Specific Heat Research Articles (Page 1)

Abstract The study of strong electron correlations has significantly advanced the frontiers of condensed matter physics, especially in relation to correlation-driven quantum phase transitions (QPTs). In the vicinity of QPTs, quantum critical fluctuations of multiple degrees of freedom enable the emergence of exotic many-body states and quantum critical behaviours beyond the Landau paradigm. Recently, magnetic frustration, traditionally associated with insulating magnets, has been recognized as pivotal to investigating new phases of matter in correlation-driven Kondo breakdown QPTs that are not clearly associated with broken symmetry. The nature of these new phases, however, remains underexplored. Here, we report quantum criticalities emerging from a cluster spin-glass in the heavy-fermion metal TiFexCu2x-1Sb, where frustration originates from intrinsic disorder. Specific heat and magnetic Grüneisen parameter measurements under varying magnetic fields exhibit quantum critical scaling, indicating a quantum critical point (QCP) near 0.13 Tesla. As the magnetic field increases, the cluster spin-glass phase is progressively suppressed. Upon crossing the QCP, resistivity and Hall effect measurements reveal enhanced screening of local moments and an expanding Fermi surface, consistent with the Kondo breakdown scenario. Our findings uncover a new family of iron-based heavy-fermion metals with intricate interplay of multiple degrees of freedom, enabling the exploration of unconventional excitations and exotic quantum critical states and behaviours.

Solar thermal energy plays a vital role among renewable energy sources, with enhancing solar collector performance remaining a key research priority. This study investigates the efficiency improvement of a mini-channel flat plate collector integrated with a novel composite phase change material (CPCM), Pb(NO3)2 -NaNO3 -NaCl/Boron Nitride. The incorporation of CPCM effectively minimizes heat loss, stores surplus thermal energy, and provides passive cooling to the collector. Experimental results revealed that the collector outlet temperature decreased from 62°C to 52°C, resulting in a thermal efficiency of 90%. The maximum power output reached 400 W, while the system stored 50 kJ of thermal energy. The CPCM exhibited a melting temperature of 110°C and a solidification temperature of 115°C, maintaining stability with only a 2°C variation after multiple thermal cycles. Thermogravimetric analysis confirmed excellent stability with 40% degradation at 700°C. Furthermore, the CPCM demonstrated a thermal conductivity of 0.92 W/m ċ K, a latent heat of 12.53 J/g, and a specific heat capacity of 0.64 J/g ċ K. The mini-channel configuration enhanced heat flux by 30% with a pressure drop of 100 Pa at 6 L/min flow rate. CFD simulations conducted using Python verified that CPCM integration and the mini-channel design substantially improved collector performance.

In this study, molybdenum disulfide (MoS2)-based water nanofluids were prepared and stabilized using two surfactants with opposite charges: the cationic cetyltrimethylammonium bromide (CTAB) and the anionic sodium lauryl sulfate (SLS). Different MoS2:surfactant ratios (1:1, 1:2, and 1:3) were examined to identify the optimal formulation ensuring stable dispersion. Stability was evaluated through dynamic light scattering (DLS), zeta potential, and UV–Vis spectroscopy analyses. The results showed that the MoS2:SLS (1:3) nanofluid achieved the highest stability, characterized by a zeta potential of −38 mV and a mean particle size of approximately 290 nm. Thermophysical properties were then investigated for nanoparticle concentrations of 0.05, 0.1, and 0.2 wt%. The 0.1 wt% nanofluid exhibited the best performance, showing a thermal conductivity enhancement of about 49% and an increased specific heat capacity compared with pure water. This improvement is attributed to uniform nanoparticle dispersion and enhanced phonon transport. Overall, the results demonstrate that the anionic SLS surfactant at a 1:3 ratio effectively enhances the stability as well as the thermal performance of MoS2–water nanofluids, making them promising candidates for thermal management and energy systems applications.

