Change In Specific Heat Research Articles

Weakly coupled Type-II superconductivity in a breathing Kagome metal ZrRe2

We present a comprehensive investigation of the superconducting properties of ZrRe2, a Re-based hexagonal Laves compounds. ZrRe2 crystallizes in a C14-type structure (space group P63/mmc), where the Re atoms form a breathing Kagome lattice, with cell parameters a = b = 5.2682(5) Å and c = 8.63045 Å. Through transport measurements, the superconducting transition is observed with Tconset = 6.44 K and Tczero = 6.06 K. In magnetization measurements(ZFC-FC) superconducting transition occurs at 6.12 K. The measured lower and upper critical fields are 6.27 mT and 7.84 T, respectively. Measurements of the specific heat capacity confirm the presence of bulk superconductivity, with a normalized specific heat change of ΔCe/γTc=1.63 and an electron-phonon strength of λep=0.69. DFT calculations revealed that the band structure of ZrRe2 is intricate and without van Hove singularity.

Impact of Acoustic and Optical Phonons on the Anisotropic Heat Conduction in Novel C-Based Superlattices.

C-based XC binary materials and their (XC)m/(YC)n (X, Y ≡ Si, Ge and Sn) superlattices (SLs) have recently gained considerable interest as valuable alternatives to Si for designing and/or exploiting nanostructured electronic devices (NEDs) in the growing high-power application needs. In commercial NEDs, heat dissipation and thermal management have been and still are crucial issues. The concept of phonon engineering is important for manipulating thermal transport in low-dimensional heterostructures to study their lattice dynamical features. By adopting a realistic rigid-ion-model, we reported results of phonon dispersions ωjSLk→ of novel short-period XCm/(YC)n001 SLs, for m, n = 2, 3, 4 by varying phonon wavevectors k→SL along the growth k|| ([001]), and in-plane k⟂ ([100], [010]) directions. The SL phonon dispersions displayed flattening of modes, especially at high-symmetry critical points Γ, Z and M. Miniband formation and anti-crossings in ωjSLk→ lead to the reduction in phonon conductivity κz along the growth direction by an order of magnitude relative to the bulk materials. Due to zone-folding effects, the in-plane phonons in SLs exhibited a strong mixture of XC-like and YC-like low-energy ωTA, ωLA modes with the emergence of stop bands at certain k→SL. For thermal transport applications, the results demonstrate modifications in thermal conductivities via changes in group velocities, specific heat, and density of states.

Exploring the denaturations in cancer and non-cancer DNA molecules by optical absorption, thermal, and electric measurements: A case study

In this article, we carried out the temperature dependent UV-Visible (UV-Vis) spectroscopy, differential scanning calorimetry (DSC), and electrical studies for normal and cancerous (glioma) DNA samples of single patient. Based on this method, we were able to monitor the denaturation process and thermal stability in these molecules. From the temperature dependent optical absorption data, we calculated various optical parameters for these two types of samples. The optical band gap of these samples were also estimated and discussed as per the experimental conditions. The various optical parameters calculated indicate that mutated (tumor) DNA is less stable than the normal one. From the DSC data, clear melting peaks were observed for the tumor and normal samples. Also various thermodynamic parameters like change in enthalpy (ΔH), entropy (ΔS), and specific heat (Cp) were estimated. From the thermal study, it seems that the tumor DNA is less stable. Further from the electrical or current-voltage (I-V) characteristics data, the resistance for normal DNA decreases with temperature. But for tumor sample, it show anomalous behavior (like decreasing and then increasing trend) with temperature. For electrical transport, small polaron hopping could be the possible transport mechanism in the current sample. Here from these studies, the tumor sample seems more disordered, and structural fluctuations due to the speculated structure could be the best reason for this behavior. If such kind of molecular (at nano scale range) studied are done more vividly, then these calculated parameters of the molecule could be explored for further confirmation/diagnostics of the diseases in addition to clinical investigations.

