Synthesis of carbon nanotubes reinforced Al matrix composites via cold spray deposition

For fabrication of high strength carbon nanotube reinforced Al matrix composites, the uniform carbon nanotubes (CNTs) dispersion, strong interface bonding and high structural integrity of CNTs have been regarded as three most important issues. In this work, two distinct approaches, namely ball mailing and slurry based process, were applied to disperse CNTs in pure Al powders. These two kinds of CNTs/Al composite powders as well as pure Al powders (as comparison) were deposited onto stainless steel plates under different spraying conditions. The deposition efficiency, microstructure, interface between CNTs and Al matrix, as well as the distribution and structural integrity of CNTs in the coatings obtained by different starting powders were comparatively investigated. XRD results showed that both composites have no phase transformation during powder preparation and cold spraying process, and the structural integrity of CNTs was well retained in the as-sprayed coatings according to Raman spectrum. Both CNTs/Al composite coatings show a significant improvement of microhardness than pure Al coating, while the composite coating by ball-milled powders possessed a higher value of 120 HV_0.1. The relationship between microstructural features and coating properties was also investigated.