Combustion synthesis of vanadium borides

An experimental study on the preparation of various vanadium borides (including V(3)B(2), VB, V(5)B(6), V(3)B(4), V(2)B(3), and VB(2)) 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, VB(2) was dominantly formed along with trivial amounts of VB and V(3)B(4). A multiphase product composed of VB and V(3)B(4) 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. (C) 2010 Elsevier B.V. All rights reserved.