DEVELOPMENT OF A NUCLEAR ANALYTICAL TECHNIQUE FOR THE ANALYSIS OF TERNARY COMPOUNDS (B+C+SI) AND APPLICATION TO THE OPTIMIZATION OF A CVD PROCESS

Composites (C/C or C/Si), have a rather poor resistance to oxidation. Coatings made out of ternary compounds (B + C + Si) of various composi tions, can provide some protection. These coatings can be obtained by CVD. However, this process has to be optimized experimentally because theoretical calculations are only indicative. On another hand, there i s a lack of accurate methods to determine the composition of thin (B C + Si) layers. In this work, we have developed a method based on (p, p'gamma) reactions B-10 and Si-28 at 3.1 MeV. It has been checked usi ng activation via the (C(d,n)N)-C-12-N-13 reaction, that the carbon co ncentration obtained by difference, is accurate. The method has been a pplied to a CVD process based on the use of BCl3, CH3Cl3Si and H-2. Th e composition of coatings obtained under various experimental conditio ns (temperature, composition of the gas phase, etc.) was determined, a s well as the homogeneity of these coatings. Optimal operating conditi ons were thus defined.