An experimental study was carried out on the reactive diffusion in the Ni-RE (RE = Ce, Pr, Nd) binary alloy systems to gain a fundamental knowledge of the reduction-diffusion (RD) method to directly produce powders of nickel-rare earth compounds, RENi5, for use of hydrogen storage materials. Firstly, phase relations were investigated at temperatures above 1100K in a concentration range of nickel above 55 mol%, using reactive diffusion and metallographic methods. The following compounds were found in the process of reactive diffusion: (a) the Ni-Ce system - CeNi2, CeNi3, Ce2Ni7 and CeNi5, (b) the Ni-Pr system - PrNi2, PrNi3, Pr2Ni7 and PrNi5, and (c) the Ni-Nd system - NdNi2, NdNi3, Nd2Ni7, NdNi4, NdNi5 and Nd2Ni15. The compounds of CeNi5, PrNi5 and NdNi5 presented solid solutions and their ranges of solubility were determined by an EPMA analysis. The widest ranges of solubility were 82.0 - 86.4 mol% Ni at 1488K, 81.7 - 85.4 mol% Ni at 1558K and 82.4 - 86.5 mol% Ni at 1573K in the Ni-Ce, Ni-Pr and Ni-Nd systems, respectively. Secondly, interdiffusion coefficients, of the PrNi5 and NdNi5 compounds were determined, using a diffusion couple of the Ni/Ni-RE melt, given as follows. PrNi5: D/m2·s-1 = 1.61×10-9 exp (-61.3 kJ·mol-1/RT) (T = 1423-1513K) NdNi5: D/m2·s-1 = 1.85×10-4 exp (-205 kJ·mol-1/RT) (T = 1443-1503K).
|Number of pages||21|
|Journal||Metallurgical Review of MMIJ (Mining and Metallurgical Institute of Japan)|
|Publication status||Published - 1993 Sep 1|
ASJC Scopus subject areas
- Metals and Alloys