Microstructure and Properties of Cu-ZrO2 Nanocomposites Synthesized by in Situ Processing

In situ chemical reaction method was used to synthesize Cu-ZrO2 nanocomposite powders. The process was carried out by addition of NH4(OH) to certain amount of dispersed Cu(NO3)2·3H2O and ZrOCl2·8H2O solution. Afterwards, a thermal treatment at 650 °C for 1 h was conducted to get the powders of CuO and ZrO2 and remove the remaining liquid. The CuO was then reduced in preferential hydrogen atmosphere into copper. The powders were cold pressed at a pressure of 600 MPa and sintered in a hydrogen atmosphere at 950 °C for 2 h. The structure and characteristics were examined by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The results showed that the nanosized ZrO2 particles (with a diameter of about 30-50 nm) was successfully formed and dispersed within the copper matrix. The density, electrical conductivity, mechanical strength measurements (compression strength and Vickers microhardness) and wear properties of Cu-ZrO2 nanocomposite were investigated. Increment in the weight % of ZrO2 nano-particles up to 10 wt.% in the samples, caused the reduction in the densification (7.2%) and electrical conductivity (53.8%) of the nanocomposites. The highest microhardness (146.5 HV) and compressive strength (474.5 MPa) of the nanocomposites is related to the Cu-10 wt.% ZrO2. Owing to the good interfacial bonding between uniformly dispersed ZrO2 nanoparticles and the copper matrix. The abrasive wear rate of the Cu-ZrO2 nanocomposite increased with the increasing load or sliding velocity and is always lower than that of copper at any load or any velocity.