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Disordered hyperuniformity (DHU) is a recently discovered novel state of amorphous systems characterized by strongly suppressed density fluctuations at large length scales as in crystalline materials, which offers great potential for achieving unusual mechanical, electronic, and photonic properties. However, despite the fundamental and technological importance of thermal transport in amorphous solids, the effect of DHU remains largely unexplored. Here, we theoretically study thermal transport in a class of two-dimensional DHU materials—monolayer amorphous carbon (MAC). Beginning with a perfect graphene lattice, we continuously apply Stone-Wales transformations to generate a series of MAC models with varied degrees of disorder and defects, which are quantified through comprehensive structural analysis including the so-called hyperuniformity index (H), where a smaller H indicates a higher degree of hyperuniformity. Subsequently, we conduct molecular dynamics simulations to obtain the thermal conductivity (κ). A significant correlation between the thermal transport behavior and degree of hyperuniformity is observed, with the room-temperature κ decreasing from 26.3 to 5.3 W m−1 K−1 while H is tuned from 0.0004 to 0.024. Remarkably, two distinct transport regimes are identified, including a nearly-DHU regime at small H (< 0.005) where κ drops sharply and a non-DHU region at larger H where κ becomes relatively flat. Mode-resolved analysis reveals longer lifetime and higher participation ratio for the heat carriers in nearly-DHU MAC, implying that the hidden long-range correlations could support extended modes that enhance transport. Our work highlights the impact of DHU on the thermal properties of amorphous materials and represents a conceptual advancement that is worthy of future exploration. [ABSTRACT FROM AUTHOR]

In response to the pressing energy crisis, thermoelectric materials have emerged as promising solutions for converting waste heat into electrical energy. Meanwhile, low-dimensional thermoelectric materials with micro/nanoscale dimensions are playing an increasingly important role in chip thermal management and self-powered wearable electronic devices. This work investigates the thermoelectric properties of three SixGey monolayers, predicted through the approach that combines the advantages of silicene and germanene. Utilizing density functional theory and semiclassical Boltzmann transport theory, we systematically analyze crystal structures, stabilities, electrical and thermal transport, and thermoelectric properties of three stable SixGey monolayers. Compared to traditional two-dimensional materials such as silicene and germanene, the SixGey monolayers exhibit significantly enhanced Seebeck coefficients (∼100 μV/K) and reduced lattice thermal conductivity, ranging from 1.15 to 1.43 W m–1 K–1 at 300 K. These results demonstrate a significant improvement in the thermoelectric figure of merit (zT) compared to silicon (0.02) and germanium (0.05) monolayers, reaching values of 0.15 (GeSi), 0.13 (GeSi2), and 0.11 (Ge2Si) at 700 K, respectively. Our findings not only underscore the potential of SixGey monolayers as promising candidates for thermoelectric generators and thermoelectric coolers but also shed light on the utilization of silicon–germanium-based materials in thermoelectric generation and semiconductor cooling micro/nanoscale electronic devices. [ABSTRACT FROM AUTHOR]

Thermophysical properties encompassing specific heat, thermal conductivity, thermal diffusivity and thermal expansion and their temperature dependence is most sought after during selection of materials for various engineering applications. In this review a broad perspective on the thermal transport in metals and alloys, thermal energy carriers and factors affecting their mean free path is presented. Following the discussion on thermal transport, various techniques available for measuring thermal diffusivity, their principle of detection, merits and demerits are deliberated with an emphasis on laser flash analyzer. Theory of laser flash analysis, possible causes for deviation in the theoretical assumptions that affect the accuracy of measured diffusivity and ways and means of improving the same is dwelt upon. Finally, few typical case studies on thermal diffusivity measurements covering broad spectrum of materials differing in chemistry, degree of deformation, and heat treatment conditions are presented to demonstrate the sensitivity of thermal diffusivity to microstructural changes in materials. [ABSTRACT FROM AUTHOR]

Understanding the origin of low thermal conductivities in ionic conductors is essential for improving their thermoelectric efficiency, although accompanying high ionic conduction may present challenges for maintaining thermoelectric device integrity. This study investigates the thermal and ionic transport in Cu7PSe6, aiming to elucidate their fundamental origins and correlation with the structural and dynamic properties. Through a comprehensive approach including various characterization techniques and computational analyses, it is demonstrated that the low thermal conductivity in Cu7PSe6 arises from structural complexity, variations in bond strengths, and high lattice anharmonicity, leading to pronounced diffuson transport of heat and fast ionic conduction. It is found that upon increasing the temperature, the ionic conductivity increases significantly in Cu7PSe6, whereas the thermal conductivity remains nearly constant, revealing no direct correlation between ionic and thermal transport. This absence of direct influence suggests innovative design strategies in thermoelectric applications to enhance stability by diminishing ionic conduction, while maintaining low thermal conductivity, thereby linking the domains of solid‐state ionics and thermoelectrics. Thus, this study attempts to clarify the fundamental principles governing thermal and ionic transport in Cu+‐superionic conductors, similar to recent findings in Ag+ argyrodites. [ABSTRACT FROM AUTHOR]

