Activity–Composition Relations in NiAl2O4─MnAl2O4Solid Solutions and Stabilities of NiAl2O4and MnAl2O4at 1300° and 1400°C
作者:
Muharrem Timuçin,
Arnulf Muan,
期刊:
Journal of the American Ceramic Society
(WILEY Available online 1992)
卷期:
Volume 75,
issue 6
页码: 1399-1406
ISSN:0002-7820
年代: 1992
DOI:10.1111/j.1151-2916.1992.tb04200.x
出版商: Blackwell Publishing Ltd
关键词: thermodynamics;solid solutions;nickel;manganese;aluminates
数据来源: WILEY
摘要:
Activities of NiO were measured in the oxide and spinel solutions of the system MnO–NiO–Al2O3at 1300° and 1400° C with the aim of deriving information on the thermodynamic properties of the spinel phases. Synthetic samples in selected phase assemblages of the system were equilibrated with metallic nickel and a gas phase of known oxygen partial pressures at a total pressure of 1 atm. The data on NiO activities and directions of conjugation lines between coexisting oxide and spinel phases were used to establish the activity–composition relations in spinel solid solutions at 1300° and 1400°C. The MnAl2O4–NiAl2O4solid solutions exhibit considerable negative deviations from ideality at these temperatures. The free energy of formation of MnAl2O4from its oxide components (MnO + Al2O3) at 1300° and 1400°C is calculated to be −24.97 and −26.56 kJ. mol−1, respectively. The activities determined in the stoichiometric spinel solid solutions are more negative as compared with those predicted from cation
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