Activity-corn position relations in MuCr(2)O(4)-CoCr2O4 solid solutions and stabilities of MnCr2O4 and CoCr2O4 at 1300 degrees C

2005-09-01
Koc, N
Timucin, M
Phase equilibria in the system MnO-CoO-Cr2O3 were investigated at 1300 degrees C under controlled oxygen partial pressures by using the gas equilibration technique. The CoO activities in various phase assemblages of the system were measured by determining the partial pressures of oxygen in the gas phase for coexistence with metallic cobalt. The activity data revealed that at 1300 degrees C, MnO-CoO and MnCr2O4-CoCr2O4 solid solutions exhibit mild positive departures from ideal behavior. The activities in the stoichiometric spinel solutions were found to be in good agreement with those predicted from a model based on cation distribution equilibria. The standard free energy of formation of the compound CoCr2O4 from its oxide components at 1300 degrees C was determined as -37636 J/mol, while that for MuCr(2)O(4) was found as -44316 J/mol.
JOURNAL OF THE AMERICAN CERAMIC SOCIETY

Suggestions

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 (Wiley, 1992-06-01)
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 ...
PHASE-RELATIONS IN THE SYSTEM CE2O3-CE2SI2O7 IN THE TEMPERATURE-RANGE 1150-DEGREES TO 1970-DEGREES-C IN REDUCING AND INERT ATMOSPHERES
TAS, AC; AKINC, M (Wiley, 1994-11-01)
The high-temperature phase relations in the system Ce2O3-Ce2Si2O7 have been studied in the temperature range 1150 degrees-1970 degrees C in inert and reducing atmospheres by conventional quenching and differential thermal analysis. Three eutectic reactions were found to occur at 1664 degrees C and 27 mol% SiO2 between Ce2O3 and Ce2SiO5, at 1870 degrees C and 54 mol% SiO2 between Ce2SiO5 and Ce-4.67(SiO4)(3)O, and at 1762 degrees C and 65 mol% SiO2 between Ce-4.67(SiO4)(3)O and Ce2Si2O7. Microstructural char...
Pressure-dependent Raman modes near the cubic-tetragonal transition in strontium titanate
KİRACI, ALİ; Yurtseven, Hasan Hamit (Wiley, 2018-03-01)
The pressure dependence of the Raman frequency shifts of various Raman modes is calculated at room temperature using the volume data from the literature for the cubic-tetragonal transition in SrTiO3. The isothermal mode Gruneisen parameters of those Raman modes are obtained, which decrease with increasing pressure for this molecular crystal. Calculated Raman frequencies are then used to predict the damping constant and the inverse relaxation time of those Raman modes as a function of pressure by means of th...
Effect of calcium carbonate addition on carbothermic formation of hexagonal boron nitride
ÇAMURLU, HASAN ERDEM; SEVİNÇ, NACİ; Topkaya, Yavuz Ali (Elsevier BV, 2008-01-01)
Effect of CaCO3 on formation of hexagonal boron nitride (h-BN) was investigated by holding CaCO3 free and CaCO3 added activated carbon-boric oxide mixtures under nitrogen atmosphere at 1500 degrees C for 30-120 min. Amount of CaCO3 addition was varied in the range of 0-50 wt.% of the initial mixture. Products were characterized by powder X-ray diffractometry, FT-IR analysis, quantitative chemical analysis, scanning electron microscopy and BET specific surface area analysis. It was observed that calcium carb...
PHASE-RELATIONS IN THE SYSTEM CE2O3-AL2O3 IN INERT AND REDUCING ATMOSPHERES
TAS, AC; AKINC, M (Wiley, 1994-11-01)
The 1:1 compound, CeAlO3, in the system Ce2O3-Al2O3 has been synthesized from the oxides and shown to have a perovskite-like tetragonal unit cell with the lattice parameters a = 3.763 and c = 3.792 Angstrom. A new XRD pattern is suggested for CeAlO3. This compound is shown to be stable up to 1950 degrees C. The 1:11 compound, CeAl11O18, has also been synthesized and shown to possess a magnetoplumbite-like hexagonal unit cell with the lattice parameters a = 5.558 and c = 22.012 Angstrom. An XRD pattern is su...
Citation Formats
N. Koc and M. Timucin, “Activity-corn position relations in MuCr(2)O(4)-CoCr2O4 solid solutions and stabilities of MnCr2O4 and CoCr2O4 at 1300 degrees C,” JOURNAL OF THE AMERICAN CERAMIC SOCIETY, pp. 2578–2585, 2005, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/66131.