AlN nanowires for Al-based composites with high strength and low thermal expansion
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Based on the synthesis of a sufficient amount of AlN nanowires (AlN-NWs), AlN-NWs/Al composites with homogenously distributed AlN-NWs were fabricated. Microstructural observations reveal that the interface between AlN-NWs and Al matrix is clean and bonded well, and no interfacial reaction product was formed at the nanowire-matrix boundary. Mechanical properties including yield and tensile strength of the composites were improved with AlN-NWs volume fraction changing from 5 to 15 vol%, and the maximum yield and tensile strengths of the composite were about 6 and 5 times, respectively, as high as those of Al matrix. Meanwhile, AlN-NWs effectively decreased the coefficient of thermal expansion (CTE) of the composites, and the CTE of 15 vol% composite was about one half that of Al matrix. The results obtained suggest that AlN nanowire is a promising reinforcement for optimizing the mechanical and thermal properties of metal matrix composites.
I. INTRODUCTION
With the progress in synthesis of one-dimensional (1D) nanostructures such as nanotubes,1 nanowires,2 and nanobelts,3 researchers begin to care about their practical applications, one of which is to incorporate them into matrices to optimize physical and mechanical properties of composite materials. The extremely high aspect ratio of 1D nanostructures allows a low loading of them to provide adequate reinforcement efficiency.4–6 Recently, there are many reports about using 1D nanostructures (carbon nanotubes, carbon nanofibers, SiC nanowires, etc.) to reinforce some matrices such as polymers, ceramics, and metals. For instance, Mukherjee and coworkers reported the synthesis of single-walled carbon nanotubes/Al2O3 composites by a spark-plasma sintering technique; the composites possessed good electrical conductivity.4 Bai et al.5 added multiwalled carbon nanotubes grown on SiC particles into epoxy to obtain composites with high Young’s moudulus and tensile strength. By using the chemical vapor infiltration method, SiC nanowire reinforcing SiC matrix composites with excellent mechanical properties have been fabricated by Yang et al.6 The above examples showed that 1D nanostructure is a promising reinforcement for functional composites. With the rapid development of microelectronics, elec-
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2007.0368 J. Mater. Res., Vol. 22, No. 10, Oct 2007
http://journals.cambridge.org
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tronic packaging materials have become vital to the success of advanced designs.7–9 Al is a potential packaging material in microelectronic industry because of its high thermal conductivity and low density.7 However, low strength and high coefficient of thermal expansion (CTE) of this metal limit its applications in above field. An effective solution to these problems is to add suitable fillers into Al matrix.7,9 AlN is expected to be an excellent reinforcement in composites for electronic packaging or structural materials because of its good mechanical properties, high thermal conductivi
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