High Temperature Thermodynamic Data for CdTe(c)

The high temperature heat capacity, Gibbs energy of formation, and standard enthalpy and entropy of formation at 298 K are combined with thermodynamic data for Cd and revised data for Te to provide an internally consistent data set for CdTe(c). Equations are given for the Gibbs energy of formation from Cd(g) and Te₂(g) and from the solid or liquid elements as a function of temperature. These give values similar to those used before. However, the derived enthalpy and entropy of formation are significantly different due to a revised heat capacity for CdTe(c). The standard enthalpy and entropy of formation at 298.15 K from the gases are −293262 J/mol and −200.593 J/mol K, respectively. From the solid elements they are −100270 and −4.5334.     

Thermodynamic properties of 1-nutyl-3-methylimidazolium chloride (C<Subscript>4</Subscript>mim[Cl]) ionic liquid

Thermodynamic properties of 1-butyl-3-methylimidazolium chloride (C₄mim[Cl]) ionic liquid were determined using thermogravimetric (TG) differential thermal analysis (DTA). A new method called DTA mass-difference baseline, was used to measure the heat capacity and enthalpy change of phase transformation of ionic liquid from DTA curves. Based on this, the changes in standard enthalpy, entropy, and Gibbs energy were determined. The results show that standard enthalpy and entropy changes of C₄mim[Cl] increase nonlinearly with increasing temperature, while the standard Gibbs energy change decreases nonlinearly with increasing temperature within the temperature range studied (298–453 K). The standard enthalpy of melting and enthalpy of vaporization were determined to be 0.93 and 11.07 kJ/mol, respectively.     

Vapor pressures and thermodynamic properties of strontium silicides

The high temperature vaporization processes of strontium silicides were studied by means of the Knudsen Effusion Mass Spectrometry and Knudsen Effusion Weight Loss techniques in the temperature range 665–1300 K, with reference to the recent reinvestigation of the Sr–Si phase diagram [Palenzona A, Pani M. J Alloys Compd 2004;373:214.]. The only species detected in the vapor phase equilibrated with two-phase solid mixtures was monoatomic gaseous strontium. The vapor pressure of Sr(g) was measured as a function of the temperature, and the enthalpy changes associated with the decomposition processes were thereafter derived. The enthalpies of formation of the strontium silicide phases reported in Ref. [Palenzona A, Pani M. J Alloys Compd 2004;373:214.] (namely Sr₂Si, Sr₅Si₃, SrSi and β-SrSi₂) were finally obtained as, respectively (values in kJ/mol atoms, T=298 K): −39.7±3.2; −43.8±3.6; −51.7±4.1; −40.3±3.7. These results are definitely at variance with the scattered, strongly exothermic calorimetric data reported for some phases in the old literature, while they are in satisfactory agreement with recent density functional theory calculations.     

Adsorption of platinum(IV) onto D301R resin

Pt(IV) was quantitatively adsorbed by D301R resin in the medium of pH = 3.47. The statically saturated adsorption capacity is 410 mg/g. Pt(IV) adsorbed on D301R resin can be eluted by 1.0-2.0 mol/L NaOH. The rate constant is k₂₉₈ = 5.43 × 10⁻⁵S⁻¹. The adsorption of Pt(IV) on D301R resin obeys the Freundlich isotherm. The adsorption parameters of thermodynamics are as follows: enthalpy change ΔH = 4.37 kJ/mol, Gibbs free energy change ΔG = −5.39 kJ/mol, and entropy change ΔS = 32.76 J/(mol·K). The apparent activation energy is E_a = 22.5 kJ/mol. The coordination molar ratio of the functional group of D301R resin to Pt(IV) is 2:1.     

Thermochemistry of holmium bismuthides

Thermodynamic properties of Ho–Bi intermediate phases (HoBi and Ho₅Bi₃) have been studied by means of calorimetric and tensimetric techniques. The heats of formation at T=298 K were determined by high temperature direct synthesis calorimetry and the molar heat capacity of HoBi was measured by differential scanning calorimetry (DSC) in the temperature range 330–920 K. The equilibrium vapour pressures over the two-phase region HoBi+Ho₅Bi₃ were measured by Knudsen Effusion–Mass Spectrometry in the temperature range 1357–1631 K. These data were analyzed by the second-law method to obtain the enthalpy changes for the atomization processes and, thereafter, the heats of formation for the two compounds. From the calorimetric measurements the heats of formation at 298 K were determined to be −93±3 and −112±4 kJ/mol atoms, respectively for the Ho₅Bi₃ and HoBi compounds, consistent with

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and obtained from the tensimetric measurements.     

