In situ formation of Cu–ZrO2 composites by chemical routes

Composite of copper and 3 mol% yttria-stabilized 5 wt.% zirconia (3-YSZ) have been prepared by hydrogen (PH2=0.1 atmPH2=0.1 atm) reduction of a homogeneous mixture of equably dispersed CuO and ZrO2 formed by three chemical processes. In these processes, the 5%ZrO2/Cu nano-composite has been formed in situ by (1) addition of NaOH solution to certain amount of dispersed Cu(NO3)2, ZrOCl2 and Y(NO3)3 alcohol solution, following filtration; or (2) by adding ammonia to ZrOCl2, Y(NO3)3 solution, then adding Cu(NO3)2 solution to the deposition; (3) the mixture of Zr(OH)4 and Cu(NO3)2·3H2O, mixing and heating the final composition in the three cases to acquire the blending. And calcined them at 500 °C for 1 h. The 5%ZrO2/Cu composites were fabricated by quenching and final sintering at 900 °C for 90 min in vacuum atmosphere. The three process were named process A, process B, and process C. The characterization of the composite samples has been done by XRD, SEM, TEM and metallography techniques. Results from XRD and TEM indicated that different crystal structure zirconia was formed in the three processes. In comparison, the composite microstructure of process B was more homogenous. The comparative conductivity and Vickers hardness were 64% IACS and 120, which were much higher than the other two processes.