Understanding the origin of low thermal conductivities in ionic conductors is essential for improving their thermoelectric efficiency, although accompanying high ionic conduction may present challenges for maintaining thermoelectric device integrity. This study investigates the thermal and ionic transport in Cu7PSe6, aiming to elucidate their fundamental origins and correlation with the structural and dynamic properties. Through a comprehensive approach including various characterization techniques and computational analyses, it is demonstrated that the low thermal conductivity in Cu7PSe6 arises from structural complexity, variations in bond strengths, and high lattice anharmonicity, leading to pronounced diffuson transport of heat and fast ionic conduction. It is found that upon increasing the temperature, the ionic conductivity increases significantly in Cu7PSe6, whereas the thermal conductivity remains nearly constant, revealing no direct correlation between ionic and thermal transport. This absence of direct influence suggests innovative design strategies in thermoelectric applications to enhance stability by diminishing ionic conduction, while maintaining low thermal conductivity, thereby linking the domains of solid‐state ionics and thermoelectrics. Thus, this study attempts to clarify the fundamental principles governing thermal and ionic transport in Cu+‐superionic conductors, similar to recent findings in Ag+ argyrodites. [ABSTRACT FROM AUTHOR]

This article uses void defects to regulate the thermal conductivity of the two-dimensional graphene/h - BN lateral heterojunction. The results of equilibrium molecular dynamics (EMD) calculations show that the introduction of interface voids can reduce the thermal conductivity of the heterojunction. Compared with the ordered void distribution, the disordered void distribution can more effectively reduce the thermal conductivity of the heterojunction, which can be explained by phonon Anderson localization. The presence of void defects leads to changes in the frequency and wave vector of phonons, making phonon scattering more frequent. When voids are randomly distributed, phonon waves undergo multiple reflections and scattering in the material, eventually forming localized vibrational modes. This study reveals the physical mechanism by which void defects reduce the thermal conductivity of the two-dimensional graphene/h - BN lateral heterojunction and has some guiding significance for the structural design of two-dimensional thermoelectric materials. [ABSTRACT FROM AUTHOR]

Using large scale molecular dynamics simulations, we study the thermal conductivity of bare and surface passivated silicon nanowires (SiNWs). For the cross–sectional widths w ⩽ 2 nm, SiNWs become unstable because of the surface amorphization and also due to the evaporation of a certain fraction of Si atoms. The observed surface (in–)stability is related to a large excess energy Δ of the surface Si atoms with respect to the bulk Si, resulting from the surface atoms being less coordinated and having dangling bonds. We first propose a practically relevant method that uses Δ as a guiding tool to passivate these dangling bonds with hydrogen or oxygen, stabilizing the SiNWs. These passivated SiNWs are used to calculate the thermal conductivity coefficient κ. While the expected trend of κ ∝ w is observed for all SiNWs, surface passivation provides an added flexibility of tuning κ with the surface coverage concentration c of passivated atoms. Indeed, with respect to the bulk κ, passivation of SiNW reduces κ by 75%–80% for c → 50 % and increases it by 50% for the fully passivated samples. Analyzing the phonon band structures via spectral energy density, we discuss separate contributions from the surface and the core to κ. Our results also reveal that surface passivation increases SiNW stiffness, contributing to the tunability in κ. [ABSTRACT FROM AUTHOR]

ABX3-type nitride perovskites offer promising avenues for the future electronic industry, renowned for exceptional ferro- and piezo-electric properties with facile integration into prevalent nitride semiconductors. However, the paucity of in-depth investigations of thermal transport of nitride perovskites poses a substantial impediment to the practical implementation. Here, we experimentally investigate the thermal conductivity of orthorhombic polar LaWN3, synthesized by high-pressure high-temperature technique. The observed thermal conductivity exhibits drastic reduction with decreasing temperature, reminiscent of the behavior in amorphous silica. We postulate the anomalous glass-like thermal conductivity to a synergistic interplay of potential Ferron–phonon interactions, lattice disorders from octahedral distortions, and wave-like atomic tunneling. This study represents a pioneering exploration of thermal transport within nitride perovskites, paving the way for future advancements in nitride-based electronics. [ABSTRACT FROM AUTHOR]

