High Temperature Reaction Calorimetry Research Articles

Thermodynamic characteristics of Li2MoO4, Li2W0.85Mo0.15O4 single crystals and stability direction for alkali molybdates

Single crystals of Li2MoO4 and Li2W0.85Mo0.15O4, as perspective materials to search for neutrino-less double beta decay, have been grown by low-temperature-gradient Czochralski technique (LTG CZ). The standard formation enthalpies for single crystals of Li2MoO4 and Li2W0.85Mo0.15O4 have been determined by two methods: (i) solution calorimetry in KOH (ΔfH0 (Li2MoO4, s, 298.15 K) = −(1521.9 ± 1.9) kJ mol−1) and (ii) high-temperature reaction calorimetry in sodium molybdate melt (3Na2O · 4MoO3) (ΔfH0 (Li2MoO4, s, 298.15 K) = −(1529.1 ± 7.3) kJ mol−1; ΔfH0 (Li2W0.85Mo0.15O4, s, 298.15 K) = −(1597.8 ± 4.3) kJ mol−1). The measured solution enthalpies of Li2CO3, MoO3, WO3, Li2MoO4, Li2W0.85Mo0.15O4 in 3Na2O · 4MoO3 melt and solution enthalpies of Li2CO3, MoO3, Li2MoO4 in KOH have been used to calculateΔfH0. The thermodynamic stability of A2MoO4 (A = Li, Na, K, Rb, Cs) with respect to simple oxides mixture has been determined. It has been found that the relative thermodynamic stability is increased from Li2MoO4 up to Cs2MoO4. This fact seems to be important from practical point of view. The lattice enthalpies for A2MoO4 compounds have been calculated using the Born-Haber cycle. The dependences of lattice enthalpies for A2MoO4 on structural parameters have been constructed, which allow one to predict the thermodynamics for compounds not investigated.

Experimental investigation and thermodynamic modeling of the Ce-Si system

Phase equilibria and thermodynamic properties of the Ce-Si system were studied experimentally by investigating a Si/(Ce,Si) diffusion couple and thirteen Ce-Si alloys. X-ray diffraction (XRD), electron probe micro-analyzer (EPMA), differential thermal analysis (DTA) and high temperature reaction calorimetry (HTRC) were utilized. A phase with close composition of CeSi1.34 and the decomposition temperature of 1469K is detected. The eutectic reaction liquid↔(Si)+CeSi2 is observed to occurs at 1502.6K. The enthalpy of formation of CeSi1.68 was measured to be −70±6kJmol-atoms−1. A thermodynamic modeling of the Ce-Si system was then performed by considering the reliable literature data and the present experimental results. A substitutional solution model was used for the description of the liquid phase, and all of the compounds are treated as stoichiometric ones. The calculated phase diagram and thermodynamic properties using the obtained thermodynamic parameters are in good agreement with the experimental data.

Experimental investigation and thermodynamic assessment of the Hf–Ge system

The Hf–Ge system has been studied via experiment, first-principles calculations and thermodynamic modeling. 15 annealed Hf–Ge alloys were analyzed by means of X-ray diffraction, scanning electron microscope with energy dispersive X-ray analysis, differential thermal analysis and high temperature reaction calorimetry. The major experimental results are as follows: (I) the heat contents of the Hf3Ge and HfGe2 phases were measured from 400 to 1050 °C; (II) the enthalpy of formation at 298 K for the HfGe2 phase (−67 ± 4 kJ/mol atoms) was measured; (III) the invariant reaction temperature of Liquid ↔ (Ge) + HfGe2 was determined to be at 932.6 ± 2.3 °C; and (IV) the previously reported phases HfGe and Hf3Ge2 were not found in the present experiment. In addition, the enthalpies of formation at 0 K for the Hf3Ge, Hf2Ge, Hf5Ge3, Hf5Ge4, Hf3Ge2, and HfGe2 phases were computed from first-principles calculations in order to provide the necessary energy levels for the thermodynamic properties of the binary compounds. Based on the present experimental results and first-principles calculations as well as the reliable literature data, the Hf–Ge system was modeled by using a CALPHAD approach.

