что их расчетный фазовый состав соответствует экспериментально полученным составам. Наличие в клинкерах ограниченных твердых растворов дефектной структуры обусловливает повышенную механическую прочность за счет возрастания свободной энергии кристаллической решетки.
Thesis for the doctor of technical sciences degree in specialty 05.17.11 – Technology of refractory nonmetallic materials. – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2015. The thesis is dedicated to the creation of theoretical foundations of refractory unshaped materials development on the base of aluminates and chromites of alkaline-earth elements with high strength, fire resistance and resistance to aggressive environments due to directed formation of clinker structure, cement stone and concrete. Thermodynamic database has been systematized; subsolidus structure of ternary and quarternary subsystems of the multicomponent (Mg, Ca, Sr, Ba)O – Al₂O₃ – Cr₂O₃ system has been clarified and researched, their geometrical-topological similarity has been established, which consists in co-existence of aluminate with chromite of alkaline-earth element and with periclase that determines stable conditions of synthesis of refractory aluminochromite binding materials and concretes on the base of their compositions. Aspects of the process of phase formation and hydration of aluminochromite cements established, mechanisms of structure formation of clinkers and cement stone have been determined. Compositions of refractory high-strength and resistant to aggressive environments aluminochromite cements and concretes on their base have been developed, their main physico-mechanical and technical characteristics have been determined. Resource and energy saving technology of preparation of aluminochromite cements with the use of chemical industry wastes has been developed. Unshaped materials developed with the use of aluminochromite cements have been approved in industrial and semi-industrial conditions with positive results, and the results have been incorporated into the practice of academic process.

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CAPES/PROSUP
The objective of the present work is to develop two modified ternary Al-Zn-Mg alloys, with Zn content about 5wt% and 8wt%, and to evaluate the precipitation hardening (solutioning and artificial ageing ? T6) as a function of solidification conditions. The 752 (Al-5%Zn-2%Mg) and 782 (Al-8%Zn-2%Mg) alloys were obtained to analyze the influence of Zn content, as well as the relationship between solidification conditions, precipitation hardening, and mechanical properties before and after heat treatments. Unidirectional vertical upward solidification was performed in a metallic mold cooled by water in the bottom and instrumented using thermocouples to obtain the ingots. Samples extracted from ingots were metallography characterized by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and the mechanical properties were determined by hardness, microhardness, tensile and wear testing. The results showed that the increase of 3% of zinc in the chemical composition improved the hardness of 44%, the superficial wear of 27.7% and the tensile strength of 31.5% (in T6 condition). When comparing the results against data from some similar wrought alloys, it is concluded that the as-cast and heat treated 782 alloy can replace those, according to design specifications.
O objetivo do presente trabalho foi desenvolver duas ligas tern?rias fundidas modificadas de Al-Zn-Mg, com varia??o de 5% e 8% em Zn (em massa), e investigar o endurecimento por precipita??o (solubiliza??o e envelhecimento artificial - T6) em fun??o das condi??es de solidifica??o. Foram produzidas as ligas 752 (Al-5%Zn-2%Mg) e 782 (Al-8%Zn-2%Mg) para analisar, al?m da influ?ncia do teor de zinco, a correla??o entre as condi??es de solidifica??o, o endurecimento por precipita??o e as propriedades mec?nicas iniciais e finais. Para obten??o dos lingotes, a solidifica??o unidirecional vertical ascendente foi realizada em molde met?lico resfriado com ?gua na base e instrumentado com termopares. Amostras foram caracterizadas por an?lises metalogr?ficas em microscopia ?ptica (MO), microscopia eletr?nica de varredura (MEV), espectroscopia de energia dispersiva (EDS), e ensaios mec?nicos para determina??o das propriedades mec?nicas como dureza, microdureza, tra??o e desgaste, antes e ap?s os tratamentos t?rmicos. Os resultados mostraram que o aumento em 3% de zinco na composi??o qu?mica melhorou a dureza em 44,4%, o desgaste superficial em 27,7% e a resist?ncia ? tra??o em 31,5% (em condi??o T6). Comparando estes resultados com dados de algumas ligas conformadas similares, conclui-se que a Liga 782, fundida e tratada termicamente, pode substituir as ligas conformadas comerciais com adi??o de cobre.

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.17.11 – технологія тугоплавких неметалічних матеріалів. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2018 р. Дисертацію присвячено розробці ресурсо- та енергоощадної технології хімічно та термічно стійкої кераміки на основі вітчизняної альтернативної природної та техногенної сировини. При проектуванні складів хімічно та термічно стійкої кераміки зі зниженою температурою синтезу використані результати теоретичних досліджень можливої взаємодії основних видів кераміки з агресивними середовищами з різним рН. Визначено найбільш інертні сполуки по відношенню до кислот та лугів, в результаті чого для фізико-хімічних досліджень обрана система фазоутворюючих оксидів (Mg, Са)O – Al2O3 – TiO2 – SiO2. На основі композицій системи, що належать елементарним тетраедрам A3S2 – CAS2 –AT–S та A3S2 – M2A2S5 – AT – S, розроблені склади мас хімічно та термічно стійкої кераміки з температурою випалу 1250 °С. Встановлено, що для інтенсифікації спікання та фазоутворення хімічно та термічно стійкої кераміки за зниженої температури випалу необхідним є використання комплексних плавнів (в тому числі PbO) та мінералізуючих добавок (що містять MgО та Fe2O3). На основі досліджень складу та властивостей пірофілітових відходів видобування кварцитів Овруцького родовища та відходів феротитанового виробництва обґрунтовано вибір сировини для виготовлення низькотемпературної хімічно та термічно стійкої кераміки. Встановлено фізико-хімічні закономірності її формування та отримані математичні моделі залежностей властивостей розробленої кераміки від складу мас. Розроблено склади і технологічні параметри виготовлення хімічно та термічно стійких керамік з комплексом високих фізико-механічних та хімічних властивостей: щільноспеченої тіалітвмісної (W = 0,15 %, ϭзг = 23 МПа, ϭст = 100 МПа, КС > 99,32 %, ЛС > 99,99 %, ТС ≥ 8 циклів, α = 3,5·10–6 град–1) та пористої муліт-тіалітвмісної (W = 11,62 %, ϭзг = 27 МПа, ϭст = 110 МПа, КС > 99,99 %, ЛС > 99,97 %, ТС ≥ 10 циклів, α = 3,0·10–6 град–1).
