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To meet the requirements of precise temperature monitoring at high temperatures in extremely corrosive environments, such as in coal gasifiers, a new sensor technology has been developed. This optical, ultra high temperature measurement system utilizes single crystal sapphire as a sensing element. A series of experiments was performed to determine the corrosion resistance of single crystal sapphire and single crystal fully stabilized cubic zirconia at high temperatures in coal slag and soda lime glass. The amount of corrosion of sapphire and zirconia in corrosive slags was measured at 1200°C, 1300°C, and 1400°C for different exposure times. The microstructural features at the interface of sapphire and zirconia were investigated using SEM and EDX analysis. The experimental measurements as well as SEM micrographs show very little or no degradation of sapphire and zirconia samples in corrosive slags. An interesting phenomenon was observed in the EDX scans of sapphire in the coal slag: the iron from the slag appears to have completely separated from the silicon and deposited at the sapphire surface. This interesting observation can be further explored to study whether this iron layer can be used to control the corrosion of sapphire. / Master of Science

The Vickers residual stress field (VRSF) in soda-lime glass results from the elastic-plastic contact event that takes place when a Vickers diamond pyramid is loaded onto the surface of the material in an indentation cycle. The importance of elastic-plastic indentation lies in the contact damage that it gives rise to in the surface of the glass. Since such surface flaws can be characterised, with respect to shape and size, they offer the opportunity to study naturally occurring flaws in glass and brittle materials in general. The residual stress field is not passive; rather it exerts a crack opening force on the associated crack system during subsequent strength testing of a Vickers-indented sample through a residual stress field coefficient, c. Besides the strength-controlling properties, the elastic-plastic contact residual stress field is also important as a region where the influence of mechanical excitation on material properties such as hardness, H, and elastic modulus, E, can be studied. This thesis concerns studies that were made to characterise the Vickers residual stress field by first measuring the magnitude and distribution of stresses around it, using nanoindentation with a cube corner tip. With a Berkovich tip in nanoindentation, experiments were conducted in the VRSF to study the dependence of hardness, H and elastic modulus, E, on stresses in soda-lime glass: a strong E dependence on stress was observed, while H was not affected unless the stresses were high. In the process, a method was developed to determine the true contact area during elastic-plastic nanoindentation when the Oliver-Pharr method is used for the data analysis. The observed elastic modulus dependence on stress was then utilised in a study where it was shown that the VRSF responds differently to relaxation annealing on either side of the glass transition temperature. This result was then used to explain strength recovery trends in annealed Vickers-indented glass specimens.

<p>The Vickers residual stress field (VRSF) in soda-lime glass results from the elastic-plastic contact event that takes place when a Vickers diamond pyramid is loaded onto the surface of the material in an indentation cycle. The importance of elastic-plastic indentation lies in the contact damage that it gives rise to in the surface of the glass. Since such surface flaws can be characterised, with respect to shape and size, they offer the opportunity to study naturally occurring flaws in glass and brittle materials in general. The residual stress field is not passive; rather it exerts a crack opening force on the associated crack system during subsequent strength testing of a Vickers-indented sample through a residual stress field coefficient, c. Besides the strength-controlling properties, the elastic-plastic contact residual stress field is also important as a region where the influence of mechanical excitation on material properties such as hardness, H, and elastic modulus, E, can be studied.</p><p>This thesis concerns studies that were made to characterise the Vickers residual stress field by first measuring the magnitude and distribution of stresses around it, using nanoindentation with a cube corner tip. With a Berkovich tip in nanoindentation, experiments were conducted in the VRSF to study the dependence of hardness, H and elastic modulus, E, on stresses in soda-lime glass: a strong E dependence on stress was observed, while H was not affected unless the stresses were high. In the process, a method was developed to determine the true contact area during elastic-plastic nanoindentation when the Oliver-Pharr method is used for the data analysis.</p><p>The observed elastic modulus dependence on stress was then utilised in a study where it was shown that the VRSF responds differently to relaxation annealing on either side of the glass transition temperature. This result was then used to explain strength recovery trends in annealed Vickers-indented glass specimens.</p>