The unique combination of large energy density and extreme environment inside a nuclear reactor imposes strict requirements on the thermal transport property of nuclear materials, which is significantly deteriorated by the irradiation damage, leading to increased service temperature, complex microstructural changes, and compromised integrity. To address this issue, tremendous efforts have been made over the years to measure, comprehend, and enhance thermal transport regulated by radiation-induced defects in advanced nuclear materials. Such efforts would be laborious and time-consuming without revolutionary innovations in characterization techniques. Herein, we review recent experimental studies on the thermal transport properties of nuclear materials, with a focus on the advancements in the measurement techniques with improved spatial resolutions. We provide a brief introduction to the mechanisms of thermal transport in nuclear materials and the impact of irradiation damage on thermal transport. A comprehensive review is presented of advanced thermal characterization techniques that encompass different length scales, ranging from millimeter to nanometer, along with their respective experimental outcomes. Finally, the practicality of each measurement technique is assessed, and research opportunities are discussed in regard to the development of physics-based fuel models. [ABSTRACT FROM AUTHOR]

The heat transfer and stability of methane hydrate in reservoirs have a direct impact on the drilling and production efficiency of hydrate resources, especially in complex stress environments caused by formation subsidence. In this study, we investigated the thermal transport and structural stability of methane hydrate under triaxial compression using molecular dynamics simulations. The results suggest that the thermal conductivity of methane hydrate increases with increasing compression strain. Two phonon transport mechanisms were identified as factors enhancing thermal conductivity. At low compressive strains, a low-frequency phonon transport channel was established due to the overlap of phonon vibration peaks between methane and water molecules. At high compressive strains, the filling of larger phonon bandgaps facilitated the opening of more phonon transport channels. Additionally, we found that a strain of −0.04 is a watershed point, where methane hydrate transitions from stable to unstable. Furthermore, a strain of −0.06 marks the threshold at which the diffusion capacities of methane and water molecules are at their peaks. At a higher strain of −0.08, the increased volume compression reduces the available space, limiting the diffusion ability of water and methane molecules within the hydrate. The synergistic effect of the strong diffusion ability and high probability of collision between atoms increases the thermal conductivity of hydrates during the unstable period compared to the stable period. Our findings offer valuable theoretical insights into the thermal conductivity and stability of methane hydrates in reservoir stress environments. [ABSTRACT FROM AUTHOR]

In this work, we employ molecular dynamics simulations with semi-empirical interatomic potentials to explore heat dissipation in Janus transition metal dichalcogenides (JTMDs). The middle atomic layer is composed of either molybdenum (Mo) or tungsten (W) atoms, and the top and bottom atomic layers consist of sulfur (S) and selenium (Se) atoms, respectively. Various nanomaterials have been investigated, including both pristine JTMDs and nanostructures incorporating inner triangular regions with a composition distinct from the outer bulk material. At the beginning of our simulations, a temperature gradient across the system is imposed by heating the central region to a high temperature while the surrounding area remains at room temperature. Once a steady state is reached, characterized by a constant energy flux, the temperature control in the central region is switched off. The heat attenuation is investigated by monitoring the characteristic relaxation time (τav) of the local temperature at the central region toward thermal equilibrium. We find that SMoSe JTMDs exhibit thermal attenuation similar to conventional TMDs (τav~10–15 ps). On the contrary, SWSe JTMDs feature relaxation times up to two times as high (τav~14–28 ps). Forming triangular lateral heterostructures in their surfaces leads to a significant slowdown in heat attenuation by up to about an order of magnitude (τav~100 ps). [ABSTRACT FROM AUTHOR]

An analytical model is presented for light scattering associated with heat transport near a cell membrane that divides a complex system into two topologically distinct half-spaces. Our analysis is motivated by experiments on vibrational photothermal microscopy which have not only demonstrated remarkably high contrast and resolution, but also are capable of providing label-free local information of heat transport in complex morphologies. In the first Born approximation, the derived Greens function leads to the reconstruction of a full 3D image with photothermal contrast obtained using both amplitude and phase detection of periodic excitations. We show that important fundamental parameters including the Kapitza length and Kapitza resistance can be derived from experiments. Our goal is to spur additional experimental studies with high-frequency modulation and heterodyne detection in order to make contact with recent theoretical molecular dynamics calculations of thermal transport properties in membrane systems.

The primary purpose of this study is to provide more information on the stable and incompressible stream of a hybrid nanofluid over a poignant tiny needle in two dimensions under slip boundary conditions. In the hybrid nanofluid flow, Al2O3 and Fe3O4 are nanoparticles, water and ethylene glycol (50:50) are considered as the base fluids. Furthermore, the impacts of Joule heating and inclined magnetic fields are considered. The PDE's governing equations are converted into ODEs by using similarity transformations and solved by a numerical technique based on Runge–Kutta fourth-order method. The results illustrate that the crucial parameters such as the magnetic parameter, Eckert number, nanoparticles of solid volume fractions, inclined angle parameter, and Prandtl numbers significantly affect the momentum and thermal profiles. The heat transfer rate and skin friction factors are used to calculate the numerical values of various parameters, which are displayed in a table. These analyses manifest that raising the magnetic parameter results in a decrease in the hybrid nanofluid velocity under slip and no-slip circumstances. The Nusselt number has also grown as a result of the volumetric fractions of nanoparticles and the intensification of the angle parameter. This analysis might include areas such as microfluidics, biomedical devices, heat exchangers, and other engineering applications where precise control over fluid behavior and temperature distribution is important. [ABSTRACT FROM AUTHOR]

