Application of nanotechnology in a silver/graphite contact material and optimization of its physical and mechanical properties

摘要

By applying nanotechnology, a new type of silver/graphite (AgC) electrical contact was fabricated and characterized. The AgC coating powders were obtained through high-energy ball milling and reducer liquid spraying-coating method. The as-prepared powders were examined by transmission electron microscope (TEM), scanning electron microscope (SEM), and X-ray diffraction (XRD). The results show that the thickness of graphite flakes milled for 10 h is about 50-60 nm and the AgC coating powders exhibit flocculent structure with quite fine and homogeneous internal rnicropores.XRD implies that the average crystalline size of silver in coating powders is about 50 nm. The mechanical and physical properties of this newly developed AgC contact made from the above-mentioned nanocrystalline powders by traditional powder metallurgy technique were measured. Compared with its counterparts made from other techniques, the properties of this new AgC contact have been optimized. High sm-face energy and high-energy interfaces of the nanocrystalline AgC coating powders provide powerful driving force for sintering densification. Moreover, the flocculent structure of the powders is also an important factor to acquire fine density ratio.