Experimental investigation and thermodynamic modeling of the Ga–Zr system

Abstract Phase equilibria of the Ga–Zr system were investigated by experiment and thermodynamic modeling. In the experimental part, eleven alloys were prepared by melting the pure elements and annealed. Both the as-cast and annealed samples were analyzed by X-ray diffraction, optical microscopy, and scanning electron microscope. The annealed alloys were investigated by differential thermal analysis and electron probe microanalysis. In order to assist the thermodynamic modeling, the enthalpies of formation at 0 K for the GaZr 2 , Ga 3 Zr 5 , Ga 2 Zr 3 , Ga 4 Zr 5 , αGaZr, Ga 3 Zr 2 , Ga 5 Zr 3 , Ga 2 Zr and Ga 3 Zr phases were computed via first-principles calculations. The enthalpy of formation at 298 K for the αGaZr was measured by high temperature reaction calorimetry. Based on the experimental phase diagram data from the present work and the literature as well as the present first-principles calculations, the Ga–Zr system was critically assessed by means of CALPHAD approach. The calculated phase diagram and thermodynamic properties agree well with the available experimental data.

Experimental Investigation and Thermodynamic Assessment of the Hf-Mn System

The Hf–Ge system has been studied via experiment, first-principles calculations and thermodynamic modeling. 15 annealed Hf–Ge alloys were analyzed by means of X-ray diffraction, scanning electron microscope with energy dispersive X-ray analysis, differential thermal analysis and high temperature reaction calorimetry. The major experimental results are as follows: (I) the heat contents of the Hf3Ge and HfGe2 phases were measured from 400 to 1050 °C; (II) the enthalpy of formation at 298 K for the HfGe2 phase (−67 ± 4 kJ/mol atoms) was measured; (III) the invariant reaction temperature of Liquid ↔ (Ge) + HfGe2 was determined to be at 932.6 ± 2.3 °C; and (IV) the previously reported phases HfGe and Hf3Ge2 were not found in the present experiment. In addition, the enthalpies of formation at 0 K for the Hf3Ge, Hf2Ge, Hf5Ge3, Hf5Ge4, Hf3Ge2, and HfGe2 phases were computed from first-principles calculations in order to provide the necessary energy levels for the thermodynamic properties of the binary compounds. Based on the present experimental results and first-principles calculations as well as the reliable literature data, the Hf–Ge system was modeled by using a CALPHAD approach.

ChemInform Abstract: Enthalpies of Formation of M3U (M: Ru, Rh, Pd) by High-Temperature Reaction Calorimetry

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Enthalpy of Formation in the Al-Ni-Ti System

The Al-Ni-Ti ternary system forms the basis of several alloy systems of practical importance. This study was undertaken to provide additional experimental thermodynamic data for the modeling of the Al-Ni-Ti system. High-temperature direct reaction calorimetry has been used to determine the standard enthalpy of formation of several Al-Ni-Ti alloys. The stability of the L21 structure over the B2 structure at the stoichiometric composition of Ni0.5Al0.25Ti0.25 was estimated from the enthalpy results to be 6.8 kJ/mol. The lattice parameters and melting temperatures of these compounds are also reported.

Iron ore sintering

Differential scanning and high temperature reaction calorimetry have been used to characterize a series of natural iron ore and flux samples commonly used during iron ore sintering. Most iron ore samples were shown to contain measurable quantities of goethite, with a characteristic dehydration peak in DSC and TG between 200 and 400°C. At higher temperatures, all samples decomposed to produce magnetite with an accompanying mass loss in the TG profile due to the evolution of oxygen. High temperature reaction calorimetry has been used to measure the heat of solution of the ore in the melt formed during iron ore sintering. The dehydration and calcination of iron ore and flux samples was also examined using high-temperature reaction calorimetry. The results support the DSC/TG findings.