The dissertation is devoted to development of resource and energy saving techno-logy of chemically stable and heat-resistant ceramics based on domestic alter-native natural and technogenic raw materials. The results of theoretical studies of the possible interaction of the main types of ceramics with aggressive environment with different pH at the design of the composition of chemically stable and heat-resistant ceramics with reduced synthesis temperature are used. The most inert compounds in relation to acids and alkalis were determined, as a result, a phase-forming system (Mg, Са)O – Al2O3 – TiO2 – SiO2 was chosen for physicochemical research, based on the compositions belonging to the elementary tetrahedron A3S2 – CAS2 –AT–S and A3S2 – M2A2S5 – AT – S. In addition, the composition of masses of chemically stable and heat-resistant ceramics with a burning temperature of 1250 °C has developed. It has been established that for the intensification of sintering and phase formation of chemically stable and thermally stable ceramics at low firing temperature it is necessary to use complex fluxes (including PbO) and mineralizing additives (containing MgO and Fe2O3). The choice of raw materials for the manufacture of chemically stable and heat-resistant ceramics was been grounded based on studies on the composition and properties of the pyrophyllite shale of the Ovrutskogo deposit and waste technogenic of ferrotitanium production. Physico-chemical regularities of its formation were established and mathe-matical models of dependencies of the properties of the developed ceramics from the com-position of masses were obtained. The compounds and technological parameters of the production of chemically stable and heat-resistant ceramics with a complex of high phys-ico-mechanical and chemical properties was been developed: containing of tialite (W = 0.25 %, σbend. = 23 MPa, σcompr. = 100 MPa, AcS > 99.32 %, AlS > 99.99 %, CTE = 3.0·10-6 deg-1) were developed.

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.17.11 – технологія тугоплавких неметалічних матеріалів. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2018 р. Дисертацію присвячено розробці ресурсо- та енергоощадної технології хімічно та термічно стійкої кераміки на основі вітчизняної альтернативної природної та техногенної сировини. При проектуванні складів хімічно та термічно стійкої кераміки зі зниженою температурою синтезу використані результати теоретичних досліджень можливої взаємодії основних видів кераміки з агресивними середовищами з різним рН. Визначено найбільш інертні сполуки по відношенню до кислот та лугів, в результаті чого для фізико-хімічних досліджень обрана система фазоутворюючих оксидів (Mg, Са)O – Al2O3 – TiO2 – SiO2. На основі композицій системи, що належать елементарним тетраедрам A3S2 – CAS2 –AT–S та A3S2 – M2A2S5 – AT – S, розроблені склади мас хімічно та термічно стійкої кераміки з температурою випалу 1250 °С. Встановлено, що для інтенсифікації спікання та фазоутворення хімічно та термічно стійкої кераміки за зниженої температури випалу необхідним є використання комплексних плавнів (в тому числі PbO) та мінералізуючих добавок (що містять MgО та Fe2O3). На основі досліджень складу та властивостей пірофілітових відходів видобування кварцитів Овруцького родовища та відходів феротитанового виробництва обґрунтовано вибір сировини для виготовлення низькотемпературної хімічно та термічно стійкої кераміки. Встановлено фізико-хімічні закономірності її формування та отримані математичні моделі залежностей властивостей розробленої кераміки від складу мас. Розроблено склади і технологічні параметри виготовлення хімічно та термічно стійких керамік з комплексом високих фізико-механічних та хімічних властивостей: щільноспеченої тіалітвмісної (W = 0,15 %, ϭзг = 23 МПа, ϭст = 100 МПа, КС > 99,32 %, ЛС > 99,99 %, ТС ≥ 8 циклів, α = 3,5·10–6 град–1) та пористої муліт-тіалітвмісної (W = 11,62 %, ϭзг = 27 МПа, ϭст = 110 МПа, КС > 99,99 %, ЛС > 99,97 %, ТС ≥ 10 циклів, α = 3,0·10–6 град–1).
The dissertation is devoted to development of resource and energy saving techno-logy of chemically stable and heat-resistant ceramics based on domestic alter-native natural and technogenic raw materials. The results of theoretical studies of the possible interaction of the main types of ceramics with aggressive environment with different pH at the design of the composition of chemically stable and heat-resistant ceramics with reduced synthesis temperature are used. The most inert compounds in relation to acids and alkalis were determined, as a result, a phase-forming system (Mg, Са)O – Al2O3 – TiO2 – SiO2 was chosen for physicochemical research, based on the compositions belonging to the elementary tetrahedron A3S2 – CAS2 –AT–S and A3S2 – M2A2S5 – AT – S. In addition, the composition of masses of chemically stable and heat-resistant ceramics with a burning temperature of 1250 °C has developed. It has been established that for the intensification of sintering and phase formation of chemically stable and thermally stable ceramics at low firing temperature it is necessary to use complex fluxes (including PbO) and mineralizing additives (containing MgO and Fe2O3). The choice of raw materials for the manufacture of chemically stable and heat-resistant ceramics was been grounded based on studies on the composition and properties of the pyrophyllite shale of the Ovrutskogo deposit and waste technogenic of ferrotitanium production. Physico-chemical regularities of its formation were established and mathe-matical models of dependencies of the properties of the developed ceramics from the com-position of masses were obtained. The compounds and technological parameters of the production of chemically stable and heat-resistant ceramics with a complex of high phys-ico-mechanical and chemical properties was been developed: containing of tialite (W = 0.25 %, σbend. = 23 MPa, σcompr. = 100 MPa, AcS > 99.32 %, AlS > 99.99 %, CTE = 3.0·10-6 deg-1) were developed.

