Properties of electric brushes made with
Cu-coated graphite composites and with copper powders
Cu-coated graphite composites and with copper powders
(College of Materials Science and Engineering, Hunan University, Changsha 410082, China)
Abstract: Cu-coated graphite composites were prepared by an electroless plating method, and the composites were examined by scanning electron microscopy (SEM). The copper content of the composites was measured to reach 73% (mass fraction). Brush samples made with composites contents of 10%, 15% and 20% and with copper powders content of 11% were obtained. The results show that the resistivity of the brush samples decreases and hardness becomes higher with increasing composites content. Copper is dispersively distributed in the brush samples made with the composites, whereas copper agglomerates in Cu-graphite mechanical mixture. For the same Cu content, Cu-coated graphite composites possess lower resistivity and higher hardness than Cu-graphite mechanical mixture. A new type of electric brush was obtained by using Cu-coated graphite composites, the wear and durability tests carried out on a HGH5435M120 AC motor indicate that its service life reaches 250 h. The electric brushes possess relatively low resistivity (275 mW∙m) and good wear resistance, so they are very suitable for high-speed micromotors.
Key words: electric brush; Cu-coated graphite; electroless plating; wear