Thermal and structural characteristics of date-pits as digested by Trichoderma reesei

The objective of this study was to develop functional date-pits by mold digestion for the potential use in food products. Whole date-pits (WDP) and defatted date-pits (DDP) were digested by mold Trichoderma reesei at 20 °C. T. reesei consumed date-pits as nutrients for their growth, and DDP showed higher growth of molds as compared to the WDP. The mold digested WDP and DDP samples showed an increased water solubility and hygroscopicity as compared to the samples prepared by autoclaved. This indicated that the mold digestion transformed date-pits to hydrophilic characteristics. Thermal analysis indicated a structural change at −3.2 °C for the untreated WDP and it was followed by a glass transition shift (i.e. onset: 138 °C and a specific heat change: 295 J/kg oC), and an endothermic peak at 196 °C with enthalpy of 68 J/g for the solids melting-decomposition. Similar characteristics were also observed for treated samples with the two glass transitions. The total specific heat changes for WDP, autoclaved-WDP, and digested-WDP were observed as 295, 367, and 328 J/kg oC, respectively. The total specific heat changes for DDP, autoclaved-DDP, and digested-DDP were observed as 778, 1329, and 1877 J/kg oC, respectively. This indicated that mold digestion transformed more amorphous fraction in the DDP. The energy absorption intensities of the Fourier Transform Infrared (FTIR) spectra for the selected functional groups decreased by the mold digestion.

Eu Doping in the GdCd7.88 Quasicrystal and Its Approximant Crystal GdCd6.

The effect of Eu doping in the Tsai quasicrystal (QC) GdCd7.88 and its periodic 1/1 approximant crystal (AC) GdCd6 are investigated. This represents the first synthesis of Eu-containing stable QC samples, where three samples with the final composition Gd1-xEuxCd7.6±α at Eu doping concentrations x = 0.06, 0.13, and 0.19 are obtained (α ∼ 0.2). They are compared to two 1/1 ACs with compositions Gd1-xEuxCd6 (x = 0.12, 0.16). In addition, a new type of 1/1 AC, differing only by the inclusion of extra Cd sites unique to the Eu4Cd25 1/1 AC, has been discovered and synthesized for the concentrations Gd1-xEuxCd6+δ (x = 0.25, 0.33, 0.45, 0.69, 0.73, and 0 < δ ≤ 0.085). Due to the preferred cube morphology of its single grains, we refer to them as c-type 1/1 ACs and to the conventional standard ones as s-type. In both QCs and s-type ACs, the Eu content appears to saturate at a concentration of ∼20%. On the other hand, any Gd| Eu ratio is allowed in the c-type ACs, varying continuously between GdCd6 and Eu4Cd25. We describe and contrast the changes in composition, atomic structure, specific heat, and magnetic properties induced by Eu doping in the quasicrystalline phase and the s-type and c-type 1/1 ACs. By comparing our results to the literature data, we propose that the occupancy of the extra Cd sites can be used to predict the stability of Tsai-type quasicrystalline phases.

Monte Carlo study of magnetocaloric effect and magnetic properties of the nano- borophene bilayer with RKKY exchange interactions of a mixed spin 2 and 3/2

In this study, we have studied the magnetic properties and magnetocaloric effect of the nano-borophene bilayer with RKKY (Ruderman-Kittel-Kasuya-Yosida) exchange interactions of mixed spin 2 and 3/2 using Monte Carlo calculations. In the first part of this investigation, the ground state phase diagrams for zero temperature are reported and discussed. We also determined the critical temperature for varying the number of non-magnetic layers (NML) and the interacting couplings Jss. In the second part, we investigated the influence of the parameter NML, the exchange couplings Jss and Jσσ, and the crystal field on the total magnetizations and the magnetic hysteresis loop. The specific heat and magnetic entropy changes versus of the temperature under the effect of different external magnetic fields and the parameter Jss. Finally, we analyzed the relative cooling power (RCP) for distinct external magnetic field and Jss.

Phase Transitions in Boron Carbide.

The idealized rhombohedral unit cell of boron carbide is formed by a 12-atom icosahedron and a 3-atom linear chain. Phase transitions are second order and caused by the exchange of B and C sites or by vacancies in the structure. Nevertheless, the impact of such minimal structural changes on the properties can be significant. As the X-ray scattering cross sections of B and C isotopes are very similar, the capability of X-ray fine structure investigation is substantially restricted. Phonon spectroscopy helps close this gap as the frequency and strength of phonons sensitively depend on the bonding force and mass of the vibrating atoms concerned. Phase transitions known to date have been identified due to significant changes of properties: (1) The phase transition near the chemical composition B8C by clear change of the electronic structure; (2) the endothermic temperature-dependent phase transition at 712 K according to the change of specific heat; (3) the high-pressure phase transition at 33.2 GPa by the drastic change of optical appearance from opacity to transparency. These phase transitions affect IR- and Raman-active phonons and other solid-state properties. The phase transitions at B~8C and 712 K mean that a well-defined distorted structure is converted into another one. In the high-pressure phase transition, an apparently well-defined distorted structure changes into a highly ordered one. In all these cases, the distribution of polar C atoms in the icosahedra plays a crucial role.

