Set Of Thermodynamic Properties Research Articles

Theoretical study of the interfacial force‐field and thermodynamic properties for HMX‐Estane mixture explosives

AbstractA transferable force‐field of HMX/Estane interface is derived by first‐principles calculation and least square optimization. Based on the force‐field, the plastic bonded explosive consists of HMX and Estane is simulated by molecular dynamics. The polycrystal structure is obtained, and a set of thermodynamic properties are calculated, including the heat capacity, thermal expansion coefficients, bulk modulus, elastic constants and Hugoniot curve. We find that the mixture explosive has higher thermal expansion coefficient than single crystal, because the interface is debonding at high temperature condition.

Operational Limits of Redox Metal Oxides Performing Thermochemical Water Splitting

Solar thermochemical hydrogen production is an attractive technology that stores intermittent solar energy in the form of chemical bonds. Efficient operation requires the identification of a redox‐active metal oxide (MOx) material that can achieve high conversion of water to hydrogen at minimal energy input. Water splitting occurs by consecutive reduction and reoxidation reactions of MOx. MOx is reduced to MOx−δ and, in the second step, is reoxidized by water recovering the initial MOx and generate H2. The material must reduce at temperatures achievable in concentrated solar receiver/reactors, while maintaining a thermodynamic driving force to split water. At equilibrium, extent of reduction depends on temperature and oxygen partial pressure, and in this analysis, a set of thermodynamic properties, namely, enthalpy and entropy of oxygen vacancy formation, is sufficient to represent MOx. Herein, a method to easily classify materials based on these thermodynamic properties under any condition of oxygen partial pressure and temperature is presented. This method is based on fundamental thermodynamic principles and is applicable for any redox material with known thermodynamic properties. Despite the simplicity of the method, it is believed that this analysis will support future research in targeting thermodynamic properties of redox‐active metal oxides.

Comments on “measurement and correlation studies of phase equilibria and thermophysical properties of 4-tert-butylbenzaldehyde”

Errors are found in the standard molar thermodynamic properties of vaporization calculated by Korsuru and coworkers based on the Clarke-Glew equation. The authors' vapor pressure - temperature data are reanalyzed, and a new set of thermodynamic properties are reported. Enthalpies of vaporization based on the Clarke-Glew equation are shown to be in good agreement with calculated values based on the Antoine equation coefficients.

Thermodynamic description of alkali metal hydroxides over a wide range of temperatures, pressures and densities of aqueous fluids

All available experimental data on dissociation constants of aqueous hydroxides of Na, K, and Li were critically assembled and together with quantum chemical estimations used to evaluate parameters of the AD EoS [1] for corresponding aqueous molecules NaOH(aq), KOH(aq), and LiOH(aq). Use of the proposed approach allows proper prediction of the whole set of thermodynamic properties of these hydroxides over a wide range of temperatures (0 – 800 °C), pressures (0.1 – 800 MPa) and solvent densities (0.03 – 1.1 g·cm-3).

Theoretical Study of the Interfacial Force-Field, Thermodynamic Property, and Heat Stress for Plastic Bonded Explosives

The force-fields across the TATB/(paraffin, fluoropolymer), RDX/TATB, RDX/graphite and fluoropolymer/graphite interfaces are obtained by first-principles calculations and parameter optimization. Based on them, the composite materials are simulated in atomistic scale, and a set of thermodynamic properties are calculated, including the heat capacity, thermal expansion coefficient, Gruneisen coefficient, isothermal curve, Hugoniot curve, pressure field, and tension field. We find that the thermal expansion coefficient difference across the explosive/additive interface induces interfacial tension in warming process, the interfacial tension induces positive pressure on the explosive particle, and the positive pressure restrains the thermal expansion of the composite material. A physical picture to describe the influence mechanism of the interface effect on the composite property is obtained.

The force-field derivation and application of explosive/additive interfaces

The inter-molecular force-field across RDX/(paraffin, fluoropolymer) interfaces are derived from first-principles calculated energies under the GGA+vdW functional. Based on the force-field, the polycrystal structures of mixture explosives are obtained, and a set of thermodynamic properties are calculated, including the elastic constants, thermal expansion coefficient, heat capacity, isothermal curve and the Hugoniot curve. The results are in good agreement with the available experiments, and provide a reasonable prediction about the properties of plastic bonded explosives. We find that the thermal expansion coefficient of a multi-component explosive is not only determined by the properties of the components, but is also affected by the thermal stress at the explosive/additive interfaces.

