SILICON CARBONITRIDE - A RIVAL TO CUBIC BORON-NITRIDE

It is common to divide hard materials into two groups: ultra-hard with diamond and cubic boron nitride and a second group of hard materials listed as SiC, TiC, etc. Between these two groups, a few ternary phase s have a hardness overlapping that of cBN. We have perviously reported on the synthesis of B-C-SI Si-O-C and Si-N-C crystalline phases. This paper reports on crystalline silicon carbonitride phase-synthesized u sing microwave plasmas with nitrogen or N-2-CH4-H-2 vapor etching sili con. The crystalline phase possesses the pseudo-alpha-Si3N4 structure. The microcrystals have a columnar form and an average size of 10 mu m . The FTIR spectrum resembles that of alpha-Si3N4, but a set of new ab sorption peaks appears. This new material is much harder than the Si3N 4 cutting tool insert, and it scratches single crystals of alpha-SiC, sapphire and even the (001) surface of diamond. (C) 1998 Elsevier Scie nce S.A. All rights reserved.