Revision of the enthalpies and gibbs energies of formation of calcium oxide and magnesium oxide

Gourishankar, K. V.; Ranjbar, Mehdi; Pierre, G. R. St.

doi:10.1007/bf02669141

Cited by 33 publications

(17 citation statements)

References 15 publications

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“…This magnesiothermic reaction is strongly favored from a thermodynamic perspective. The values of the standard Gibbs free energy change for this reaction at 650° and 700°C (i.e., assuming condensed phase reference states for magnesium) are −327.5 and −324.9 kJ/mol, respectively 40,41 . Hence, the equilibrium partial pressures of Mg gas required for reaction (1) to proceed spontaneously at 650° and 700°C are only 4.1 × 10 −7 and 1.5 × 10 −6 Torr, respectively 40,41 .…”

Section: Resultsmentioning

confidence: 97%

Three‐Dimensional Magnesia‐Based Nanocrystal Assemblies Via Low‐Temperature Magnesiothermic Reaction of Diatom Microshells

Cai

Allan

Sandhage

et al. 2005

Journal of the American Ceramic Society

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A low-temperature (r7001C) magnesiothermic reaction has been used for the first time to convert three-dimensional (3-D) silica-based diatom microshells into nanocrystalline magnesiabased replicas. Exposure of diatom microshells to Mg(g) at only 6501-7001C resulted in the initial (direct) formation of MgO and Si nanocrystals (r5 nm), that is, no intermediate magnesium silicate compounds were detected. Further reaction of Si with Mg(g) led to the formation of Mg 2 Si, and then a Mg-Si liquid that sweated away to yield free-standing, nanocrystalline MgO-based replicas. Such direct low-temperature magnesiothermic conversion of diatom microshells enables the synthesis of large numbers of 3-D nanocrystal assemblies with well-controlled morphologies for catalytic/chemical, biological, optical, and other applications. 2005 S. Bhandarkar-contributing editor Supported by the Air Force Office of Scientific Research (Hugh De Long, Program Manager).

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Section: Resultsmentioning

confidence: 97%

Three‐Dimensional Magnesia‐Based Nanocrystal Assemblies Via Low‐Temperature Magnesiothermic Reaction of Diatom Microshells

Cai

Allan

Sandhage

et al. 2005

Journal of the American Ceramic Society

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“…Bookey 19) determined the free energy change accompanying the reaction As pointed out by Gourishankar et al, 24) DG°T of Eq. (36) is ϩ33 kJ/mol CaO higher than that given in JANAF Tables.…”

Section: Compilation Of Free Energy Datamentioning

confidence: 99%

Assessment of P2O5 Activity Coefficients in Molten Slags.

Turkdogan¹

2000

ISIJ International

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From a critical review of the existing experimental data, the free energy equations are presented. A new estimate is made of the standard free energy of formation of the hypothetical pure liquid P 2 O 5 , which is used in calculating the P 2 O 5 activity coefficients from the experimental data of independent studies of slagmetal reactions. It is found that in low P 2 O 5 slags, log(g P 2 O 5 ) is a linear function of CaO from 0 to 60 %, independent of temperature. Whereas, in slags containing P 2 O 5 Ͼ10 %, log(g P 2 O 5 ) is a linear function of CaO contentϾ40 % only and increases with an increasing temperature. A novel concept of a slag-P 2 O 5 emf sensor is presented for experimental evaluation.KEY WORDS: Free energies of calcium phosphates and P 2 O 5 ; P 2 O 5 activity coefficients in slags; Slag-P 2 O 5 sensor; Phosphate capacity of slags; Limeϩcalcium phosphate saturated slags.

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“…43,44 The equilibrium partial pressure of ZrCl 4 vapor required for reaction (2) to proceed spontaneously at 6501C (assuming unit activities for pure condensed phase reactants and products) is only 4.3 Â 10 À2 Torr, which is much smaller than the pressure of ZrCl 4 vapor generated from condensed ZrCl 4 at this temperature (the sublimation temperature of ZrCl 4 is only 3361C). 43,44 Upon cooling to room temperature, the MgCl 2 product of this reaction may be selectively removed from the ZrO 2 product by dissolution in water. Indeed, zirconium chloride was preferred over zirconium fluoride as a gaseous reactant because the solubility of magnesium chloride in water is much higher than for magnesium fluoride.…”

Section: Resultsmentioning

confidence: 98%

Three‐Dimensional Assemblies of Zirconia Nanocrystals Via Shape‐Preserving Reactive Conversion of Diatom Microshells

Shian

Cai

Weatherspoon

et al. 2005

Journal of the American Ceramic Society

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The synthesis of three-dimensional (3-D) assemblies of zirconia nanocrystals via the shape-preserving reactive conversion of biologically reproducible, silica-based microtemplates (diatom microshells) is demonstrated for the first time. Silica diatom microshells were first converted into magnesia replicas via an oxidation-reduction displacement reaction with magnesium gas. The magnesia replicas were then converted into zirconia replicas via a metathetic displacement reaction with zirconium tetrachloride gas. By utilizing both types of shape-preserving displacement reactions, bioclastic silica microtemplates may be converted into functional nanocrystalline assemblies with a variety of complex, but well-controlled 3-D shapes and chemistries for catalytic/chemical, biological, electrical, thermal, mechanical, and other applications. J ournal

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Revision of the enthalpies and gibbs energies of formation of calcium oxide and magnesium oxide

Cited by 33 publications

References 15 publications

Three‐Dimensional Magnesia‐Based Nanocrystal Assemblies Via Low‐Temperature Magnesiothermic Reaction of Diatom Microshells

Three‐Dimensional Magnesia‐Based Nanocrystal Assemblies Via Low‐Temperature Magnesiothermic Reaction of Diatom Microshells

Assessment of P2O5 Activity Coefficients in Molten Slags.

Three‐Dimensional Assemblies of Zirconia Nanocrystals Via Shape‐Preserving Reactive Conversion of Diatom Microshells

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