Synthesis of Carbon Nanotube-Reinforced Al2024 Matrix Nanocomposite Using Flake Powder Metallurgy Method
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entation of aluminum matrix nanocomposites reinforced by carbon nanotubes (CNTs) has been developed during last decades as a result of their good mechanical strength and lightweight properties.[1] Nevertheless, the agglomeration of CNTs within an Al matrix has remained a main challenge of nanocomposite synthesis. Consequently, the initial dispersion step can be introduced as a more important level of processing to achieve the homogeneous distribution of embedded CNTs in Al powder. Many different processing routes have been applied to reduce this critical problem in bulk nanocomposites manufacturing such as powder metallurgy (PM), casting, melt infiltration, metal forming, and the recent combinative techniques.[2–7] The PM methods have been found attractive for most researchers because
F. RIKHTEGAR, Postgraduate Student, is with the School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), 16846-13114, Narmak, Tehran, Iran. Contact e-mail: [email protected] S.G. SHABESTARI, Professor, and H. SAGHAFIAN, Associate Professor, are with the Center of Excellence for High Strength Alloys Technology (CEHSAT), School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), 16846-13114, Narmak, Tehran, Iran. Manuscript submitted April 10, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS A
of their lower temperature and the controllable interactions between the matrix and the reinforcement.[8–14] The ball milling method has been used in many studies as a common route to produce Al/CNT nanocomposites. In this procedure, the mechanical forces are applied to break the CNT bundles and the mixing process is performed in a dry batch state.[15–22] The employed impact stresses can lead to destruction of the tube structure of CNTs, and finally, the expected mechanical strength cannot be accessible. The new solution ball milling route has been recently promoted to reduce the energy level of the process using an isopropyl alcohol based solution in containers of the planetary ball milling machine.[23] In semi-wet procedures, the ultrasonic waves have been applied as a single step or combinative with low-energy ball milling to disperse the CNTs.[24,25] Also, the nanoscale dispersion method has been introduced as a novel semi-wet process that uses natural rubber to maintain dispersion of CNTs in metallic powder.[26–28] But the results show that the effectiveness of these techniques decreases in high content of CNTs in Al matrix. The new category has been developed in PM processing during recent years, known as slurry based methods, which involve more complicated steps to produce Al/ CNT nanocomposites. These methods apply the fluid
dispersive environment and chemical reactions to make the desired products such as flake PM (FPM) and in situ chemical vapor deposition (CVD).[29–31] In this group of PM processing, some important preparations are considered in raw materials before mixing of nanocomposite constituents. The uniform dispersion of CNTs has not yet been observed
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