Among the various mysteries in cuprate high temperature superconductors, the pseudogap (PG) phase stands out for the difficulty in pinning down its origin and its close connection to unconventional superconductivity. It appears above the superconducting transition temperature ​, where part of the low energy spectral weight becomes depleted and several competing or intertwined orders such as charge and pair density waves, nematicity, and spin fluctuations begin to develop. A persistent challenge lies in the systematic discrepancies revealed by different experimental probes, as transport measurements locate the critical doping near , spectroscopic studies around , and symmetry sensitive techniques close to . These variations reflect the distinct sensitivities of each probe to correlation length scales and electronic coherence rather than experimental inconsistency. This review brings together evidence from angle resolved photoemission spectroscopy (ARPES), scanning tunneling microscopy or spectroscopy (STM or STS), nuclear magnetic resonance (NMR), resonant X ray scattering (RXS), and optical conductivity, showing that the pseudogap is a spatially heterogeneous, symmetry breaking electronic state whose onset temperature decreases roughly linearly with doping and terminates sharply at . Three complementary theoretical frameworks, namely quantum criticality, Mott physics, and intertwined orders, collectively describe these observations. Experiments showing the abrupt disappearance of nematic order and a logarithmic rise in the electronic specific heat coefficient suggest that the pseudogap terminates at a quantum critical point. This transition appears to separate a correlation dominated pseudogapped metal from a coherent Fermi liquid phase rather than occurring through a gradual crossover. The doping level identified from transport data aligns with optimal superconductivity, implying that the recovery of long range phase coherence rather than the complete removal of pseudogap features is what ultimately enhances . Unresolved questions include reconciling probe dependent boundaries through systematic cross technique studies on identical crystals and developing correlation length resolved probes to distinguish spatial scales of electronic reconstruction. A major theoretical challenge remains to unify competing frameworks and to elucidate how the pseudogap terminates and coherence emerges at , which represents a key step toward a microscopic theory of high temperature superconductivity in cuprates.

Abstract Thermoelectric materials convert heat directly into electricity and are therefore promising for energy harvesting and environmental applications. Ideal high-performance thermoelectrics combine ultralow lattice thermal conductivity, κ L , with high carrier mobility, a paradigm commonly termed phonon-glass electron-crystal. However, strong coupling between electronic and phononic transport complicates simultaneous optimization of these properties. Because κ L is largely independent of electronic transport, targeted suppression of κ L is an effective route to partially decouple heat and charge transport. This Review summarizes recent advances in reducing κ L via two complementary approaches: phonon engineering of bulk nanostructured systems and phonon engineering of low-dimensional materials. In bulk systems, κ L may be minimized while retaining high electrical conductivity and maximizing the thermoelectric figure of merit ZT by controlling three fundamental phonon parameters: the volumetric specific heat c v , the phonon group velocity v g , and the phonon relaxation time τ . Low-dimensional architectures, including superlattices, nanowires, and nanocomposites, supply additional levers to suppress lattice heat transport and to tailor the electronic structure. Integrating multiscale and multimodal phonon-control strategies enables significant reductions in κ L without sacrificing electronic performance, thereby advancing the phonon-glass electron-crystal paradigm.

