高岭土在真空下的热分解行为

Characterization of Vacuum Thermal Decomposted Kaolin Vacuum

摘要以含高岭石、-水硬铝石、黄铁矿的高岭土为原料，经过压块烘干后，在真空（15-50Pa）、不同加热温度下，采用同步热分析仪（DSG-TGA）、X射线衍射（XRD）等分析手段对高岭土在真空下的热分解进行研究。DSC．TGA的结果与高岭石、-水硬铝石、黄铁矿三种矿物常压下的热力学计算出的分解温度相符。实验产物的XRD结果表明：在真空条件（15-50Pa）下，-水硬铝石A10（OH）在100-200℃之间脱水，300℃时脱水完全；黄铁矿Fe是在500-600℃分解，分解产物为FleS和S2，在700℃时，黄铁矿Fe岛分解完全；高岭石A12si205（0H）4在实验煅烧过程中，在200-300℃之间脱水，生成非晶态的偏高岭石，比该矿在常压的脱水温度提前200℃左右。继而转变成Al-Si尖晶石，最后形成莫来石与方石英。实验结果与热力学计算符合，充分说明真空条件对高岭土中各种矿物分解产生气体的反应有较大的促进作用。在本实验三种矿物分解产生气体的过程中，先进行的反应对后一反应的发生影响不明显。

Here, we addressed the vacuum decomposition of kaolin, mainly consisting of kaolinite, diaspore, and pyrite, to explore the possible applications of the decomposed compounds. The impacts of the decomposition conditions, such as the decomposition temperature and time, pressure, and impurities, on microstructures and stoichiometries of the decomposed compounds were evaluated with scanning electron microscopy, X-ray diffraction and differential scanning calorimetry-thermogravimetric analysis. The results show that the low pressure strongly affects the dehydration of diaspore and decomposition of pyrite. For instance, at a pressure of 15- 50 Pa, starting at 100℃, the complete dehydration of the diaspore occurred at 300℃ .At a temperature ranging from 500℃-600℃ ,the decomposition of the pyrite into FeS and Sz took place, and completed at 700℃. The dehydration temperature of kaolinite into metakaolinite was about 200-300℃ ,200℃ lower than that at atmospheric pressure. The experimental data agree fairly well with the calculated results based thermodynamics at a pressure from 10s Pa to 50 Pa. We found that the decomposition sequence of the three main components little affects the decomposition of the kaolin.