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The two-dimensional laser-based Ångstrom method measures the in-plane thermal properties for anisotropic film-like materials. It involves periodic laser heating at the center of a suspended film sample and records its transient thermal response by infrared imaging. These spatiotemporal temperature data must be analyzed to extract the unknown thermal conductivity values in the orthotropic directions, an inverse parameter fitting problem. Previous demonstration of the metrology technique used a least-squares fitting method that relies on numerical differentiation to evaluate the second-order partial derivatives in the differential equation describing transient conduction in the physical system. This fitting approach is susceptible to measurement noise, introducing high uncertainty in the extracted properties when working with noisy data. For example, when noise of a signal-to-noise ratio of 10 is added to simulated amplitude and phase data, the error in the extracted thermal conductivity can exceed 80%. In this work, we introduce a new alternative inverse parameter fitting approach using physics-informed neural networks (PINNs) to increase the robustness of the measurement technique for noisy temperature data. We demonstrate the effectiveness of this approach even for scenarios with extreme levels of noise in the data. Specifically, the PINN-approach accurately extracts the properties to within 5% of the true values even for high noise levels (a signal-to-noise ratio of 1). This offers a promising avenue for improving the robustness and accuracy of advanced thermal metrology tools that rely on inverse parameter fitting of temperature data to extract thermal properties. [ABSTRACT FROM AUTHOR]

The binary high-pressure phase diagram of the Ta–Sb system was constructed for the first time in this study, utilizing the evolutionary algorithm USPEX and density functional theory (DFT). Ten pressurized dynamically and mechanically stable or metastable novel phases of Ta–Sb were discovered, including I4/mmm-TaSb2, P4/nmm-TaSb, P-3-Ta2Sb7, I4/mmm-Ta2Sb3, P-4m2-Ta7Sb, Pm-3-Ta7Sb, Pmm2-Ta15Sb, P4/nmm-TaSb3, I4/mmm-Ta3Sb4, and I4/mmm-Ta2Sb5. The compounds P-4m2-Ta7Sb and Pmm2-Ta15Sb exhibit promising characteristics as non-centrosymmetric superconductors (NCSs), with their superconducting critical temperature (TC) being 3.831 and 3.221 K, respectively. The application of pressure tuning is predicted to transform the topological characteristics of P4/nmm-TaSb, causing it to transition from a topological insulator state to a Dirac semimetal state and ultimately reverting back to a topological insulator state. Therefore, the P4/nmm-TaSb compound is considered a promising candidate to investigate topological and superconducting excitations. Moreover, the mechanical and thermal properties of Ta–Sb binary phases were also investigated. The thermal conductivity of I4/mmm-TaSb2, P4/nmm-TaSb, and P4/nmm-TaSb3 all surpasses 20 W m−1 K−1 at 1000 K, showcasing their excellent thermal conductivity properties. The present study addresses the research gap concerning high-pressure structures in the Ta–Sb binary system, thereby offering valuable insights for the design and development of intermetallic compounds within this binary system. [ABSTRACT FROM AUTHOR]

Owing to the unique asymmetric geometry, Janus monolayer compounds exhibit various exotic thermal properties and have promising applications in thermal management. In this study, we combine machine learning potentials and the phonon Boltzmann transport equation to perform a comparative study of the thermal transport properties in Janus XBAlY (X = Se, S, Te; Y = S, Se, O; X ≠ Y) monolayers. Our findings unveil a thermal conductivity (κ p) ranking as SeBAlS > TeBAlO > SBAlSe, contradicting the conventional expectation that a higher κ p is typically observed when the average atomic mass is smaller. At room temperature, the κ p of SeBAlS is 174 Wm−1 K−1, which is 4.8 times that of SBAlSe when considering three-phonon scattering processes. Moreover, the consideration of four-phonon scatterings does not alter such ranking. The anomalous κ p phenomenon was explained through a detailed analysis of the phonon–phonon scattering mechanism, phonon bandgap, phonon anharmonicity, and chemical bond strength. This study highlights the intricate relationship between atomic mass, bonding characteristics, and thermal properties, offering insights for designing Janus materials with tailored thermal conductivity. [ABSTRACT FROM AUTHOR]

