Gas-phase combustion synthesis of titanium boride (TiB₂) nanocrystallites

Abstract

Two techniques are described for synthesizing nanometer-sized TiB 2 particles by gas-phase combustion reactions of sodium vapor with TiCl 4 and BCl 3 : a low-pressure, low-temperature burner and a high-temperature flow reactor. Both methods produce TiB 2 particles that are less than 15 nm in diameter. The combustion by-product, NaCl, is efficiently removed from the TiB 2 by water washing or vacuum sublimation. Material collected from the low-temperature burner and annealed at 1000 ± 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 Ti͞B͞Cl͞Na system indicates that near 100% yields of TiB 2 are possible with appropriate reactant concentrations, pressures, and temperatures.TiCl 4 1 2BCl 3 1 10Na°! TiB 2 1 10NaCl . (1) Calcote and Felder 9,10 have recently proposed producing metals and nonoxide ceramics from reactions of 948

A flame process for synthesis of unagglomerated, low-oxygen nanoparticles: Application to Ti and TiB2

“…Glassman et al [7] developed a thermodynamic criterion for the reactive-metal/halide system and showed, experimentally, that a number of refractory materials, including titanium diboride, can be produced by burning droplets of a sodium-potassium eutectic in various halide atmospheres. To develop this technology for nanostructured materials, Axelbaum and co-workers [8][9][10][11] demonstrated the production of nanocrystalline powders of titanium diboride in three different reactors: a low-pressure, low-temperature reactor, a high-temperature flow reactor, and a coflow diffusion flame.…”

“…[10,11] Thus, flame conditions can be adjusted to allow for encapsulation while still maintaining stable flames with high yields.…”

A convenient solid-state reaction route to nanocrystalline TiB2

“…Recently, various efforts have been made to synthesize TiB 2 at lower temperatures, control morphology or simplify reaction procedures. For example, Gu et al [6] prepared nanocrystalline titanium diboride via a benzene-thermal reaction of metallic sodium with amorphous boron powder and titanium tetrachloride at 400°C; Axelbaum et al [7] reported to synthesize nanometer-sized TiB 2 particles by gas-phase combustion reaction of sodium vapor with TiCl 4 and BCl 3 in a high-temperature flow reactor; Bates et al [8] reported a solution-phase reaction of NaBH 4 and TiCl 4 to produce an amorphous precursor powder, which was then annealed at 900-1100°C to obtain nanocrystalline TiB 2 .…”

Effect of the solid precursors on the formation of nanosized TiBx powders in RF thermal plasma

“…Processes for nanopowder synthesis such as self-propagating high temperature synthesis (SHS) [5], vapor-phase synthesis [3,6,7], carbothermal reduction process [1] and high energy ball milling [8] have also been developed. All the mentioned processes have their merits and limitations over the others such as the cheaper precursors they use or the lower reaction temperature, the higher purity of the obtained product, smaller particle size, etc.…”