Behavior Of Heat Capacity Research Articles

Heat Capacities of α-, β-, and γ- Polymorphs of Glycine.

As a part of our effort to establish reliable thermodynamic data for amino acids, the heat capacity and phase behavior are reported for two stable polymorphs (α and γ) of glycine (aminoacetic acid, CAS RN: 56-40-6). Prior to heat capacity measurement, thermogravimetric analysis and X-ray powder diffraction were performed to determine decomposition temperatures and initial crystal structures, respectively. The literature heat capacities obtained by adiabatic calorimetry are available in the temperature interval (7-304). The literature data were used for validating performance of our relaxation (heat-pulse) calorimeter, which was used for measurement of the heat capacity of α-glycine in the temperature interval (2-267) K. The crystal heat capacities of the α- and γ-glycine were extended towards higher temperatures using Tian-Calvet calorimetry in the temperature interval (262-358) and power compensation DSC in the temperature interval (310-449) K. As a result, reference heat capacities and thermodynamic functions for the crystalline phase from 0 K up to 450/435 K for α/γ-glycine were developed. The literature heat capacities for β-glycine over the range 0 K to 295 K were treated in the same manner in order to provide thermodynamic data for all three polymorphs existing at the atmospheric pressure.

Experimental investigation and thermodynamic modeling for isobaric heat capacity of ethanol at elevated temperatures and pressures

Ethanol is a promising sustainable fuel for its environmental friendliness and renewability. Due to the association effect in ethanol molecules, the particular behavior in isobaric heat capacity was explored by combining experimental and theoretical methods. Experimental isobaric heat capacity measurements of ethanol were performed over the temperature range from (298.15 to 573.15) K and at pressures up to 15 MPa in both liquid and vapor phases by a flow calorimeter. Different association schemes were combined respectively with PC-SAFT equation of state and SAFT-VR Mie equation of state to compare their accuracy in isobaric heat capacity prediction, and it could be concluded that two-site (2B) model was better than three-site (3B) model. It was also found that PC-SAFT equation of state was able to yield good results in predicting the isobaric heat capacity far from the saturated state and critical region, however, SAFT-VR Mie equation of state showed better prediction performance near the saturated state and critical region.

The scandium effect in Gd-rich BMGs: How and why does this ingredient work better than others?

Scandium is commonly known as a superior modifier for most alloys and compounds, substantially improving their phase stability and physical properties, as well as glass-forming ability. A special case is rare-earth based magnetic metallic glasses, which are an unique platform for intra-elemental substitution due to the chemical affinity of the lanthanides, yttrium and scandium. The latter, used as an alloying additive and being the smallest atom among the entire family, can drastically affect structure formation and magnetism in these metallic glasses. The main issue is that its modifying role is not well understood due to scarce information on the scandium effects in such rare-earth systems. This study is focused on thermal and magnetic analysis of some popular Gd-based BMGs redesigned with minor Sc additives. Here, we consider temperature behavior of specific heat capacity and entropy functions for both amorphous and crystalline phases to estimate the scandium effect on GFA and thermal stability of the glasses. As well, we inspect magnetic and magnetocaloric properties of these BMGs to understand whether this very expensive metal can radically improve the alloy magnetism and make these materials suitable for potential applications.

The Cohesive Interactions in Phenylimidazoles.

This work presents a comprehensive study exploring the thermodynamics of the solid phase of a series of phenylimidazoles, encompassing experimental measurements of heat capacity, volatility, and thermal behavior. The influence of successive phenyl group insertions on the imidazole ring on thermodynamic properties and supramolecular behavior was thoroughly examined through the evaluation of 2-phenylimidazole (2-PhI), 4-phenylimidazole (4-PhI), 4,5-diphenylimidazole (4,5-DPhI), and 2,4,5-triphenylimidazole (2,4,5-TPhI). Structural correlations between molecular structure and thermodynamic properties were established. Furthermore, the investigation employed UV-vis spectroscopy and quantum chemical calculations. Additive effects arising from the introduction of phenyl groups were found through the analysis of the solid-liquid and solid-gas equilibria, as well as heat capacities. A good correlation emerged between the thermodynamic properties of sublimation and the molar volume of the unit cell, evident across 2-PhI, 4,5-DPhI, and 2,4,5-TPhI. In contrast to its isomer 2-PhI, 4-PhI exhibited greater cohesive energy due to the stronger N-H···N intermolecular interactions, leading to the disruption of coplanar geometry in the 4-PhI molecules. The observed higher entropies of phase transition (fusion and sublimation) are consistent with the higher structural order observed in the crystalline lattice of 4-PhI.

