Sintering reactions of clay bodies have previously been studied by numerous experiments that involve quenching of the sintered ceramic bodies to room temperature and analyzing the reaction product by different analytical techniques. In this study, green bodies containing quartz, alkali feldspar, kaolinite, and calcite, were progressively fired in air at various temperatures from room temperature to about 1060°C. For the first time, mineral reactions and textural relationships were studied in situ as a function of temperature and time with a spatial resolution of a few micrometers by confocal hyperspectral Raman imaging. Gehlenite, wollastonite, and pseudowollastonite could unambiguously be identified as newly formed phases during sintering, and their textural evolution could be followed with temperature and time. From 800°C onwards wollastonite formed at the direct contact to gehlenite, whereby at temperatures higher than 990°C wollastonite seems to be gradually replacing gehlenite. The crystallization of pseudowollastonite was observed already ~290°C below the accepted critical temperature (~1125°C) for the wollastonite-to-pseudowollastonite transformation, suggesting that pseudowollastonite can form metastably. The results of this study demonstrate that hyperspectral Raman imaging is a powerful method to study in situ phase transitions and recrystallization processes at grain boundaries during high-temperature sintering of ceramic materials. This article is protected by copyright. All rights reserved.

中文翻译：

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原位高光谱拉曼成像揭示烧结过程中含碳酸盐高岭土的演变

粘土体的烧结反应以前已经通过许多实验研究过，这些实验涉及将烧结陶瓷体淬火到室温并通过不同的分析技术分析反应产物。在这项研究中，包含石英、碱长石、高岭石和方解石的生坯在空气中从室温到约 1060°C 的不同温度下逐渐烧制。首次通过共聚焦高光谱拉曼成像以几微米的空间分辨率原位研究了矿物反应和纹理关系作为温度和时间的函数。在烧结过程中，钙黄长石、硅灰石和假硅灰石可以明确地被识别为新形成的相，它们的结构演变可以随着温度和时间而变化。从 800°C 开始，在与钙黄长石直接接触时形成硅灰石，而在高于 990°C 的温度下，硅灰石似乎逐渐取代了钙黄长石。在硅灰石到假硅灰石转变的公认临界温度 (~1125°C) 下，已经观察到假硅灰石的结晶约 290°C，表明假硅灰石可以亚稳态形成。这项研究的结果表明，高光谱拉曼成像是研究陶瓷材料高温烧结过程中晶界原位相变和再结晶过程的有力方法。本文受版权保护。版权所有。在硅灰石到假硅灰石转变的公认临界温度 (~1125°C) 下，已经观察到假硅灰石的结晶约 290°C，表明假硅灰石可以亚稳态形成。这项研究的结果表明，高光谱拉曼成像是研究陶瓷材料高温烧结过程中晶界原位相变和再结晶过程的有力方法。本文受版权保护。版权所有。在硅灰石到假硅灰石转变的公认临界温度 (~1125°C) 下，已经观察到假硅灰石的结晶约 290°C，表明假硅灰石可以亚稳态形成。这项研究的结果表明，高光谱拉曼成像是研究陶瓷材料高温烧结过程中晶界原位相变和再结晶过程的有力方法。本文受版权保护。版权所有。这项研究的结果表明，高光谱拉曼成像是研究陶瓷材料高温烧结过程中晶界原位相变和再结晶过程的有力方法。本文受版权保护。版权所有。这项研究的结果表明，高光谱拉曼成像是研究陶瓷材料高温烧结过程中晶界原位相变和再结晶过程的有力方法。本文受版权保护。版权所有。