In many physical situations in which many-body assemblies exist at temperature T, a characteristic quantum-mechanical time scale of approximately h/kBT can be identified in both theory and experiment, leading to speculation that it may be the shortest meaningful time in such circumstances. This behavior can be investigated by probing the scattering rate of electrons in a broad class of materials often referred to as "strongly correlated metals". It is clear that in some cases only electron-electron scattering can be its cause, while in others it arises from high-temperature scattering of electrons from quantized lattice vibrations, i.e., phonons. In metallic oxides, which are among the most studied materials, analysis of electrical transport does not satisfactorily identify the relevant scattering mechanism at "high" temperatures near room temperature. We therefore employ a contactless optical method to measure thermal diffusivity in two Ru-based layered perovskites, Sr3Ru2O7 and Sr2RuO4, and use the measurements to extract the dimensionless Lorenz ratio. By comparing our results to the literature data on both conventional and unconventional metals, we show how the analysis of high-temperature thermal transport can both give important insight into dominant scattering mechanisms and be offered as a stringent test of theories attempting to explain anomalous scattering. [ABSTRACT FROM AUTHOR]

Topological phononics, a fascinating frontier in condensed matter physics, holds great promise for advancing energy‐related applications. Topologically nontrivial phonons typically possess gapless edge or surface states. These exotic states of lattice vibrations, characterized by their nontrivial topology, offer unique opportunities for manipulating and harnessing energy transport. The exploration of topological phonons opens new avenues in understanding and controlling thermal transport properties, with potential applications in fields such as thermoelectric materials, phononic devices, and waste heat recovery. Here, an overview of concepts such as Berry curvature and topological invariants, along with the applications of phonon tight‐binding method and nonequilibrium Green's function method in the field of topological phononics is provided. This review encompasses the latest research progress of various topological phonon states within crystalline materials, including topological optical phonons, topological acoustical phonons, and higher‐order topological phonons. Furthermore, the study delves into the prospective applications of topological phonons in the realm of thermoelectric conversion, focusing on aspects like size effects and symmetry engineering. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials have drawn extensive attention due to their exceptional characteristics and potential uses in electronics and energy storage. This investigation employs simulations using molecular dynamics to examine the mechanical and thermal transport attributes of the 2D silicene–germanene (Si-Ge) lateral heterostructure. The pre-existing cracks of the Si-Ge lateral heterostructure are addressed with external strain. Then, the effect of vacancy defects and temperature on the mechanical attributes is also investigated. By manipulating temperature and incorporating vacancy defects and pre-fabricated cracks, the mechanical behaviors of the Si-Ge heterostructure can be significantly modulated. In order to investigate the heat transport performance of the Si-Ge lateral heterostructure, a non-equilibrium molecular dynamics approach is employed. The efficient phonon average free path is obtained as 136.09 nm and 194.34 nm, respectively, in the Si-Ge heterostructure with a zigzag and armchair interface. Our results present the design and application of thermal management devices based on the Si-Ge lateral heterostructure. [ABSTRACT FROM AUTHOR]

We report theoretical results for the electronic contribution to thermal and electrical transport for chiral superconductors belonging to even or odd-parity E1 and E2 representations of the tetragonal and hexagonal point groups. Chiral superconductors exhibit novel properties that depend on the topology of the order parameter and Fermi surface, and--as we highlight--the structure of the impurity potential. An anomalous thermal Hall effect is predicted and shown to be sensitive to the winding number, ], of the chiral order parameter via Andreev scattering that transfers angular momentum from the chiral condensate to excitations that scatter off the random potential. For heat transport in a chiral superconductor with isotropic impurity scattering, i.e., point-like impurities, a transverse heat current is obtained for v = ±1, but vanishes for |v| > 1. This is not a universal result. For finite-size impurities with radii of order or greater than the Fermi wavelength, R ≥ ħ/p[sub f], the thermal Hall conductivity is finite for chiral order with |v| ≥ 2, and determined by a specific Fermi-surface average of the differential cross-section for electron-impurity scattering. Our results also provide quantitative formulae for analyzing and interpreting thermal transport measurements for superconductors predicted to exhibit broken time-reversal and mirror symmetries. [ABSTRACT FROM AUTHOR]