Nous étudions la réponse élastoplastique des verres silicatés à de fortes contraintes par diffusion Brillouin de la lumière. Des cartographies micro-Brillouin 3D du champ de densité résiduelle sont obtenues dans l'empreinte plastique laissée par une indentation Vickers et comparés à des modélisations par éléments finis. L'analyse conjointe des mesures réalisées en enclumes diamants sur la silice dans le domaine de déformation élastique et des données de la littérature fait apparaître que le durcissement anormal des modules élastiques avec la température est d'origine dynamique. La température à laquelle le durcissement est mis en évidence augmente avec la pression hydrostatique appliquée. Nous observons également que la densification progressive de la silice diminue fortement l'amplitude du maximum dans le frottement interne observé à 2 GPa de même qu'elle supprime l'anomalie dans la compressibilité. / We study the elastoplastic response of silicate glasses at high stresses with Brillouin light scattering. 3D micro-Brillouin mapping residual density field are obtained in the plastic region left by a Vickers indentation. Maps are compared with finite element modeling. The joint analysis of new high-pressure measurements in a diamond anvil cell on silica in the elastic domain and literature data revealed that the abnormal hardening of elastic moduli with temperature is of dynamical origin. The onset temperature of the hardening increases with increasing applied hydrostatic pressure. We also observe that densification of silica strongly reduces the amplitude of the maximum in internal friction observed at 2 GPa as well as it suppresses the compressibility anomaly.

Esta dissertação poderia ser dividida em duas partes, sem que houvesse prejuízo para o seu entedimento: uma tratando do topázio natural (Al IND.2 SiO IND.4[F, OH] IND.2) e outra, a respeito dos vidros silicatos tipo soda-lime (SiO IND.2+CaO+Na IND.2 O). Em ambas se procura contribuir para o estudo de defeitos com algumas técnicas experimentais, mais enfaticamente as correntes de despolarização termicamente estimuladas (CDTE). Com relação ao topázio, há diversos estudos tratando de sua termoluminescência (TL) e de possíveis aplicações no que tange ao seu emprego como dosímetro termoluminescente. Procuramos complementar esses resultados com medidas de CDTE, técnica que ainda não havia sido utilizada para este material. Localizamos no topázio três bandas de CDTE, porém os resultados não são conclusivos no que se refere às origens dessas bandas. Em parte porque temos consciência de que os resultados variam bastante quando se estudam amostras naturais, com composições que variam dentro de um mesmo pedaço de cristal. No que diz respeito aos vidros soda-lime, o estudo foi mais abrangente. Há várias trabalhos no sentido de se conhecer melhor os efeitos causados pela irradiação de vidros silicatos. Acredita-se que o sódio desempenhe um papel fundamental nas principais mudanças processadas nesse material após irradiação gama. Assim, este estudo procurou comparar os resultados de TL e CDTE, além de absorção óptica, de vidros soda-lime com diferentes concentrações de Na POT.+ e K POT.+. Ao que tudo indica os processos responsáveis pela TL e CDTE dependem da relação entre as concentrações desses íons. Verificaram-se também variações com a taxa de dose, e os efeitos de tratamentos térmicos para situações onde um ou outro íon prevalece. / This work could be split in two different parts without impairment understanding. One of them, on natural topaz (Al2SiOdF,OH] 2) and the other on soda-lime silicate (SLS) glasses (Si02 + CaO + Na20) . In both of them we intend to contribute with more information on their defect composition, using some experimental techniques, especially the so called thermally stimulated depolarization currents (TSDC) . There are many surveys on topaz thermoluminescence (TL) and the possibility of its use as a TL dosimeter. So, one of the purposes of this study was to make a contribution with a technique not used so far with such material. We have detected three TSDC peaks. The results are not conclusive about the origin of those peaks, in part because we are dealing with a natural material whose composition can vary even within the same piece of crystal. As the SLS glasses, the study was more comprehensive. There are plenty of papers on irradiation effects in silicate glasses and attempts to understand the mechanisms responsible for them. It is believed that sodium plays a fundamental role in the main modifications caused by gamma irradiation of these glasses. In addition, this study attempts to compare the TL and TSDC results in SLS glasses with different concentrations of Na+ and K+. From our observations, the processes responsible for both TL and TSCD peaks depend on the relative concentrations of those ions. Furthermore, variations on the signals were also noticed; depending on the irradiation rate and on the thermal treatments performed, in samples where one or another ion prevails.

