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

The relation between retention characteristics and compositional chang e in the surface layer of B4C was investigated. The release temperatur e of implanted deuterium was 100 degrees C lower for her-pressed B4C a nd 90 degrees C lower for CVD boron carbide that were implanted with b ase pressure of higher vacuum, than of lower vacuum. This temperature shift would be owing to the decrease in the amount of boron oxide form ed in the surface layer of B4C. This decrease of baron oxide in the su rface layer is ascribed to the improvement of base pressure in a chamb er for implanting deuterium ion from 3 x 10(-6) to 9 X 10(-8) Pa. On t he contrary, the deuterium release temperature of graphite varied hard ly with base pressure in implantation.