Study on the evolution feature and formation mechanism of Cu layer on the surface of copper-iron composite powder

This article examined the preparation process of copper-iron composite powder using a chemical displacement method. It focused on how various process parameters, such as the amount of additives in the copper sulfate solution, the wet powder stacking time after coating, and the reduction temperature, impact the surface morphology, composition, and structure of the copper coating layer. The surface morphology and composition of the copper-iron composite powder were characterized using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), the cross-sectional thickness of the copper coating layer was characterized using a metallurgical microscope, and the crystal phase structure of the copper-iron composite powder was detected using an X-ray diffractometer (XRD). It indicated that when the amount of additives in the copper salt solution was ≥ 5 times (calculated as 1 time based on 0.5% of the iron powder amount), noticeable accumulation of copper coating layer and grooves appeared on the surface, leading to a decrease in surface smoothness. Additionally, if the stacking time of the wet powder exceeded 0.5 hours, the surface copper content decreased and the volume of the deposited material increased, resulting in the formation of CuO and Cu ₂ O phases. Furthermore, when the reduction temperature was between 600 and 650℃, the surface copper coating layer remained smooth and continuous, with oxygen content measured below 4000ppm.