Analisis Kalor pada Pengeringan Garam dengan Alat Pengering Garam Berkapasitas 25 Kg/Proses

This study aimed to analyze the heat in a salt dryer with a capacity of 25 kg/process. The material used in this research is coarse salt, which is salt that has cystic grains with a larger size but tastes the same as ordinary salt in general. It has a larger and coarser texture than the salt we usually use, which is fine salt. The analysis was carried out by considering changes in temperature and specific heat. The results of the salt drying test with a capacity of 25 kg/process obtained an average heat transfer of 765.08 Joules. The average heat capacity obtained from the salt drying test is 19.106 J/°K. The average shrinkage of the water content is 6.6% according to the SNI 3556-2016 standard, which is a maximum of 7%. The average yield in the salt drying test process is 93.3%.

Electrocaloric effect and ferroelectric properties of the graphene bilayer with mixed spins S=5/2 and σ=2: A Monte Carlo simulations

Monte Carlo simulations are utilized to investigate the electrocaloric and ferroelectric properties of a bilayer graphene with mixed spins S = 5/2 and σ = 2. Ground state phase diagrams are provided for several physical parameters. Additionally, the effects of exchange couplings (S-S), (σ-σ), and the crystal field on partial and total polarizations, electric susceptibilities, and electric hysteresis loops have been investigated. Critical temperatures for the graphene bilayer have been determined. The influence of an external electric field on specific heat change, electric entropy change, and relative cooling power (RCP) has been studied. This research holds potential benefits for the design of refrigeration devices and the evaluation of their efficiency.

Three-dimensional critical behavior and magnetocaloric effect in Yb14MnSb11

Systematic investigations were performed on the nature of the magnetic properties of Yb14MnSb11, which is the first ferromagnetic Kondo lattice compound in the underscreened limit and one of the highest thermoelectrically efficient materials with p-type conduction. The Rhode-Wohlfarth ratio (RWR) is estimated to be 1.01, which demonstrates the localized nature of the ferromagnetism in Yb14MnSb11, consistent with the predicted Ruderman–Kittel–Kasuya–Yosida (RKKY) like exchange interaction. Detailed analyses on critical behavior indicate a second-order ferromagnetic phase transition with critical exponents β = 0.307(2), γ = 0.923(9), and δ = 4.003(4), demonstrating a three-dimensional critical behavior with long-range interaction. Furthermore, the magnetocaloric effect and relative cooling power are estimated to be 0.772 J kg−1 K−1 and 16.43 J kg−1 at 5 T, respectively. The magnetic transition temperature of TC = 51.9(3) K is strictly estimated by evaluating the magnetic change of specific heat [ΔCp(T,H)]. The rare d-electron ferromagnetic Kondo lattice, small magnetocaloric effect, and high-temperature large thermoelectric efficiency making Yb14MnSb11 to be a system of considerable interest.

Influence of calcium on specific heat capacity and changes in thermodynamic functions of aluminum conductor alloy AlTi0.1

Influence of calcium on specific heat capacity and changes in thermodynamic functions of aluminum conductor alloy AlTi0.1

Study of Magnetic and Magnetocaloric Properties of the Nano‐Graphene of Mixed Spins S = 3/2 and σ = 2: A Monte Carlo Simulation

The magnetic and magnetocaloric properties of the nano‐graphene monolayer structure consisting of mixed spins S = 3/2 and σ = 2 are studied by using Monte Carlo simulations. The ground‐state phase diagrams corresponding to several physical parameters are first discussed. The influence of the number of lattice sites on the total and partial magnetizations and the magnetic susceptibilities has been investigated. The critical temperature is deduced. The effect of exchange interaction, external magnetic, and crystal field on total magnetizations is studied. Magnetic hysteresis cycles are obtained. Specific heat change and magnetic entropy changes are inferred for several magnetic fields. Finally, the relative cooling power is determined.

