Low‐temperature preparation of titanium diboride fine powder via magnesiothermic reduction in molten salt

Abstract

Phase pure titanium diboride (TiB2) powder of 100‐200 nm was synthesized from TiO2 and B2O3 using a molten‐salt‐assisted magnesiothermic reduction technique. The effects of salt type, Mg amount, reaction temperature, and TiO2 raw materials on the synthesis process were examined and the relevant reaction mechanisms discussed. Among the three chloride salts (NaCl, KCl, and MgCl2), MgCl2 showed the best accelerating‐effect. To synthesize phase pure TiB2, 20 mol% excessive Mg had to be used to compensate for the evaporation loss of Mg. Particle shape and size of raw material TiO2 showed little effect on the formation of TiB2 and its shape and size, suggesting that relatively cheaper and coarser TiO2 raw materials could be used for low‐temperature synthesis of TiB2 fine particles. The “dissolution‐precipitation” mechanism governed the overall molten salt synthesis process.

Low temperature synthesis of TaB2 nanorods by molten‐salt assisted borothermal reduction

“…It is clear that pure TaB 2 phase is obtained only when the mass ratio of NaCl/KCl salts and the reactant powders ranges from 0:1 to 20:1. As the ratio increases to 30:1, the NaCl/KCl salts react with the reactants to form impurities such as Na 2 Ta 4 O 11 , K 2 Ta 4 O 11 , and Na 2 Ta 8 O 21 . The results indicate that the suitable amount of the salts is essential important for the molten salt method to obtain product with a high purity.…”

Low Temperature Synthesis of Phase Pure MoAlB Powder in Molten NaCl

“…At the test temperatures, the NaCl (melting point~714 • C) melted, forming a homogeneous molten salt medium in which the Al (melting point 660.3 • C) melted, forming corresponding droplets. Although the exact solubility data of the Al, Mo and B in the NaCl molten salt are not available, based on the previous studies on the molten salt synthesis of Mo 2 C [17], borides [18][19][20] and TiB 2 -Al 2 O 3 [21], it can be considered that the solubility values should be in the following order: Mo> Al> B. At a relatively low firing temperature (850 • C), Mo was partially dissolved in the liquid salt, diffused quickly through it onto the Al droplets (or met with dissolved Al) and B particles and then reacted to form intermediate phases Al 8…”

Low‐temperature synthesis of ultrafine TiB2 nanopowders by molten‐salt assisted borothermal reduction

“…Recently, a novel low temperature molten salt assisted synthesis technique has been proposed to synthesize ultrafine NbB 2 nanopowders with the particle size of around 32 nm at 1073 K using Nb 2 O 5 and B as precursors within a KCl/NaCl salt . Motivated by this result, Bao et al synthesized ultrafine TiB 2 powders with the particle size of 100 ~ 200 nm via a molten salt assisted magnesiothermic reduction technique at 1273 K using TiO 2 , B 2 O 3 , and Mg as precursors within a KCl/NaCl/MgCl 2 salt. Nevertheless, it is still difficult to synthesize the high‐purity ultrafine TiB 2 powders due to the evaporation of Mg and the complexity in the chemical reactions.…”