Surface Acidity and Surface Treatment of Silicon Nitride

Abstract

For surface treatment of silicon nitride, surface properties such as the amount of surface hydroxyl groups, and surface acidity and basicity were examined. The surface reactions of the silicon nitride with various organic acids, amines and propylene oxide were also carried out in an autoclave at 200°C for 3 h and degree of surface reaction was determined by ESCA. The effect of the surface treatment was evaluated by disperisibility in hexane-water system and sedimentation in hexane.
The followings were known by this study. ( 1 ) The amount of surface hydroxyl groups on silicon nitride (Fig.1) was comparable to that on silicon oxide ( 2 ) Weak acidity (Ho>3.3)probably due to surface hydroxyl groups was found for silicon nitride. The amount of the acid site was maximal (23 μmol/g) by heat treatment at the temperature around 800°C (Fig.3). ( 3 ) Highly lipophilic surface of silicon nitride was formed by the treatment with propylen e oxide and amines having a long carbon chain such as hexadecyl amine and octadecyl a mine (Table 4).