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The overall objective of this work is to analyze the influence of Si and Mg contents, the percentage of porosity and the effects of hardening precipitation heat treatment on the mechanical properties of Al-Si-Mg alloys. Two alloys: Al-3,8%Si-0,25%Mg (Alloy I) and Al-6,5%Si-0,6%Mg (Alloy II) were prepared and characterized by thermal analysis and optical emission spectroscopy. After that, the alloys were solidified in a metallic mold, with and without degasification. Transversal samples were extracted from solidified ingots to analyze the as-cast structures and mechanical properties (tensile and hardness tests). Part of ingots were submitted to hardening precipitation heat thermal treatments by solutioning at 540?C for 6 hours and artificial aging at 180?C for 4 hours. After the solidification structure analysis in the Alloys I and II in samples along the ingot, it was observed that the grain medium size and the secondary dendrite arm spacing presented small variations that do not influence the variations on the mechanical properties. Regarding porosity, it was noted that Alloy II, which contains a higher content of Si and Fe, presented higher porosity percentage when compared to Alloy I. The degasification process decreased at about 50% porosity volumetric percentage. During the analysis of the mechanical properties of the alloys in the states of crude solidification, it was observed that the samples referring to Alloy II, in the degassed condition, presented higher limits of tensile strength and hardness, 175,5 MPa and 70,7 HB, respectively . Due mainly to the higher content of Si found in alloy II. In relation to the ductility, the Alloy I, in the degassed condition, presented the highest percentage of specific deformation (greater deformation ? = 1.82%), due to the lower percentage of porosity and lower content of Si and Fe. With the treatment (T6), a significant increase in the properties of both alloys can be observed. Alloy II showed the best results with thermal treatment, generating an increase of: 25% in tensile strength, 57% in deformation and 23% in hardness of the samples analyzed. Thus, alloy II, due to the higher percentage of Mg, responded better to the heat treatment. For the analysis of the correlation of the chemical composition, the percentage of porosity and the effects of the thermal treatments with the variation in the mechanical properties, mathematical models were developed that allow to predict the limit of tensile strength, deformation and hardness in Al-Si-Mg. In the analysis of the mathematical models, it was possible to identify the negative effect of the iron and porosity percentages on tensile strength and specific deformation. The increase of silicon and magnesium contents and the application of T6 contributed to higher tensile strength, specific deformation and hardness as well.
O objetivo geral desse estudo foi correlacionar ? composi??o qu?mica, a porosidade e os efeitos dos tratamentos t?rmicos de endurecimento por precipita??o em algumas propriedades mec?nicas em ligas de Al-Si-Mg fundidas. Duas ligas Al-3,8%Si-0,25%Mg (Liga I) e Al-6,5%Si-0,6%Mg (Liga II) foram preparadas e caracterizadas por an?lise t?rmica e espectroscopia de emiss?o ?ptica. Ap?s, foram solidificadas em molde met?lico, com e sem desgaseifica??o. Amostras transversais foram extra?das ao longo do comprimento dos lingotes para an?lises da estrutura de solidifica??o e determina??o das propriedades mec?nicas (ensaios de tra??o e dureza). Parte dos lingotes foram submetidos a tratamentos t?rmicos de endurecimento por precipita??o, com solubiliza??o a temperatura de 540oC por 6 horas, e posterior envelhecimento artificial a temperatura de 180?C por 4 horas. Ap?s as an?lises da estrutura de solidifica??o das Ligas I e II, observou-se que os tamanhos m?dios de gr?o e os espa?amentos dos bra?os dendr?ticos secund?rios apresentaram pequenas varia??es que n?o influenciaram nas varia??es das propriedades mec?nicas. Em rela??o ? porosidade, observou-se que a Liga II, por ter mais Si e Fe na sua composi??o, apresentou maior percentual de porosidade do que a Liga I. O processo de desgaseifica??o reduziu em aproximadamente 50% a porosidade em ambas as ligas. Durante a an?lise das propriedades mec?nicas das ligas nos estados bruto de solidifica??o, observou-se que as amostras referentes ? Liga II, na condi??o desgaseificada, apresentaram maiores limites de resist?ncia ? tra??o e dureza, 175,5 MPa e 70,7 HB, respectivamente, devido principalmente ao maior teor de Si encontrado na Liga II. A Liga I, na condi??o desgaseificada apresentou os maiores percentuais de deforma??o espec?fica (? = 1,82%), devido ao menor percentual de porosidade e menores teores de Si e Fe. Com a aplica??o do tratamento t?rmico (T6), pode-se observar um aumento significativo nas propriedades mec?nicas. Na Liga II, observou-se os melhores resultados com tratamento t?rmico, gerando aumento de: 25% na resist?ncia ? tra??o, 57% na deforma??o e 23% na dureza. Dessa forma, a Liga II por apresentar maior percentual de Mg respondeu melhor ao tratamento t?rmico. Na an?lise da correla??o da composi??o qu?mica, o percentual de porosidade e os efeitos dos tratamentos t?rmicos com a varia??o nas propriedades mec?nicas desenvolveu-se modelos matem?ticos que permitem prever o limite de resist?ncia ? tra??o, deforma??o e dureza em ligas de Al-Si-Mg. Analisando os modelos matem?ticos, identificou-se o efeito negativo do percentual de ferro e porosidade no limite de resist?ncia ? tra??o e deforma??o espec?fica, j? o aumento do teor de sil?cio, de magn?sio e aplica??o do tratamento t?rmico T6 contribu?ram para maiores limites de resist?ncia ? tra??o, percentuais de deforma??o e dureza.

