Temperature Dependence Of Heat Capacity Research Articles

Zn-Mo-O system: Insights into the thermodynamic stability and applicability in lithium ion batteries

A detailed experimental investigation on the thermochemical stability of Zn2Mo3O8(s) in the Zn-Mo-O system was reported for the first time using high temperature oxide melt solution calorimetry in conjunction with solid oxide based electrochemical measurements. The temperature dependence of molar heat capacity of this compound was determined employing thermal relaxation calorimetry and differential scanning calorimetry. The values of standard molar enthalpy of formation (∆fH298.15°), standard molar entropy (S298.15°), molar heat capacity (Cp) and Debye temperature (θD) for Zn2Mo3O8(s) were determined for the first time in this study. The present study also focuses on the investigation of electrochemical performance of α-ZnMoO4(s) for lithium ion battery applications which demonstrated the effective utilization of this compound as anode material due to its remarkable cycling stability and rate capability.

Phase Separation in the Double Perovskite Sr2FeNbO6-δ

The ceramic perovskite Sr2FeNbO6-δ was synthesized via the solution combustion precursor method. X-ray phase analysis showed that the sample is single-phase and does not contain impurities. The specific heat capacity and the Mössbauer spectra were measured for the Sr2FeNbO6-δ ceramic in the temperature range of 4–300 K. The observation of an asymmetric doublet in the Mössbauer spectra and the literature data on the magnetic susceptibility indicated the presence of two magnetic subsystems in Sr2FeNbO6-δ with antiferromagnetic exchange interactions. Based on the analysis of the temperature dependence of the specific heat capacity, we determined the Debye and Einstein temperatures.

Superconductivity in a breathing kagome metals ROs2 (R = Sc, Y, Lu)

We have successfully synthesized three osmium-based hexagonal Laves compounds ROs2 (R = Sc, Y, Lu), and discussed their physical properties. LeBail refinement of pXRD data confirms that all compounds crystallize in the hexagonal centrosymmetric MgZn2-type structure (P63/mmc, No. 194). The refined lattice parameters are a = b = 5.1791(1) Å and c = 8.4841(2) Å for ScOs2, a = b = 5.2571(3) Å and c = 8.6613(2) Å for LuOs2 and a = b = 5.3067(6) Å and c = 8.7904(1) Å for YOs2. ROs2 Laves phases can be viewed as a stacking of kagome nets interleaved with triangular layers. Temperature-dependent magnetic susceptibility, resistivity and heat capacity measurements confirm bulk superconductivity at critical temperatures, Tc, of 5.36, 4.55, and 3.47 K for ScOs2, YOs2, and LuOs2, respectively. We have shown that all investigated Laves compounds are weakly-coupled type-II superconductors. DFT calculations revealed that the band structure of ROs2 is intricate due to multiple interacting d orbitals of Os and R. Nonetheless, the kagome-derived bands maintain their overall shape, and the Fermi level crosses a number of bands that originate from the kagome flat bands, broadened by interlayer interaction. As a result, ROs2 can be classified as (breathing) kagome metal superconductors.

The physical properties of Sc2PbC: A first-principles calculations

The structural, electronic, elastic, hardness, fracture toughness, and thermodynamic properties of the newly synthesized MAX phase Sc2PbC were studied for the first time through the first-principles calculations. The optimized lattice parameters are in agreement with the experimental data. The thermodynamic and mechanical stability of Sc2PbC is verified based on the formation enthalpy and single-crystal elastic constants. By analyzing the polycrystalline elastic moduli, it is found that Sc2PbC is brittle, very soft, easily machinable, and exhibits elastic anisotropy. Finally, thermodynamic properties such as Debye temperatures, thermal conductivity, melting temperature, and the temperature dependence of heat capacity are investigated.

Magnetic properties and magnetocaloric effect of a metallic triangular lattice antiferromagnetic DyAl2Ge2 single crystal

We report the synthesis, magnetic susceptibility, magnetization, electrical resistivity, heat capacity, and magnetocaloric properties of the metallic triangular lattice antiferromagnetic DyAl2Ge2 single crystal. High-quality rare-earth intermetallic compound DyAl2Ge2 single crystals were synthesized by the metallic flux method. DyAl2Ge2 crystallizes in a trigonal CaAl2Si2-type structure with Dy atoms forming a triangular lattice in the ab plane. The paramagnetic-antiferromagnetic transition occurs at 8 K, as determined by temperature dependencies of magnetic susceptibility and heat capacity. No observable hysteresis was found in the field-induced antiferromagnetic to the ferromagnetic metamagnetic transition of DyAl2Ge2. The electrical resistivity shows an overall metallic behavior with an upturn at the ordering temperature. For a magnetic field change of 0–70 kOe, the maximum magnetic-entropy change is −14.2 J kg−1 K−1 at 11 K and the relative cooling power is 327 J kg−1 with the applied magnetic field along the ab plane.