Temperature dependent mechanical unfolding and refolding of a protein studied by thermo-regulated optical tweezers

Temperature is a useful system variable to gather kinetic and thermodynamic information from proteins. Usually, free energy and the associated entropic and enthalpic contributions are obtained by quantifying the conformational equilibrium based on melting experiments performed in bulk conditions. Such experiments are suitable only for those small single-domain proteins whose side reactions of irreversible aggregation are unlikely to occur. Here, we avoid aggregation by pulling single-protein molecules in a thermo-regulated optical tweezers. Thus, we are able to explore the temperature dependence of the thermodynamic and kinetic parameters of MJ0366 from Methanocaldococcus jannaschii at the single-molecule level. By performing force-ramp experiments between 2°C and 40°C, we found that MJ0366 has a nonlinear dependence of free energy with temperature and a specific heat change of 2.3 ± 1.2 kcal/mol∗K. These thermodynamic parameters are compatible with a two-state unfolding/refolding mechanism for MJ0366. However, the kinetics measured as a function of the temperature show a complex behavior, suggesting a three-state folding mechanism comprising a high-energy intermediate state. The combination of two perturbations, temperature and force, reveals a high-energy species in the folding mechanism of MJ0366 not detected in force-ramp experiments at constant temperature.

An analytical approach to the anomalous specific heat of water

In this paper, we use the recent confirmed water two-liquid model to give an analytical description of the observed anomalous behavior of water specific heats. We will show how the two-liquid model implies that water net excluded volume, ve, can not be taken constant but depends on the sample thermal conditions. Combining these ideas, it will be shown that, at constant volume, the specific heat (CV) is invariant with changes of ve. Otherwise, at constant pressure, the specific heat (CP) changes with the changing ve, giving CP a very characteristic shape. This is how our model explains the physical origin of the contrast between the ”normal” behavior of CV and the non-usual behavior observed in CP and CP – CV. Finally we give an analytical form to these issues that agree with the experimental data.

Superconducting properties of the C15-type Laves phase ZrIr2 with an Ir-based kagome lattice

We report systematic studies on superconducting properties of the Laves phase superconductor ZrIr2. It crystallizes in a C15-type (cubic MgCu2-type, space group ) structure in which the Ir atoms form a kagome lattice, with cell parameters a = b = c = 7.3596(1) Å. Resistivity and magnetic susceptibility measurements indicate that ZrIr2 is a type-II superconductor with a transition temperature of 4.0 K. The estimated lower and upper critical fields are 12.8 mT and 4.78 T, respectively. Heat capacity measurements confirm the bulk superconductivity in ZrIr2. ZrIr2 is found to possibly host strong-coupled s-wave superconductivity with the normalized specific heat change ΔC e/γ T c ∼ 1.86 and the coupling strength Δ0/k B T c ∼ 1.92. First-principles calculations suggest that ZrIr2 has three-dimensional Fermi surfaces with simple topologies, and the states at Fermi level mainly originate from the Ir-5d and Zr-4d orbitals. Similar to SrIr2 and ThIr2, spin–orbit coupling has dramatic influences on the band structure in ZrIr2.

Characteristics of crystalline and amorphous fractions of date-pits as treated by alcohol-water pressure cooking

Date-pits are waste from date fruit processing industry and their valorisation as a lignocellulose biomaterial could generate economic gain. In this work, defatted date-pits (DDP) from whole date-pits (WDP), was soaked in alcohol-water followed by pressure-cooking. Two fractions of date-pits were developed, one as residue fraction (REP) and another one was supernatant fraction (SUP). REP showed higher level of hemicellulose and lower level of lignin (P < 0.05) compared to SUP. Similar water absorption, increased hygroscopicity, and decreased solubility were observed for REP compared to SUP. SEM showed that REP with bigger size particles as compared to the SUP fraction. SUP fraction showed two glass transitions, while REP showed single glass transition. Total specific heat changes of REP, and SUP fractions were 149 and 1032 J/kg oC, respectively, which indicated that SUP is mainly amorphous in composition. This was also supported by XRD data having Ruland-crystallinity of 52.0% (i.e. REP) and 9.6% (i.e. SUP), respectively. FTIR analysis indicated different molecular structure of SUP as compared to REP fraction as evidenced from the highest energy absorption for all selected functional groups. Overall, the results showed that this extraction method was effective to produce two distinctive fractions of date-pits with varied crystallinity.