Thermodynamics of mixtures containing a very strongly polar compound. 11. 1-Alkanol + alkanenitrile systems

1-Alkanol+alkanonitrile systems have been studied by means of the DISQUAC, ERAS and UNIFAC (Dortmund) models. DISQUAC and ERAS parameters for the alkanol/nitrile interactions are reported. DISQUAC describes a whole set of thermodynamic properties: phase equilibria, vapor–liquid (VLE), liquid–liquid (LLE) and solid–liquid (SLE) equilibria, molar excess functions: Gibbs energies, GmE, enthalpies, HmE, and partial excess molar enthalpies at infinite dilution, HmiE,∞ using the same set of interaction parameters for each solution. The dependence on the molecular structure of the interaction parameters is similar to that observed in other previous applications to mixtures formed by 1-alkanols and a strongly polar compound, in such way that the quasichemical interchange coefficients can be kept constant from 1-propanol. However, methanol and ethanol solutions behave differently. From the analysis of experimental data for HmE, TSmE(=HmE−GmE), and molar excess volumes, VmE, it is concluded that the studied systems are characterized by dipolar interactions and strong structural effects. The former are more relevant in acetonitrile solutions. Association effects are more important in butanenitrile mixtures. DISQUAC gives better results than the ERAS model. ERAS results on HmE for systems containing acetonitrile are also improved by UNIFAC. This remarks the importance of dipolar interactions in the investigated mixtures. ERAS describes the variation of VmE (x1=0.5) with the 1-alkanol size for mixtures with a given nitrile, but the concentration dependence of this excess function is poorly represented.

Thermodynamics of Mixtures Containing Amines. X. Systems with Cyclic Amines or Morpholine

Cyclic amine or morpholine + organic solvent mixtures have been investigated in terms of DISQUAC and of the Kirkwood–Buff formalism. The amines considered are cyclohexylamine; (c-CH2)uNH (u = 2–7) and (c-CH2)uN–CH3 (u = 4,5). The organic solvents are alkanes and methanol or ethanol. The DISQUAC interaction parameters are reported. The model describes correctly a whole set of thermodynamic properties: vapor–liquid equilibria (VLE); excess Gibbs energies, GmE; excess enthalpies, HmE; excess heat capacities at constant pressure, CP,mE; and partial excess enthalpies at infinite dilution, H1E,∞, as well as the main features of the Kirkwood–Buff integrals. In (c-CH2)uNH + C6H12 mixtures, amine–amine interactions become weaker with increased u values. This is supported by the corresponding decrease of HmE and H1E,∞ and of the effective dipole moment. Interactions between amine molecules are also weakened when passing from a primary cyclic amine to an isomeric tertiary cyclic amine. The existence of an aromatic ring in the amine, as in aniline or pyridine, leads to stronger amine–amine interactions. Dipolar interactions between morpholine molecules are stronger than those between piperidine molecules, and reveal the existence of proximity effects between the two groups of morpholine. In systems with alkanes, interactions between amine molecules are preferred to those between unlike molecules. In piperidine + methanol and pyrrolidine + ethanol systems, the mixture structure is close to random mixing.

Thermodynamic properties of Al-Mn melts

The thermochemical properties of Al-Mn melts have been studied at 1835 ± 3 K by high-temperature calorimetry under isoperibolic conditions. The Δmix H and Δmix $$ \overline H _i $$ , data obtained correlate well with earlier data obtained at a lower temperature of 1628 K. The enthalpies of formation of manganese aluminides determined by calorimetry agree only qualitatively with the Δmix H of Al-Mn melts. We have calculated the partial and integral entropies of mixing of Al-Mn melts. Analysis of the entire set of thermodynamic properties indicates that, in liquid Al-Mn alloys, the interaction between dissimilar atoms is significant even well above the liquidus temperature.

