Production of spherical Mo and Mo-Si powders by spray drying of Si suspension in a water-soluble Mo precursor

Abstract

The study focuses on the production of molybdenum (Mo) and molybdenum-silicon (Mo-Si) powders using the spray drying method, followed by calcination and reduction steps. Mo powder was produced from an aqueous solution of ammonium hexamolybdate (AHM), while composite Mo-Si powders were produced from the same solution with suspended submicrometric Si particles. The as-sprayed powders were amorphous and had spherical hollow-shell morphology. In the case of Mo-Si composite powders, the powders had uniformly embedded Si aggregates on the surface. The spherical hollow-shell morphology of the powders was retained after calcination and reduction treatments. The observed chemical transition was AHM → MoO3 → Mo for Mo powders and AHM-Si → MoO3-Si → Mo-Si for composite powders. Extrusion tests demonstrated the suitability of the produced powders for extrusion-based additive manufacturing. The powders were extrudable at low load, resulting in stable filaments that stack layer by layer without deformation. The extruded filaments were then subjected to debinding and sintering processes, reaching an intermediate state of densification. Filaments fabricated from composite Mo-Si powders confirmed the alloying of Mo grains with Si during the sintering process.