Gas-phase combustion synthesis of titanium boride (TiB 2 ) nanocrystallites

Two techniques are described for synthesizing nanometer-sized TiB{sub 2} particles by gas-phase combustion reactions of sodium vapor with TiCl{sub 4} and BCl{sub 3}: a low-pressure, low temperature burner and a high-temperature flow reactor. Both methods produce TiB{sub 2} particles that are less than 15 nm in diameter. The combustion by-product, NaCl, is efficiently removed from the TiB{sub 2} by water washing or vacuum sublimation. Material collected from the low-temperature burner and annealed at 1000{degree}C consists of loosely agglomerated particles 20 to 100 nm in size. Washed material from the high-temperature flow reactor consists of necked agglomerates of 3 to 15 nm particles. A thermodynamic analysis of the Ti/B/Cl/Na system indicates that near 100{percent} yields of TiB{sub 2} are possible with appropriate reactant concentrations, pressures, and temperatures. {copyright} {ital 1996 Materials Research Society.}