Historical and registered earthquakes of great magnitude have caused destruction with injuries and deaths in mainland Portugal. This work uses data not yet used to investigate a possible increase of the temperature of the water in the region and possible consequences when materials with different thermal properties are in physical contact. A temporal link between geomagnetic anomalies recorded by Permanent Geomagnetic Observatories and earthquakes detected in the Iberian Peninsula and adjacent regions during the month of February in 1969 was found using data from 3 Observatories located in the Iberian Peninsula. The anomaly recorded on February 27,1969 is due to large alterations in the direction (inclination) of the geomagnetic field and associated variations in the electric field of the atmosphere recorded in Lisbon. The source of the first earthquake filled and registered in the early morning of February 28 was in the Atlantic Ocean. The variations in the geomagnetic inclination, detected in the records, may have led to rotations of the water molecules to align their electric dipoles with the electric field in the region, originating heat release. As consequence, an increase of temperature occurred. The analysis of the arrival times of the first seismic waves at the seismic stations located in Lisbon, Coimbra and Porto (cities located near the Atlantic Ocean at different latitude values) combined with the distances of the cities to the earthquake source, shows different values of the average speed of propagation of the seismic waves. The values found decrease from Porto to Lisbon. Seismic velocity values change with temperature and pressure. As we are talking about the same earthquake, different temperature values found in the last part of the wave paths seems to be responsible for this fact. This means that temperature values at lower latitude values (Lisbon city and earthquake source) are higher. The increase of the temperature values of water contributes to the opening of cracks and faults in the region with the entry of hot water that can reach great depths, increasing the temperature, the volume, and the pressure of the materials. When materials with different values of thermodynamic properties like specific heat, thermal conductivity and thermal expansion coefficient are in physical contact, the heat received from the water can originate perturbations like pressure gradients of thermal origin whose value can increase causing rupture of the materials. The presence of water with elevated temperatures in deep regions can also change the velocity of chemical reactions with heat release, increasing the described effect.

In this study, we systematically investigated the mechanisms enabling localized solidification crack-free welding of directionally solidified (DS) 247LC superalloy using a single-mode fiber laser, with a particular focus on the correlation with the columnar-to-equiaxed transition (CET) theory. Welding was performed on a single DS grain under twelve conditions, varying heat input (1, 1.5, 2 J/mm), welding speed (500, 750 mm/s), and energy density (7.1, 14.0 J/mm<sup>2</sup>). The weld bead geometry was found to depend on the energy density, resulting in either heat conduction mode (7.1 J/mm<sup>2</sup>) or keyhole mode (14.0 J/mm<sup>2</sup>). In the heat conduction mode, solidification cracking was completely suppressed across all conditions, while in the keyhole mode, cracking was prevented under some conditions but appeared along the bead centerline under specific high heat input conditions (C-3 and C-4). Crystallographic analysis revealed that reduced epitaxial growth rates and increased high-angle grain boundaries were associated with crack formation in these cases. CET maps were calculated using the Thermo-Calc Additive Manufacturing module to elucidate the relationship between weld morphology and crack susceptibility, reflecting rapid solidification behavior under laser welding conditions. The results showed that heat conduction mode welds remained within the columnar growth region, while keyhole mode welds under higher heat input shifted towards the CET boundary or equiaxed region, correlating strongly with crack formation. These findings demonstrate that the suppression of CET and the promotion of epitaxial growth are critical for achieving crack-free welding in DS 247LC superalloy using single-mode fiber lasers, providing practical guidelines for advanced manufacturing and repair of turbine components under rapid solidification conditions.

The recent development of first-principles molecular dynamics (MD) simulations for calculating the specific heat ($C$) of liquids and glasses is reviewed. Liquid and glass states share the properties in that there is no periodicity and the atom relaxation plays a crucial role in their thermodynamic properties. For a long time, these properties have hindered the development of an appropriate theory of $C$ for these states. The total energy approach based on density-functional theory (DFT) provides a universal method for calculating $C$, irrespective of the material states. However, even DFT-based MD simulations yield different values for a thermodynamic property of liquids and glasses, depending on the setup of MD simulations, aside from the convergence problem. The essential problem is atom relaxation, which affects the relationship between the energy and temperature ($T$). While temperature is determined by the equilibrium state, glasses exhibit many metastable states. These metastable states are stable within their relaxation times, leading to the difficult problem of hysteresis, which is the most profound consequence of irreversibility. Notably, irreversibility occurs even in quasistatic processes. This is the most difficult and confusing point in the thermodynamics literature. Here, a consistent treatment of equilibrium properties and irreversibility in adiabatic MD simulations, which has no frictional term, is presented by considering multi-timescales. The leading principle to determine the equilibrium is provided by the second law of thermodynamics. The basic concepts and the usefulness of the total energy approach in real calculations are explained.&#xD.