Schwarzschild black hole surrounded by a cavity and phase transition in the non-commutative gauge theory of gravity

In this work, we investigate the phase transition of the Schwarzschild black hole (SBH) inside an isothermal spherical cavity in the context of the non-commutative (NC) gauge theory of gravity, by using the Seiberg–Witten (SW) map and the star product. Firstly, we compute the NC correction to the Hawking temperature and derive the logarithmic correction to the entropy, then we derive the local temperature and local energy of NC SBH in isothermal cavity. Our results show that the non-commutativity removes the commutative divergence behavior of temperature, and prevents the SBH from the complete evaporation, which leads to a remnant black hole, and this geometry has predicted a minimal length in the order of Planck scale Θ∼lplanck. Therefore, the thermodynamic stability and phase transition is studied by analyzing the behavior of the local heat capacity and the Helmholtz free energy in the NC spacetime, where the results show that, the NC SBH has a two second-order phase transition and one first-order phase transition, with two Hawking–Page phase transition in the NC gauge theory.

Compositional behavior of heat capacity and magnetic properties in double spinel ferrites

The purpose of the work is to identify the effects of the substitution of paramagnetic ions in ferromagnetic ferrites by diamagnetic components of zinc and aluminum. The following isomorphic spinel series are the object of review: Me(1-x)ZnxFe2O4 (Me – Ni, Co, Li, Cu, Mg) and Li0.5Fe2.5-xAlxO4 (x= 0-2.5). The single-phased samples were synthesized by ceramic procedure. Heat capacity near standard temperature Cp (298.15) was studied using calorimeter methods: drop calorimeter and DSC. Magnetic parameters – magnetic moments (M) and Curie temperatures (Tc) - were determined. All Me-Zn ferrite systems are characterized by dome-shaped correlations between heat capacity Cp(298) and composition (x), which have maximum values in the equimolecular region (x=0.4-0.6). This fact coincides with the nature of the compositional dependence of magnetic moments and indicates a significant effect of the excess magnetic contribution on the total heat capacity. A noticeable influence of the cooperative Jahn-Teller effect and the associated tetragonal distortion of the cubic lattice of Cu-Zn ferrites with a low Zn content (x<0.2) is observed, which causes overestimated values of the heat capacity of these compositions. Curie temperatures reveal the rectilinear decrease with increasing diamagnetic Zn and Al content in ferrite systems. The results are presented by graphs and tables.

Computation insights of kagome structure for probing electronic and thermodynamic properties by applying external factors such as strain, spin-orbital coupling, and external magnetic field

In this study, we explored the electronic properties of a two-dimensional (2D) kagome lattice in the presence of an external magnetic field, spin-orbit coupling (SOC), and strain. Our focus was on investigating the energy-dependent behavior of the electronic heat capacity and paramagnetic spin susceptibility in response to changing factors. Employing the Green's function approach, we successfully determined the energy dependence of the electronic heat capacity and paramagnetic susceptibility using the tight-binding model. Notably, at low energies, the electronic heat capacity almost reaches the Schottky anomaly peak, while the paramagnetic susceptibility sharply decreases. Furthermore, we conducted a detailed investigation of the energy-dependent paramagnetic susceptibility and electronic heat capacity of a kagome lattice monolayer, considering the influences of SOC and magnetic field factors. Our investigation of the density of states (DOS) in the presence of SOC suggests that semimetal-to-insulator phase transitions occur. Additionally, throughout our study, we observed variations in the DOS spectrum, indicating the influence of both compressive and tensile strains. We found that these alterations, along with the splitting of levels under different conditions, led to changes in the material's electrical properties.

