Nanocrystalline Ni-Mo alloys and their application in electrocatalysis
- PDF / 1,973,131 Bytes
- 11 Pages / 576 x 792 pts Page_size
- 9 Downloads / 216 Views
S. Jin, A. Lamarre, E. Ghali, and A. Van Neste Departement de Mines et Metallurgie, Universite Laval, Ste-Foy, Quebec, G1K 7P4, Canada (Received 23 August 1993; accepted 26 July 1994)
The structural and electrocatalytic properties of metastable Ni-Mo alloys have been investigated for the hydrogen evolution reaction in alkaline solutions. Amorphous and nanocrystalline phases have been prepared by mechanically alloying the elemental components under various milling conditions. Fee nanocrystals are formed when the Mo concentration is smaller than 30 at. %. The nanocrystalline state becomes unstable with respect to the amorphous phase when the Mo content in the solid solution exceeds 30 at. %. The electroactive phase for the hydrogen evolution reaction in alkaline solutions is the nanocrystalline supersaturated solid solution. The presence of oxygen during the milling process improves the properties of the alloys.
I. INTRODUCTION In the last few years, the nanocrystalline solids have become an important field of research in materials science. The structure and the properties of these new materials have now been discussed by several authors. 12 The extremely small crystals, typically a few nanometers in size, and the large number of grain boundaries, which represent nearly half of the total volume of the material, are at the origin of the unusual properties. Among them, the electrocatalytic activity is one of great interest because the nanocrystalline state can provide a very large number of active sites for catalysis. In this paper, the electrocatalytic activity of nanocrystalline Ni-Mo alloys has been studied for the hydrogen evolution reaction in alkaline solutions, and chemical properties have been correlated with structural properties such as the crystal size, the lattice parameter of the solid solutions, and the chemical composition of the alloys. Previously, most nanocrystalline solids were produced by the evaporation-condensation technique3 or by heat-treating some amorphous metals.4'5 Recently, the high-energy mechanical alloying technique (MA) has been used extensively to produce nanocrystalline materials.6 The repeated mechanical deformations induce a solid state reaction between the components of the initial mixture. Numerous structural defects that increase the interdiffusion of the elements are being created.
a)Present
address: Centre de Technologie Noranda, Pointe Claire, Quebec, H9R 1G5, Canada. b)Present address: Energy Diversification Research Laboratory, Canmet, Department of Energy Mines and Resources of Canada, Varennes, Quebec, J3X 1S2, Canada. 2998
J. Mater. Res., Vol. 9, No. 11, Nov 1994
Strain is introduced in the lattice, and as a result, crystals fracture into smaller pieces. This technique, which has the advantage of being very simple, has a major drawback: the addition of impurities produced by the milling tools. In several cases, these impurities have a strong influence on the structure and properties of the final product.7 In this paper, we will show that the presence of oxygen durin
Data Loading...
