PREPARATION OF NICKEL-COATED ALUMINA COMPOSITE POWDER BY AN AQUEOUS-PHASE REDUCTION PROCESS

A nickel coating on the surface of alumina particles, used as a reinfo rcement in metal-ceramic composite materials, substantially improves t heir wettability by molten metals. Nickel was deposited on alumina par ticles by reducing nickel ions from a solution under hydrogen pressure in the presence of ammonia as a complexing agent. It was found that t he addition of Fe2+ ions and anthraquinone was necessary for forming a n adequate nickel coating on the alumina surface. The optimum conditio ns were the [NH3]/[Ni2+] ratio of 1.6, 2760 kPa hydrogen pressure, 175 degrees C, and an anthraquinone addition of 0.04 gl(-1).