Thermodynamic investigation on the si-ge binary system by calorimetry and knudsen cell mass spectrometry

The partial enthalpy of Si in Si-Ge liquid alloys was determined by drop calorimetry at 1327 K in the 0 < Xsi< 0.03 concentration range with a high-temperature Calvet calorimeter. The excess Gibbs energy of formation of the melt was derived from Knudsen cell mass spectrometric measurements over the entire range of composition using the intensity ratio method. The thermodynamic behavior of the liquid phase of the system is regular and presents positive deviations from ideal mixing. It corresponds to the following thermodynamic functions for the melt: G^ex = 6.0XSiXGe kj/mol at 1723 K; and H^ex = 6.61XSiXGe kj/mol. The phase diagram calculated assuming such a behavior agrees well with the data of the literature. Some liquidus points obtained from the breaks existing in the logarithm of the vapor pressure versus the inverse temperature plots also agree.     

Assessment of rheological and thermodynamic properties of the Pd40Ni40P20 bulk metallic glass around glass transition using an indentation creep technique

The thermodynamic and rheological properties of the Pd₄₀Ni₄₀P₂₀ bulk metallic glass are explored by means of an indentation creep technique around the glass transition. We have developed a dedicated instrumented indentation apparatus allowing to assess the mechanical properties at elevated temperatures. The analysis of results is made possible by using the viscoelastic solutions of contact mechanics. We also analyse the thermodynamics of creep around glass transition to estimate the activation free energy changes from the activation free enthalpy changes via the shear modulus – temperature data. The shear viscosity values extracted using this technique allow for the derivation of activation energies (free enthalpy 210 kJ/mol, enthalpy 456 kJ/mol, entropy 410 J/mol/K) for the flow process. All these properties were found to closely match with those obtained using conventional techniques for viscosity measurements. Compared to the latter, the indentation creep technique requires small volumes and samples are easy to prepare. It is therefore expected that such a technique might be employed for the study of glass transition in metallic glasses.     

Adsorption of platinum (Ⅳ) onto D301R resin

Pt (Ⅳ) was quantitatively adsorbed by D301R resin in the medium of pH=3.47. The statically saturated adsorption capacity is 410 mg/g.Pt (Ⅳ) adsorbed on D301R resin can be eluted by 1.0-2.0 mol/L NaOH. The rate constant is k298=5.43×10-5s-1. The adsorption of Pt (Ⅳ) on D301R resin obeys the Freundlich isotherm. The adsorption parameters of thermodynamics are as follows: enthalpy change ΔH=4.37 kJ/mol, Gibbs free energy change ΔG=-5.39 kJ/mol, and entropy change ΔS=32.76 J/(mol.K). The apparent activation energy is Ea=22.5 kJ/mol. The coordination molar ratio of the functional group of D301R resin to Pt(Ⅳ) is 2:1.     

Thermodynamic investigation of the Lu---Pb system

The Lu---Pb alloys were studied by different techniques. The molar heat capacities of the solid compounds Lu₅Pb₃ and Lu₆Pb₅ were determined in the range 525–823 K using differential scanning calorimetry. The enthalpy of formation of LuPb₂ was obtained by both emf and calorimetric methods. Potentiometric measurements were performed in the range 610–730 K and a value of −35 ± 2 kJ (mol at.)⁻¹ was obtained for the enthalpy of formation of LuPb₂ in the solid state at 298 K. By using a direct isoperibolic aneroid differential calorimeter the value Δ_formH = −34 ± 2 kJ (mol at.)⁻¹ was determined. The data obtained in this study are compared with those of other similar rare earth-lead compounds and discussed briefly.     

