Effect of in-situ phase transition of (MgCoNiCuZn)O high-entropy oxides on microstructure and performance of Ag-based electrical contact materials

Abstract

Reducing arc corrosion on the surface of electrical contact is beneficial for the stability of electrical systems. For improving the anti-arc erosion performance of composites, a reinforcement with good arc extinction and thermal stability is still a need. In this work, by annealing the as-prepared single-phase (MgCoNiCuZn)O high-entropy oxides (SHEO) reinforced Ag composites at 700 °C, the reinforcement was in-situ transformed in multi-phase (MgCoNiCuZn)O high-entropy oxides (MHEO) consisting of ZnCo2O4, CuO, and non-equiatomic (MgCoNiCuZn)O high-entropy oxides (NHEO). In this process, a semi-coherent interface is formed between CuO (firstly precipitated) and NHEO, and a coherent interface is formed between ZnCo2O4 (secondary precipitated) and NHEO. During arcing, the endothermic phase transformation from MHEO to SHEO reduced arc energy. A comparative study of the composites was carried out with 12 wt% reinforcement. Ag-MHEO possessed exceeded hardness than that of Ag-SnO2 and electrical conductivity similar to Ag-SnO2. Under the DC load of 24 V/8A, Ag-MHEO exhibited 60% less mass loss and 26% less burning arc energy than Ag-SnO2In2O3 during 10,000 times contacts. Compare with Ag-SHEO and Ag-SnO2In2O3, the arc corrosion on Ag-MHEO surface was the weakest after the mentioned contact. This study paves a feasible way to improve anti-arc erosion performance by in-situ reversible endothermic phase transformation.