Interface chemistry effects in nanofluids: Experimental and computational study of oil-based nanofluids with gold nanoplates

The chemistry of interfaces and its relation with energy storage at and transport through solid–liquid interfaces in heat transfer nanofluids is a very unexplored terrain. Here we discuss how the magnitude of the changes in specific heat and thermal conductivity of the base fluid, upon dispersion of a nanomaterial, depends on the surface chemistry of that nanomaterial. We focus on nanofluids with Au nanoplates from an integrated experimental and theoretical perspective, and compared our findings with those previously reported for nanofluids with Pd nanoplates in the same base fluid. Pd and Au are known to have different surface chemistry, and so are the structures of the solid–liquid interfaces and the thermal properties of these nanofluids. It was experimentally found that for mass fractions in the order of 0.01 wt%, Pd and Au nanoplates provide enhancements of 5.9% and 1.6% in specific heat, and enhancements of 12.5% and 17.9% in thermal conductivity, at 373 K. It was verified using density functional theory and classical molecular dynamics simulations that base fluid molecules can chemisorb on Pd surfaces, but not on Au surfaces. This work suggests that the stronger interactions between species at solid–liquid interfaces, the higher the specific heat enhancements and the lower the thermal conductivity enhancements at high temperature.

Thermodynamic properties and magnetocaloric effect of a graphdiyne bilayer with RKKY interaction

Based on the Monte Carlo method, a ferromagnetic mixed spin-3/2 and spin-5/2 Ising model is extended to research the thermodynamic and magnetocaloric properties of the graphdiyne bilayer under the presence of the external magnetic field. The results of the finite-size effect show that the thickness of the nonmagnetic layers and the total number of the atoms have the significant influence on the studied quantities including magnetization, susceptibility, internal energy, specific heat, magnetic entropy, and magnetic entropy change. In addition, the maximum of the magnetic entropy change -ΔSm can be improved by increasing the exchange interaction between atoms b in the bottom magnetic surface Jb/Ja and adding the nonmagnetic layers L. We also obtain the relative cooling power RCP under the change of the external field Δh/Ja.

Evaluation of Different Slip Mechanisms in Relation to Various Nanofluid Consideration Factors

In this study, the influence of various factors: nanoparticle type (Al2O3, SiO2, and TiO2), concentration (0.05%, 0.1%, and 1%), and flow velocity (Re = 50, 100, and 200) on various forces (slip mechanism) act on nanoparticles is analyzed which can affect heat transport characteristics. The study reveals that the concentration is a more significant parameter for enhancement in Nusselt number compared to others. All nanoparticles have the same size of 50 nm and are spherical in shape. The variation in nanoparticle type results in change in density, thermal conductivity, specific heat, and viscosity of nanofluids. The variation in nanoparticle type influences the gravity, Brownian, Thermophoresis the most. On the other hand, the change in velocity of nanofluids influences the Drag, Thermophoresis, Shaffman Lift, Magnus force the most.

Possible quadrupole-order-driven commensurate-incommensurate phase transition in B20 CoGe

The B20-type cobalt germanide CoGe was investigated by measuring the specific heat, resistivity, and $^{59}$Co nuclear magnetic resonance (NMR). We observed a phase transition at $T_Q=13.7$ K, evidenced by a very narrow peak of the specific heat and sharp changes of the nuclear spin-spin ($T_2^{-1}$) and spin-lattice ($T_1^{-1}$) relaxation rates. The fact that the entropy release is extremely small and the Knight shift is almost independent of temperature down to low temperatures as anticipated in a paramagnetic metal indicates that the $T_Q$ transition is of non-magnetic origin. In addition, we detected a crossover scale $T_0\sim30$ K below which the resistivity and the NMR linewidth increase, and $T_1^{-1}$ is progressively distributed in space, that is, a static and dynamical spatial inhomogeneity develops. While the order parameter for the $T_Q$ transition remains an open question, a group-theoretical analysis suggests that the finite electric quadrupole density arising from the low local site symmetry at cobalt sites could drive the crystal symmetry lowering from the P2$_1$3 symmetry that is commensurate to the R3 symmetry with an incommensurate wavevector, which fairly well accounts for the $T_Q$ transition. The quadrupole-order-driven commensurate-incommensurate phase transition may be another remarkable phenomenon arising from the structural chirality inherent in the noncentrosymmetric B20 family.