CrossRef Listing of Deleted DOIs

The enthalpies of mixing of liquid copper with liquid silver and with solid titanium, zirconium, and hafnium have been measured by high temperature reaction calorimetry at 1371 to 1373 K. A least squares treatment of the data for copper-silver alloys yields the following expression for the molar enthalpy of mixing: ΔHmix = ϰAgϰCu(17.66 − 5.46 ϰAg) kJ mol−1. The enthalpies of solution of solid titanium, zirconium, and hafnium in dilute solutions in liquid copper are all exothermic; the following values were found: -2.0 kJ mol−1 for Ti, -52.5 kJ mol−1 for Zr, and -46.3 kJ mol−1 for Hf. These values are all significantly less exothermic than predicted by the semiempirical theory of Miedema. The enthalpies of formation of congruent melting intermetallic phases in the systems Cu-Ti, Cu-Zr, and Cu-Hf were measured by drop calorimetry or by solution calorimetry in liquid copper. The enthalpies of formation of the solid alloys have been compared with corresponding data for the liquid alloys.

Thermodynamic investigation of the Cu–Zr system

High temperature heat contents of the Cu–Zr system alloys were measured over temperature range from 880 to 1470 K using a drop calorimeter. The enthalpies of fusion of some solid compounds were determined by the heat content—temperature plots and the entropies of fusion were calculated. Enthalpies of mixing in the liquid Cu–Zr system were measured by high temperature reaction calorimetry in the concentration range of x Zr = 0.182–0.667 at 1443 K. This system has negative enthalpies of mixing over the measured concentration range. The standard enthalpies of formation at 298.15 K of Cu 9Zr 2, Cu 51Zr 14, Cu 8Zr 3, Cu 10Zr 7 and CuZr 2 compounds were determined from the obtained data for the heat contents and enthalpies of mixing. Based on the experimental data, published thermodynamic and phase diagram data, the Cu–Zr binary system was analyzed using Redlich–Kister polynomial equation. The thermodynamic properties and the phase diagram calculated from the optimized parameters agree well with the experimental data.

Enthalpies of Formation in the Al—Ni—Ru System by Direct Reaction Synthesis Calorimetry.

Abstract The enthalpies of formation of ternary compounds in the Al–Ni–Ru system have been determined by high temperature reaction calorimetry. The composition dependence of the enthalpy of formation and lattice parameter of the compounds with B2 structure were determined in the region of 0.40 ≤ Al ≤ 0.5 mole fraction. Unusual behavior is observed for the composition dependence of the enthalpy of formation suggesting that formation of a miscibility gap in the B2 phase field occurs. For some compositions, the experimental enthalpy data therefore represent the formation enthalpy of the metastable B2 phase.

Enthalpies of formation in the Al–Ni–Ru system by direct reaction synthesis calorimetry

The enthalpies of formation of ternary compounds in the Al–Ni–Ru system have been determined by high temperature reaction calorimetry. The composition dependence of the enthalpy of formation and lattice parameter of the compounds with B2 structure were determined in the region of 0.40 ≤ Al ≤ 0.5 mole fraction. Unusual behavior is observed for the composition dependence of the enthalpy of formation suggesting that formation of a miscibility gap in the B2 phase field occurs. For some compositions, the experimental enthalpy data therefore represent the formation enthalpy of the metastable B2 phase.