Thermodynamic Properties of YbRhO<Subscript>3</Subscript> and Phase Relations in the System Yb-Rh-O

Thermodynamic properties of the ternary oxide YbRhO₃ were determined by using a solid-state electrochemical cell incorporating calcia-stabilized zirconia as the solid electrolyte in the temperature range from 900 to 1300 K. The standard Gibbs energy of formation of YbRhO₃ from component binary oxides Yb₂O₃ with C-rare earth type structure and Rh₂O₃ with orthorhombic structure can be represented by the equation,

$$\Delta_{\text{f(ox)}} G^{\text{o}} ( \pm 130)/{\text{J/mol}} = - 43164 + 3.436\,({\text{T/K}}).$$

Standard enthalpy of formation of YbRhO₃ from elements in their normal standard states is ?1153.18(±3) kJ/mol and its standard entropy is 100.93(±0.6) J/K/mol at 298.15 K. The decomposition temperature of YbRhO₃ is 1671(±3) K in pure oxygen, 1566(±3) K in air and 1047(±3) K at an oxygen partial pressure of \(\left( {P_{{{\text{O}}_{2} }} /{\text{P}}^{\text{o}} } \right) = 10^{ - 6}\), where P^o = 0.1 MPa is the standard pressure. Decomposition temperature was confirmed by DTA/TGA. Phase diagrams for the system Yb-Rh-O are computed using the thermodynamic data.

     

Thermodynamics of the dehydrogenation of the LiBH4-YH3 composite: Experimental and theoretical studies

Pressure-composition-temperature curves were constructed for the dehydrogenation of the LiBH₄-YH₃ composite. The Van’t Hoff plot of the plateau pressure values showed that the reaction enthalpy and entropy were 51 kJ/mol H₂ and 101 J/K mol H₂, respectively. Thermodynamic calculations were performed for the reaction in combination with first principles calculation. The calculated reaction enthalpy and entropy are in good agreement with the measured values. The equilibrium temperature for the reaction at 1 bar of hydrogen was estimated to be 232 °C.     

A Regular Solution Model for a Single-Phase High Entropy and Enthalpy Alloy

A regular solution, 3-component model suggested by J.L. Meijering in which binary interaction parameters were equal and positive has been extended to 5 and 6-component high entropy alloys (HEAs). On cooling, Meijering’s model develops miscibility gaps containing a low temperature eutectoid at the equiatomic composition. Similar behavior is found in this work on HEAs with the eutectoid temperature decreasing, while both the entropy and enthalpy are increasing, as additional components are added to the system. An equation for the chemical spinodal at the equiatomic composition is derived from the same thermodynamic model that was used to predict miscibility gaps. The spinodal temperature is at a cone point where multiple spinodal surfaces meet and is dominated by entropy. A proposal is made to categorize HEAs as having low, medium or high enthalpy. Low enthalpy HEAs are defined as having mixing enthalpies less than 1.25 kJ/mol, high enthalpy HEAs having mixing enthalpies greater than 2.9 kJ/mol, and medium HEA as between the extremes. A possible approach for designing high enthalpy HEAs is suggested to incorporate Meijering’s method of analyzing potential HEAs according to their individual binary interaction parameters instead of their total mixing enthalpy.     

Thermodynamic Properties of Beryllium

The thermodynamic properties of beryllium have been evaluated up to 2800 K. A further evaluation is justified by the inclusion of not only new specific heat measurements at low temperature but also new enthalpy measurements at high temperature which lead to a reassessment of the enthalpies and entropies of transition and fusion. Selected values include an enthalpy of sublimation of 324 ± 5 kJ/mol at 298.15 K and a boiling point at one atmosphere pressure of 2745 K.     

直流电弧制备的Mg-TiO2复合材料的储氢性能

采用直流电弧等离子体法蒸发Mg＋5%Ti O2的混合物并将其在空气中钝化,制备粉体Mg-Ti O2复合储氢材料。利用电感耦合等离子光谱发生仪（ICP）、X射线衍射仪（XRD）、扫描电子显微镜（SEM）表征粉体复合材料的成分、相组成及形貌。采用压力–成分–温度（PCT）和差示扫描量热仪（DSC）对Mg-Ti O2样品的吸放氢性能进行研究。由PCT测量结果可知,Mg-Ti O2复合粉体中镁的氢化焓和氢化熵分别为-71.5 kJ/mol和-130.1 J/（K·mol）,而粉体的氢化激活能为77.2 k J/mol。结果表明,采用电弧等离子体法在超细镁颗粒中加入Ti O2催化剂可显著增强镁的吸放氢动力学性能。     

