发现静电稳定的碳化硅浆料在碳化硅粉体表面的无定形氧化硅层的影响下，可以象氧化硅溶胶一样发生溶胶－凝胶转变，并将这一发现用于碳化硅陶瓷的成型．通过预先加入的酯或内酯的水解反应，把浆料的ｐＨ值从碱性区降至有利于凝胶的中性区，体系发生固化． 利用小幅震荡剪切技术对影响固化过程的各种因素进行研究表明，固化速度及固化强度不仅依赖于体系最终的ｐＨ值，还取决于体系最初的ｐＨ值以及ｐＨ值变化的速度．这些影响因素说明，体系的固化不是一个简单的凝聚的过程，而是一个凝胶的过程，浆料的固化是碳化硅颗粒间形成Ｓｉ－Ｏ－Ｓｉ键的结果．
It was found that sol-gel transition may occur to electrostatically stabilized silicon carbide suspensions when their pH values are shifted from alkaline
region to neutral. SiC slips may set when they are neutralized by the hydrolysis or esters or lactones. This process was used in the forming of SiC ceramics.
Rheological studies on various factors influencing the setting process by small amplitude oscillatory measurements show that the gelation of the SiC suspensions
depends not only on the final pH, but also on the initial pH and the pH-shifting rates of the systems. These effects indicate that this solidification is not a simple coagulation process
but a gelation process that takes place by forming Si--O--Si bonds between the particles. SiC ceramic green bodies with complex shapes were prepared with this method.
参考文献
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