Tungsten and molybdenum borides are widely used in ultra-high temperature ceramics (UHTCs) and electrode material. In this research, ultra-fine and ultra-coarse binary borides (WB, W 2 B 5 , MoB, Mo 2 B 5 ) and MoAlB powders were prepared with W/Mo and B 4 C as raw materials and Ca/Al as the decarbonization agent. The feasibility of using Ca and Al as decarburizing agents was assessed by thermodynamic calculations. Meanwhile, the effects of reaction temperature, decarbonization agent type and its additional amount on the phase, morphology and size distribution of the powder products were thoroughly investigated. The results revealed that single phase products with carbon content of less than 1 wt% could be prepared. Moreover, the morphology and particle size of products were significantly affected by the reaction temperature and type of decarburization agent. When using Ca as the decarburizing agent, ultra-fine WB and MoB powders were effectively prepared, probably owing to the fact that W/Mo are essentially insoluble in Ca melt. However, the great solubility of W/Mo in Al makes it easily to synthesize ultra-coarse borides at high temperatures via the dissolution-precipitation mechanism. Additionally, ultra-fine borides particle can also be prepared by lowering the temperature and amount of Al to weak the dissolution-precipitation mechanism.
Spent LiFePO 4 (LFP) battery black mass (SLFPB) recycling is important and faces significant challenges due to complex composition. This work presents a novel molten CaCl 2 -based leaching-electrolysis method for comprehensive valuable component recovery. This process yields recovery percentages exceeding 95 % for Fe, Cu, and P, 87 % for graphite, and 70 % for Al, while enriching Li in the melt. The molten salt shows potential for cyclic operation. Mechanistically, LiFePO 4 and FePO 4 in SLFPB react with molten CaCl 2 to form metal chlorides, Ca 5 (PO 4 ) 3 Cl, and Ca 2 PO 4 Cl intermediates, which subsequently dissociate into soluble ions. Most Fe escapes as FeCl 2 vapor. Graphite, due to its lower density, floats to the melt surface. The distinct thermodynamic properties of Fe 2+ , Cu + , and PO 4 3– allow their separation and recovery as metals and P 4 through two-step electrolysis. Differences in leaching and volatilization rates leads to the accumulation of Li. This approach provides a simple pathway for comprehensive SLFPB recycling.
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