ACTIVITY COMPOSITION RELATIONS IN NIAL2O4-MNAL2O4 SOLID-SOLUTIONS AND STABILITIES OF NIAL2O4 AND MNAL2O4 AT 1300-DEGREES-C AND 1400-DEGREES-C


TIMUCIN M., MUAN A.

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, cilt.75, sa.6, ss.1399-1406, 1992 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 75 Sayı: 6
  • Basım Tarihi: 1992
  • Doi Numarası: 10.1111/j.1151-2916.1992.tb04200.x
  • Dergi Adı: JOURNAL OF THE AMERICAN CERAMIC SOCIETY
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Sayfa Sayıları: ss.1399-1406
  • Anahtar Kelimeler: THERMODYNAMICS, SOLID SOLUTIONS, NICKEL, MANGANESE, ALUMINATES, EQUILIBRIUM, SYSTEM, NICKEL, OXYGEN, NIO
  • Orta Doğu Teknik Üniversitesi Adresli: Hayır

Özet

Activities of NiO were measured in the oxide and spinel solutions of the system MnO-NiO-Al2O3 at 1300-degrees and 1400-degrees-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-degrees and 1400-degrees-C. The MnAl2O4-NiAl2O4 solid solutions exhibit considerable negative deviations from ideality at these temperatures. The free energy of formation of MnAl2O4 from its oxide components (MnO + Al2O3) at 1300-degrees and 1400-degrees-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 distribution models.