Promoting effect of silicon particles on gas-diffusion-reaction system: In-situ synthesis of AlN in Al-Si materials

A novel Al-AlN-Si composite was prepared by gas-in-liquid in-situ synthesized diffusion-reaction-system. The microstructure and thermal properties of Al-AlN-Si materials can be controlled by Si particles. The effect of Si particles on gas-diffusion-reaction system can be categorized into two classes: (i) The Si content: Al-AlN-Si materials with high Si content can form many nitrogen diffusion channels which improve the concentration quadratic-gradient of N2 and promote the flow-reaction of N2 with Al; (ii) The particle morphology and size: high-energy ball milled powder has many defects of high activation energy, and it exists a chemical potential gradient which stimulates the diffusion-reaction of interface and the formation of semi-continuous structure. Subsequently, we further investigated the effect of high-energy ball milling on structure continuity and thermal properties of Al-AlN-50Si materials. The results indicate that the Al-AlN-50SiB materials (ball milled powders) show lower continuity-coefficient (αnc), more continuous structures and better thermal properties compared with that of Al-AlN-50SiM materials (mixed powders).