This study examines the thermophysical properties of ethylene glycol–glycerol (60:40 v/v) hybrid nanofluids containing graphene nanoplatelets (GNPs) and silver nanoparticles (Ag) at concentrations of 0.1–0.5 vol.%. The nanofluids were synthesized using a two-step method with Tween-80 surfactant to enhance dispersion stability. High-resolution transmission electron microscopy (TEM) and Raman spectroscopy confirmed the morphology, lateral size, few-layer structure of GNPs, and the attachment of Ag nanoparticles. The addition of surfactant increased the zeta potential from 15.7 mV to 35.2 mV for the 0.1 vol.% GNPs/Ag formulation, indicating a marked improvement in colloidal stability. Thermal conductivity enhancement reached 102.85% at 0.1 vol.% with only a 19.84% viscosity increase. Higher nanoparticle loadings improved conductivity further but caused significant viscosity increases and reduced stability. Specific heat capacity decreased by up to 46.45%, potentially benefiting rapid thermal response applications but limiting heat storage capacity. Comparison with recent literature showed that the present formulation outperforms several similar Ag- and GNP-based nanofluids in thermal conductivity enhancement while maintaining manageable viscosity. This study is the first to report such high conductivity improvement in an EG–GLY-based hybrid nanofluid at ultra-low loading, achieved through optimized surfactant use, validated structural characterization, and benchmarking against literature. Low-concentration GNPs/Ag hybrid nanofluids, particularly at 0.1 vol.%, offer strong potential for thermal management applications where high heat transfer performance and acceptable pumping requirements are critical. However, stability limitations at higher concentrations and viscosity–conductivity trade-offs highlight the need for further optimization before large-scale deployment.

High-fidelity shock experiments were performed on copper powders with controlled porosity via improved target fabrication and assembly. Optical velocimetry and multi-channel pyrometry were used to obtain Hugoniot data, isentropic release paths, and interface temperature histories. The results validate a modified two-phase equation of state (EOS) for copper based on the framework of Greeff et al. The measured Hugoniot shows good agreement with the present model but exhibits significant softening above ∼156 GPa relative to the original Greeff EOS, indicating that reduction in lattice specific heat becomes essential when shock temperatures exceed three times the melting point (T > 3Tm). Unloading behavior matches hydrodynamic simulations incorporating the recalibrated EOS, confirming its accuracy for off-Hugoniot states. Theoretical analysis of temperature release profiles suggests that the thermal conductivity of shocked copper powders may be considerably higher than first-principles predictions. Crucially, despite heterogeneity in shock heating, the macroscopic dynamic response of copper powders with a porosity of ∼1.7 is well captured by an average-density EOS model, supporting the use of porous material experiments for EOS validation under extreme conditions.

The article discusses an approach to modeling thermodynamic processes in food industry production systems using MATLAB PDE Toolbox. The main goal of the research is to create digital twins that allow simulating thermal processes and optimizing production operations. The work focuses on the application of heat equations taking into account the Neumann and Dirichlet boundary conditions, which ensures the accuracy and reliability of modeling. The results of computational experiments demonstrating dynamic changes in temperature fields in 2D space are presented. The main attention is paid to the influence of physical parameters such as thermal conductivity, density and specific heat capacity on temperature distribution. The obtained data can be used to improve energy efficiency and quality of production processes in the food industry.As a result of the research, a model describing temperature fields was developed in the MATLAB PDE Toolbox. The developed model serves as a basis for further research in the field of digital twins and integration with industrial modeling tools such as SIEMENS NX, as well as PML platforms. During this study, various heat transfer coefficients and boundary conditions were tested, which made it possible to determine the optimal model parameters. The final result, presented at the end of the article, demonstrates a smooth and correct distribution of thermodynamic processes, confirming the effectiveness of the proposed approach. In the future, this approach can be used to create more complex virtual production systems that allow not only to analyze thermal processes, but also to develop intelligent heat treatment control systems, improving the adaptability and efficiency of technological processes.

