Spark plasma sintering and hot isostatic pressing of nickel nanopowders elaborated by a modified polyol process and their microstructure, magnetic and mechanical characterization

The microstructure, magnetic and mechanical properties of spark plasma sintered (SPS) and hot isostatic pressed (HIP) nickel nanopowders are investigated. The microstructure study shows that the increase in the particle size was more limited when consolidation was performed by the SPS than by the HIP process. The grain size is in the range 0.17–0.2 μm in the case of the SPS consolidated sample while it is in the range 0.4–0.62 μm in the case of the HIPed sample. The ratio of the yield stress in the HIP and SPS consolidated samples to the yield stress in the bulk nickel sample is greater than two and three times, respectively. Vickers microhardness measurements give the same ratios. A ferromagnetic behaviour was deduced from the magnetic characterizations of the as-prepared nickel powder as well as the consolidated samples.