高温高压下叶蜡石和白云石的结构研究

Study on the Structure of Pyrophyllite and Dolomite under High Temperature and Pressure

摘要: 叶蜡石和白云石是金刚石高温高压合成工艺中重要的辅助原材料，直接影响着高压合成过程中的设备安全及产品质量。同时，高温高压环境必然会对叶蜡石和白云石的结构性能产生重要影响。采用X射线衍射和热重分析研究了叶蜡石模具和白云石套管在高温高压使用前后的成分和结构变化。结果表明：经高温高压使用后，叶蜡石模具，包括其边角处、外侧、中部和内侧均未产生相变，与使用前具有相似的结构和热稳定性。而白云石则发生明显改变，高温高压下套管外侧的白云石会部分分解，生成CaCO₃和MgCO₃，而套管内侧白云石则相对稳定。但是由于高温扩散作用，石墨会扩散并在白云石套管内侧形成聚集。因此，该结果表明，高温高压使用后的叶蜡石存在再次循环使用的可能性。

Abstract: Pyrophyllite and dolomite are two important auxiliary materials in the high-temperature and high-pressure synthesis process for diamond. Both pyrophyllite and dolomite directly affect the equipment safety and product quality during the diamond production process. Simultaneously, the high-temperature and high-pressure environment will inevitably affect the structural properties of pyrophyllite and dolomite. The composition and structure changes of pyrophyllite and dolomite after the high-temperature and high-pressure process were studied by X-ray diffraction and thermo gravimetric analysis. The results show that there is no phase change in the corner, outside, middle and inside of the pyrophyllite mold after the process of high-temperature and high-pressure. Its structure and thermal stability are similar to the initial pyrophyllite before use. Different from pyrophyllite, under high temperature and high pressure, the dolomite outside the casing will be partially decomposed into CaCO₃ and MgCO₃, while the dolomite inside the casing is relatively stable. However, due to the high temperature diffusion, the graphite will diffuse and form aggregation in the casing. Therefore, the results show that pyrophyllite after high temperature and high pressure use has the possibility of recycling in theory.