Al/Ni formation reactions: characterization of the metastable Al9Ni2 phase and analysis of its formation

✍ Scribed by K.J. Blobaum; D. Van Heerden; A.J. Gavens; T.P. Weihs

• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 743 KB
• Volume: 51
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/s1359-6454(03)00211-8

✦ Synopsis

The metastable phase Al 9 Ni 2 was investigated in order to characterize the thermodynamics and kinetics of its formation. Here, Al 9 Ni 2 was observed as the first phase to form in a series of sputter-deposited Al/Ni multilayer foils, but it did not form in foils with a very small bilayer period (12.5 nm). In these foils, the stable phase Al 3 Ni was the first phase observed. Using differential scanning calorimetry, the heat of formation and the Gibbs free energy for the formation of Al 9 Ni 2 were both calculated to be Ϫ28 kJ/mole•atom. The average activation energy for Al 9 Ni 2 was determined using a Kissinger analysis and was found to vary with bilayer thickness, with an average value of 1.58 ± 0.06 eV. In light of these experimental results, a simple nucleation model based on thermodynamics and diffusional intermixing is proposed to explain why Al 9 Ni 2 forms before Al 3 Ni in most cases, except in foils with very small bilayers where it is absent.