This work aims to analyze the impacts of the magnetic field, activation of energy, thermal radiation, thermophoresis, and Brownian effects on the hybrid nanofluid (HNF) (Ag++silicon oil) flow past a porous spinning disk. The pressure loss due to porosity is constituted by the Darcy-Forchheimer relation. The modified Buongiorno model is considered for simulating the flow field into a mathematical form. The modeled problem is further simplified with the new group of dimensionless variables and further transformed into a first-order system of equations. The reduced system is further analyzed with the Levenberg-Marquardt algorithm using a trained artificial neural network (ANN) with a tolerance, step size of 0.001, and 1,000 epochs. The state variables under the impacts of the pertinent parameters are assessed with graphs and tables. It has been observed that when the magnetic parameter increases, the velocity gradient of mono and hybrid nanofluids (NFs) decreases. As the input of the Darcy-Forchheimer parameter increases, the velocity profiles decrease. The result shows that as the thermophoresis parameter increases, temperature and concentration increase as well. When the activation energy parameter increases, the concentration profile becomes higher. For a deep insight into the analysis of the problem, a statistical approach for data fitting in the form of regression lines and error histograms for NF and HNF is presented. The regression lines show that 100% of the data is used in curve fitting, while the error histograms depict the minimal zero error -7.1e6 for the increasing values of Nt. Furthermore, the mean square error and performance validation for each varying parameter are presented. For validation, the present results are compared with the available literature in the form of a table, where the current results show great agreement with the existing one. [ABSTRACT FROM AUTHOR]

The carbides and nitrides of transition metals known as "MXenes" refer to a fast-growing family of two-dimensional materials discovered in 2011. Thanks to their unique nanolayer structure, superior electrical, mechanical, and thermal properties, MXenes have shown great potential in addressing the critical overheating issues that jeopardize the performance, stability, and lifetime of high-energy-density components in modern devices such as microprocessors, integrated circuits, and capacitors, etc. The outstanding intrinsic thermal conductivity of MXenes has been proved by experimental and theoretical research. Numerous MXenes-enabled high thermal conductivity composites incorporated with polymer matrix have also been reported and widely used as thermal management materials. Considering the booming heat dissipation demands, MXenes-enabled thermal management material is an extremely valuable and scalable option for modern electronics industries. However, the fundamental thermal transport mechanisms behind the MXenes family remain unclear. The MXene thermal conductivity disparities between the theoretical prediction and experimental results are still significant. To better understand the thermal conduction in MXenes and provide more insights for engineering high-performance MXene thermal management materials, in this article, we summarize recent progress on thermal conductive MXenes. The essential factors that affect MXenes intrinsic thermal conductivities are tackled, selected MXenes-polymer composites are highlighted, and prospects and challenges are also discussed. [ABSTRACT FROM AUTHOR]

Considerable evidence shows that the heavy fermion material UTe2 is a spin-triplet superconductor, possibly manifesting time-reversal symmetry breaking, as measured by Kerr effect below the critical temperature, in some samples. Such signals can arise due to a chiral orbital state or possible nonunitary pairing. Although experiments at low temperatures appear to be consistent with point nodes in the spectral gap, the detailed form of the order parameter and even the nodal positions are not yet determined. Thermal conductivity measurements can extend to quite low temperatures, and varying the heat current direction should be able to provide information on the order parameter structure. Here, we derive a general expression for the thermal conductivity of a spin-triplet superconductor and use it to compare the low-temperature behavior of various states proposed for UTe2. [ABSTRACT FROM AUTHOR]

Carbon nanocoils (CNCs) have been discovered and studied for years. Its good electrical conductivity and low lattice thermal conductivity suggest the application potential in thermoelectricity, which was studied for the first time in this work. Individual CNCs were suspended between two substrates with electrical heaters to create the desired temperature differences. Employing a transient electro-thermal technique, the thermoelectric, electrical, and heat transport properties of CNCs from 298 to 343 K before and after in situ Joule annealing were characterized simultaneously. CNCs exhibit asymmetric thermoelectric responses, with average Seebeck coefficients along the two length directions of 1.5 and 0.9 μV/K. This asymmetry results from different bandgaps along the growth direction, and the small Seebeck coefficient results from strong mixed electrical conductivity. The Fermi energy and optical bandgap of CNCs were measured to be 11.2 and 58.2 meV, respectively, with a small hole–electron conductivity ratio (1.36). The Seebeck coefficient shows a negative correlation with the electrical conductivity, while the thermal conductivity shows no observable correlation with them, hovering around 8.3 W/m K at room temperature. Doping may be an effective strategy to increase the Seebeck coefficient and electrical conductivity while decreasing the thermal conductivity for improved thermoelectric conversion. In addition, a flexible nanothermocouple based on two intertwined single CNCs was developed, which shows excellent response to thermal excitation. [ABSTRACT FROM AUTHOR]

