Molybdenum Powder To Restore The Processes And Process Optimization Studies

The phase transformation of producing molybdenum powder by hydrogen reduction was investigated by XRD and SEM analysis. The effect of morphology and size of raw materials on the final product and the kinetics of reducing molybdenum powder were also analysed. The reduction technique is optimized by quadratic general rotary unitized design, the results are as follows:1. The raw materials of different ammonium molybdates have different phase transformations, Mo₄O₁₁ is a stable middle phase to the first step of reducing molybdenum powder. The product constituents are idential when calcinated-products with different ammonium molybdates as raw materials are reduced with the same technology.2.The dimension of ammonium molybdate particles have the feature of "inheritance" . The morphology of raw materials have no effect to the product.3.Interface-chemical reaction is the major control step when MoO₃ powder changes into MoO₂. Chemical vapour transport model exist when fine MoO₃ particles change into other phases. Inner diffusion is the major control step when MoO₂ particles change into Mo powder particles. Fine MoO₂ particles obey chemical vapour transport model when MoO₂ powder changes into Mo powder.4. Statistic test shows the regression equations of average gain size, free holding density and oxygen content of molybdenum to each process parameter are significant. The ranges of the parameter optimized are reasonable.