Thermodynamics of Cr2O3, FeCr2O4, ZnCr2O4 and CoCr2O4
Abstract
High temperature heat capacity measurements were obtained for Cr{sub 2}O{sub 3}, FeCr{sub 2}O{sub 4}, ZnCr{sub 2}O{sub 4} and CoCr{sub 2}O{sub 4} using a differential scanning calorimeter. These data were combined with previously-available, overlapping heat capacity data at temperatures up to 400 K and fitted to 5-parameter Maier-Kelley C{sub p}(T) equations. Expressions for molar entropy were then derived by suitable integration of the Maier-Kelley equations in combination with recent S{sup o}(298) evaluations. Finally, a database of high temperature equilibrium measurements on the formation of these oxides was constructed and critically evaluated. Gibbs energies of Cr{sub 2}O{sub 3}, FeCr{sub 2}O{sub 4} and CoCr{sub 2}O{sub 4} were referenced by averaging the most reliable results at reference temperatures of 1100, 1400 and 1373 K, respectively, while Gibbs energies for ZnCr{sub 2}O{sub 4} were referenced to the results of Jacob [Thermochim. Acta 15 (1976) 79-87] at 1100 K. Thermodynamic extrapolations from the high temperature reference points to 298.15 K by application of the heat capacity correlations gave {Delta}{sub f}G{sup o}(298) = -1049.96, -1339.40, -1428.35 and -1326.75 kJ mol{sup -1} for Cr{sub 2}O{sub 3}, FeCr{sub 2}O{sub 4}, ZnCr{sub 2}O{sub 4} and CoCr{sub 2}O{sub 4}, respectively.
- Authors:
- Publication Date:
- Research Org.:
- Knolls Atomic Power Laboratory (KAPL), Niskayuna, NY
- Sponsoring Org.:
- USDOE
- OSTI Identifier:
- 903084
- Report Number(s):
- LM-06K145
Journal ID: ISSN 0021-9614; JCTDAF; TRN: US200720%%73
- DOE Contract Number:
- DE-AC12-00SN39357
- Resource Type:
- Journal Article
- Resource Relation:
- Journal Name: Journal of Chemical Thermodynamics
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 42 ENGINEERING; ENTROPY; OXIDES; SPECIFIC HEAT; THERMODYNAMICS
Citation Formats
Ziemniak SE, Anovitz LM, Castelli RA, Porter WD. Thermodynamics of Cr2O3, FeCr2O4, ZnCr2O4 and CoCr2O4. United States: N. p., 2007.
Web. doi:10.1016/j.jct.2007.03.001.
Ziemniak SE, Anovitz LM, Castelli RA, Porter WD. Thermodynamics of Cr2O3, FeCr2O4, ZnCr2O4 and CoCr2O4. United States. doi:10.1016/j.jct.2007.03.001.
Ziemniak SE, Anovitz LM, Castelli RA, Porter WD. Tue .
"Thermodynamics of Cr2O3, FeCr2O4, ZnCr2O4 and CoCr2O4". United States.
doi:10.1016/j.jct.2007.03.001. https://www.osti.gov/servlets/purl/903084.
@article{osti_903084,
title = {Thermodynamics of Cr2O3, FeCr2O4, ZnCr2O4 and CoCr2O4},
author = {Ziemniak SE, Anovitz LM, Castelli RA, Porter WD},
abstractNote = {High temperature heat capacity measurements were obtained for Cr{sub 2}O{sub 3}, FeCr{sub 2}O{sub 4}, ZnCr{sub 2}O{sub 4} and CoCr{sub 2}O{sub 4} using a differential scanning calorimeter. These data were combined with previously-available, overlapping heat capacity data at temperatures up to 400 K and fitted to 5-parameter Maier-Kelley C{sub p}(T) equations. Expressions for molar entropy were then derived by suitable integration of the Maier-Kelley equations in combination with recent S{sup o}(298) evaluations. Finally, a database of high temperature equilibrium measurements on the formation of these oxides was constructed and critically evaluated. Gibbs energies of Cr{sub 2}O{sub 3}, FeCr{sub 2}O{sub 4} and CoCr{sub 2}O{sub 4} were referenced by averaging the most reliable results at reference temperatures of 1100, 1400 and 1373 K, respectively, while Gibbs energies for ZnCr{sub 2}O{sub 4} were referenced to the results of Jacob [Thermochim. Acta 15 (1976) 79-87] at 1100 K. Thermodynamic extrapolations from the high temperature reference points to 298.15 K by application of the heat capacity correlations gave {Delta}{sub f}G{sup o}(298) = -1049.96, -1339.40, -1428.35 and -1326.75 kJ mol{sup -1} for Cr{sub 2}O{sub 3}, FeCr{sub 2}O{sub 4}, ZnCr{sub 2}O{sub 4} and CoCr{sub 2}O{sub 4}, respectively.},
doi = {10.1016/j.jct.2007.03.001},
journal = {Journal of Chemical Thermodynamics},
number = ,
volume = ,
place = {United States},
year = {Tue Jan 09 00:00:00 EST 2007},
month = {Tue Jan 09 00:00:00 EST 2007}
}
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Excited Carrier Dynamics of α-Cr2O3/α-Fe2O3 Core-Shell Nanostructures
In this work ?-Cr2O3/?-Fe2O3 core-shell polycrystalline nanostructures were synthesized using ?-Cr2O3 nanoparticles as seed crystals during aqueous nucleation. The formation of ?-Fe2O3 polycrystallites on ?-Cr2O3 surfaces were confirmed by x-ray diffraction, transmission electron microscopy, and energy dispersive x-ray analysis. The excited state relaxation dynamics of as-grown core-shell structures and ''pure'' ?-Fe2O3 particles of the same size were measured using femtosecond transient absorption spectroscopy. The results show the carrier lifetimes decay within a few picoseconds regardless of sample. This is likely due to fast recombination/trapping of carriers to defects and iron d-states.