Rol' vakansiy v spin-zhidkostnoy modeli Yao–Li

We consider the effect of vacancies on the low-energy excitation spectrum of a quantum spin liquid realized in the exactly solvable Yao–Lee model [H. Yao and D.-H. Lee, Phys. Rev. Lett. 107, 087205 (2011)]. Physically, vacancies can appear for different reasons (e.g., because of zero magnetic moments on the lattice, or the presence of nonmagnetic impurities, or a random reduction of local bonds of magnetic moments with the remaining lattice). It is shown numerically that the finite density of random vacancies in this model leads to the accumulation of states near zero energy, which can be detected from the change of the behavior of heat capacity at low temperatures. Moreover, it is shown that the low-energy modes are localized more strongly than remaining eigenmodes. This effect is illustrated using the inverse participation ratio (IPR). In the case of time reversal symmetry breaking (e.g., due to the presence of a magnetic field), a gap is opened in the fermion spectrum of the model, and vacancy-induced localized states appear. The energies of these states depend on the structure of the interactions responsible for the time inversion symmetry breaking.

Uniaxial Quadrupole Order in a Magnet With Strong Biquadratic Exchange

Abstract—It is shown that in a magnet with a sufficiently strong biquadratic exchange interaction (compared to bilinear exchange) and spin S 1, the temperature transition from a disordered paramagnetic state to the ground ferromagnetic state passes through an intermediate magnetically ordered phase—uniaxial quadrupole ordering. For a magnet with spin S = 3/2, a phase diagram of magnetic states was constructed in the region of large values of the biquadratic exchange and it was studied how the sequence of two phase transitions—“paramagnetic state–quadrupole state” and “quadrupole state–ferromagnetic state”—manifests itself in the temperature behavior of the magnetic heat capacity and the initial magnetic susceptibility.

Uniaxial Quadrupole Order in a Magnet with Strong Biquadratic Exchange

It is shown that the temperature transition from a disordered paramagnetic state to the ground ferromagnetic state in a magnet with sufficiently strong biquadratic exchange interaction (compared to bilinear exchange) and spin S > 1 passes through an intermediate magnetically ordered phase (uniaxial quadrupole ordering). For a magnet with spin S = 3/2, a phase diagram of magnetic states in the region of large values of the biquadratic exchange is constructed in the mean-field approximation and the influence of the sequence of two phase transitions (paramagnetic state−quadrupole state and quadrupole state–ferromagnetic state) on the temperature behavior of the magnetic heat capacity and the initial magnetic susceptibility is investigated.

Low-temperature behavior of heat capacity and pho-toluminescence of a binuclear pivalate complex [Eu2(bath)2(piv)6

The low-temperature behavior of the heat capacity and photoluminescence of the previously structurally characterized binuclear pivalate complex [Eu2(bath)2(piv)6] (monoclinic, I2/a) (1), where bath = 4,7-diphenyl-1,10-phenanthroline, piv = (CH3)3CCO2-. Using the adiabatic calorimetry method, the temperature dependence of the heat capacity was measured in the temperature range 5.96–302.88 K and the thermodynamic functions Cp0(T), S0(T), Ф0(Т) and Н0(Т) - Н0(0) were calculated. The absence of low-temperature phase transformations of complex 1 was shown. It was established that in the temperature range 98-295 K, complex 1 demonstrates high temperature stability of the integral intensity of photoluminescence of the transitions of the Eu3+ ion 5D0-7Fj (j = 0.6).

Exploring magnetocaloric and heat capacity behavior in Fe doped Mn5Ge3 alloy

Magnetocaloric properties of hexagonally structured Mn5−xFexGe3 (x=0.15, 0.3, and 0.5) alloys have been investigated using DC magnetization and heat capacity measurements. The maxima of entropy change, −ΔSmmax∼5.04(5.57) J/kg K, along with an adiabatic temperature change of ΔTadmax∼5.05(7.25) K was observed for x=0.15(0.5) at an applied magnetic field H=5 T. With the scaling analysis of −ΔSm, the rescaled curves collapse onto a single universal curve anticipated by the mean-field theory, revealing a second-order type of magnetic transition. Furthermore, −ΔSmmax follows a power law of Hn with n=0.597(3), 0.591(3), and 0.586(3) for Mn5−xFexGe3 (x=0.15, 0.3, and 0.5) alloys, respectively. The refrigerant capacity (RC) is increased from 400 J/kg (for x=0.15) to 420 J/kg (for x=0.5) with Fe doping in Mn5Ge3. Moreover, the coefficient of refrigerant performance (CRP) enhances with Fe doping from 0.06 (for x=0.15) to 0.1 (for x=0.5). Thus, high RC and reasonable CRP values for earth-abundant Mn-based Mn–Fe–Ge alloys promise the potential to replace the high-cost rare-earth (Gd) and heavy metal-based metallic magnetocaloric systems for use in environment-friendly magnetic refrigeration technology.

