在硫酸钠熔盐中合成莫来石的热力学研究

THERMODYNAMICS STUDY ON MULLITE PREPARATION IN MOLTEN SODIUM SULFATE

以硫酸铝和二氧化硅为原料,以硫酸钠为介质合成莫来石粉体。利用差示扫描量热法研究了合成过程中的热量变化。由理论数据与实验数据分别经过计算得到的反应热变化基本一致,从而确定了合成反应的温度范围应在950～1000℃之间。利用X射线衍射仪和场致发射扫描电子显微镜等手段对合成粉体的相组成、结构和形貌进行了研究。结果表明:在1000℃保温3h合成的莫来石粉体基本无其他相存在,其粉体呈针状晶须,直径约50～100nm,长度约3～8μm。该方法工艺简单,合成温度较其它方法低200～400℃。

Using aluminum sulfate and silica as raw materials, mullite powders was prepared successfully in molten sodium sulfate. The heat change during the synthesizing process was investigated by the differential scanning calorimetry. It is found that the theoretical calculation agrees well with experimental data, then the temperature of mullite formation was confirmed in the range of 950-1 000℃. The phase composition and microstructure of mullite powders were investigated by X-ray diffraction and field emission scanning election microscopy techniques. The results show that no other phases exist in the mullite synthesized at 1 000℃ for 3 h. The powders exhibit crystals of needle-like whiskers, which are about 50-100 nm in diameter and 3-8 μm in length. This preparation method is characterized by simplicity, and the temperature of mullite formation is 200-400℃ lower than that of conventional methods.