Estudo realizado acerca da utilização de dois resíduos sólidos industriais (RSI) gerados em grande quantidade no Brasil, na obtenção de vidros soda-cal destinados à produção de embalagens. Os resíduos avaliados foram a cinza de casca de arroz (CCA) e resíduo do catalisador usado das unidades de Craqueamento Catalítico Fluido das Petroquímicas (ECAT), ambos podem ser classificados como resíduos sólidos de classe II de acordo com a norma NBR 10.004. Esta nova proposta para destinação desses resíduos é uma alternativa às atuais disposições, buscando não apenas minimizar os impactos ambientais gerados, mas também a valorização dos mesmos como matérias-primas. Para a produção das amostras, além da utilização dos RSIs, foram também utilizados óxidos fundente (Na2CO3) e estabilizante (CaO). Os resultados obtidos demonstraram que ambos podem ser usados como recebidos (sem tratamento prévio) substituindo matérias-primas importantes, fontes de Al2O3 e SiO2, necessárias para a formação de vidros. As amostras obtidas apresentaram a cor âmbar devido a presença de níquel (íons Ni2+) proveniente do ECAT e transmitância óptica de 18%. Estas, ainda demonstraram boa homogeneidade, i.e., ausência de bolhas e estriais e, resistências hidrolíticas média de 1,33x10-8 g/cm²·dia (superior à um vidro comercial de composição semelhante) de acordo com a ISO695-1984. O vidro obtido é adequado para aplicações que exigem baixa transmitância como embalagens de vidros em geral, os quais não requerem perfeita visibilidade e transparência. O teor de incorporação na composição final das amostras foi de aproximadamente 78% em massa. / In this study, the use of two industrial solid wastes (ISW), generated in large quantities in Brazil, were presented in production of soda-lime silicate glasses destined for packaging. The evaluated wastes were rice husk ash (RHA) and the spent catalyst at the Petrochemical Fluid Catalytic Cracking units (ECAT), both may be classified as a class II solid waste according to NBR 10.004. This new proposal for the allocation of such wastes is an alternative to current provisions, seeking not only to minimize environmental impacts, but also enrich them as raw materials. For the samples production, besides ISW were used melting oxide (Na2CO3) and stabilizer oxide (CaO).The results demonstrate that both can be used in their raw form (without treatment) replacing important raw materials, sources of Al2O3 and SiO2, essential for glass formation. The samples obtained presented amber color due to the presence of nickel (Ni²+ ion) from ECAT and 18% of optical transmittance. They also showed a good homogeneity, i.e., absence of bubbles and striae and 1,33x10-8 g/cm²·day of hydrolytic resistance according to ISO695-1984. Thus, the obtained glass is suitable for applications requiring low light transmittance such as colored glasses containers in general, which does not require perfect visibility and transparency. The incorporation in the final composition was approximately 78% in mass.

Estudo realizado acerca da utilização de dois resíduos sólidos industriais (RSI) gerados em grande quantidade no Brasil, na obtenção de vidros soda-cal destinados à produção de embalagens. Os resíduos avaliados foram a cinza de casca de arroz (CCA) e resíduo do catalisador usado das unidades de Craqueamento Catalítico Fluido das Petroquímicas (ECAT), ambos podem ser classificados como resíduos sólidos de classe II de acordo com a norma NBR 10.004. Esta nova proposta para destinação desses resíduos é uma alternativa às atuais disposições, buscando não apenas minimizar os impactos ambientais gerados, mas também a valorização dos mesmos como matérias-primas. Para a produção das amostras, além da utilização dos RSIs, foram também utilizados óxidos fundente (Na2CO3) e estabilizante (CaO). Os resultados obtidos demonstraram que ambos podem ser usados como recebidos (sem tratamento prévio) substituindo matérias-primas importantes, fontes de Al2O3 e SiO2, necessárias para a formação de vidros. As amostras obtidas apresentaram a cor âmbar devido a presença de níquel (íons Ni2+) proveniente do ECAT e transmitância óptica de 18%. Estas, ainda demonstraram boa homogeneidade, i.e., ausência de bolhas e estriais e, resistências hidrolíticas média de 1,33x10-8 g/cm²·dia (superior à um vidro comercial de composição semelhante) de acordo com a ISO695-1984. O vidro obtido é adequado para aplicações que exigem baixa transmitância como embalagens de vidros em geral, os quais não requerem perfeita visibilidade e transparência. O teor de incorporação na composição final das amostras foi de aproximadamente 78% em massa. / In this study, the use of two industrial solid wastes (ISW), generated in large quantities in Brazil, were presented in production of soda-lime silicate glasses destined for packaging. The evaluated wastes were rice husk ash (RHA) and the spent catalyst at the Petrochemical Fluid Catalytic Cracking units (ECAT), both may be classified as a class II solid waste according to NBR 10.004. This new proposal for the allocation of such wastes is an alternative to current provisions, seeking not only to minimize environmental impacts, but also enrich them as raw materials. For the samples production, besides ISW were used melting oxide (Na2CO3) and stabilizer oxide (CaO).The results demonstrate that both can be used in their raw form (without treatment) replacing important raw materials, sources of Al2O3 and SiO2, essential for glass formation. The samples obtained presented amber color due to the presence of nickel (Ni²+ ion) from ECAT and 18% of optical transmittance. They also showed a good homogeneity, i.e., absence of bubbles and striae and 1,33x10-8 g/cm²·day of hydrolytic resistance according to ISO695-1984. Thus, the obtained glass is suitable for applications requiring low light transmittance such as colored glasses containers in general, which does not require perfect visibility and transparency. The incorporation in the final composition was approximately 78% in mass.

