Properties and microstructure of Ni-alumina composite materials prepared by the sol/gel method

Sol-gel techniques have been used to make mm-size pieces of Ni-alumina gels for abrasive use. The microstructure was studied extensively by electron microscopy methods and by electron and x-ray diffraction. The hardness, stiffness, and toughness were measured by indentation methods. Seeding of the gel with small additions of nm-size α-Al₂O₃ grains resulted in enhanced α-Al₂O₃ crystallization, a denser structure and better mechanical properties. The best Ni-alumina gel specimens had hardnesses and stiffnesses comparable to successful abrasive products and even better fracture toughnesses.