An ab initio characterization of the impact of tert‐Butyl isocyanate (C5H9NO${\rm C}_5{\rm H}_9{\rm NO}$) functionalization on TaS2${\rm TaS}_2$ lattice thermal conductivity is presented. Such a system has been previously synthetized and experimentally charachterized, showing that the incorporation of covalently bonded C5H9NO${\rm C}_5{\rm H}_9{\rm NO}$ on bulk TaS2${\rm TaS}_2$ leads to a dramatic in‐plane lattice thermal conductivity decrease by more than two orders of magnitudes. To elucidate these experimental findings, detailed calculations of the phonon dispersion relations and scattering rates in TaS2${\rm TaS}_2$ are performed. The analysis is addressed to discern the impact of inter‐layer covalently bonded C5H9NO${\rm C}_5{\rm H}_9{\rm NO}$ molecules on these phonon properties, providing insights into the underlying mechanisms of the observed thermal conductivity decrease. Present calculations provide evidence that the observed lattice thermal conductivity reduction is attributed to two effects: i)$i)$ the increase of inter‐layer separation and ii)$ii)$ the presence of low‐frequency molecular optical modes. The first inhibits specific Van der Waals quasi‐acoustic inter‐layer vibrational modes contributing as much as ≈55%$\approx \!\! 55\%$ in bulk TaS2${\rm TaS}_2$. The second effect dramatically decreases the phonon group velocities as a consequence of phonon‐crossing phenomena among low‐frequency molecular modes and TaS2${\rm TaS}_2$ acoustic modes, eventually leading to a strong reduction of all phonon lifetimes. [ABSTRACT FROM AUTHOR]

Significance: The CuO, Al2O3, and TiO2 nanoparticles find extensive applications in advanced chemical reaction-based thermal transport and quadratic convective nanofluids due to their exceptional thermal properties and chemical stability. Increased thermal conductivity of these nanoparticles used to enhance heat transfer in various chemical reactors, resistance to chemical degradation and photocatalytic reactors and solar energy applications. Motive: This study brings the investigation about quadratic convection-based thermal transport to infinite shear rate for magnetized ternary radiative cross nanofluid with homogeneous-heterogeneous chemical reactions. Water is taken as base fluid and three nanoparticles are Copper oxide (CuO), aluminium oxide (Al2O3), and titanium dioxide (TiO2). Heat transport analysis is made through quadratic convection, magnetic field and thermal radiation. Concentration of nanofluid is scrutinized though homogeneous-heterogeneous chemical reactions. Method: ology: Physical problem with assumptions generates the system of partial differential equations (PDEs) and these PDEs are transformed into ordinary differential equations (ODEs) through similarity variables. Furthermore, a unique combination of Bvp4c and Levenberg Marquardt neural network (LM-NN) schemes is utilized to fetch the numerical solutions. Bvp4c is utilized to solve the governing equations, while LM-NN serves to enhance predictive capabilities and capture intricate nonlinear relationships. Findings: Magnetic environment, chemical process, radiations effects and volumetric fraction of nanoparticles make better heat transfer efficiency and control.

Exploring new prototypes for a given chemical composition is of great importance and interest to several disciplines. As a famous semiconducting binary compound, InSe usually exhibits a two-dimensional layered structure with decent physical and mechanical properties. However, it is less noticed that InSe can also adopt a monoclinic structure, denoted as mcl-InSe. The synthesis of such a phase usually requires high-pressure conditions, and the knowledge is quite scarce on its chemical bonding, lattice dynamics, and thermal transport. Here in this work, by developing a facile method combining mechanical alloying and spark plasma sintering, we successfully synthesize mcl-InSe bulks with well-crystallized nanograins. The chemical bonding of mcl-InSe is understood as compared with layered InSe via charge analysis. Low cut-off frequencies of acoustic phonons and several low-lying optical modes are demonstrated. Noticeably, mcl-InSe exhibits a low room-temperature thermal conductivity of 0.6 W·m−1·K−1, which is smaller than that of other materials in the In–Se system and many other selenides. Low-temperature thermal analyses corroborate the role of nanograin boundaries and low-frequency optical phonons in scattering acoustic phonons. This work provides new insights into the non-common prototype of the InSe binary compound with potential applications in thermoelectrics or thermal insulation.

