Optimizing interface microstructure of diamond reinforced Al matrix composites via nano-scale Si-Al coatings towards enhanced thermophysical performance

Abstract

Diamond reinforced Al matrix (Diamond/Al) composites have garnered significant attention owing to their excellent heat dissipation and low density. However, preventing the interfacial Al₄C₃ while optimizing interface thermal conductance and thermal expansion mismatch remains a challenge. Herein, nano-scale Si-Al coatings were introduced on the diamond surface via a low-temperature synthesis strategy, which developed a multilayer structure comprising SiC, Al₄SiC₄, and Si when annealed at 900 °C. The phase transition of SiC from 3C– to 4H-type is crucial for forming Al₄SiC₄. During the infiltration, the crystalline Si within the coatings effectively inhibits the interaction between molten Al and elemental C. First-principles calculations confirmed superior interfacial bonding and phonon matching with the introduction of SiC and Al₄SiC₄. By regulating the coating thickness, an excellent thermal conductivity (TC) of 723.18 W∙m⁻¹∙K⁻¹ and a suitable coefficient of thermal expansion of 5.96 × 10⁻⁶ K⁻¹ at 373 K are achieved. The 50 nm Si-Al coated diamond/Al composites exhibit remarkable service stability, with a 6.1 % reduction in TC after 200 cycles of temperature shock tests, and a 0.2 % decrease after 200 h of soaking water treatments. These findings highlight the Si-Al coatings to address interfacial challenges in diamond/Al composites, laying the groundwork for their practical application.