Gel-combustion synthesis of NiO-MoO3 mixtures and their reduction to Ni-Mo alloys

The oxide mixtures xNiO-(1-x)MoO3 (0.2 <= x <= 1) were synthesized by gel-combustion procedure, using mixed aqueous solutions of ammonium molybdate, nickel nitrate and citric acid as the precursor solution. The oxide products were characterized by scanning electron microscopy and X-ray diffractometry. The X-ray diffractograms indicated the presence of NiMoO4 and either NiO or MoO3 in the oxide products. By heating in hydrogen atmosphere, the oxide mixtures were transformed into Ni-Mo alloys. Thermogravimetric study of the reduction procedure evidenced that temperature indispensable to complete reduction increased progressively from 400 to 900 degrees C if x decreased from 1 toward 0. The structure of Ni-Mo alloys was examined by X-ray diffractometry, and the following alloys were evidenced: Ni(Mo) solid solutions, Ni4Mo, and NiMo. (C) 2008 Elsevier B.V. All rights reserved.