Dephosphorization of copper phosphide to copper

The formation of copper phosphide phases during brazing can negatively impact the mechanical properties of copper joints and the overall performance of the resulting product. For instance, copper tubes in air conditioning heat exchangers are brazed using Cu-P filler alloy, resulting in unnecessary brittle Cu₃P compounds. This study investigates a novel process of dephosphorization of copper phosphide nanoparticles to pure copper nanoparticles under a high vacuum, focusing on the temperature dependency on the phosphorus removal rate. Using energy-dispersive X-ray spectroscopy (EDX) and environmental transmission microscopy (ETEM), we quantify phosphorus loss at 500°C, 600°C, and 700°C experiments. There was no phosphorus loss at 500°C experiment, setting a threshold temperature below which phosphorus remains stable. For the 600°C experiment, phosphorus was gradually removed over time, while nearly complete dephosphorization occurred quickly for the 700°C experiment. These findings provide a promising approach to eliminating brittle Cu₃P compounds in Cu-P brazed joints, potentially improving their mechanical performance in industrial applications.