Carbon‐Nanotube‐Based Electrical Brush Contacts

Abstract

Sliding electrical contacts are ubiquitous in electric motors and various forms of monolithic metal – carbon composite brushes and filamentous precious metal brushes represent the highest performance materials available. There is a tremendous opportunity to develop a whole new class of high-performance brush contacts using aligned films of carbon nanotubes, possessing super-compressibility, [1] high electrical and thermal conductivity, [2–3] mechanical strength, [4] tunable friction behavior, [5] and environmental insensitivity. Here, we demonstrate the feasibility of aligned multiwalled carbon nanotube (MWCNT) brushes as a new and superior alternative to the traditional high-performance brushes for electrical contacts. These brushes have been shown to provide stable low-noise operation for extended sliding durations. We investigate both the direct-current (DC) and alternating-current (AC) properties of these nanotube brush contacts and demonstrate their reliable low-noise electrical performance as rotating axels as well as sliding contacts in motors. Our results demonstrate a new materials approach to producestable, intimate,andultralight electricalbrushcontactsat moving interfaces. Both the DC and AC current-carrying properties of macroscopic CNT contacts were investigated. The most common applications for sliding contacts are brushes that carry electrical current in motors and generators. [6] Solid brushed-type electric motors are still widely used and desirable because of their intrinsically low magnetic fields and noise and potential for high power density applications. The low cost, ease of controlling the speed, and demonstrated operation over a range of challenging conditions make brushes popular choices for electric motors. In most applications the brushes are fixed on flexible cantilevers that are designed ideally to provide compliance and low applied normal load, yet to follow the rotational error motions of the shaft without bouncing (an extremely detrimental process that leads to arcing and rapid brush deterioration). [6,7] The relatively high