Laser-driven synthesis and densification of ultrafine boron carbide powders

Ultrafine (34 nm) B4C powders have been produced by the CO2 laser-driven pyrolysis of BCI3/H2/CH4 (C2H4) mixtures. Powders of B4C stoichiometry, free of excess boron or carbon, are produced through optimization of gas flow rates and laser intensity. These powders are loosely agglomerated and of high purity, consisting of particles which are equiaxed and exhibit a narrow size distribution. The laser-synthesized powders have been hot-pressed in argon to yield parts of theoretical density at 20500C. Examination of the microstructure reveals examples of uniform as well as exaggerated grain growth. Porosity is uniformly distributed throughout the B4C matrix. Microhardness, Young's modulus, transverse rupture strength, and fracture values of 32 GPa, 492 GPa, 455 MPa, and 3.7 MN/m32/, respectively, have been measured