PREDICTION OF THE THERMOPHYSICAL BEHAVIOR OF AMORPHOUS OF ALLOYS Ni<sub>0.333</sub>Zr<sub>0.667</sub> AND La<sub>80</sub>Al<sub>20</sub> ACCORDING TO PROPERTIES OF METALS

Amorphous alloys (metallic glasses) are obtained by ultrafast cooling of melts. As a result of this process, the chaotic distribution of atoms in space is “frozen” while maintaining the short-range order characteristic of liquids. The high homogeneity of the solid state leads to unique mechanical, magnetic and other physical properties. This has led to the fact that cheaper metallic glasses have replaced a number of traditional materials in some industries. On the other hand, significant disadvantages of disordered media are temperature and time instabilities. The solution to this problem is possible with knowledge of the thermophysical properties of amorphous alloys: heat capacity, thermal expansion coefficient, thermal conductivity and thermal diffusivity. Even estimating, for example, their temperature dependences is a complex and urgent task. Therefore, in this paper, it is proposed to use the mixing rule for components whose thermophysical properties are known. This makes it possible to predict the temperature dependences of heat capacity, thermal expansion coefficient and thermal diffusivity at known values of thermal conductivity for different temperatures. Note that the obtained curves for the Ni0.333Zr0.667 and La80Al20 amorphous alloys are in good agreement with the experimental data.

The Influence of Physical Properties on the Membrane Morphology Formation during the Nonisothermal Thermally Induced Phase Separation Process.

The physical properties of a polymer solution that are composition- and/or temperature-dependent are among the most influential parameters to impact the dynamics and thermodynamics of the phase separation process and, as a result, the morphology formation. In this study, the impact of composition- and temperature-dependent density, heat capacity, and heat conductivity on the membrane structure formation during the thermally induced phase separation process of a high-viscosity polymer solution was investigated via coupling the Cahn-Hilliard equation for phase separation with the Fourier heat transfer equation. The variations of each physical property were also investigated in terms of different boundary conditions and initial solvent volume fractions. It was determined that the physical properties of the polymer solution have a noteworthy impact on the membrane morphology in terms of shorter phase separation time and droplet size. In addition, the influence of enthalpy of demixing in this case is critical because each physical property showed a nonhomogeneous pattern owing to the heat generation during phase separation, which in turn influenced the membrane morphology. Accordingly, it was determined that investigating spinodal decomposition without including heat transfer and the impact of physical properties on the morphology formation would lead to an inadequate understanding of the process, specifically in high-viscosity polymer solutions.

Phase transition and thermodynamic properties of CaV2O6 at high temperature

CaV2O6 is widely utilized in optoelectronic materials, dielectric ceramics, magnetic candidates, and catalytic materials due to its unique physical and chemical properties. CaV2O6 was synthesized by a conventional solid-state reaction technique in this study. The CaV2O6 crystallizes in a monoclinic system belonging to space group C2/m, with the lattice parameters of a = 10.06 Å, b = 3.675 Å, c = 7.039 Å, and β = 104.843°. The congruent melting of CaV2O6 was detected at 1045 K by performing DSC. Enthalpy increments of CaV2O6 were experimentally measured for temperatures ranging from 573 K to 1023 K employing drop calorimetry for the first time. The temperature dependence of the molar heat capacity of CaV2O6 was then calculated on the basis of the enthalpy increments results. Thermodynamic properties (enthalpy change, entropy, and Gibbs free energy) were also calculated in the temperature range of 300–1000 K.