Thermodynamics of 1-alkanol + aromatic compound mixtures. Systems with dimethylbenzene, ethylbenzene or trimethylbenzene

Binary mixtures of 1-alkanols and ethylbenzene, dimethylbenzenes or trimethylbenzenes have been studied in the framework of the DISQUAC model. The interaction parameters for the hydroxyl/aromatic contacts are reported. DISQUAC represents well a set of thermodynamic properties: vapor-liquid equilibria (VLE), liquid–liquid equilibria (LLE), molar excess enthalpies ( H E) and the concentration–concentration structure factor ( S CC(0)). The model predicts correctly H E of 1-alkanol + 1,4-dimethylbenzene + cyclohexane systems using binary parameters only, that is neglecting ternary interactions. The available database on H E and molar excess volume ( V E) is examined in order to gain insight into the interactions present in the studied mixtures: (i) dipolar interactions are stronger in systems with benzene; (ii) interactions between unlike molecules decrease with the increase of the chain length of the 1-alkanol for solutions with a given aromatic hydrocarbon; (iii) self-association of 1-alkanols is more important in systems with alkylbenzenes than in those including benzene; (iv) benzene is a more active molecule than other aromatic compounds when breaking the alcohol structure.

Thermodynamic Properties of High-Temperature Weakly Nonideal Flinabe (LiF-NaF-BeF2) Gas

The set of thermodynamic properties of high-temperature, weakly nonideal Flinabe (LiF-NaF-BeF2) gas is calculated and presented. High-temperature Flinabe gases (plasmas) appear in the inertial fusion energy chamber over a wide range of temperatures and pressures due to the absorption of X-rays and debris, emitted from the target microexplosion, within a very thin surface layer of the Flinabe liquid wall. The equation-of-state (EOS) and ionization equilibrium data of the resulting high-temperature gas were computed and are presented in another paper. In this paper, the set of thermodynamic properties (specific enthalpy, specific heats, adiabatic exponent, and sound speed) that are required, in conjunction with the Flinabe EOS, to perform gas dynamics calculations and the required assessments of many research and development issues in nuclear fusion is modeled and computed consistently with the previously presented EOS and ionization equilibrium data. This set of Flinabe thermodynamic properties is missed in the literature, and the need to model and estimate these properties seems to be immediate rather than justifiable. Computational results for Flinabe thermodynamic properties are presented and discussed. These properties have been presented as a set of isobars that have been validated by obtaining the limiting conditions at very high temperatures for a fully dissociated/fully ionized gas.

Thermodynamics of 1-alkanol + cyclic ether mixtures

1-Alkanol + cyclic ether mixtures have been investigated in terms of the DISQUAC and ERAS models and using the concentration–concentration structure factor ( S CC(0)). The corresponding interaction parameters are reported. DISQUAC interaction parameters for the systems 1-alkanol + 1,7,10,13,16-hexaoxacyclooctadecane (18CE) and methanol + 1,3,5-trioxane are also given. DISQUAC correctly describes a whole set of thermodynamic properties: vapor–liquid equilibria, VLE, molar excess enthalpies, H E, solid–liquid equilibria, SLE, and S CC(0) of the binary systems. H E of 1-alkanol + cyclic ether + alkane mixtures are fairly well represented by DISQUAC using binary parameters only. ERAS provides a semiquantitative description of the investigated mixtures due to the fact that main contribution to their thermodynamic properties is usually the physical one. 1-Alkanol + cyclic ether systems are characterized by dipolar interactions and homocoordination. Interactions between unlike molecules are stronger in mixtures with tetrahydrofuran (THF) or 1,3-dioxolane, when are compared with those present in solutions with tetrahydropyran (THP) or 1,4-dioxane. The DISQUAC interaction parameters underline that proximity effects are more relevant in systems with 1,3-dioxolane or 1,3,5-trioxane. THP, 1,4-dioxane and 18CE form a homologous series in the framework of DISQUAC.

