Electrochemical Determination of Gibbs Energies of Formation of Calcium Chromite and Chromate

Jacob, Κ. T.; Kale, Girish M.; Abraham, K. P.

doi:10.1149/1.2069248

Cited by 14 publications

(18 citation statements)

References 6 publications

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“…When composite CZ-51-LaCaCr samples were heated at 1200 • C for 2 h, the recorded XRD diffraction patterns displays reflects corresponding to the LaCrO 3 or CaZrO 3 phase as well as Fig. 15 presents the linear dependence of measured EMF of cell (4) in the range 800-1200 • C. The EMF values were stable for more than 2 h. The EMF results obtained from cell (5) with the electrode MCr 2 O 4 , M = Ca, Mg are in good agreement with data existing in literatures [25,31]. The overall cell reaction in the cell (5) with the MgCr 2 O 4 electrode can be described by Eq.…”

Section: Resultssupporting

confidence: 87%

Some observations on synthesis and electrolytic properties of nonstoichiometric calcium zirconate

Dudek

Drożdż

2009

Journal of Alloys and Compounds

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Section: Resultssupporting

confidence: 87%

Some observations on synthesis and electrolytic properties of nonstoichiometric calcium zirconate

Dudek

Drożdż

2009

Journal of Alloys and Compounds

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“…A similar response was noticed when Cr employing ThO 2 (Y 2 O 3 ) solid electrolyte. [17] According to the DTA results obtained in this study, shown in Figure 5, NiTiO 3 (ilm) probably undergoes an order-disorder type of transformation. The critical transformation temperature obtained in this study (T c ϭ 1568 ‫ע‬ 2 K) is in good agreement with that reported by Lerch and Laqua [13] (T c ϭ 1563 K) from the DTA measurements.…”

Section: Discussionmentioning

confidence: 52%

Electrochemical determination of gibbs energy of formation of NiTiO3 (ilmenite)

Kale

1998

Metall Mater Trans B

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Gibbs energy of formation of NiTiO 3 (ilmenite) relative to its component oxides, NiO (rock salt) and TiO 2 (rutile), has been measured employing the solid-state electrochemical cell, (Ϫ)Pt,Ni ϩ TiO 2 ϩ NiTiO 3 //(Y 2 O 3 )ZrO 2 //Ni ϩ NiO,Pt(ϩ) between 994 and 1371 K. The open-circuit electromotive force (emf) of the preceding solid-state galvanic cell was found to be reversible and to vary linearly as a function of temperature in the range of measurement. The results obtained in this study give for the reactionCombining the Gibbs energy of formation of NiTiO 3 (ilm) from the component oxides with that for the formation of NiO (rs) from its elements gives for the reaction Ni (s) ϩ TiO 2 (rut) ϩ 1/2O 2 (g) → NiTiO 3 (ilm) ⌬GЊ ϭ Ϫ246,442 ϩ 88.78T ‫)051ע(‬ J mol Ϫ1 Differential thermal analysis (DTA) of NiTiO 3 (ilm) between 373 and 1623 K indicated that NiTiO 3 (ilm) undergoes a reversible order-disorder phase transformation between 1540 and 1594 K. Based on the ideal mixing of cations on the cationic sublattice of NiTiO 3 (ilm) and a critical phase transformation of 1568 K obtained from the DTA, the Gibbs energy change for the order-disorder phase transformation in NiTiO 3 (ilm) is obtained as ϭ 18,073 Ϫ 11.526T ‫)0001ע(‬ J mol Ϫ1 ⌬GЊ Tr

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“…The standard Gibbs free energy of the formation of CaCrO 4 was determined in a few studies. [17][18][19][20] In the following formation reaction of Figure 3 shows the free-energy diagram for the formation of CaCrO 4 , CaO, and Cr 2 O 3 based on these results, in which the annealing conditions of high and low partial pressures of oxygen employed in the present study are also plotted.…”

Section: Xrd Analysesmentioning

confidence: 99%

Chemical State of Chromium in CaO–SiO2 Base Oxides Annealed under Different Conditions

et al. 2008

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In order to understand the formation mechanism of Cr(VI) in chromium-containing steel slag, X-ray diffractiometry (XRD), X-ray absorption spectroscopy (XAS) in the region of X-ray absorption near edge structure (XANES), and X-ray photoelectron spectroscopy (XPS) measurements were performed for analyzing the chromium contained in the model slag of CaO-SiO 2 base. The model slag was annealed under different temperatures and atmospheres to change the chemical state of chromium. XRD results showed that a diffraction peak that can be assigned to CaCrO 4 comprising of Cr(VI) was detected in the model-slag sample annealed under a high partial pressure of oxygen (air). XANES results showed that the Cr(VI) concentration in the slag increased by annealing under a high partial pressure of oxygen, while it was very low in the slag sample annealed under a low partial pressure of oxygen. The XANES results were consistent with the XRD results. The formation conditions of Cr(VI) were discussed on the basis of the thermodynamic characteristics of a Ca-Cr-O system. The XPS results for the slag surface were dependent on the leaching tests performed on the slag, while the XANES results were insensitive to the leaching tests. This indicates that Cr(VI) dissolved from only a surface layer of the model slag. The chromium that dissolved from the slag in an aqueous solution by the leaching test was also analyzed and was found to be in the form of Cr(VI); further, its concentration depended on the annealing conditions of the slag.

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Electrochemical Determination of Gibbs Energies of Formation of Calcium Chromite and Chromate

Cited by 14 publications

References 6 publications

Some observations on synthesis and electrolytic properties of nonstoichiometric calcium zirconate

Some observations on synthesis and electrolytic properties of nonstoichiometric calcium zirconate

Electrochemical determination of gibbs energy of formation of NiTiO3 (ilmenite)

Chemical State of Chromium in CaO–SiO2 Base Oxides Annealed under Different Conditions

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