Effect of diamond surface chemistry and structure on the interfacial microstructure and properties of Al/diamond composites

Diamond particle reinforced aluminum matrix (Al/diamond) composites have been considered as promising thermal management materials. As the reinforcement phase, the surface chemistry and structure of the diamond particles can significantly affect the interfacial microstructure and the properties of the composites. Thus, understanding and controlling the diamond surface chemistry and structure are crucial for the improvement of the properties of Al/diamond composites. Herein, we report the modification of the diamond surface by controlling the pre-annealing period during fabrication. Our study reveals the sp(3) to sp(2) carbon transformation on both diamond (111) and (100) surfaces ((111)(D) and (100)(D) surfaces). This transformation is more preferential on (111)(D) surfaces, whereas the transformation on (100)(D) surfaces is relatively slow and associated with the formation of (111)(D) facets. The formation of sp(2) carbon enhances the interfacial reaction and intensifies the formation of (111)(D) steps on the diamond surfaces. Therefore, interfacial bonding is improved with mechanical interlocking by larger Al4C3 particles penetrating deeper into both the Al matrix and diamond surface, which promotes both the mechanical and thermal properties of Al/diamond composites. We conclude that the modification of diamond surface chemistry and structure may serve as a simple yet powerful strategy to improve the properties of Al/diamond composites for their practical application.