Structure and thermoelectric properties of half-Heusler-like TiFeCuxSb alloys

Previous research on the ternary Ti-Fe-Sb system has revealed that stoichiometric TiFeSb cannot exist as a stable compound, whereas a single-phase TiFe1.33Sb alloy with the half-Heusler-like structure has been synthesized by adding excessive Fe. In this work, we report that TiFeSb can also be stabilized by filling additional Cu to the vacant 4d site of the half-Heusler lattice. Our experiments indicate that the TiFeCuxSb (x = 0–0.25) samples exhibit a p-type conduction with extremely high carrier concentration ((0.5 –2.5) × 1022 cm−3)), while these samples attain very large Seebeck coefficients, over 100 μV/K in the whole measured temperature range for the samples with x = 0.15–0.25. In addition, a logarithmic divergence of the temperature-dependent specific heat capacity (CP/T) is observed at low temperatures, implying the strange-metal behavior of TiFeCuxSb samples. The partial filling of the vacant 4d site results in significantly reduced lattice thermal conductivity, leading to the low total thermal conductivity of 2.8 W·m−1·K−1 at 823 K for the TiFeCu0.20Sb sample. Consequently, a dimensionless figure of merit zT of 0.54 at 923 K is realized for TiFeCu0.20Sb, demonstrating that promising thermoelectric materials with intriguing physical properties can be discovered in the composition gap of half- and full-Heusler alloys.

Structure-thermal property relationships of aikinite PbCuBiS3

Understanding the structural properties and chemical bonding in complex multinary chalcogenides is highly valuable, as it provides vital information for controlling their physical properties to suit various technological applications. We report on the structural, thermal, and electronic properties of PbCuBiS3 by incorporating an experimental and theoretical investigation of this material. Analysis of the experimental temperature-dependent heat capacity and thermal conductivity data show that weak bonding and strong lattice anharmonicity give rise to ultralow thermal conductivity. Chemical bonding information obtained from the density functional theory electronic calculations reveal significant antibonding interactions that underscore the dominant role of the Cu-S tetrahedra on occupied antibonding states, as well as a highly distorted Pb/Bi-S environment inducing weak bonding and strong lattice anharmonicity. This study broadens our understanding of the structure-property relationships for this material, and can be useful for developing this and similar chalcogenide materials for potential applications of interest.

Thermodynamic and High-Temperature Properties of KFe0.33W1.67O6

This paper presents the results of a study of the KFe0.33W1.67O6 system. The compound was obtained by a solid-phase synthesis method at a temperature of 1073 K. The structural, morphological, and spectroscopic properties of KFe0.33W1.67O6 were characterized using XRD, SEM-EDS. The compound crystallizes in a cubic lattice with the space group Fd–3m (227). The obtained lattice parameter a = 10.3697 (3) Å. The phase transitions of KFe0.33W1.67O6 were determined by low-temperature and high-temperature X-ray diffraction. The temperature dependence of heat capacity of KFe0.33W1.67O6 has been measured for the first time in the range from 5 to 638 K by precision adiabatic vacuum calorimetry and differential scanning calorimetry. The experimental data were used to calculate standard thermodynamic functions, namely the heat capacity C∘p∘(T), enthalpy H°(T) − H°(0), entropy S°(T) − S°(0), and Gibbs function G°(T) − H°(0), for the range from T → 0 to 630 K.

Temperature Dependence of Heat Capacity and the Change in Thermodynamic Functions of Cadmium-Doped Lead Antimony Alloy PbSb3

Temperature Dependence of Heat Capacity and the Change in Thermodynamic Functions of Cadmium-Doped Lead Antimony Alloy PbSb3

On Simultaneous Determination of Thermal Conductivity and Volume Heat Capacity of Substance

The study of nonlinear problems associated with heat transfer in substance is important for practice. Earlier, the authors proposed an efficient algorithm for determining the thermal conductivity from experimental observations of the dynamics of the temperature field in an object. In this work, we explore the possibility of extending the algorithm to the numerical solution of the problem of simultaneous identification of the temperature-dependent volume heat capacity and the thermal conductivity of the substance under study. The consideration is based on the Dirichlet boundary value problem for the one-dimensional nonstationary heat equation. The coefficient inverse problem in question is reduced to a variational problem, which is solved by applying gradient methods based on the fast automatic differentiation technique. The uniqueness of the solution to the inverse problem is analyzed.

Theoretical Investigation of Heat Capacities as a Function Temperature of Stannous Selenide (SnSe) Using Einstein-Debye Approximation

A new alternative approach has been suggested for evaluating the heat capacities of stannous selenide (SnSe), based on the Einstein-Debye approximation. It is well known the thermal behavior of solids is a very important theoretical problem that has been explored thoroughly with the development of Einstein, Debye and recently developed Einstein-Debye approximations. Many additional thermophysical characteristics of materials may be analyzed using the Einstein-Debye approach employed in this study. As an application, the heat capacities have been computed by using the Einstein-Debye method for SnSe in the temperatures range between 40 and 900 K. The temperature dependence of heat capacities have been computed and found to be in good accord with the literature throughout a wide temperature range.

Heat Capacity and Thermodynamic Functions of Titanium-Manganites of Lanthanum, Lithium and Sodium of LaLi2TiMnO6 and LaNa2TiMnO6.

