Ceramic/metal nanocomposites by lyophilization: Spark plasma sintering and hardness

The present study is focused on the procedure of spray-drying and lyophilization techniques for the preparation of ceramic/metal nanocomposites. The results of the study at all stages are compared with those corresponding to powders conventionally dried by heating in furnace. Starting from aqueous solutions of metal salts and ceramic powders, the procedure follows with spray-drying, lyophilization, calcination of the resulting powders and subsequent Spark Plasma Sintering (SPS). X-ray diffraction analysis of the powders at different stages of the processing routes was used for phase indexing; further characterization was performed by Transmission Electron Microscopy and Energy Dispersive X-Ray Spectroscopy, revealing that the sizes of the metal particles obtained are in the nanometer range and appear homogeneously and well dispersed on the zirconia surface. The mechanical performance of the SPSed compacts was studied by means of the Vickers hardness, showing excellent results: an increase of 30% with respect to pure zirconia.