Accessing the thermal transport properties of glasses is a major issue for the design of production strategies of glass industry, as well as for the plethora of applications and devices where glasses are employed. From the computational standpoint, the chemical and morphological complexity of glasses calls for atomistic simulations where the interatomic potentials are able to capture the variety of local environments, composition, and (dis)order that typically characterize glassy phases. Machine-learning potentials (MLPs) are emerging as a valid alternative to computationally expensive ab initio simulations, inevitably run on very small samples which cannot account for disorder at different scales, as well as to empirical force fields, fast but often reliable only in a narrow portion of the thermodynamic and composition phase diagrams. In this article, we make the point on the use of MLPs to compute the thermal conductivity of glasses, through a review of recent theoretical and computational tools and a series of numerical applications on vitreous silica and vitreous silicon, both pure and intercalated with lithium. [ABSTRACT FROM AUTHOR]

This work aims to analyze the impacts of the magnetic field, activation of energy, thermal radiation, thermophoresis, and Brownian effects on the hybrid nanofluid (HNF) (Ag++silicon oil) flow past a porous spinning disk. The pressure loss due to porosity is constituted by the Darcy–Forchheimer relation. The modified Buongiorno model is considered for simulating the flow field into a mathematical form. The modeled problem is further simplified with the new group of dimensionless variables and further transformed into a first-order system of equations. The reduced system is further analyzed with the Levenberg–Marquardt algorithm using a trained artificial neural network (ANN) with a tolerance, step size of 0.001, and 1,000 epochs. The state variables under the impacts of the pertinent parameters are assessed with graphs and tables. It has been observed that when the magnetic parameter increases, the velocity gradient of mono and hybrid nanofluids (NFs) decreases. As the input of the Darcy–Forchheimer parameter increases, the velocity profiles decrease. The result shows that as the thermophoresis parameter increases, temperature and concentration increase as well. When the activation energy parameter increases, the concentration profile becomes higher. For a deep insight into the analysis of the problem, a statistical approach for data fitting in the form of regression lines and error histograms for NF and HNF is presented. The regression lines show that 100% of the data is used in curve fitting, while the error histograms depict the minimal zero error −7.1e6 for the increasing values of Nt. Furthermore, the mean square error and performance validation for each varying parameter are presented. For validation, the present results are compared with the available literature in the form of a table, where the current results show great agreement with the existing one.

Considerable evidence shows that the heavy fermion material UTe2 is a spin-triplet superconductor, possibly manifesting time-reversal symmetry breaking, as measured by Kerr effect below the critical temperature, in some samples. Such signals can arise due to a chiral orbital state or possible nonunitary pairing. Although experiments at low temperatures appear to be consistent with point nodes in the spectral gap, the detailed form of the order parameter and even the nodal positions are not yet determined. Thermal conductivity measurements can extend to quite low temperatures, and varying the heat current direction should be able to provide information on the order parameter structure. Here, we derive a general expression for the thermal conductivity of a spin-triplet superconductor and use it to compare the low-temperature behavior of various states proposed for UTe2.

PbTe and PbSe are among the most promising thermoelectric materials used in the mid-temperature (400–900 K) power generation range. In these materials the efficiency increase in thermoelectric performance is critically related to the lowering of lattice thermal conductivity (κL), without compromising the electronic power factor. By means of state-of-the-art equilibrium molecular dynamics (EMD), we investigate heat transport in several nanostructured PbTe/PbSe models as a function of material morphology. Layered composites show a reduction of the average κL of about 35 % with respect to the bulk. The insertion of PbSe nanoparticles into a PbTe matrix, or viceversa PbTe into PbSe reduces κL by up to 45 % while in more anisotropic nanocomposites the reduction exceeds PbSe/PbTe alloys. Layered composites show the lowest lattice thermal conductivity in the direction of layer stacking, for which an optimal thickness is identified. Along this line we provide a full account of the impact of alloying and (sub)nanostructuring on heat transport for this important class of materials. Particularly anisotropic nano-dot morphologies and layered (sub)nanocomposites emerge as a paradigm for outstanding thermoelectric materials.

Due to their broad range of uses in thermo-electric devices, aerospace, and other industries, thermoelectric materials have garnered much attention. To expand the scope of their applications, thermoelectric materials’ thermoelectric characteristics must be effectively improved. Improved thermoelectrical properties with advancement is one of the critical strategies. Even though it is challenging to do small-scale measurements, it is crucial to precisely gauge the thermoelectric characteristics of varying materials (organic/inorganic/MXenes). Two-dimensional materials have drawn much interest for technological applications because of their unique properties. MXenes are a class of two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides that have garnered significant attention for their promising properties by showing high electrical conductivity, controllable thermal conductivity, and high Seebeck coefficient value making suitable candidates for thermoelectric energy conversion. Thermal and electrical parameters are currently measured using a variety of techniques. However, the advanced thermoelectric properties with advanced thermoelectric materials, such as thermopower, thermal conductance, and electrical conductivity, are compiled in this review. Also outlined are measurement techniques for thermoelectric properties of selected advanced and 2D materials. Lastly, the challenges of integrated measurement methods are suggested, and a few integrated measurement solutions that work well with many inorganic/organic composites and two-dimensional materials MXenes are most proposed.

