Synthesis of MoAlB from MoB/Al2O3 Mixtures via Molten Salt Electro-Deoxidation

High-purity MoAlB powder was synthesized using MoB and Al₂O₃ as precursors via molten salt electro-deoxidation(EDO) in a NaCl–CaCl₂ system at 950°C and 3.2 V for 12 hours. The effects of Al₂O₃ content, electrolytic voltage, and electrolysis time on the preparation and synthesis mechanism of MoAlB were investigated. Results indicate that an excess of 50% Al₂O₃(nMoB:nAl 2 O 3 =1:0.75) and increasing the voltage to 3.2 V effectively suppress the retention of byproduct Al₈Mo₃ in the final product, yielding predominantly MoAlB. The synthesis of MoAlB in this system occurred in three stages: Al₂O₃ electrolytic deoxidation produced Al, which then reacted preferentially with MoB to form Al₈Mo₃. Next, MoAlB formed through reactions between Al₈Mo₃ and B (mainly during 0~6 hours) and between MoB and Al (mainly during 6~12 hours). The MoAlB powder produced shows single crystals with granular shapes. TEM measurements confirm its interplanar spacing matches standard values. Successfully producing MoAlB through molten salt electrolytic deoxidation with an “oxide + alloy” feedstock presents a new, eco-friendly, and low-cost way to create the MAB phase.