Titanium-manganites of LaLi2TiMnO6 and LaNa2TiMnO6 were synthesized by the methods of ceramic technology from the oxides of lanthanum, titanium (IV), manganese (III), and the carbonates of lithium and sodium. The types of their syngony and the parameters of their gratings were determined radiographically. The isobaric heat capacities of titanium-manganites were measured with experimental calorimetry in the range of 298.15-673 K. It was found that on the dependence curve of heat capacity versus temperature of C°p~f(T), for LaLi2TiMnO6 at 348 K and 598 K, and LaNa2TiMnO6 at 348 K, there are abnormal jumps in heat capacity, probably related to phase transitions of the second kind. Taking into account the temperatures of the phase transitions, the equations of the temperature dependence of the heat capacity of titanium-manganites were derived. Their standard entropies were calculated by the ion increments method. Temperature dependences of the thermodynamic functions of S°(T), H°(T)-H°(298.15), and Φxx(T) were calculated using the experimental data on heat capacities and the calculated values of the standard entropies. The standard heat capacities of the studied compounds were calculated by the independent methods of ion increments and Debye, the values of which were in satisfactory agreement with the experimental data. The standard enthalpy of the formation of LaLi2TiMnO6 and LaNa2TiMnO6 was calculated according to the methodology developed by the authors. The conducted electrophysical studies determined the nature of the second-order phase transition and the semiconductor features of their conductivity. Thus, all the above-mentioned data on the experimental and calculated studies of the temperature dependence of heat capacity, the thermodynamic functions to determine a standard enthalpy of formation of LaLi2TiMnO6 and LaNa2TiMnO6, and the investigation of their electrical properties are absolutely new, and they have no analogues.

Noncollinear commensurate antiferromagnetic structure in metallic Pr2PdAl7Ge4

We report the crystal structure, magnetic structure, magnetic properties, electrical- and magnetotransport properties, and heat capacity of the rare-earth transition-metal compound ${\mathrm{Pr}}_{2}{\mathrm{PdAl}}_{7}{\mathrm{Ge}}_{4}$. ${\mathrm{Pr}}_{2}{\mathrm{PdAl}}_{7}{\mathrm{Ge}}_{4}$ crystallizes in the noncentrosymmetric tetragonal structure $P\overline{4}{2}_{1}m$ (No. 113) with unit cell parameters $a=6.0059(3)\phantom{\rule{4pt}{0ex}}\AA{}$ and $c=15.2278(13)\phantom{\rule{4pt}{0ex}}\AA{}$. The N\'eel temperature ${T}_{\mathit{N}}$ of ${\mathrm{Pr}}_{2}{\mathrm{PdAl}}_{7}{\mathrm{Ge}}_{4}$ was determined to be 6 K by the temperature dependences of magnetization, heat capacity, and electrical resistivity. The magnetic-field-induced antiferromagnetic to ferromagnetic transition occurs for magnetic fields $H$ along both the $ab$ plane and the $c$ axis. The electrical resistivity shows a metallic behavior with an upturn at the ordering temperature due to a superzone gap. Negative linear magnetoresistance is observed since the magnetic field increases the order degree of the antiferromagnetic state, reducing the magnetic correlation scattering. Neutron powder diffraction experiments reveal that metallic ${\mathrm{Pr}}_{2}{\mathrm{PdAl}}_{7}{\mathrm{Ge}}_{4}$ has an unusual noncollinear commensurate antiferromagnetic structure with the propagation vector $\mathbit{k}=(0,\phantom{\rule{0.28em}{0ex}}0,\phantom{\rule{0.28em}{0ex}}0.5)$. Magnetic Pr atom layers stack with the ABBA sequence along the $c$ axis. Within the layers, the Pr moments lie in the $ab$ plane, and the angle between the nearest-neighbor spins is $67.{1}^{\ensuremath{\circ}}$. This magnetic structure can well explain the magnetic properties of ${\mathrm{Pr}}_{2}{\mathrm{PdAl}}_{7}{\mathrm{Ge}}_{4}$.

