| 摘要 |
A powder composition consisting essentially of an intimate mixture of boron carbide and titanium diboride, the mixture having an average particle size of less than about 0.5 micron, the particles being uniformaly dispersed such that elemental analytical techniques show all discrete concentrations of boron carbide and titanium diboride to be less than or equal to about 0.5 micron in diameter, is disclosed. The powder is useful for making a densified ceramic composition comprising titanium diboride grains, having an average grain size of less than or equal to about 3 microns in diameter, uniformly dispersed with boron carbide grains, having an average grain size of less than about 5 microns in diameter. The densified composition exhibits improved hardness and toughness when compared with titanium diboride or boron carbide compositions. The powder can be prepared by a process comprising subjecting a stream of reactant gases consisting essentially of a volatile boron source, a volatile titanium source, a volatile carbon source, and a hydrogen source to an amount of laser radiation and at a pressure effective to convert as least a portion of the volatile boron, carbon and titanium sources to an intimate mixture of boron carbide and titanium diboride.
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