Desenvolvimento de vitrocerâmico utilizando escória de fundição
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Data
2019-10-31
Autores
Leme, Thariany Sanches
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Universidade Estadual Paulista (Unesp)
Resumo
Neste trabalho, vidro e material vitrocerâmico foram obtidos a partir de uma composição baseada no diagrama ternário SiO2-Al2O3-CaO, utilizando escória de ferro fundido, provenientes de empresas de fundição, e, cal hidratada (comercial). A escória foi caracterizada através de: espectrometria de fluorescência de raios X (FRX), para determinar sua composição química; difratometria de raios X (DRX), para a identificação das fases cristalinas e análise térmica (TG), para evidenciar as reações térmicas associadas à desidratação e decomposição dos compostos presente no material. O vidro foi obtido através do processo de fusão/resfriamento (melt-quenching), fundido na temperatura de 1450°C. Foram caracterizados através de: calorimetria exploratória diferencial (DSC), para determinar as temperaturas de transição vítrea e de cristalização e difratometria de raios X (DRX), para identificar a sua estrutura amorfa. O estudo da cinética de cristalização do vidro foi realizado através de métodos cinéticos não isotérmicos baseados na descrição teórica formulada por Johnson-Mehl-Avrami (JMA). Estes métodos descrevem os processos de nucleação e cristalização utilizando dados provenientes da curva de DSC. O estudo cinético teve início com a obtenção do material vitrocerâmico tratado termicamente à 900ºC por 1,5h e identificação das fases cristalinas formadas, utilizando DRX. Considerando a formação de três fases cristalinas, os parâmetros cinéticos foram determinados a partir dos ajustes dos dados de DSC, pelos métodos de Kissinger, Augis-Bennett, e, Matusita e Sakka. O melhor ajuste resultou em três picos de cristalização. A energia de ativação (Ea) do processo de cristalização foi obtida usando os modelos de Kissinger, Augis-Bennett. Os resultados de Ea mostram irrelevantes variações comparando os métodos utilizados, porém o fator de correlação (r) da reta pelo método de Augis-Bennett é ligeiramente melhor que pelo modelo de Kissinger. O índice de Avrami (n) foi determinado através da equação modificada de Kissinger. Os valores do índice de Avrami para o pico I e III indica uma taxa de nucleação crescente, para o pico II indicando uma taxa de nucleação decrescente. O mecanismo de crescimento dos cristais (m) foi determinado de acordo com o método de Matusita e Sakka, indicando um crescimento tridimensional, caracterizado por partículas poliédricas com diferentes morfologias.
In this work, glass and glass-ceramic materials were obtained from a composition based on the ternary diagram SiO2-Al2O3-CaO using cast iron slag from foundry companies and hydrated lime (commercial). The slag was characterized by: X-ray fluorescence (XRF) to determine its chemical composition; X-ray diffractometry (XRD), to the crystalline phases identification and thermal analysis (TG), to show the thermal reactions associated with dehydration and decomposition of the compounds present in the material. The glass was obtained by melt quenching at 1450°C. They were characterized by differential scanning calorimetry (DSC) to determine glass transition and crystallization temperatures and X-ray diffraction (XRD) to identify their amorphous structure. The study of crystallization kinetics was performed by non-isothermal kinetic methods based on the theoretical description formulated by Johnson-Mehl-Avrami (JMA). These methods describe the nucleation and crystallization processes using data from the DSC data. The kinetic study began by obtaining heat-treated glass-ceramic material, at 900ºC for 1.5h, and identifying the crystalline phases formed using XRD. Considering three crystalline phases formation, the kinetic parameters were determined from the DSC data adjustments by the Kissinger, Augis-Bennett, and Matusita and Sakka methods. The best fit resulted in three crystallization peaks. The activation energy (Ea) of the crystallization process was obtained using the Kissinger and Augis-Bennett models. The Ea results show irrelevant variations comparing the methods used, but the correlation factor (r) of the line by the Augis-Bennett method is slightly better than the Kissinger model. The Avrami index (n) was determined by the modified Kissinger equation. Avrami index values for peak I and III indicate an increasing nucleation rate, for peak II indicating a decreasing nucleation rate. The crystal growth mechanism (m) was determined according to the Matusita and Sakka method, indicating a three-dimensional growth, characterized by polyhedral particles with different morphologies.
In this work, glass and glass-ceramic materials were obtained from a composition based on the ternary diagram SiO2-Al2O3-CaO using cast iron slag from foundry companies and hydrated lime (commercial). The slag was characterized by: X-ray fluorescence (XRF) to determine its chemical composition; X-ray diffractometry (XRD), to the crystalline phases identification and thermal analysis (TG), to show the thermal reactions associated with dehydration and decomposition of the compounds present in the material. The glass was obtained by melt quenching at 1450°C. They were characterized by differential scanning calorimetry (DSC) to determine glass transition and crystallization temperatures and X-ray diffraction (XRD) to identify their amorphous structure. The study of crystallization kinetics was performed by non-isothermal kinetic methods based on the theoretical description formulated by Johnson-Mehl-Avrami (JMA). These methods describe the nucleation and crystallization processes using data from the DSC data. The kinetic study began by obtaining heat-treated glass-ceramic material, at 900ºC for 1.5h, and identifying the crystalline phases formed using XRD. Considering three crystalline phases formation, the kinetic parameters were determined from the DSC data adjustments by the Kissinger, Augis-Bennett, and Matusita and Sakka methods. The best fit resulted in three crystallization peaks. The activation energy (Ea) of the crystallization process was obtained using the Kissinger and Augis-Bennett models. The Ea results show irrelevant variations comparing the methods used, but the correlation factor (r) of the line by the Augis-Bennett method is slightly better than the Kissinger model. The Avrami index (n) was determined by the modified Kissinger equation. Avrami index values for peak I and III indicate an increasing nucleation rate, for peak II indicating a decreasing nucleation rate. The crystal growth mechanism (m) was determined according to the Matusita and Sakka method, indicating a three-dimensional growth, characterized by polyhedral particles with different morphologies.
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Palavras-chave
Vidro, Vitrocerâmico, Escória, Cinética, Cristalização, Glass, Glass-ceramics, Slag, Kinetics, Crystallization