Microstructures, thermal and mechanical properties of Al–Si-CNT composites for thermal management applications

In this work, a novel electronic packaging material, Al–Si-CNT composite, is fabricated by ball milling and hot extrusion of Al20Si powder blended with different amount of carbon nanotubes (CNTs). The influences of CNTs content on the microstructures, thermal properties and mechanical properties of the composites are investigated. The ball milling produces flake powders in which CNTs, accompanied by refined Si particles and in-situ formed k'-Al₂O₃, are uniformly dispersed in the Al matrix. The homogenous microstructures are subsequently inherited by the extruded composites. Compared to the Al20Si sample without CNT addition, the CNT-contained composites are more thermally stable and resistant to structural coarsening caused by Ostwald ripening effect. The composite with 2 wt % CNT content exhibits the best properties among all samples. It has a high tensile yield strength ∼235 MPa, and low thermal expansion coefficient ∼16.8 × 10⁻⁶ K⁻¹ (at 50–400 °C) as well as acceptable thermal conductivity ∼102 Wm⁻¹K⁻¹ (at 50–400 °C). This study using hybrid reinforcements Si and CNTs to enhance the Al matrix composite is inspiring to design high performance thermal management materials.