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Nos ?ltimos anos, o setor Joalheiro vem demonstrando uma import?ncia cada vez mais significativa no cen?rio econ?mico nacional e internacional. O Brasil aparece entre os maiores produtores de J?ias do mercado mundial, assim como, o Rio Grande do Sul entre os estados brasileiros, com destaque regional para o Munic?pio de Guapor? que t?m mais de 100 f?bricas, onde s?o produzidas pe?as em Folhado, Prata ou Ouro. Entretanto, vale enfatizar que a literatura dispon?vel referente a estudos cient?ficos voltados para o setor Joalheiro ? escassa, particularmente em n?vel nacional. Nesse contexto, esta pesquisa tem como objetivo principal investigar a liga ? base de Zn-Al-Cu-Mg que recentemente tem sido aplicada na fabrica??o de j?ias folheadas, com a finalidade de obter informa??es sobre suas propriedades de interesse aos processos de fabrica??o e de revestimento. A metodologia experimental utilizada no desenvolvimento desse trabalho envolveu as seguintes etapas: an?lise dos defeitos de acabamento em semi-j?ias folhadas com Ouro e Prata confeccionadas com a liga comercial ? base de Zn-Al-Cu-Mg e determina??o de suas caracter?sticas microestruturais e mec?nicas; modifica??o composicional dessa liga pela adi??o extra de Cobre e Magn?sio e estudo dos seus efeitos nas propriedades da mesma e por fim avalia??o da capacidade de revestimento com Ouro da liga comercial e modificada pela adi??o de Cobre e Magn?sio. Este estudo mostra que varia??es composicionais da liga Zn-Al-Cu-Mg modifica de forma significativa a microestrutura da referida liga e conseq?entemente suas propriedades mec?nicas, bem como sua capacidade de revestimento. As t?cnicas de caracteriza??o utilizadas, CA-CCA (Computer-Aided Cooling Curve Analysis), DTA (Differential Thermal Analysis), Dilatometria e Microscopias ?ptica e Eletr?nica de Varredura, foram fundamentais para entender melhor a influ?ncia da composi??o qu?mica na microestrutura e propriedades da liga ? base de Zn-Al-Cu-Mg. Contudo, observou-se que um outro fator de grande influ?ncia na qualidade do revestimento dessa liga ? o procedimento e qualidade de limpeza pr?via efetuadas nas pe?as para o posterior folhamento.

The knowledge of phase equilibria and thermodynamic properties of liquid and solid oxides can help us better understand metallurgical, ceramic or geological processes. The main aim of the present study is the critical evaluation and thermodynamic optimization of solid and liquid (MnO-Al2O3 based) oxides which are of interest to the steelmaking and ferro-Mn industries. These newly developed databases coupled with the previous databases can be used along with any software for Gibbs energy minimization to predict the phase relationships and the thermodynamic properties of any relevant system. Usually, thermodynamic databases can save both cost and time, which, otherwise would have been spent to optimize the existing process and develop any new process. The production of steels with higher amounts of manganese and aluminum has gained considerable importance in the recent past. Steels with high concentration of manganese and aluminum like TWIP steel and TRIP steel have exceptional properties which classify them as special steels; needless to say the various range of applications they can cater to. Ferromanganese, which contains a large amount of manganese, is also a very useful product required in the production of high manganese steels. The production of these alloys results in the generation of slags which are rich in MnO and Al2O3. Hence, knowledge of the phase relations between these two components is of utmost importance in order to maximize the efficiency of the production process. Only a very good knowledge of Gibbs energy of all the phases present in the binary system MnO-Al2O3 can allow us to predict the correct equilibrium conditions during the production process. The critical evaluation and thermodynamic optimization of all the available phase diagram data and thermodynamic properties of the system Mn-Al-O have been carried out in the first part of the present work. Thermodynamic modeling for different phases such as slag, spinel (cubic and tetragonal) and bixbyite has been performed using Modified Quasichemical Model, Compound Energy Formalism and random mixing model, respectively. The sublattice structure of solid solution phases were properly taken into account in the thermodynamic modeling and their thermodynamic properties and structural data were reproduced using the physically meaningful model parameters. All the reliable experimental data of the Mn-Al-O system were reproduced within error limits from room temperature to above the liquidus temperatures at all compositions and oxygen partial pressure ranging from metal saturation to air. The present MnAl2O4-Mn3O4 spinel solutions can be integrated with all the other spinel solutions developed earlier to obtain an extensive spinel solution database. This database along with the software for Gibbs energy minimization can be utilized to perform various calculations and predict the phase relations at any given condition. In the next part of the present work, the binary MnO-Al2O3 system was extended to the higher order systems like MnO-Al2O3-SiO2, CaO-MnO-Al2O3, FeO-MnO-Al2O3, MgO-MnO-Al2O3 and CaO-MnO-Al2O3-SiO2. Other calculations related to inclusion engineering in steelmaking were also carried out. This was done to check the accuracy of the database developed for the binary MnO-Al2O3 system. The database of model parameters can be used with thermodynamic software like Factsage for thermodynamic modeling of various industrial and natural processes. Calculations pertaining to prediction of thermodynamic properties of phases, cation distribution in spinel solutions, phase equilibria at any temperature, composition and oxygen partial pressure where no experimental data are available can also be performed.