Comment on “Crossover description of transport properties for some hydrocarbons in the supercritical region”

In this comment, we discuss Kaghazchi et al.’s recent paper “Crossover description of transport properties for some hydrocarbons in the supercritical region”. Their method employs the PC-SAFT equation of state’s (EoS) heat capacity predictions to estimate crossover thermal conductivity. However, we mention that this approach is inadequate due to the PC-SAFT EoS’s limitations near critical points. The PC-SAFT EoS assumes fluid homogeneity, which breaks down near the critical point, leading to significant density fluctuations and heterogeneity. The PC-SAFT EoS also fails to accurately predict the singularity behavior of heat capacities (Cp) and (Cv). Therefore, while the PC-SAFT EoS is generally reliable for predicting fluid properties, its limitations near the critical point should be considered.

Critical behavior of the fluctuation heat capacity near the glass transition of metallic glasses

The high-frequency shear modulus of five Zr-, Pd-, Cu-based conventional and two high-entropy bulk metallic glasses was measured in a wide temperature range up to the beginning of crystallization. Using these data and general thermodynamic relations, the “fluctuation” heat capacity ΔCf determined by local structural fluctuations in the defect regions is introduced and calculated. It is found that ΔCf temperature dependence for all metallic glasses has a large peak located slightly below or above the glass transition temperature but clearly lower than the crystallization onset temperature. The form of this peak resembles the characteristic λ-peak typical for order–disorder phase transitions. It is suggested that this ΔCf-peak reflects certain underlying critical phenomenon. The critical temperature T0 (peak temperature) and corresponding critical index α are determined. Averaged over all seven metallic glasses under investigation in the initial and relaxed states, the critical index <α>=0.26. The results obtained indicate that the fluctuations of thermal energy near the glass transition bear the marks of a continuous phase transition. However, the derived critical index is between those corresponding to a second-order phase transition (α≈0.1) and a critical transition characterized by a tricritical point (α≈0.5).

Impact of barrow entropy on geometrothermodynamics of specific black holes

In this paper, we study the effect of Barrow entropy on the thermodynamic properties and geometry of specific black holes along with the nonlinear source. We investigate the mass, temperature, thermodynamic variable, and electric potential of the black hole as well. Furthermore, we examine the behavior of heat capacity to check the stability of a black hole. Geometrothermodynamics allows us to describe interactions between thermodynamics, critical points, and phase transitions by considering the geometric characteristics of the thermodynamic equilibrium space. Our analysis demonstrates that these findings are consistent with the results derived from the classical thermodynamics of black holes.

Methodology to Characterize Thermal Properties of Thin Film Superconductors Using a DynaCool Physical Property Measurement System

We describe a methodology to characterize heat capacity <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C<inline-formula><tex-math notation="LaTeX">$_{p}$</tex-math></inline-formula></b> of 1 μm thick Nb thin films at a temperature range of 60 K to 1.8 K. We used a commercially available relaxation calorimeter device by Quantum Design DynaCool Physical Property Measurement System (PPMS). The mass of thin films is negligible compared to the minimum coarse estimate required by the heat capacity module of the PPMS. To overcome this limitation, a vertical stack of multiple diced substrates of the same material with uniform dimensions of 2.5 mm x 2.5 mm was joined by cryogenically compatible grease to form a stack resulting in a larger effective mass of the target film. The critical behavior of heat capacity in the region of the transition temperature is demonstrated. The heat capacity of Nb thin films was measured by subtracting the total heat capacity of the joining grease and stack of substrate used as addenda. Results in this work prove that a vertical stacking approach is viable for measuring the behavior of deposited thin films.

Heat Capacities of N-Acetyl Amides of Glycine, L-Alanine, L-Valine, L-Isoleucine, and L-Leucine.

As a follow-up to our effort to establish reliable thermodynamic data for amino acids, the heat capacity and phase behavior are reported for N-acetyl glycine amide (CAS RN: 2620-63-5), N-acetyl-L-alanine amide (CAS RN: 15962-47-7), N-acetyl-L-valine amide (CAS RN: 37933-88-3), N-acetyl-L-isoleucine amide (CAS RN: 56711-06-9), and N-acetyl-L-leucine amide (CAS RN: 28529-34-2). Prior to heat capacity measurement, thermogravimetric analysis and X-ray powder diffraction were performed to determine decomposition temperatures and initial crystal structures, respectively. The crystal heat capacities of the five N-acetyl amino acid amides were measured by Tian-Calvet calorimetry in the temperature interval (266-350 K), by power compensation DSC in the temperature interval (216-471 K), and by relaxation (heat-pulse) calorimetry in the temperature interval (2-268 K). As a result, reference heat capacities and thermodynamic functions for the crystalline phase from 0 K up to 470 K were developed.

