Functionally Graded Dual-nanoparticulate-reinforced Aluminium Matrix Bulk Materials Fabricated by Spark Plasma Sintering

Functionally graded (FG) carbon nanotubes (CNT) and nano-silicon carbide (nSiC) reinforced aluminium (Al) matrix composites have been successfully fabricated using high-energy ball milling followed by solid-state spark plasma sintering processes. The CNTs were well-dispersed in the Al particles using the nSiC as a solid mixing agent. Two different types of multi-walled CNTs were used to add different amounts of CNTs in the same volume. The ball milled Al–CNT–nSiC and Al–CNT powder mixtures were fully densified and demonstrated good adhesion with no serious microcracks and pores within an FG multilayer composite. Each layer contained different amounts of the CNTs, and the nSiC additions showed different microstructures and hardness. It is possible to control the characteristics of the FG multilayer composite through the efficient design of an Al–CNT–nSiC gradient layer. This concept offers a feasible approach for fabricating the dual-nanoparticulate-reinforced Al matrix nanocomposites and can be applied to other scenarios such as polymer and ceramic systems.