Molten salt reactors, as a leading candidate for Generation IV nuclear energy systems, exhibit thermal performance critically dependent on the thermal properties of fluoride molten salts. Addressing the challenges of severe corrosivity and beryllium toxicity encountered in high-temperature experiments on the NaF-BeF2 system, this study pioneers the application of active learning-enhanced sampling strategies to the fluoride molten salt system. A high-precision deep potential model spanning a broad temperature range (773-1173 K) was constructed. Through seven rounds of iterative optimization using the deep potential generator (DP-GEN) framework, the potential function was optimized, enabling the correlation of an atomic-scale microstructure with macroscopic thermal properties. The results reveal that the molten salt exhibits an amorphous structure characterized by short-range order and long-range disorder. Be2+ ions dominate the formation of [BeF4]2- tetrahedra and polymeric clusters such as [Be2F7]3- and [Be3F10]4-. The Be-F bond demonstrates significantly higher stability than the Na-F bond. However, reduced energy barriers at elevated temperatures intensify cluster dissociation. The DP model also successfully predicted the key thermal properties, including density (error within 1.62%), specific heat capacity (error within 6.79%), diffusion coefficients, viscosity, and thermal conductivity. Its accuracy significantly surpasses that of ab initio molecular dynamics simulations. Furthermore, the model elucidates the microscopic mechanisms underlying property variations, providing an atomic-scale theoretical foundation for molten salt reactor design.

The current study's simulation made use of COMSOL Multiphysics' CFD. Blood was used as the basic fluid in this simulation. Blood was considered to be a laminar, unstable, and incompressible Newtonian fluid, and its Newtonian nature is tolerable at high shear rates. The behavior of blood flow was investigated to ascertain the effects of temperature, velocity, and pressure through vascular stenosis. Gold (Au) and silver (Ag) nanoparticles were the two types utilized in this investigation. The mass, momentum, and energy equations were solved using the CFD method. A fine element size mesh was made using COMSOL. The analysis's conclusions show that the artery's velocity fluctuates over constrained sections, falling both before and after the stenotic zone and being higher in a diseased location. The heat transfer feature's upper and lower boundary temperatures were selected to be 24.85°C and 27.35°C, respectively. The nanoparticles affected the density, specific heat, dynamic viscosity, and thermal conductivity of blood. The use of gold and silver nanoparticles prevented overheating since they both have high thermal conductivity, which is essential for quickly dispersing heat. Nusselt number variations were also calculated, and the results show that the curve decreases inside the stenosis. At t = 0.7 s and 1 s, recirculation occurs right after the stenosed area, and it is possible to infer that the streamlines behave abnormally. These discoveries will have a significant impact on the treatment of stenosed arteries.

We have studied the thermal effects in quasi-ballistic plasmonic field effect transistors (FETs), for which the total energy of the plasma fluids does not dissipate, because the inelastic scattering is negligible. Instead, losses of the fluid momentum lead to redistribution of energy, lost during the deceleration of the flux between “chaotic” degrees of freedom, i.e., a specific heating of the fluid. For the steady-state regimes and nondegenerate electrons, we have found the exact solutions for the distribution of fluid velocity, plasma concentration, and temperature along the FET channel. The fluid heating demonstrates an unusual feature—the heating is small for large currents (for the large ballisticity of the electrons) and is larger for small currents (lesser ballisticity). Spatial distributions of the electron temperature are monotonous at moderate currents, but they become non-monotonous, approaching critical currents. The found thermal effects point out the highly nonlocal characteristic of the heat generation and transport in quasi-ballistic plasmonic FETs. The heating effects are illustrated for the GaAs- and GaN-based devices.

