structural transitions during leaching of Ni2Al3 phase in a Raney Ni-Al alloy

• Published in: Journal of materials science Vol. 36; no. 23; pp. 5649 - 5657
• Main Authors: Wang, Rong, Lu, Zhilong, Ko, Tsun
• Format: Journal Article
• Language: English
• Published: Heidelberg Kluwer Academic Publishers 01-12-2001; Springer; Springer Nature B.V
• Subjects: alloys; Applications; Applied sciences; Catalysis; Catalysts; Catalytic activity; Crystallites; Engineering techniques in metallurgy. Applications. Other aspects; Exact sciences and technology; hydrogenation; Leaching; Materials science; Metals. Metallurgy; Microstructure; Nickel; Nickel aluminides; Nickel base alloys; Nickel compounds; Others applications; Phases; Rapid solidification; Selectivity; transmission electron microscopy; X-ray diffraction; Nickel base alloys; Intermetallic compound; Rapidly solidified alloy; Lixiviation; Raney nickel; Aluminium alloy; Microstructure; Catalyst; Hydrometallurgy
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1023/A:1012578002418

The microstructure transitions during leaching of a rapidly solidified Ni-Al alloy have been investigated by means of X-ray diffraction, transmission electron microscopic (TEM) and high resolution electron microscopic (HREM) techniques. Ni₂Al₃ was the main phase in the starting Ni-Al alloy. The microstructure of the Raney nickel catalyst consists of nano-scale nickel crystallites, residue of source phases surrounded by nano-scale boundary regions. The transformation during leaching of Ni₂Al₃ phase was an advancing interface type process. Clusters of AuCu-structure type face-centrered tetragonal Ni₃Al₂ as an intermediate phase seems to appear in the reaction front. Based on an analysis of the atomic configurations of phases Ni₂Al₃, Ni₃Al₂ and nickel, a reasonable explanation for the transition mechanism during leaching of Ni₂Al₃ phase and the arc characteristic of diffraction spots was proposed. The nickel crystallites generated during leaching obey an orientation relationship with the source Ni₂Al₃ phase, which is consistent with the Delannay's orientation relationship proposed for nickel and NiAl phases. The nano-scale structural characteristic of the Raney nickel catalyst, especially its porous structure at the boundary regions, provides an excellent hydrogenation catalytic activity and selectivity of the catalyst.