Thermochemistry of GaBO3 and phase equilibria in the Ga2O3–B2O3 system

Employing a Tian-Calvet-type calorimeter operating in the scanning mode at temperatures from 1120 to 1220 K, the enthalpy change, Δ_dH, associated with the decomposition of GaBO₃ (=1/2β-Ga₂O₃+1/2B₂O₃(liq.)) and the corresponding decomposition temperature, T_d, were determined: Δ_dH=30.34±0.6 kJ/mol, T_d=1190±5 K. Using the transposed-temperature-drop method the thermal enthalpy, H(T)−H(295 K), of GaBO₃ was measured as a function of temperature, T, in the region from 760 to 1610 K; the results obtained are

[H(T)−H(295 K)]/(J/mol)=104.8·(T/K)−31 300 (760 K<T<1190 K),

[H(T)−H(295 K)]/(J/mol)=138.8·(T/K)−41 480 (1190 K<T<1590 K).

On the basis of the experimental results, the enthalpy and entropy of formation, Δ_fH and Δ_fS, respectively, of GaBO₃ from the component oxides were derived:

Δ_fH=−30.34 kJ/mol,Δ_fS=−25.50 J/(K·mol) at 1190 K,

Δ_fH=−10.55 kJ/mol,Δ_fS=−5.48 J/(K·mol) at 298 K.

The enthalpy versus temperature curve shows, apart from a step associated with the decomposition of GaBO₃, a further step at 1593 K which is attributed to a monotectic equilibrium.     

Vapor pressure measurements of arsenic and arsenic trioxide over condensed phases

The solid-vapor relations for arsenic in the temperature range from 680 to 840 K and the liquid-vapor relations for arsenic trioxide in the temperature range from 650 to 740 K were determined by direct vapor pressure measurements carried out with a quartz gauge. The resulting InP (total) vsT are : InP (atm) = 2545.1/T + 22.27 InT− 154.02 (for arsenic) and InP (atm) = −50983/T + 6.869 (for arsenic trioxide). Calculated enthalpy of vaporization (ΔH_v,T ⁰) for arsenic trioxide and enthalpy of sublimation (ΔH_s,298 ⁰) for arsenic are 42.36 kJ/mol and 156.13 kJ/mol, respectively.     

Vapor pressure measurements of arsenic and arsenic trioxide over condensed phases

The solid-vapor relations for arsenic in the temperature range from 680 to 840 K and the liquid-vapor relations for arsenic trioxide in the temperature range from 650 to 740 K were determined by direct vapor pressure measurements carried out with a quartz gauge. The resulting InP (total) vsT are : InP (atm) = 2545.1/T + 22.27 InT− 154.02 (for arsenic) and InP (atm) = −50983/T + 6.869 (for arsenic trioxide). Calculated enthalpy of vaporization (ΔH_v,T ⁰) for arsenic trioxide and enthalpy of sublimation (ΔH_s,298 ⁰) for arsenic are 42.36 kJ/mol and 156.13 kJ/mol, respectively.     

Enthalpies of formation of AlNi: Experiment versus theory

The thermodynamic properties of theB2 AlNi phase have been revisited with calorimetric and a priori theoretical estimates of the enthalpy of formation of the stoichiometric compound. The calorimetric study has surveyed the temperature dependence of the enthalpy of formation and extrapolated it to zero temperature (for which the a priori estimates have been made), while the theoretical estimate explores the consequences of an apparent error in local density-based potentials in yielding the magnetic contribution to the reference energy of Ni metal. The present experimental value, extrapolated to 0 K, is 65.915 kJ/g-atom while the local density-based calculated value is 67.5 kJ/g-atom. These are in accord with each other and with much, but not all, the previous experimental data. An estimate of the error in the local density magnetic energy was made by comparing experimental and calculated heats for nonmagnetic Fe compounds, where the energy and its associated error are much larger, and scaling the result to Ni. This yields a “corrected” theoretical heat of 66 kJ/g-atom.     

Thermodynamic Properties of Hafnium

New enthalpy measurements above 2000 K have resulted in a complete reassessment and revision of the high temperature thermodynamic properties of hafnium. Values have been assessed to 4900 K and include a selected enthalpy of sublimation at 298.15 K of 621 ± 5 kJ/mol and a derived boiling point of 4850 K at one atmosphere pressure. A comparison is given between selected properties of the Group 4 elements to consider periodic trends.