Fabrication And Properties Of Carbon Nanotubes-aluminum Composites Prepared By Pressureless Infiltration Technique

Aluminum composites reinforced with carbon nanotubes have a very good and attentive application perspective. This kind of composites fabricated by the incorporation of reinforcement CNTs and Al has very excellent properties that does not exist in the single component. The pressureless infiltration process employs a spontaneous infiltration of molten Al alloy into CNTs-Mg-Al preform though capillary press produced by the soakage of the reinforcement and the matrix. And this method is a novel way in the area of the metal matrix composites (MMC) fabrication, and is characterized by the simple process and low cost. We fabricated CNTs/Al composites using this method in this study and explored the process condition that the molten Al infiltrated into the preform. In the mean time we studied the tribological and wear properties of these composites.In this paper, CVD method was used to fabricate multi-carbon nanotubes. In order to make the CNTs become more disperse, ultrasonic machine was used before milling. In the same time the CNTs were investigated by SEM, TEM and Raman. The biggest problem of the metal matrix composites fabrication using pressureless infiltration is the wetting between reinforcement and metal matrix. In this experiment the most difficult is the bad wetting in the CNTs/Al system. This problem led to the hard infiltration of aluminium liquid into the matrix. In order to make the infiltration become easier, the follow methods were adapted: 1) Mg was added properly in the reinforcement;2) N2 was full of the oven;3) Temperature of infiltration was enhanced. The fabrication processes of the composites are as follows: firstly, press the milled powder into block, and then put the Al block and the preform into the oven protected with N₂. After heating the oven to 800 and hold 5 hours. The composites formed and then take out of the oven. The microstructure and the component of the composites were investigated by TEM, SEM, XRD and EDS. And the factors affecting the pressureless infiltration and the mechanism were analysed. Theexperiment results indicated that Mg could greatly improve the wetting ability by consuming N2, reaction wetting, wetting transition, breaking up the alumina film and other mechanisms. The variation of the hardness of the composites with the content of CNTs was tested. The friction coefficent and wear rate of the composites were measured using a pin-on-disk wear tester. The fracture surface of the composite was observed using SEM and the results indicate that CNTs are well dispersed and embedded in the Al matrix. The friction coefficients and wear rates of the composites decrease with the volume fraction of CNTs. The favorable effects of CNTs on wear resistance are attributed to their excellent self-lubricating property, being well dispersed in the matrix of composites and the efficiency of the reinforcement of CNTs.