Solid state reactions between CuO and Cu(Al) or Cu9Al4 in mechanically milled composite powders

Solid state reactions between CuO and Cu–14 at.%Al solid solution or Cu9Al4 intermetallic compound during high energy mechanical milling or during heating mechanically milled CuO/Cu(Al) and CuO/Cu9Al4 composite powders have been investigated. It was found that during milling the reaction between Cu–14 at.%Al and CuO occurs gradually, while the reaction between Cu9Al4 and CuO occurs rapidly, once being initiated through forming sufficiently fine Cu9Al4/CuO composite structure. During heating the mechanically milled composite powders, the reaction between CuO and Cu(Al) or Cu9Al4 proceeds in two separate steps: the reaction between CuO and Cu(Al) or Cu9Al4 forming (Cu(Al))2O and the decomposition of (Cu(Al))2O into Cu and Al2O3. The first reaction starts at temperatures below 450 °C, while the second reaction occurs at temperatures above 800 °C. The high energy milling enhances the kinetics of both reactions by refining the composite structure of the powder particles which leads to a significant increase of the interface area and reduction of the length of diffusion pathway.