Synthesis and characterization of Al2O3/Zno nanocomposite by pressureless sintering

Alumina (Al2O3) based ceramic matrix nanocomposite reinforced by 2 wt.% of zinc oxide (ZnO) nanoparticles, has been prepared and consolidated by pressureless sintering method. Nearly fully dense composite could be obtained by sintering at 1600 °C for 2 h. X-ray diffraction (XRD) has been used to characterize the milled and annealed powders. Scanning electron microscopy (SEM) analysis has shown a good homogeneity of the dispersion of ZnO nanoparticles in the alumina matrix. The second phase nanoparticles have been located either within the alumina grains or at the grain boundaries. According to SEM micrographs, the mean size of ZnO particle, after sintering at 1400 °C for 2 h, has been approximately 80 nm, in agreement with TEM micrographs and DLS analysis. Particle size analysis, based on X-ray diffraction, has shown the presence of zinc oxide of crystallite size about 60 nm homogeneously distributed in the alumina matrix. Mechanical measurements have shown that the incorporation of 2 wt.% of nanometric zinc oxide has increased the hardness by about 30% to 680 HV and the rupture strength by about 30% to 1360 MPa at 1600 °C.