ABSTRACT The development of advanced composite materials for thin‐walled pressure vessels demands a balance between mechanical strength and thermal insulation. In this study, a novel three‐phase composite system comprising epoxy resin, silica (SiO 2 ) micro‐particles, and glass fiber reinforcement was fabricated and characterized for potential application in high‐performance thin vessel structures. Specimens were cured at varying temperatures (60°C to 160°C) to systematically investigate the influence of curing conditions on the structural and thermal properties. Comprehensive material characterization, including Fourier transform infrared (FTIR) spectroscopy and x‐ray diffraction (XRD) analysis, confirmed the successful integration of silica and glass fiber within the amorphous epoxy matrix. Thermogravimetric analysis (TGA) revealed a two‐stage degradation process, with maximum thermal stability observed at 120°C curing temperature. Specific heat capacity ( C p ) and measurements indicated decreasing trends with increasing curing temperature, enhancing thermal insulation. Mechanical testing demonstrated that hoop strength ( S H ) and burst pressure ( P b ) improved significantly with curing temperatures up to 140°C, following third‐degree polynomial relationships. Notably, the composite cured at 120°C exhibited the highest combination of hoop strength (341.3 ± 6.5 MPa), burst pressure (16.66 ± 0.3 MPa), C p (2.33 J/g·K), thermal conductivity (0.198 W/m·K) and Factor of Safety (1.39 ± 0.024), while maintaining superior thermal resistance. Theoretical predictions showed strong agreement with experimental results across all evaluations. Overall, the optimized epoxy/SiO 2 /glass fiber composites offer a lightweight, thermally stable, and mechanically robust alternative to traditional metallic vessels, highlighting their potential for use in chemical, oil, and pharmaceutical industries requiring durable thin‐walled pressure containment solutions.

Exploring Co2TiRE (RE = Nd and Tb) as a promising shape memory alloy using DFT methods

The low-temperature specific heat C(T) of multiwalled carbon nanotubes (MWCNTs) with mean outer diameter 9.4 nm, subjected to grinding and grinding-oxidation modifications, was measured from 1.8 K to 275 K. A comparative analysis was performed against initial MWCNTs, bundles of single-walled carbon nanotubes (SWCNT) and graphite. Results indicate that grinding of oxidized MWCNTs increases specific heat relative to initial MWCNTs, maintaining a similar temperature dependence. In contrast, grinding of initial MWCNTs causes different C(T) behavior below 5 K. Above 60 K, the C(T) of all MWCNTs variants, SWCNTs bundles, and graphite converge, reflecting the dominance of 2D graphene sheet phonon density of states. Discrepancies below 60 K are attributed to structural symmetries, potential energies of interaction between walls/sheets/tubes, layer/wall numbers, and defects.

An injectable nanosuspension based on orthoester and biomimetic carboxymethyl chitosan nanoparticles for chemo/thermo-synergistic tumor therapy.

In this research, we studied the dynamics of acceleration waves in a non-ideal dusty gas medium under the influence of a transverse magnetic field, incorporating relaxation effects. Using the characteristic coordinates of the governing quasilinear hyperbolic system, we analyze the nonlinear evolution of wave steepening and derive the threshold amplitude, which distinguishes between disturbances that decay over time and those that evolve into shock waves within a finite period. When the compressive disturbance's initial amplitude exceeds this critical threshold, it inevitably develops into a shock wave; otherwise, if it falls below the threshold, the disturbance diminishes without leading to shock formation. A Bernoulli-type transport equation is formulated to describe weak shocks, and the effects of various parameters, including dust mass fraction, magnetic field strength, adiabatic index, relaxation parameter, van der Waals excluded volume, and the specific heat ratio of solid particles to gas, are systematically analyzed. The results indicate that increased dust loading, relaxation, and magnetic field strength delay shock formation, while higher adiabatic indices and non-ideal parameters accelerate it. This multi-faceted interaction not only offers an enhanced understanding of the dynamics of shock in complex fluids on a theoretical scale, but it also has immense implications for astrophysical plasma processes, high-enthalpy propulsion systems, and industrial processes, where management of shock behavior is essential.

Electronic specific heat and thermal conductivity of bilayer graphene with pristine and parametrically doped layers: A study in the low-energy regime