The kinetics of the alpha to beta transition in synthetic nickel monosulfide
Date
2006
Authors
Wang, H.
Pring, A.
Ngothai, Y.
O'Neill, B.
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Journal article
Citation
American Mineralogist, 2006; 91(1):171-181
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Haipeng Wang, Allan Pring, Yung Ngothai, and Brian O'Neill
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Abstract
The kinetic behavior of the α-Ni<inf>1-x</inf>S → β-NiS transition was investigated via a series of anneal-quench experiments using Rietveld quantitative phase analysis of powder X-ray diffraction data. Initial compositions of α-Ni<inf>1-x</inf>S were found to play an important role in the kinetics of the transition. The activation energy (E<inf>a</inf>) for this α- to β-phase transition is 16.0 (±0.5) kJ/mol for NiS in the temperature range 343 to 423 K, and 13.0 (±0.5) kJ/mol in the temperature range 523 to 623 K. For Ni<inf>0.97</inf>S, however, E<inf>a</inf> decreases from 73.0 (±0.5) to 17.0 (±0.5) kJ/mol over the course of the reaction in the temperature range 573 to 593 K. The relationship between E<inf>a</inf> and extent of transition (y) for the initial bulk Ni<inf>0.97</inf>S was derived using the Refined Avrami method. For Ni-deficient compositions, α-Ni<inf>1-x</inf>S, the transformation to β-NiS is accompanied by the exsolution of a progressively more Ni-deficient α-Ni<inf>1-x</inf>S and Ni<inf>3</inf>S<inf>4</inf>, and the reactions become more sluggish for more metal-deficient compositions.
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© 2006 Mineralogical Society of America