Preparation of nickel and copper coated fine tungsten powder

Fine tungsten powders with an average particle size of 5 mu m were coated w ith nickel and copper via high pressure hydrogen reduction from nickel sulp hate and ammonia solution at 130-140 degrees C, 4000 kPa pressure and via f ormaldehyde reduction of copper sulphate, ethylenediamine tetra acetic acid (EDTA) and sodium hydroxide solution at ambient temperature respectively. The nickel and copper contents coated on tungsten varied from 2 to 10 wt.% and 2 to 30 wt.% respectively. As-coated tungsten powders were characterise d using X-ray diffraction and scanning electron microscopy. It was found th at nickel and copper were homogeneously distributed around the tungsten par ticles in exceeding 4 to 5 wt.% of Ni/Cu content. No impurities, such as re sidual chemical agents and oxides were detected by chemical and XRD analysi s. However, the aggregation of tungsten powder became serious for copper co ntents larger than 20 wt.%, which affects the fluidity of tungsten powders during the subsequent press operation. The penetration depth of a perforati on device prepared from coated tungsten powders increased by 20 compared wi th that manufactured from conventionally blended elemental powders. (C) 199 9 Elsevier Science S.A. All rights reserved.