Preparation of copper coated tungsten powders by intermittent electrodeposition

Abstract

This paper reported the findings that copper-coated tungsten (W@Cu) powders were successfully fabricated by intermittent electrodeposition. The influence of process parameters such as stirring frequency, load of tungsten powders, current density and deposition time were investigated. As-coated tungsten powders were characterized using scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. The optimum technical parameters were established for preparing W@Cu composite powders. The composite powders with uniform, dense, and consistent Cu coating were obtained under the conditions of tungsten powder content 8–12g·dm−3 in the electrolyte, current density 12–16A·dm−2, and stirring frequency 20–30h−1. The uncoated W particles were not observed after 22.5min of deposition. W particles were homogeneously coated by copper in >30.0wt.% of copper content. The composite powders in the bath could be effectively prevented from agglomeration by controlling proper stirring frequency and current density. The W@Cu powders with a copper coating thickness of ~2.5μm and with copper content of ~54wt.% were produced without copper adhering to the cathode plate. The nucleation mechanisms of copper electrodeposition were examined by fitting the experimental chronoamperogram data into Scharifker–Hills nucleation models. The results indicated that copper nucleates according to instantaneous nucleation mechanisms under the high current density. High current density is necessary to produce high over-potential and to increase the fraction of nucleation, which was beneficial to the preparation of W@Cu powders with dense, uniform Cu films. The findings laid a foundation for fabricating W@Cu powders with improved properties via electrodeposition.