Enthalpies of Formation of La1−xAxMnO3±δ (A=Ca and Sr) Measured by High-Temperature Solution Calorimetry

High-temperature reaction calorimetry using molten lead borate as a solvent has been used to study the thermochemistry of La1−xAxMnO3 (A=Ca and Sr, 0≤x≤1). The structural properties and the oxygen stoichiometry of the calcined powders were characterized by powder X-ray diffraction, thermogravimetry, and iodometry. The enthalpy of formation of the materials from their binary constituents has been calculated from measured enthalpy of solutions. The enthalpy of formation of La1−xCaxMnO3 from the component oxides becomes more exothermic with increasing substitution level x due to the increasing valence state of Mn, and demonstrates a nearly linear dependence of the average valence state of manganese. La1−xSrxMnO3 has a significantly more exothermic enthalpy of formation from the binary constituents than the Ca-substituted materials, and demonstrates a negative deviation from ideal behavior. The present thermodynamic data are discussed in relation to the Goldschmidt tolerance factor for the perovskite structure. Finally, the phase stability of Sr- and Ca-substituted LaMnO3 is addressed in relation to the application of these materials in solid oxide fuel cells.

Composition dependence of the enthalpies of formation of NiAl

The enthalpy of formation of Ni x Al 1− x as a function of composition has been determined by high temperature reaction calorimetry over the range 0.44≤ x≤0.58. The value for the Ni 0.5Al 0.5 composition is −61.8±1.1 kJ/mol. The present results are compared with previously published results on the enthalpy of formation of Ni x Al 1− x . In several cases the experiments were performed at two different calorimeter temperatures and the difference in heat content values is compared with the heat capacity of NiAl.

ChemInform Abstract: Standard Enthalpies of Formation of Cerium Gallides by High Temperature Reaction Calorimetry

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Evolution and application of high-temperature reaction calorimetry at the University of Chicago from 1952 to 2000

Evolution and application of high-temperature reaction calorimetry at the University of Chicago from 1952 to 2000

ChemInform Abstract: Standard Enthalpies of Formation of Lanthanum Gallides by High Temperature Reaction Calorimetry

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Standard enthalpies of formation of lanthanum gallides by high temperature reaction calorimetry

The standard enthalpies of formation (Δ f H 0 298.15) of La 5Ga 3, LaGa and LaGa 2 at 298.15 were determined by high temperature liquid gallium solution calorimetry to be −62.6±4.5, −74.8±3.7 and −69.0±3.7 kJ gatom −1 respectively. The enthalpy of formation of La x Ga 1− x where x=0.19 at 1125 K was determined by using precipitation calorimetry, to be −37.5±3.7 kJ gatom −1. The partial enthalpy of solution of lanthanum in liquid gallium at infinite dilution (ΔH̄ ∞ La) at 1099 K was determined to be −167.9±6.8 kJ gatom −1.

Standard enthalpies of formation of cerium gallides by high temperature reaction calorimetry

The standard enthalpies of formation (Δ f H 0 298.15) of Ce 3Ga 2, CeGa, CeGa 2 and CeGa 6 at 298.15 were determined by high temperature liquid gallium solution calorimetry to be −(71.1±2.7), −(84.1±1.9), −(51.5±1.4) and −(48.2±3.7) kJ gatom −1 respectively. The enthalpies of formation of Ce 0.21Ga 0.79 at 1125 K and CeGa 6 at 876 K were determined by using precipitation calorimetry to be −(36.7±2.9) and −(52.8±3.0) kJ gatom −1. The partial enthalpies of solution of cerium in liquid gallium at infinite dilution (ΔH̄ ∞ Ce) at 874 K and 1094 K were determined to be −(186.4±5.4) and −(213.0±3.7) kJ gatom −1 respectively.

Standard enthalpies of formation of yttrium gallides by high temperature reaction calorimetry

The standard enthalpies of formation (Δ f H 0 298.15) of Y 5Ga 3, YGa and YGa 2 at 298.15 were determined by high temperature liquid gallium solution calorimetry to be −59.6±3.6, −68.9±2.8 and −64.4±2.5 kJ gatom −1 respectively. The enthalpy of formation of YGa 2 at 1125 K was determined by using precipitation calorimetry, to be −61.8±2.8. The partial enthalpy of solution of yttrium in liquid gallium at infinite dilution ( Δ H ̄ Y ∞) was determined to be −184.4±5.3 kJ gatom −1.