Electrochemical Determination of the Gibbs Energy of Formation of MgAl<sub>2</sub>O<sub>4</sub>

Jacob, Κ. T.; Jayadevan, K. P.; Waseda, Yoshio

doi:10.1111/j.1151-2916.1998.tb02316.x

Cited by 22 publications

(12 citation statements)

References 22 publications

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“…The ΔGD caused by the cation exchange reaction in the MgAl 2 O 4 -spinel can be evaluated by resorting to the difference of the Gibbs energies of formation of the MgAl 2 O 4 -spinels (ΔGf) at different temperatures. Rosén and Muan [58], Chamberlin et al [59], Jacob et al [60], and Fujii et al [61] determined the values of the Gf at different temperatures using different methods, as summarized in Figure 7a. Fitting these experimental results leads to the following Gf~ T correlation, Gf = −2.613 × 10 −8 × T 3 + 8.159 × 10 −5 × T 2 − 0.090 × T + 5.281.…”

Section: Discussionmentioning

confidence: 99%

Kinetics and Thermodynamics of Mg-Al Disorder in MgAl2O4-Spinel: A Review

Liu

2019

Molecules

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The MgAl2O4-spinel has wide applications in various industries and in geosciences. It shows a significant inter-site Mg-Al cation exchange (denoted by the inversion parameter x), which modifies structural features, such as the unit-cell parameters and the sizes of the component polyhedra, and influences the physical and chemical properties. Previous studies mainly focused on the kinetics and thermodynamics of the Mg-Al exchange reaction, with the aim to ascertain the correlation between the inversion parameter and temperature; these studies, however, reached conflicting results. Here, we first reviewed the kinetics studies on the Mg-Al cation exchange reaction, and then reviewed all thermodynamic experiments, with special attention paid to the Mg-Al cation exchange equilibrium and the quench process, which might have modified the cation distributions once attained at high temperatures. We also assessed the accuracies in the temperature measurements and in the quantifications of the x by different analytical methods. With some necessary temperature correction and data removal, we have landed with a generally reliable x-T dataset covering the T-x space of 873 < T < 1887 K and 0.18(1) < x < 0.357(60) (71 data pairs in total). Fitting these x-T data to three most commonly used thermodynamic models, we have obtained more accurate model parameters. Further, we also evaluated the constituent items of the Gibbs free energy for the Mg-Al cation exchange reaction with experimental results from different research fields and reached the conclusion that highly possibly the T Δ S D should not be neglected. Based on this review, we suggest that: (1) Further kinetics study on the Mg-Al exchange reaction should be performed at both low T (<~973 K) and high T (>~1173 K); (2) further Mg-Al exchange equilibrium studies should be carried out at relatively low T and ambient P, as well as in vast ranges of simultaneous high P and high T; and (3) direct experimental measures about the entropies or the enthalpies of the MgAl2O4-spinels disordered to different extents should be conducted with full characterization of the starting materials and detailed description of the experimental procedures.

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Section: Discussionmentioning

confidence: 99%

Kinetics and Thermodynamics of Mg-Al Disorder in MgAl2O4-Spinel: A Review

Liu

2019

Molecules

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“…[44][45][46] Gibbs energies of formation of MgAl 2 O 4 from MgO and Al 2 O 3 were measured by several authors [37,[47][48][49][50] using different techniques. Taylor and Schmalzried, [49] and more recently Jacob and Jayadevan, [47] used a MgF 2 electrolyte to measure the Gibbs energy of MgAl 2 O 4 . Chamberlin et al [48] equilibrated spinel and liquid Pd and measured the Mg and Al contents in the Pd.…”

Section: Summary Of Available Experimental Datamentioning

confidence: 99%

“…The data of Taylor and Schmalzried [49] are not in agreement with the data of other authors. Also it was difficult to reproduce the measurements of Jacob and Jayadevan [47] who used emf cells with MgF 2 electrolytes as did Taylor and Schmalzried.…”

Section: Evaluation and Optimizationmentioning

confidence: 99%

Critical thermodynamic evaluation and optimization of the MgO-Al2O3, CaO-MgO-Al2O3, and MgO-Al2O3-SiO2 Systems

Jung

Decterov

Pelton

2004

J Phs Eqil and Diff

128

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A complete literature review, critical evaluation, and thermodynamic modeling of the phase diagrams and thermodynamic properties of all oxide phases in the MgO-Al 2 O 3 , CaO-MgO-Al 2 O 3 , and MgO-Al 2 O 3 -SiO 2 systems at 1 bar total pressure are presented. Optimized model equations for the thermodynamic properties of all phases are obtained that reproduce all available thermodynamic and phase equilibrium data within experimental error limits from 25°C to above the liquidus temperatures at all compositions. The database of the model parameters can be used along with software for Gibbs energy minimization to calculate all thermodynamic properties and any type of phase diagram section. The modified quasichemical model was used for the liquid slag phase and sublattice models, based upon the compound energy formalism, were used for the spinel, pyroxene, and monoxide solid solutions. The use of physically reasonable models means that the models can be used to predict thermodynamic properties and phase equilibria in composition and temperature regions where data are not available.

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“…In their study on NiSn/MgOAl 2 O 3 materials Penkova et al[30] attributed this shift to the formation of magnesium aluminate phase. In this sense Jacob et al[31] also reported that the formation of MgAl 2 O 4 from MgO and Al 2 O 3 could start at around 800 ºC.…”

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confidence: 94%