Improved MWCNT dispersion and enhanced strength of Cu-coated MWCNTs reinforced magnesium matrix composites via powder refinement

Abstract

Poor dispersion and insufficient interface strength have always been the major obstacles hindering the development of multi-walled carbon nanotube reinforced magnesium-based composites (MWCNTs/Mg). In this study, the finer magnesium powder with a higher surface area enabled the better dispersion of multi-walled carbon nanotubes, thereby significantly enhancing the mechanical properties of the MWCNTs/Mg composites. Furthermore, by incorporating copper-coated multi-walled carbon nanotubes (Cu-MWCNTs) into the magnesium matrix, Cu₂Mg and CuMg₂ phases were formed, which in turn strengthened the interface between the reinforcement and the matrix. The optimal content of multi-walled carbon nanotubes was found to be 0.75 vol.%; compared with the refined magnesium matrix, the composite’s strength was increased by 48% to 226% without the sacrifice of toughness. Its ultimate tensile strength, yield strength and elongation reached 428 MPa, 337 MPa and 5.7%, respectively. However, an excessive addition of multi-walled carbon nanotubes would lead to nanoparticle agglomeration, which consequently compromised the composite’s mechanical strength and crack propagation resistance. This study demonstrates that copper-coated multi-walled carbon nanotubes act as highly efficient reinforcements in magnesium-based composites, and it also emphasizes that achieving a homogeneous dispersion of MWCNTs is an essential prerequisite for significantly improving the mechanical properties of such composites.