Preparation Of Ultrafine W-Cu Composite Powders And Dispersion Research

Abstract:In the present investigation, ultrafine W-Cu composite powders were prepared by hydrogen reduction of CuWO4-WO3precursors which were calcined from concentrated wet ball milled WO3-CuO powder mixtures, and the dispersion behavior of the high-density ultrafine W-Cu composite powders in high concentrated slurry was researched. The powders were characterized by XRD, SEM, TEM and laser-diffraction diameter tester,with emphasis on the morphology, components and particle size of the resulting powders. Results were shown as follows:1) The WO3-CuO powder mixtures were synthesized by high concentrated wet ball-milling. After5hours of the wet milling, the mean particle size of W03-CuO powder mixtures decreased from44.88to0.24μm and the specific surface area increased from1.4568to26.59m2/g, while the distribution of particle size was narrow. As milling time increased, the particle sizes of WO3-CuO powder mixtures did not change, and the phase of WO3appeared obvious lattice deformation while the phase of CuO disappeared. High concentrated wet ball-milling not only solves the problem such as low efficiency, impurity, uneven particle size distributions of dry milling, but also creates the condition for the mass production of unltrafine W-Cu composite powders.2) The effect of calcined temperature on the morphology, components and particle size of the precursors was researched. High concentrated wet ball milling effectively reduced the preparation temperature of precursors, and the optimum calcined temperature was800℃. The calcined CuWO4-WO3precursors had homogenous particle size and dispersed well with mean particle size of0.69μm.3) As reduced temperature increased, the crystallite size of W and Cu grew from28.51to30.76nm and33.28to33.42nm, respectively. The W-Cu composite powders reduced from700℃were fine and homogeneous, and its mean particle size was0.38μm. The result of EDS and TEM suggested that composition of reduced W-Cu composite powder was uniform. This is because the wet ball milling and calcination promoted the compound of W and Cu phase.4) The effect of dispersion mediums, dispersant species, ultrasonic times and dispersant concentrations on the dispersion stability of slurries was studied. The best dispersion processes were showed as follows:dispersion medium was premixed solution; dispersing agent was polyvinylpyrrolidone; ultrasonic time was10min and dispersant concentration was2.0wt%. This lays the foundations for the preparation of complex shape W-Cu parts by gel-casting.