Fabrication of aluminum matrix compositesreinforced by aluminum coated carbonnano-fibers and carbon nanotubes

摘要

Carbon nanotubes (CNF's) are attractive reinforcements for composite materials due to their outstanding properties such as mechanical strength, elastic modulus. In recent years, extensive research on CNF's reinforced composites is conducted, especially on polymer and ceramic matrix composites. However, study on metal matrix composites (MMCs) reinforced by CNT 's is relatively limited. In general, MMCs are fabricated by powder metallurgy or casting process. In powder met-allurgy route, composite powder is made by mechanical mixing of CNF's and metal powders and then the powder is consolidated by sintering. In this process, dispersion of CNF's in matrix is dif-ficult and composites of only a small amount of CNF's e.g. 0.5wt % can be obtained[1]. CNF's aggregate and residual pores in clusters or stress concentration around it deteriorate properties of composite at high volume fraction. Therefore, fabrication by casting or sintering with liquid phase is preferred to obtain composites of superior mechanical properties and thermal conductivity. How-ever, CNF's are not easily wetted by molten metal. Notch formation on CNF's after contact with molten aluminum is confirmed by TEM observation[2]. Coating matrix metal or their compounds on surface of CNF's would be one of the solutions for this problem. Load transfer from matrix to CNF's might be also improved by coating. Coating of metals on CNF's is generally produced via electronic or electroless plating. But, coating by plating is relatively complex and expensive. In this study, coating method of aluminum and their compounds on surface of CNF's by simple, inexpen-sive Chemical Vapour Deposition (CVD) is investigated. In this method, source gas was formed in-situ by reaction of coating materials i.e. aluminum and halide. X-ray diffraction and microscope ob-servation of sample was conducted and effects of composition of coating materials and temperature on coating layer morphology and structure were studied.