La connaissance des équilibres de phase et des propriétés thermodynamiques des oxydes solides et liquides peut aider à mieux comprendre les processus métallurgiques, céramiques et géologiques. Le but de cette étude est l'évaluation critique et l'optimisation thermodynamique des oxydes solides et liquides impliquant MnO-Al2O3 qui sont utiles pour les industries de l'acier et du ferromanganèse. Les bases de données développées, couplées avec d'anciennes bases de données, peuvent être utilisées avec n'importe quel logiciel de minimisation de l'énergie de Gibbs pour prédire les équilibres de phase et les propriétés thermodynamiques de tout système. Souvent, les bases de données permettent de sauver temps et argent qui, autrement, auraient pu être utilisés pour optimiser des processus existant ou en développer de nouveaux. La production d'aciers à teneur élevé en Mn et Al a acquis une importance considérable. Les aciers à teneur élevé en Mn et Al, comme les aciers TWIP et TRIP, ont des propriétés exceptionnelles qui les classifient comme aciers spéciaux; inutile de mentionner toutes les applications auxquels ils peuvent répondre. Le ferromanganèse, qui contient de grandes quantités de Mn, est aussi un produit très utile dans la production d'aciers à haute teneur en Mn. La production de tels aciers génère des scories riches en MnO et Al2O3. Par conséquent, la connaissance des relations de phases entre ces deux composés est d'une importance capitale pour maximiser l'efficacité de la production. Seule une bonne connaissance de l'énergie de Gibbs de toutes les phases du système MnO-Al2O3 peut nous permettre de prédire les conditions d'équilibre lors de la production. L'évaluation critique et l'optimisation de toutes les données disponibles de diagrammes de phase et de propriétés thermodynamiques du système Mn-Al-O ont été réalisées dans la première partie de ce travail. La modélisation thermodynamique des différentes phases telles que le laitier, le spinelle (cubique et tétragonal) et la bixbyite a été effectuée, respectivement, à l'aide du Modèle Quasichimique Modifié, du Formalisme de l'Énergie des Composés et du modèle de mélange aléatoire. La structure du sous-réseau des solutions solides fut correctement prise en compte dans la modélisation et les propriétés thermodynamiques et données structurales furent reproduites en utilisant des paramètres ayant une signification physique. Toutes les données expérimentales fiables du système Mn-Al-O ont été reproduites à l'intérieur des limites d'erreur de la température ambiante jusqu'au-dessus du liquidus pour toutes les compositions et à des pressions partielles d'oxygène allant de la saturation en métal jusqu'à l'air. Les solutions de spinelle MnAl2O4-Mn3O4 peuvent être intégrées à toutes les autres solutions de spinelle développées antérieurement pour obtenir une base de données étendue pour le spinelle. Celle-ci, combinée à un logiciel de minimisation de l'énergie de Gibbs, peut être utilisée pour effectuer divers calculs et prédire les relations de phase dans n'importe quelles conditions données. Dans la seconde partie de ce travail, le système MnO-Al2O3 a été ajouté aux systèmes d'ordre supérieur tels que MnO-Al2O3-SiO2, CaO-MnO-Al2O3, FeO-MnO-Al2O3, MgO-MnO-Al2O3 et CaO-MnO-Al2O3-SiO2. Des calculs liés à l'ingénierie des inclusions impliquées dans la fabrication de l'acier ont également été réalisées. Ceci a été fait pour vérifier l'exactitude de la base de données du système MnO-Al2O3. Les paramètres du modèle peuvent être utilisés avec un logiciel comme FactSage pour la modélisation de divers procédés industriels et naturels. Les calculs relatifs à la prédiction des propriétés thermodynamiques des phases, la distribution des cations dans les solutions spinelle et les équilibres entre phases à n'importe quelle température, composition et pression partielle d'oxygène où aucune donné expérimentale n'existe, peuvent également être effectuées.

La demande en hydrogène, en tant que produit chimique et énergie, augmente, mais les principales méthodes de production d'hydrogène ne sont ni durables ni respectueuses de l'environnement. La production d'hydrogène à partir de ressources renouvelables (comme le biogaz composé principalement de CH4 et de CO2) est requise. Le reformage à sec du méthane (DRM) est une méthode prometteuse pour produire H2 et CO à partir des gaz. Dans cette thèse, des catalyseurs à base de Ni, CeNiXOY, CeZr0.5NiXOY, CeAl0.5NiXOY, et AlMg2NiXOY sont étudiés pour la réaction de reformage à sec du méthane. L'effet de la température de réaction, de la teneur en Ni, du prétraitement in situ sous H2, de la masse de catalyseur, de la calcination et du rapport CO2/CH4 sont analysés. Sur certains composés choisis, des tests de stabilité à long terme sont aussi reportés. L’optimisation des performances catalytiques avec une formation réduite de carbone, sont obtenues sur des catalyseurs partiellement réduits. Diverses méthodes de caractérisation sont utilisées pour analyser les propriétés physico-chimiques des catalyseurs, telles que XRD, Raman, XPS et TPR. Certains catalyseurs sont également caractérisés après la réaction catalytique (DRM) pour analyser leur évolution. Enfin, un site actif impliquant des espèces Ni en interactions fortes avec d'autres cations est proposé. Ce site est obtenu sur un catalyseur partiellement réduit impliquant des lacunes anioniques, des espèces O2- et des cations
The demand for hydrogen, as a chemical product and as energy is increasing, but the main hydrogen production methods are unsustainable and not environmentally friendly. Hydrogen production from renewable resources (such as biogas mainly composed of CH4 and CO2) is required. Dry reforming of methane (DRM) is a promising method to produce H2 and CO from greenhouse gases. In this thesis, Ni-based CeNiXOY, CeZr0.5NiXOY, CeAl0.5NiXOY, and AlMg2NiXOY catalysts are studied in dry reforming of methane reaction. The effect of reaction temperature, Ni content, in situ H2 pretreatment, mass of catalyst, calcination, and CO2/CH4 ratio are studied. Moreover, long duration stability tests are reported on some chosen samples. The optimized catalytic performance associated with resistance to carbon formation is obtained on partially reduced catalysts. Various physicochemical characterizations are used to analyze the properties of the catalysts, such as XRD, Raman, XPS, and H2-TPR. Some chosen catalysts are also characterized after DRM reaction to analyze their evolution. Finally, an active site involving Ni species in close interactions with other cations is proposed. It is related to a partially reduced catalyst involving anionic vacancies, O2- species, and cations

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Este trabalho estudou a influência dos teores dos solutos Mg e Ni na modificação das propriedades térmicas, elétricas e mecânicas de uma liga Al-Cu-Fe para aplicação como condutor de energia elétrica. Para a realização do presente estudo, as ligas foram obtidas por fundição unidirecional horizontal, a partir da base do alumínio de pureza comercial com adição dos teores 0,05%p Cu e [0,24 a 0,28]%p Fe. Tal base foi modificada em uma primeira etapa com teores de 0,45, 0,60 e 0,80%p Mg. As ligas obtidas com estes teores tiveram suas propriedades estudadas para que se selecionasse um teor de Mg para posterior adição de Ni à liga. O estudo destas propriedades na primeira etapa passou pela análise das propriedades térmicas: velocidade de solidificação (VL) e taxa de resfriamento (Ṫ). A caracterização elétrica estudou a propriedade condutividade elétrica (φ) e o levantamento das propriedades mecânicas: limite de resistência à tração (σ) e microdureza Vickers (HV). A liga com adição de Ni passou por tratamentos térmicos de envelhecimento, por 1, 4 e 8h. Estas amostras foram analisadas em um microscópio eletrônico de varredura - MEV pelos sinais de elétrons retroespalhados – ERE e espectroscopia de energia dispersiva – EDS. Como resultados do estudo, encontrou-se que adições de Mg influenciaram significativamente a viscosidade das ligas, elevando as velocidades de solidificação nos instantes finais. Os ensaios de microdureza das amostras envelhecidas mostraram que houve um acréscimo significativo de dureza na quarta hora de envelhecimento, da mesma forma que as análises de EDS mostraram que a concentração de Ni também elevou-se nesta condição de tratamento.
