Microstructure and performance of carbon fiber reinforced aluminum matrix composites with molybdenum carbide coating on carbon fibers

In this work, a molybdenum carbide coating on the surface of short carbon fibers prepared using molten salt method was proposed to ameliorate the interfacial bonding and improve the performance of carbon fiber/Al composites. The carbon fiber/Al composites were produced using vacuum hot pressing. The characteristics of molybdenum carbide coating were analyzed. Besides, the microstructures, bending strength and thermal properties of the carbon fiber/Al composites were explored. Furthermore, the interfacial thermal resistance of the composites was investigated in relation to theoretical evaluations derived from the combined Maxwell-Garnett effective medium approach and acoustic mismatch model schemes. The results indicated that a homogeneous Mo₂C coating with a thickness of 0.5 μm was obtained by proper molar ratio of carbon fibers, MoO₃ and chloride salts mixture and heated at 1000 °C for 60 min. The Mo₂C coating greatly enhanced the bond between the aluminum matrix and carbon fiber, leading to improvements in the densification behavior and bending strength of the coated composites. The enhanced thermal properties including improved thermal conductivity and reduced coefficient of thermal expansion (CTE) were also achieved by the Mo₂C coating. The in-plane thermal conductivity of 60 vol.% Mo₂C-coated carbon fiber/Al composite was 221 W·m⁻¹·K⁻¹ enhanced by 92% compared to that of uncoated composite and the CTE was 6.0 × 10^–6 K⁻¹ which was suitable for electronic packaging materials.