Molten salt synthesis of orthorhombic CrB and Cr2AlB2 ceramics

High-purity and fine CrB powders are firstly synthesized from Cr and B powders in (Na, K)Cl molten salt at 850 °C for 2 h. Then the as-achieved CrB powders are used as precursors to synthesize homogeneous and size-controlled Cr2AlB2 powders in (Na, K)Cl molten salt at 900 °C for 2 h. Additionally, the formation mechanisms of CrB and Cr2AlB2 in (Na, K)Cl molten salt are also investigated. Results show that the Cr atom, formed by disproportionation of Cr2+ ions in molten salt, reacts in-situ with B powders to form CrB. For the formation of Cr2AlB2, Al and CrB migrate mutually and assemble firstly in the molten salt, and then Al intercalates into CrB to generate Cr2AlB2.