Thermodynamics of mixtures containing alkoxyethanols: Part XIX. Systems with linear monoethers or 1-alkanols

Alkoxyethanol + linear monoether, or + 1-alkanol mixtures have been investigated in terms of the DISQUAC and ERAS models and using the so-called concentration–concentration structure factor, S CC(0). DISQUAC and ERAS interaction parameters are reported. DISQUAC describes consistently a whole set of thermodynamic properties: vapor–liquid equilibria, VLE, molar excess functions as Gibbs energy, G E, enthalpy, H E, or heat capacity at constant pressure, C P E and S CC(0). In the framework of DISQUAC, the intramolecular H-bonds between the O and OH of the cellosolve are independent, except for short chain ethers, of the molecular environment (linear ether, or 1-alcohol). ERAS describes systems with dibutylether by means of a large physical contribution to the excess thermodynamic properties. The model overestimates the self-association of the lower 1-alkanols in their mixtures with 2-alkoxyethanols, which leads to a poor representation of the properties of such systems. Mixtures with dibutylether are characterized by homocoordination with interactions which can be assumed to be of dipolar type. In systems with 1-alkanols, interactions between like and unlike molecules and structural effects are compensated, and S CC(0) is nearly ideal.

Thermodynamics of organic mixtures containing amines: V. Systems with pyridines

Binary mixtures containing pyridine (PY), or 2-methylpyridine (2MPY) or 3-methylpyridine (3MPY) or 4-methylpyridine (4MPY) and an organic solvent as benzene, toluene, alkane, or 1-alkanol are investigated in the framework of DISQUAC. The corresponding interaction parameters are reported. The model describes accurately a whole set of thermodynamic properties: vapor–liquid equilibria (VLE), liquid–liquid equilibria (LLE), solid–liquid equilibria (SLE), molar excess Gibbs energies ( G E), molar excess enthalpies, ( H E), molar excess heat capacities at constant pressure ( C P E ) and the concentration–concentration structure factor ( S CC(0)). It is remarkable that DISQUAC correctly predicts the W-shaped curve of the C P E of the pyridine + n-hexadecane system. The model can be applied successfully to mixtures with strong positive or negative deviations from the Raoult's law. DISQUAC improves the theoretical results from UNIFAC (Dortmund version). The replacement of pyridine by a methylpyridine leads to a weakening of the amine–amine interactions, ascribed to the steric effect caused by the methyl group attached to the aromatic ring. This explains that for a given solvent (alkane, 1-alkanol) H E(pyridine) > H E(methylpyridine).

Thermodynamics of binary mixtures of N-methyl-2-pyrrolidinone and ketone. Experimental results and modelling of the (solid + liquid) equilibrium and the (vapour + liquid) equilibrium. The modified UNIFAC (Do) model characterization

The (solid + liquid) equilibrium (SLE) of eight binary systems containing N-methyl-2-pyrrolidinone (NMP) with (2-propanone, or 2-butanone, or 2-pentanone, or 3-pentanone, or cyclopentanone, or 2-hexanone, or 4-methyl-2-pentanone, or 3-heptanone) were carried out by using a dynamic method from T = 200 K to the melting point of the NMP. The isothermal (vapour + liquid) equilibrium data (VLE) have been measured for three binary mixtures of NMP with 2-propanone, 3-pentanone and 2-hexanone at pressure range from p = 0 kPa to p = 115 kPa. Data were obtained at the temperature T = 333.15 K for the first system and at T = 373.15 K for the second two systems. The experimental results of SLE have been correlated using the binary parameters Wilson, UNIQUAC ASM and two modified NRTL equations. The root-mean-square deviations of the solubility temperatures for all the calculated values vary from (0.32 K to 0.68 K) and depend on the particular equation used. The data of VLE were correlated with one to three parameters in the Redlich–Kister expansion. Binary mixtures of NMP with (2-propanone, or 2-butanone, or 2-pentanone, or 3-pentanone, or cyclopentanone, or 2-hexanone, or 4-methyl-2-pentanone, or 3-heptanone) have been investigated in the framework of the modified UNIFAC (Do) model. The reported new interaction parameters for NMP-group (c-CONCH 3) and carbonyl group ( C O) let the model consistently described a set of thermodynamic properties, including (solid + liquid) equilibrium, (vapour + liquid) equilibrium, excess Gibbs energy and molar excess enthalpies of mixing. Our experimental and literature data of binary mixtures containing NMP and ketones were compared with the results of prediction with the modified UNIFAC (Do) model.

