Production of Bsub 4C coatings by CVD method in a dual impinging-jet reactor: Chemical yield, morphology, and hardness analysis

-rhombohedral boron carbide (...) was deposited on a tungsten substrate from a ... gas mixture in a dual impinging-jet chemical vapor deposition reactor. On-line FTIR analysis of the product stream proved the formation of BHCl... and HCl as by products, in a competing parallel reaction. A maximum of 13% chemical yield of boron carbide was observed, and the yield was found to have increasing trend with an increase in temperature. XRD analysis proved the existence of rhombohedral B...C phase at 1300...C without any other B...C phases or impurities. At this temperature, the formation of 5-fold icosahedral boron carbide crystals up to 30 micron sizes was observed. Such highly symmetric crystalline regions were observed to have a very high hardness value of 4750 kg/mm... as revealed from the microhardness analysis. The change in product morphology at low substrate temperatures resulted in a decrease in the hardness values. (ProQuest: ... denotes formulae/symbols omitted.)