Combustion synthesis of vanadium borides

An experimental study on the preparation of various vanadium borides (including V3B2, VB, V5B6, V3B4, V2B3, and VB2) in the V–B system was conducted by self-propagating high-temperature synthesis (SHS) from the elemental powder compacts. Close flame-front velocities and comparable combustion temperatures were observed for the reactant compacts with V:B = 1:1, 5:6, and 3:4, and they were much higher than those for the samples of other compositions. The lowest combustion velocity and temperature were detected in the sample of V:B = 1:2. According to the XRD analysis, pure VB was produced not only from the sample of V:B = 1:1, but also from those of V:B = 5:6 and 3:4. For the powder compact with V:B = 1:2, VB2 was dominantly formed along with trivial amounts of VB and V3B4. A multiphase product composed of VB and V3B4 at comparable quantities was yielded from the sample of V:B = 2:3. The only V-rich sample formulated at V:B = 3:2 generated monoboride VB and left the end product a large amount of unreacted vanadium.

Research highlights▶ A comparative study on the preparation of various V–B compounds (including V3B2, VB, V5B6, V3B4, V2B3, and VB2) was firstly conducted by the SHS process. ▶ Sustainability of solid state combustion depended strongly on the starting stoichiometry and preheating temperature of the reactant compact. ▶ Variations of the combustion temperature and flame-front velocity with sample stoichiometry were presented. ▶ The phase composition of the final products was examined and the associated activation energy was determined.