Exploring the heat capacity and magnetocaloric behaviors of rare-earth based multicomponent (Ce0.71Pr0.07Nd0.22)2Fe17‐xSix alloys

The rare–earth based multicomponent (Ce0.71Pr0.07Nd0.22)2Fe17−xSix (x = 0–0.6) alloys were fabricated by conventional arc melting following the standard annealing and quenching processes. The prepared alloys were characterized by X-ray diffraction (XRD), backscattered scanning electron (BSE) microscope, energy dispersive X-ray (EDX) spectroscopy, magnetization, and heat capacity measurements. Combination of Rietveld refinement of XRD patterns, EDX/BSE analyses confirm the formation of stable rhombohedral Th2Zn17 type crystal structure with R-3 m space group in all studied samples. The investigated samples experience second-order phase transition as confirmed through phenomenological universal scaling analysis. The magnetic entropy change (−ΔSM) and associated relative cooling power (RCP) values for all compositions were found in the range of 1.1–1.4 Jkg−1K−1 and 55–66 Jkg−1 under magnetic field change (ΔH) of 0–1 T. The ΔSM curves as a function of temperature exhibit a wide working temperature range (δTFWHM) over 40 K for all studied compositions. The performance-cost ratio − ΔSM/cost and RCP/cost values are estimated to be 0.1 JK−1$−1 and 5.0 J$−1, respectively. In particular, a large adiabatic temperature change of 7.36 K and 8.09 K was achieved for x = 0.2 and x = 0.4, respectively, at low ΔH= 0–1 T. The better performance-cost ratio and good magnetocaloric properties with near-zero magnetic hysteresis loss may make these alloys promising candidates for magnetic refrigeration.

Review on PCM Heat Sink for Electronic Thermal Management Application

A significant challenge in thermal management has arisen as a result of the rising demand for high-performance electronic devices. The efficiency, size, and weight of conventional cooling methods like liquid and air cooling are constrained. Due to their high storage of latent heat capacity and isothermal phase transition behavior, phase change materials (PCMs) have become a promising thermal management solution. The purpose of this experimental study is to evaluate the performance of a PCM heat sink for electronic thermal regulation. The PCM heat sink is made up of a PCM module attached to a typical heat sink. To improve heat dissipation capabilities, the PCM module uses a PCM material with a suitable phase change temperature and encapsulation. The experimental setup involves simulating real-world operating conditions by applying controlled heat loads to electronic components. By observing temperature changes, thermal resistance, and transient response, the PCM heat sink’s thermal performance is assessed. To evaluate the superiority of the PCM heat sink, a comparison is made with traditional air-cooled and liquid-cooled heat sink configurations. The experimental investigation’s findings show that the PCM heat sink performs better in terms of thermal management than traditional cooling techniques. The phase change process used by the PCM efficiently absorbs and stores extra heat produced by electronic parts, improving temperature regulation and lowering temperature gradients. Lower component temperatures and higher operational reliability are the results of the PCM heat sink’s improved thermal resistance and heat dissipation efficiency. A further benefit of the PCM heat sink’s isothermal behavior during the phase transition is that it prevents temperature spikes and lessens the effects of heat stress on the electronic devices. The long cooling times provided by the PCM material’s high latent heat storage capacity allow for prolonged operation without affecting device performance. This experimental study concludes by demonstrating the efficiency of a PCM heat sink for electronic thermal management. The design of heat sinks with PCM integration offers notable enhancements in temperature control, thermal resistance, and system overall reliability. The results of this research help to advance thermal management strategies, which makes it easier to create efficient electronic devices with better cooling capacities.

Peculiarities of the Eutectic Mg–Li Alloy Thermal Expansion, Heat Capacity and Thermal Conductivity Behavior in the Temperature Range of 80 K to 293 K

Peculiarities of the Eutectic Mg–Li Alloy Thermal Expansion, Heat Capacity and Thermal Conductivity Behavior in the Temperature Range of 80 K to 293 K