This work studied the influence of Mg and Ni solute content on the modification of the thermal, electrical and mechanical properties of an Al-Cu-Fe alloy for application as an electrical conductor. To realize the present study, the alloys were obtained by unidirectional horizontal casting, starting from the commercial pure aluminum with the addition of 0.05wt% Cu and [0.24 to 0.28]wt% Fe content. This basis was modified on a first stage with 0.45, 0.60 and 0.80wt% of Mg content. The alloys obtained with these contents had its properties studied for the selection of a Mg content for further Ni addition at the alloy. The study of these properties on the first stage passed through the analysis of the thermal properties: growth rate (VL) and cooling rate (Ṫ). The electrical characterization studied the electrical conductivity property (φ) and the following mechanical properties were determined: ultimate tensile strength (σ) and Vickers microhardness (HV). The alloy which has Ni additions passed through ageing heat treatments of 1, 4 and 8 hours. These samples were analyzed in a scanning electron microscope – SEM by the electrons backscattered – EBS and energy dispersive spectroscopy – EDS signals. As a result of the research, it was found that Mg additions had significantly influenced the alloys viscosity, increasing its growth rates at the final moments of the solidification. The microhardness tests for the aged samples showed that they suffered a significant gain of hardness at the fourth hour of ageing, also, the EDS analysis showed that Ni content increased at the same treating conditions.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES
The demand for electricity production, and the need for thermoelectric use as power generating units, makes it necessary to search for less polluting matrices. In this search the catalytic combustion of methane, both from natural gas and other sources (residue disposal, for example) have shown promising. It is known the use of cobalt oxides is an alternative to the use of catalysts based on noble metals which has shown high performance. In order to potentiate the activity of the cobalt based catalyst, thus reducing both the ignition temperature and the temperature of total burning of methane, this work proposes the production of cobalt-based precursors using different types of layered double hydroxides (LDHs). Cobalt based catalysts partially substituted in layered double hydroxides (LDH Mg, Al and CO32-) were prepared by co-precipitation and impregnation with a nominal content of 9% CoII in LDH, or by impregnating a commercial hydrotalcite (HT). The LDH precursors were characterized by X-ray powder diffraction (XRD) and infrared absorption spectroscopy (FTIR). The XRD patterns indicated a LDH of 3R polytype. XRD showed the presence of Gibbisite in the HT precursor. The infrared spectra of precursor LDHs presented bands related to ?1, ?2 and ?3 vibrations of the carbonate anion, and interlayer water characteristic bands, thus in line with the XRD data. Analysis by XRD of the catalysts after calcination at 800 ?C showed the presence of periclase and spinel phases. Infrared spectra showed bands ascribed to the Mg-O and Co-O stretching in tetrahedral and octahedral sites as well as bands attributed to the Mg-O-Al bond and the cobalt spinel. The catalytic activity of these materials was investigated in the catalytic combustion of methane under kinetic regime, using predetermined reaction conditions to avoid diffusional limitations, resulting in a significant decrease in the combustion temperature, with the higher activity observed for the catalyst prepared by impregnating a commercial HT. Scanning electron microscopy (SEM) and quantitative chemical analysis (EDS) of catalysts with improved performance show both the homogeneous dispersion of the components in the sample surface and the higher aluminum content of the sample supported on HT.
A demanda de produ??o de energia el?trica, e a necessidade do uso de termel?tricas como unidades geradoras de energia, fazem com que seja necess?ria a busca por matrizes menos poluentes. Nessa busca a combust?o catal?tica do metano, tanto proveniente do g?s natural como de outras fontes (res?duo do tratamento de lixo, por exemplo), tem se mostrado promissora. Sabidamente o uso de ?xidos de cobalto ? uma alternativa, que vem mostrando alto desempenho, ao uso de catalisadores a base de metais nobres. Com o intuito de potencializar a atividade do catalisador a base de cobalto, reduzindo assim tanto a temperatura de igni??o quanto a de queima total do metano, esse trabalho prop?e sua produ??o utilizando como precursor diferentes tipos de hidr?xidos duplos lamelares (HDLs). Catalisadores ? base de cobalto parcialmente substitu?dos em hidr?xidos duplos lamelares (HDL de Mg, Al e CO32-) foram preparados por co-precipita??o e impregna??o num teor nominal de 9% de CoII em HDL, ou por impregna??o em hidrotalcita comercial (HT). Os HDLs precursores foram caracterizados por difra??o de raios?X pelo m?todo de p? (DRX) e por espectroscopia de absor??o no infravermelho (FTIR). Os difratogramas indicaram a obten??o de um HDL de politipo 3R. Por meio do DRX foi identificada a presen?a de Gibbisita no suporte de HT. Os espectros de infravermelho dos HDLs precursores presentaram bandas referentes ?s vibra??es ?1, ?2 e ?3 do ?nion carbonato, al?m de bandas caracter?sticas de ?gua interlamelar, estando portanto de acordo com os dados de DRX. A an?lise por difra??o de raios-X dos catalisadores ap?s calcina??o a 800?C mostrou apenas as fases espin?lio e pericl?sio. Os espectros de infravermelho apresentaram bandas atribu?das aos estiramentos Mg?O e Co?O em s?tios tetra?dricos e octa?dricos, assim como bandas caracter?sticas de Mg?O?Al e de Co3O4. A atividade catal?tica desses materiais foi investigada na combust?o catal?tica do metano, em regime cin?tico, empregando-se condi??es reacionais preestabelecidas de forma a evitar limita??es difusionais, obtendo-se uma significativa diminui??o na temperatura de combust?o, sendo que a maior atividade foi observada para o catalisador preparado por impregna??o em HT comercial. Foi realizada microscopia eletr?nica de varredura (MEV) e an?lise qu?mica quantitativa (EDS) para os catalisadores com melhor desempenho, mostrando tanto a dispers?o homog?nea dos componentes na superf?cie das amostras como o maior teor de alum?nio presente na amostra suportada em HT.

