电流对碳纳米管-银-石墨复合材料摩擦磨损性能的影响

采用粉末冶金方法制备了碳纳米管-银-石墨复合材料,研究了复合材料在机械磨损和带电磨损2种状态下的摩擦磨损性能及接触电压降的变化情况.结果表明,复合材料在带电磨损条件下的摩擦系数和磨损体积损失均比不带电条件下的大.这是由于外加电场不利于保持摩擦副接触表面在摩擦热等作用下形成润滑膜的均匀性和完整性所致.此外,在带电磨损条件下,阳极的磨损体积损失比阴极的大.其原因在于,摩擦副接触表面润滑膜中的水在电场作用下发生离解,在正刷侧释放出活性氧,活性氧与电刷表层中的碳或金属发生氧化反应,从而使得磨损加剧.

Effect of Electric Current on the Friction and Wear Behavior of Carbon Nanotubes-Silver-Graphite Composite

Carbon nanotubes-Ag-graphite (abridged as CNTs-Ag-G) composite was fabricated by means of powder metallurgy. The friction and wear behavior of the CNTs-Ag-G composite sliding against a copper alloy in the presence of electric current was evaluated and compared with that in the absence of the external electric field using a ring-on-block friction and wear tester. The effect of the electric current on the contact drop of the composite electric brush was also examined. Moreover, the worn surface morphologies of the composite at different sliding durations were observed using a scanning electron microscope. It was found that, as compared to the no-electric current condition, the composite sliding against the copper alloy in the presence of 10 A/cm~2 electric current recorded a larger friction coefficient and wear volume loss. This was attributed to the negative effect of the electric current on the uniformity and integrity of the lubricating film formed on the contact surfaces of the frictional pair, owing to the action of the friction-induced heat. Besides, the positive brush had a larger wear volume loss than the negative brush. This was because the water entrapped in the lubricating film was ionized in the presence of the electric current to generate highly active negative oxygen ions, which led to the oxidation of the positive brush and accelerated its wear.