We report theoretical results for the electronic contribution to thermal and electrical transport for chiral superconductors belonging to even or odd-parity E1 and E2 representations of the tetragonal and hexagonal point groups. Chiral superconductors exhibit novel properties that depend on the topology of the order parameter and Fermi surface, and—as we highlight—the structure of the impurity potential. An anomalous thermal Hall effect is predicted and shown to be sensitive to the winding number, ν, of the chiral order parameter via Andreev scattering that transfers angular momentum from the chiral condensate to excitations that scatter off the random potential. For heat transport in a chiral superconductor with isotropic impurity scattering, i.e., point-like impurities, a transverse heat current is obtained for ν=±1, but vanishes for |ν|>1. This is not a universal result. For finite-size impurities with radii of order or greater than the Fermi wavelength, R≥ℏ/pf, the thermal Hall conductivity is finite for chiral order with |ν|≥2, and determined by a specific Fermi-surface average of the differential cross-section for electron-impurity scattering. Our results also provide quantitative formulae for analyzing and interpreting thermal transport measurements for superconductors predicted to exhibit broken time-reversal and mirror symmetries.

Accessing the thermal transport properties of glasses is a major issue for the design of production strategies of glass industry, as well as for the plethora of applications and devices where glasses are employed. From the computational standpoint, the chemical and morphological complexity of glasses calls for atomistic simulations where the interatomic potentials are able to capture the variety of local environments, composition, and (dis)order that typically characterize glassy phases. Machine-learning potentials (MLPs) are emerging as a valid alternative to computationally expensive ab initio simulations, inevitably run on very small samples which cannot account for disorder at different scales, as well as to empirical force fields, fast but often reliable only in a narrow portion of the thermodynamic and composition phase diagrams. In this article, we make the point on the use of MLPs to compute the thermal conductivity of glasses, through a review of recent theoretical and computational tools and a series of numerical applications on vitreous silica and vitreous silicon, both pure and intercalated with lithium.

Nanostructured materials and nanocomposites have shown great promise for improving the efficiency of thermoelectric materials. Herein, Fe nanoparticles were imbedded into a CrN matrix by combining two physical vapor deposition approaches, namely, high-power impulse magnetron sputtering and a nanoparticle gun. The combination of these techniques allowed the formation of nanocomposites in which the Fe nanoparticles remained intact without intermixing with the matrix. The electrical and thermal transport properties of the nanocomposites were investigated and compared to those of a monolithic CrN film. The measured thermoelectric properties revealed an increase in the Seebeck coefficient, with a decrease of hall carrier concentration and an increase of the electron mobility, which could be explained by energy filtering by internal phases created at the NP/matrix interface. The thermal conductivity of the final nanocomposite was reduced from 4.8 W m–1 K–1 to a minimum of 3.0 W m–1 K–1. This study shows prospects for the nanocomposite synthesis process using nanoparticles and its use in improving the thermoelectric properties of coatings. [ABSTRACT FROM AUTHOR]

The miniaturization and higher power density of modern electronics pose a significant challenge in thermal management. A key focus in addressing this challenge revolves around the advancement of thermal interfaces within microchip packaging, aiming to enhance thermal energy dissipation and optimization of performance. Copper nanowires are extensively employed in the chip industry as interconnects for signal transmission and thermal management purposes. Investigating the impact of reduced cross-section on the thermal transport properties of nanowires is crucial. In this study, the thermal conductivity of copper and silicon nanowires is studied with variations in the length of the nanowires. The simulation is conducted with the Equilibrium Molecular Dynamics (EMD) process. The cross-section of the nanowire is kept fixed (10 × 10 nm) and with the increase in length, its thermal conductivity is studied. At room temperature for a 50 nm length, the lattice thermal conductivity value is 1.68 and 0.037 W m − 1 K − 1 for silicon and copper nanowires, respectively. We further studied the phonon scattering, mean free path, and group velocity of silicon and copper lattices. Our study may help to design more thermally efficient microchips and innovate new cooling methods of microelectronics. [ABSTRACT FROM AUTHOR]

The precise control and understanding of heat flow in heterostructures is pivotal for advancements in thermoelectric energy conversion, thermal barrier coatings, and efficient heat management in electronic and optoelectronic devices. In this study, we employ high-angular-resolution time-resolved X-ray diffraction to structurally measure thermal resistance in a laser-excited AlGaAs/GaAs semiconductor heterostructure. Our methodology offers femtometer-scale spatial sensitivity and nanosecond time resolution, enabling us to directly observe heat transport across a buried interface. We corroborate established Thermal Boundary Resistance (TBR) values for AlGaAs/GaAs heterostructures and demonstrate that TBR arises from material property discrepancies on either side of a nearly flawless atomic interface. This work not only sheds light on the fundamental mechanisms governing heat flow across buried interfaces but also presents a robust experimental framework that can be extended to other heterostructure systems, paving the way for optimized thermal management in next-generation devices. [ABSTRACT FROM AUTHOR]

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