SURFACE COMPOSITIONAL CHANGE OF B4C UNDER D-2(+) IMPLANTATION IN HIGH AND LOW VACUA AND ITS EFFECT ON HYDROGEN RETENTION

The relation between retention characteristics and compositional change in the surface layer of B4C was investigated. The release temperature of implanted deuterium was 100 degrees C lower for her-pressed B4C and 90 degrees C lower for CVD boron carbide that were implanted with base pressure of higher vacuum, than of lower vacuum. This temperature shift would be owing to the decrease in the amount of boron oxide formed in the surface layer of B4C. This decrease of baron oxide in the surface layer is ascribed to the improvement of base pressure in a chamber for implanting deuterium ion from 3 x 10(-6) to 9 X 10(-8) Pa. On the contrary, the deuterium release temperature of graphite varied hardly with base pressure in implantation.