Thermodynamics of liquid mixtures containing a very strongly polar compound: Part 6. DISQUAC characterization of N, N-dialkylamides

Systems of N, N di( n-alkylamides) (hereafter, N, N-dialkylamides) with alkane, benzene, toluene, 1-alkanol or 1-alkyne have been investigated in the framework of the DISQUAC model. The corresponding interaction parameters are reported. They change regularly with the molecular structure of the mixture components. This variation is similar to those encountered when treating other systems in terms of DISQUAC. The model describes consistently a whole set of thermodynamic properties: liquid–liquid equilibria (LLE), vapor–liquid equilibria (VLE), solid–liquid equilibria (SLE), molar excess Gibbs energies ( G E), molar excess enthalpies ( H E), molar excess heat capacities at constant pressure ( C P E), partial molar excess properties at infinite dilution, enthalpies and heat capacities. The model also provides good results for the Kirkwood–Buff integrals and for the linear coefficients of preferential solvation. For ternary systems, DISQUAC predictions on VLE and H E, obtained using binary parameters only, are in good agreement with the experimental data. A short comparison between DISQUAC and Dortmund UNIFAC results is shown. DISQUAC improves UNIFAC results on H E and C P E, magnitudes which strongly depend on the molecular structure. The investigated mixtures behave similarly to those characterized by thermodynamic properties which arise from dipolar interactions. Association/solvation effects do not play, as a whole, an important role in the studied systems. This may explain that the ERAS model fails when representing the thermodynamic properties of dimethylformamide + 1-alkanol mixtures.

Thermodynamic Properties of Aqueous Potassium Fluoride under Superambient Conditions

Using the ion-interaction or virial coefficient approach developed by Pitzer, the pressure dependences of the osmotic and activity coefficients for KF (aq.) up to 473.15 K and 2.5.0 mol-kg−1 have been calculated from literature data for the apparent molar volumes of KF (aq.). These pressure dependencies were combined with the osmotic and activity coefficient at 0.1 MPa or psat, obtained from the model of Saluja et al. to yield a comprehensive set of thermodynamic properties for KF (aq.) at temperatures from 298.15 through 473.15 K, pressures 10, 20, and 30 MPa, and molalities to 2.5 mol-kg−1.

Cobalt(II) Oxide Solubility and Phase Stability in Alkaline Media at Elevated Temperatures

A platinum-lined, flowing autoclave facility was used to investigate the solubility behavior of cobalt(II) oxide (CoO) in deoxygenated ammonium and sodium hydroxide solutions between 22 and 288°C. Co(II) ion activity in aqueous solution was controlled by a hydrous Co(II) oxide when nitrogen was used for deoxygenation and by metallic cobalt when hydrogen was used. Measured cobalt solubilities are interpreted using a Co(II) ion hydroxo- and amminocomplexing model and thermodynamic functions for these equilibria were obtained from a least-squares analysis of the data. A common set of thermodynamic properties for the species Co(OH)+, Co(OH)2(aq) and Co(OH)(NH3)+ is provided to permit accurate cobalt oxide solubility calculations over broad ranges of temperature and alkalinity.

Thermodynamic properties of {xNa2O+(1−x)P2O5}(l)

An e.m.f. study of {xNa2O+(1−x)P2O5}(1) containingx=0.43 to 0.75 has been carried out over the temperature range 750 K to 1300 K. The set of thermodynamic properties, both partial and integral, is obtained. Significant negative deviations from ideal behaviour of ΔfGmand ΔfHmare observed. The results obtained are discussed in terms of the ideal-associated-mixture model. Computer-simulated and experimental results are in good agreement.

Legendre transforms in chemical thermodynamics

Legendre transforms are used to introduce intensive variables as natural variables in the fundamental equations of thermodynamics. Natural variables are important because when a thermodynamic potential can be determined as a function of its natural variables, all the other thermodynamic properties of the system can be obtained by taking partial derivatives. It is usually more convenient to use thermodynamic potential that have intensive natural variables because they are often more easily controlled than the conjugate extensive variables. This is illustrated for chemical reaction systems in which it is of interest to specify the chemical potentials of phases in a multi-phase system are not natural variables of the Gibbs free energy, it is useful to define a transformed Gibbs free energy, for which electric potentials of phases are natural variables. The use of a Legendre transform brings in a new set of thermodynamic properties, new Maxwell equations, Gibbs–Duhem equations, and Gibbs–Helmholtz equations.