Se han preparado vidrios, correspondientes a tres sistemas vítreos, basados en la sustitución de oxígeno por nitrógeno y/o flúor, de composición general Ca-M-Si-Al-O-(N)-(F) (siendo M= Ca, Y o Mg, con una relación Ca:M única, en cada caso), modificando el contenido en nitrógeno entre el 0 y 20 % eq, y el contenido en flúor entre el 0 y el 7 % eq. Todas las sustituciones estudiadas en los sistemas Ca-Ca (con un contenido de 20% equivalentes de Ca) y Ca-Y (con un contenido en 10% equivalentes de Ca y 10% de Y) han originado vidrios de naturaleza amorfa. Sin embargo, la sustitución de oxígeno por flúor en cantidades superiores a 3 % eq ha originado sólidos de naturaleza cristalina en el sistema vítreo Ca-Mg. Por ello, ha sido necesario modificar la relación catiónica en este sistema incrementando el número de equivalentes de Ca y Mg al 15%, respectivamente, ajustando la relación Si:Al, y modificado el contenido en nitrógeno entre el 0 y 15 % eq y el contenido en flúor entre el 0 y el 5 % eq. Se ha observado que la densidad, compacidad, microdureza y módulo de Young aumentan de manera lineal con el contenido en nitrógeno, mientras que el volumen molar, la temperatura de transición vítrea y la temperatura de reblandecimiento disminuyen, también linealmente, con el contenido en nitrógeno. Por otro lado, todas las propiedades permanecen invariables con el contenido en flúor, excepto las temperaturas de transición vítrea y de reblandecimiento, que disminuyen de una manera drástica y lineal con el contenido del mismo. Asimismo, se ha estudiado la relación entre las propiedades mecánicas, la compacidad y el volumen libre, así como la relación entre las propiedades térmicas y la densidad de reticulación. Se ha concluido que los efectos del contenido en flúor sobre las propiedades de los vidrios de composición general Ca-M-Si-Al-O-(N)-(F) (siendo M= Ca, Y o Mg, con una relación Ca:M única, en cada caso), son totalmente independientes y aditivos a los del nitrógeno. Se han preparado vidrios, correspondientes a cuatro sistemas vítreos, basados en la sustitución de Ca por M, de composición general (Ca)-(M)-Si-Al-O-N-F (donde M=Mg, Er, Nd o Y), manteniendo un contenido en nitrógeno y flúor constante. La sustitución total de Ca únicamente se ha realizado con Mg, mientras que el caso de los elementos de Er, Nd e Y la sustitución parcial máxima realizada ha sido del 20 % eq. El análisis de los efectos producidos en las propiedades físicas ha demostrado que éstas solamente dependen de la intensidad de campo catiónico efectiva si la valencia de los cationes modificadores es la misma (es decir, Ca y Mg). Sin embargo, cuando se reemplaza el Ca por cationes trivalentes (es decir, Y, Er y Nd), las propiedades dependen tanto de la intensidad de campo catiónico efectiva como del número de tetraedros (Si, Al) (O, N, F)4 asociados con cada catión modificador. Finalmente, se han obtenido expresiones empíricas para cada una de las diferentes propiedades físicas estudiadas de los vidrios del sistema Ca-M-Si-Al-O-N-F, que relacionan dicha propiedad bien con el contenido en nitrógeno y flúor (efectos independientes pero aditivos) o bien con la intensidad catiónica efectiva y el número de tetraedros asociados a cada catión modificador.