Magnetic properties of a multicomponent intermetallic compound Tb$_{0.25}$Dy$_{0.25}$Ho$_{0.25}$Er$_{0.25}$Al$_2$

Polycrystalline multicomponent Laves phase rare earth intermetallic compound Tb_{0.25}0.25 Dy_{0.25}0.25Ho_{0.25}0.25Er_{0.25}0.25Al_{2}2 has been synthesized by arc-melting and characterized by powder X-ray diffraction, magnetization and heat capacity measurements. The sample has MgCu_22-type cubic structure (space group Fd-3m) at 300 K. The compound Tb_{0.25}0.25Dy_{0.25}0.25Ho_{0.25}0.25Er_{0.25}0.25 Al_{2}2 orders ferromagnetically at 50 K (T_CC). This value is almost equal to the average of the ferromagnetic ordering temperatures of the individual RAl_22 (R = Tb, Dy, Ho and Er) compounds. Field dependence of magnetization below T_CC indicates soft-ferromagnetic nature. From the magnetization vs field data obtained near T_CC and the temperature dependence of heat capacity, low field magnetocaloric effect has been estimated.

Implications of a temperature-dependent heat capacity for temperature-gated ion channels

Temperature influences dynamics and state-equilibrium distributions in all molecular processes, and only a relatively narrow range of temperatures is compatible with life-organisms must avoid temperature extremes that can cause physical damage or metabolic disruption. Animals evolved a set of sensory ion channels, many of them in the family of transient receptor potential cation channels that detect biologically relevant changes in temperature with remarkable sensitivity. Depending on the specific ion channel, heating or cooling elicits conformational changes in the channel to enable the flow of cations into sensory neurons, giving rise to electrical signaling and sensory perception. The molecular mechanisms responsible for the heightened temperature-sensitivity in these ion channels, as well as the molecular adaptations that make each channel specifically heat- or cold-activated, are largely unknown. It has been hypothesized that a heat capacity difference (ΔCp) between two conformational states of these biological thermosensors can drive their temperature-sensitivity, but no experimental measurements of ΔCp have been achieved for these channel proteins. Contrary to the general assumption that the ΔCp is constant, measurements from soluble proteins indicate that the ΔCp is likely to be a function of temperature. By investigating the theoretical consequences for a linearly temperature-dependent ΔCp on the open-closed equilibrium of an ion channel, we uncover a range of possible channel behaviors that are consistent with experimental measurements of channel activity and that extend beyond what had been generally assumed to be possible for a simple two-state model, challenging long-held assumptions about ion channel gating models at equilibrium.

Atomistic simulations, meso-scale analyses and experimental validation of thermal properties in ordinary Portland cement and geopolymer pastes

Ordinary Portland Cement (OPC)- and alternative binder-based materials have been widely used in Thermal Energy Storage (TES) applications due to their excellent TES capacities, good mechanical properties and low-cost. In this attempt, this work proposes an upscaling procedure to model the TES properties of two hydrated pastes made of OPC and a Hybrid cement (i.e., an alternative H-Cement binder), the latter employed for a GEOpolymer-based composite (GEO). Firstly, an atomistic approach based on energy minimization and molecular dynamics is employed for modelling the thermal behaviors and heat storage capacities of CSH (calcium silicate hydrate) and NASH (sodium aluminosilicate hydrate) phases, being those the main phases for OPC-based paste and GEO, respectively. Then, an up-scaling optimization procedure and meso-scale FEM homogenization techniques are proposed to link the TES parameters of the atomistic main phases of OPC-based paste and GEO with the homogenized upper meso/macro scale values. To this end, the results of an experimental program on both OPC and GEO pastes have been considered as benchmark to calibrate/validate the numerical tools. Promising simulations at several scales and up-scaling procedures are demonstrated in terms of homogenized temperature-dependent heat capacity and thermal diffusivity, showing a good agreement with the experimental data of the analyzed mixtures.

Theoretical prediction method of Young's modulus and yield strength of micron particle reinforced metal matrix composites at different temperatures

To begin with, a theoretical characterization model of temperature and porosity dependent Young's modulus for micron particle reinforced metal matrix composites is established by considering the evolution of properties of reinforced particles and metal matrix with temperature. Additionally, combining the existing strengthening mechanism theory and incorporating the influence of grain boundary slip on the related strengthening mechanism and the yield strength of metal matrix, a temperature dependent yield strength analysis model of micron particle reinforced metal matrix composites is proposed. These models only require material parameters at room temperature and temperature dependent specific heat capacity at constant pressure for application. In addition, the predicted results from these models are reasonable and consistent with measured results. Moreover, based on the established models, the effects of key material parameters and main mechanisms on Young's modulus and yield strength of composites and their variation with temperature are explored. Furthermore, the variation of various control mechanisms with the particle size and temperature is clarified. It lays a theoretical foundation for the development of micron particle reinforced metal matrix composites that are suitable for high-temperature environments and for the optimization of their key parameters.