Esta dissertação poderia ser dividida em duas partes, sem que houvesse prejuízo para o seu entedimento: uma tratando do topázio natural (Al IND.2 SiO IND.4[F, OH] IND.2) e outra, a respeito dos vidros silicatos tipo soda-lime (SiO IND.2+CaO+Na IND.2 O). Em ambas se procura contribuir para o estudo de defeitos com algumas técnicas experimentais, mais enfaticamente as correntes de despolarização termicamente estimuladas (CDTE). Com relação ao topázio, há diversos estudos tratando de sua termoluminescência (TL) e de possíveis aplicações no que tange ao seu emprego como dosímetro termoluminescente. Procuramos complementar esses resultados com medidas de CDTE, técnica que ainda não havia sido utilizada para este material. Localizamos no topázio três bandas de CDTE, porém os resultados não são conclusivos no que se refere às origens dessas bandas. Em parte porque temos consciência de que os resultados variam bastante quando se estudam amostras naturais, com composições que variam dentro de um mesmo pedaço de cristal. No que diz respeito aos vidros soda-lime, o estudo foi mais abrangente. Há várias trabalhos no sentido de se conhecer melhor os efeitos causados pela irradiação de vidros silicatos. Acredita-se que o sódio desempenhe um papel fundamental nas principais mudanças processadas nesse material após irradiação gama. Assim, este estudo procurou comparar os resultados de TL e CDTE, além de absorção óptica, de vidros soda-lime com diferentes concentrações de Na POT.+ e K POT.+. Ao que tudo indica os processos responsáveis pela TL e CDTE dependem da relação entre as concentrações desses íons. Verificaram-se também variações com a taxa de dose, e os efeitos de tratamentos térmicos para situações onde um ou outro íon prevalece. / This work could be split in two different parts without impairment understanding. One of them, on natural topaz (Al2SiOdF,OH] 2) and the other on soda-lime silicate (SLS) glasses (Si02 + CaO + Na20) . In both of them we intend to contribute with more information on their defect composition, using some experimental techniques, especially the so called thermally stimulated depolarization currents (TSDC) . There are many surveys on topaz thermoluminescence (TL) and the possibility of its use as a TL dosimeter. So, one of the purposes of this study was to make a contribution with a technique not used so far with such material. We have detected three TSDC peaks. The results are not conclusive about the origin of those peaks, in part because we are dealing with a natural material whose composition can vary even within the same piece of crystal. As the SLS glasses, the study was more comprehensive. There are plenty of papers on irradiation effects in silicate glasses and attempts to understand the mechanisms responsible for them. It is believed that sodium plays a fundamental role in the main modifications caused by gamma irradiation of these glasses. In addition, this study attempts to compare the TL and TSDC results in SLS glasses with different concentrations of Na+ and K+. From our observations, the processes responsible for both TL and TSCD peaks depend on the relative concentrations of those ions. Furthermore, variations on the signals were also noticed; depending on the irradiation rate and on the thermal treatments performed, in samples where one or another ion prevails.