La céramique spinelle oxynitrure d'aluminium et de magnésium est obtenue transparente dans le visible et l'infra-rouge par frittage réactif d'un mélange de poudres d'alumine, nitrure d'aluminium et oxyde de magnésium. L'oxynitrure d'aluminium et de magnésium se forme par réaction en phase solide entre une structure spinelle hôte (aluminate de magnésium ou oxynitrure d'aluminium) et du nitrure d'aluminium ou de l'oxyde de magnésium. Son apparition est généralement effective au dessus de 1350 0c mais peut être observée a 1200c (par réaction oxyde de magnésium oxynitrure d'aluminium). La présence de nitrure d'aluminium induit le départ d'espèces gazeuses magnésium et azote par réaction avec l'oxyde de magnésium ou l'aluminate de magnésium. Ces départs affaiblissent les teneurs en azote et de magnésium de la solution solide et modifient la microstructure. Mais ce départ peut être limite en utilisant un environnement stabilisateur constitue d'oxyde de magnésium et de nitrure d'aluminium. La microstructure des matériaux est étroitement liée aux matières premières. Un caractère binodal est note lorsque la structure hôte spinelle aluminate de magnésium est présente au départ alors qu'une taille de grains fins et homogènes est observée si le spinelle hôte est forme in situ. Des recuits successifs en dessous de 1750c ne modifient que légèrement la taille des grains. Une post compression isostatique à chaud est nécessaire pour éliminer la fine porosité résiduelle et l'évolution microstructurale différé selon les matières premières, les conditions de pré-traitement par frittage sous charge et la température de post compression isostatique à chaud

Ce travail apporte une contribution a la caracterisation des couches minces par ellipsomerie spectroscopique a angle variable. Nous presentons les differentes modifications apportees a l'ellipsometre d'origine et decrivons les procedures d'etalonnage utilisees. La reduction des erreurs systematiques et aleatoires est egalement traitee. Une etude originale a ete menee sur les derivees partielles des angles ellipsometriques psi et delta par rapport aux differents parametres de l'echantillon (epaisseurs, indices, angle d'incidence). Celle-ci nous a conduit a introduire le concept de sensibilite integrale relative (sir) qui s'est avere tres utile pour localiser les zones angulaires les plus interessantes et pour comparer entre elles les sensibilites de la mesure ellipsometrique aux divers parametres de l'echantillon. L'interet de mesures spectroscopiques a plusieurs angles d'incidence est discute. Deux applications principales ont ete traitees dans ce memoire: la premiere concerne la mesure des indices de semi-conducteurs ii-vi a grands gaps. L'etude realisee porte sur des substrats massifs de cdmnte et sur des couches epitaxiees de cdmgte. Une loi d'indice permettant de decrire le comportement de la fonction dielectrique du cdmgte sur l'ensemble du domaine spectral est proposee. Dans la zone transparente, deux lois de sellmeier donnant les indices du cdmnte et du cdmgte pour toute concentration de manganese ou de magnesium, ont ete etablies. La seconde porte sur la caracterisation de couches a gradient d'indice. Une methode permettant d'analyser des couches de profil d'indice a priori quelconque est proposee. Elle a ete validee sur des couches inhomogenes de gaalas et d'oxy-nitrure de silicium. L'ellipsometrie s'est revelee etre une technique bien adaptee a ce type de caracterisation puisque des profils polynomiaux du quatrieme degre ont pu etre mis en evidence sur des couches d'oxy-nitrure de silicium a fort gradient d'indice

碩士
國立中央大學
化學工程與材料工程研究所
90
In this study,we prepared different Mg/Al ratios and Ni loading precursor by coprecipitation method,and then calcined at high temperature to prepare Ni/HTc(x) catalysts. XRD 、BET、XPS、H2-TPR、H2-TPD were used to study the structure and surface properties. The effect of different calcination temperature、reducing temperature、Mg/Al ratios、Ni loading and reaction temperature was studied by CH4/CO2 reforming.H2-TPSR was used to study coking resistance of catalyst. Ni/HT(x) has the same structure with hydrotalcite,after calcined at high temperature,the layer stuucture was collased and became Mg-Al-O mixed-oxides,the surface also increased. As the calcined temperature increased NiO and MgO became solid solution. It is hard to reduce Ni/HTc(x) catalyst,and reducing temperature is higher than Ni/γ-Al2O3 and Ni/SiO2 catalyst. XPS found that Ni/(Mg+Al) ratio reduce as calcination temperature increase,furthre prove NiO and MgO were formed solid solution. In CH4/CO2 reformimg we found that 8%Ni/HTc(3) catalyst ,calcined at 800℃ ,reduced at 500℃ , Mg/Al ratio is 3,and 700℃ reaction temperature had the best stability than 8%Ni/γ-Al2O3,8%Ni/SiO2. H2-TPSR also found that 8%Ni/HTc(3) had best coking resistance.

碩士
大同大學
材料工程學系(所)
95
o-LiMnO2 and LiMn1-xMxO2(M = Fe, Cr, Al, or Mg; x = 0.05, 0.10) were prepared by Pechini method. The effects of doping on the composition, the crystalline structure, morphology, and the electrochemical properties of the prepared powders were investigated with ICP, XRD, SEM, cycling voltammetry, and capacity retention study. Powders doped with Al3+ or Fe3+ remain orthorhombic, and show similar electrochemical performances as o-LiMnO2. However, samples doped with Cr3+ and Mg2+ manifested as monoclinic and tetragonal structured with orthorhombic as minor, respectively. They do not show increasing capacity during the initial cycles due to the transformation into spinel like structure as the cycling performance of o-LiMnO2. Furthermore, no capacity fade was observed after 30 cycles. Among the prepared samples, that the powders doped with Cr3+ exhibit the most promising cycling performance. LiMn0.9Cr0.1O2 show reversible discharge capacity of 180 mAh/g.

碩士
中原大學
化學工程研究所
105
CO2 is the primary greenhouse gas which causes global warming in recent years. As the carbon capture and storage (CCS) getting maturing, the reuse of carbon dioxide which made from CCS is the important issue. In this way, the most common method is the synthesis of cyclic carbonate chemicals from the cycloaddition reaction of carbon dioxide and epoxide. The catalyst plays an important role in the CO2/epoxide cycloaddition reactions. The Lewis acidic and basic sites are both needed on the catalyst surface for the help of epoxide ring opening, leading to the synthesis of cyclic carbonate. Furthermore, the larger specific surface area and more active site of the catalyst are also needed to enhance the efficiency of the CO2/epoxide cycloaddition reactions. 　　Aerogel is a mesoporous nanomaterial (pore size between 2~50 nm) with high specific surface area and porosity (at least 90%) and low density. In this study, for the first time, the ternary metal oxide aerogels, Mg-doped Al2O3 aerogels, with higher specific surface area and Lewis acidic and basic sites on the aerogel surface are successfully prepared using a facile sol-gel reaction. The as-prepared Mg-doped Al2O3 aerogels are also served as a heterogeneous catalyst for the CO2/propylene oxide cycloaddition reaction. Compared to the pristine Al2O3 aerogels, the Mg-doped Al2O3 aerogels possessed both Lewis acidic and basic sites on the surface are able to enhance the efficiency of the CO2/propylene oxide cycloaddition reactions. As a result, the as-prepared Mg-doped Al2O3 aerogels are a promising and novel catalyst for the CO2/epoxide cycloaddition reactions.