Reduction and Sintering of a Nickel–Dispersed‐Alumina Composite and Its Properties

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Abstract
High‐density nickel–dispersed‐alumina (Al2O3/nickel) composites with superior mechanical properties were obtained by the hydrogen reduction and the hot pressing of alumina–nickel oxide (Al2O3/NiO) mixed powders. The mixtures were prepared by using NiO or nickel nitrate (Ni(NO3)2·nH2O) as a dispersion source of nickel metal. Microstructural investigations of the composite fabricated using nitrate powder revealed that fine nickel particles, } 100 nm in diameter, dispersed homogeneously at the matrix grain boundaries, forming the intergranular nanocomposite. High strength (.1 GPa) and high‐temperature hardness were registered for the composite that contained a small amount of nickel dispersion. The ferromagnetic properties of nickel, such as high coercive force, were observed, because of the fine magnetic dispersions, which indicates a functional value of structural composites.