Combustion synthesis of CaB6 powder from calcium hexaborate and Mg

As one of the important metal-borides, calcium hexaboride (CaB6) is applied in refractory materials, metal deoxidant, neutron absorbent, wear-resisting agent and functional ceramic materials. Generally, CaB6 is produced from B4C or B2O3 which is obtained at high temperature and high cost. In this study, the CaB6 powder was prepared through combustion synthesis by using calcium hexaborate and magnesium as starting materials. The calculated adiabatic temperature of CaB6O10–Mg system reached 2406.69 K. The XRD analyses of combustion products showed that there existed a small amount of Mg3B2O6 and Ca3(BO3)2 besides CaB6 and MgO. The XRD patterns of products leached by HCl indicated the major part of the leached sample is comprised by CaB6, showing that MgO and by-products were efficiently leached out. In addition, the technological conditions for combustion synthesis were investigated. It is resulted that larger particle size of CaB6O10 and higher compacting pressure is beneficial to the production of CaB6.