【作者】 徐屹；

【导师】 凤仪；

【作者基本信息】 合肥工业大学 ， 材料学， 2006， 硕士

【摘要】 本试验采用粉末冶金方法制备碳纳米管-银-石墨复合材料,初压压力200MPa,在H₂保护气氛下烧结并保温1h,复压压力400 MPa制得复合材料。复合材料中石墨和碳纳米管分布均匀,没有明显孔洞和团聚现象发生。 研究了电流密度（0-25A/cm²）对复合材料电磨损性能的影响。试验结果表明:随着电流密度增大,发热量增大,粘着磨损加剧,接触表面的接触方式发生改变,导致收缩电阻和过渡电阻减小,接触电压降略有上升;随着电流密度的增大,润滑膜遭到破坏,导致复合材料的摩擦系数增大、磨损量增大;比较电刷正、负极磨损量可以发现,由于接触表面的理化反应和金属转移的存在,导致正刷磨损量大于负刷磨损量,正刷磨损量随电流密度增大而成倍增长,而负刷磨损量与电流密度关系不大,电流密度越大磨损极性的差异越明显; 研究了圆周速度（5-15m/s）对复合材料电磨损性能的影响。试验结果表明:当压力一定时,随着圆周速度的增大,复合材料的接触电压降略有增加,而圆周速度增大到一定值后,接触电压降和磨损量急剧增加并伴有火花磨损出现:压力较小时（1N/cm²）圆周速度为7.5m/s时就出现电火花,压力较大时（2.5N/cm²）圆周速度为15m/s出现电火花。在圆周速度不变的条件下,接触电压降先升后降最后趋于稳定;随着速度的增大机械磨损的摩擦系数有所下降,而电磨损的摩擦系数随着速度的增大反而增大;电磨损磨损量随速度增大增大,而机械磨损的磨损量随速度的增大反而减小;机械磨损的相对磨损率随着速度的增大而减小,而电磨损相对磨损率出现了最小值,这是由于电刷压力、电流、温度等因素综合作用的结果。更多还原

【Abstract】 In this paper, CNTs-Ag-G composite brushes were fabricated by means of powder metallurgy method. The process included mixing powder, pressing at 200 MPa, sintering for 1h in pure H₂ protective atmosphere at 700℃ and repressing at 400 MPa. The distribution of graphite and CNTs is homogenous in the CNTs -Ag-G composite without obvious micropore and cluster.The effect of the electrical current （0-25A/cm²） on the electrical wear properties of CNTs-Ag-G composite was studied. The results indicate that the temperature of interface rises and the probability of sticking wear becomes more with the increase of the electrical current. Due to the altering of contact manner, the contact resistance decreases and contact voltage drop increases little. With the increase of the electrical current, the sticking wear aggravates, the lubrication film gets damaged, and finally the friction coefficient and the wear mass loss both become bigger. After the comparison of the positive brush and negative brush, it can be found that the wear mass loss of the positive brush is more than the loss of the negative brush because of the physical and chemical reaction on the interface and the existence of the metal transference. The wear mass loss of the positive brush multiplies with the increase of the electrical current, but the loss of negative brush has little relation with the electrical current. The bigger the electrical current is, the more difference between the wear mass loss of the two brushes is.The effect of the circular velocity （5-15m/s） on the electrical wear properties of the composite was studied. The results indicate when the pressure is certain, the contact voltage drop increases a little with the increase of the circular velocity. While the circular velocity reaches a definite value, the contact voltage drop and the wear mass loss increases sharply as the appearance of electric spark. When the pressure is low （1N/cm²）, electric spark comes out when the circular velocity reaches 7.5m/s. While the pressure becomes higher （2.5N/cm²）, electric spark comes out until 15m/s. Under the condition of constant circular velocity, the contact voltage drop curve falls down after it ascends first, and finally tends to be stable. As the circular velocity increasing, the friction coefficient and the wear mass loss of the mechanical wear decreases, but those of the electrical wear increase. With the increase of the circular velocity, the mechanical relative wear rate increase and the relative electrical wear rate varies as "U" because of co-action of press, electrical current and temperature.更多还原