INSITU BORON-NITRIDE COATING AND COMPARISON WITH EXISTING BORONIZATIONS

Two new types of boronization were demonstrated in a laboratory apparatus bakable up to 350-degrees-C: (i) amorphous boron nitride films (B/N approximately 1) were deposited by a dc glow discharge of a 0.1 B2H6 +0.3 N2 +0.6 He mixture, and (ii) decaborane B10H14, a less hazardous powder, was used to deposit pure boron films. A feasibility boronization of fusion devices with the new method was demonstrated by basic experiments on hydrogen recycling, helium glow conditioning, and oxygen gettering. In the laboratory experiment, time variations in relevant partial pressures were measured in pulsed glow discharges in D2, He, and 1% O2/He. Standard boronization and carbonization using B2H6 and/or CH4 were also done in an identical apparatus at the same temperature (150 or 300-degrees-C). A comparison among them revealed that the boron nitride coating is a new candidate competing with existing boronizations. The first results of boronization using decaborane indicate the new technique to be easy and safe for handling.