W – Cu ultrafine/nanocomposite powders have high sintering activity, so ultrafine/nanotechnology of W – Cu composite powders is one of the main methods to obtain fully dense, high-performance W – Cu composite materials. Cu -coated ultrafine W composite powders were synthesized by ultrasonic-assisted electroless plating process with non-noble metal activation pretreatment at room temperature in this paper. The growth mechanism of Cu layers and surface morphologies and composition of initial ultrafine W powders, pretreated W powders and Cu -coated W powders were analyzed by field emission scanning electron microscopy (FE-SEM), and energy dispersion spectrometry (EDS). The results show that the uniformly Cu coated W composite powder is successfully synthesized without conventional sensitization and activation steps by ultrasonic-assisted electroless plating at room temperature. The Cu layers on the ultrafine W powders had cell structure with dense, uniform distribution. The growth mechanism of Cu layers appears as follows: the surfaces of pretreated W powders appear linear-like and lamellar-like surface defects which act as activated sites. The reactants in the plating solution were adsorbed on catalytic activity surfaces of powders and happened oxidation–reduction reaction. The growth and aggregation mechanisms of Cu particles after nucleation are stripy Cu -cells grew up, bend, bifurcated, and aggregated, then wounding into a cellular structure, like "wrapping wool clusters" in the life. Finally, Cu cells grow up and merge into a layer.
Fe3 Cluster Anchored on the C2N Monolayer for Efficient Electrochemical Nitrogen Fixation