Hafnia (HfO2) is a potential candidate for the high-k gate dielectrics in next-generation high-power electronics. Its thermal transport properties, which determine the performance of these related high-power electronics, are critical while rarely investigated. Here, the thermal transport properties of HfO2 in a wide temperature range of 300–2000 K with a phase transition between monoclinic and tetragonal phases at ∼1765 K, are systematically studied based on the temperature-dependent effective potential landscapes with both propagating and coherence thermal transport considered. It is found that the cage-like structure of monoclinic HfO2 results in the avoid crossing in the phonon band structures, which increases the three-phonon scattering largely. Some phonon modes with significant scattering matrix can have relatively larger 3ph and 4ph scattering rates in tetragonal HfO2. Consequently, the thermal conductivity of HfO2 is only 11.95–1.72 W/mK at 300–2000 K. Our results further show that propagating phonon channels dominate the thermal transport in HfO2 and contribute at least 70% to the total thermal conductivity. The rest of the thermal conductivity of HfO2 results from the coherence thermal transport channels, which is caused by the overlap of phonons. Four-phonon scatterings are found to be significant for the thermal transport in tetragonal HfO2, which can result in a thermal conductivity reduction of ∼50%. Our results here advance the understanding of the thermal transport in HfO2, which may benefit the performance optimization of HfO2-related electronics. [ABSTRACT FROM AUTHOR]

The lattice thermal conductivity (LTC) of Ga 2 O 3 is an important property due to the challenge in the thermal management of high-power devices. In this work, we develop machine-learned neuroevolution potentials (NEPs) for single-crystalline β - Ga 2 O 3 and κ - Ga 2 O 3 and demonstrate their accuracy in modeling thermal transport properties. Combining NEP-driven homogeneous non-equilibrium molecular dynamics simulations with tensor analysis, we determine the spatial distributions of LTCs for two Ga 2 O 3 crystals, showing dissimilar thermal behaviors. Specifically, β - Ga 2 O 3 shows isotropic thermal transport properties, with the LTCs along [100], [010], and [001] directions being predicted to be 10.3 ± 0.2 , 19.9 ± 0.2 , and 12.6 ± 0.2 W/(m K), respectively, consistent with previous experimental measurements. For κ - Ga 2 O 3 , our predictions suggest nearly isotropic thermal transport properties, with the LTCs along [100], [010], and [001] being estimated to be 4.5 ± 0.1 , 3.9 ± 0.1 , and 4.0 ± 0.1 W/(m K). The reduced LTC of κ -Ga 2 O 3 vs β -Ga 2 O 3 stems from its restricted low-frequency phonons up to 5 THz. Furthermore, we find that the β phase exhibits a typical temperature dependence slightly stronger than ∼ T − 1 , whereas the κ phase shows a weaker temperature dependence, ranging from ∼ T − 0.5 to ∼ T − 0.7 . [ABSTRACT FROM AUTHOR]

The carbon nano-peapod is a representative structure with interlayer van der Waals (vdW) interactions, in which encapsulated fullerene molecules play a critical role in modulating the transport properties of the carbon nanotubes (CNTs). In particular, their influence on the thermal transport characteristics has been the focal point of considerable attention. In this study, we trained an accurate machine learning potential for fullerene-encapsulated CNTs based on the efficient NEP model to investigate their thermal properties. Using equilibrium molecular dynamics simulation along with the spectral decomposition method for thermal conductivity, we find that the thermal conductivity of fullerene-encapsulated CNTs is roughly 55 % lower than that of empty CNTs, aligning with experimental observations for CNT bundles with fullerene encapsulation [Kodama et al., Nat. Mater. 16, 892 (2017)]. The research suggests that weak vdW interactions between both the fullerene and CNTs, as well as between fullerene molecules themselves, hinder phonon propagation. The encapsulated fullerene contributes to an increase in phonon scattering within the CNTs, ultimately leading to a reduction in thermal conductivity. We utilized machine learning potential to investigate the structure of fullerene-encapsulated CNTs and their heat transport property. This approach provides valuable insights for performance research of complex systems featuring interlayer vdW interactions. [ABSTRACT FROM AUTHOR]

When an impurity with a light mass is inserted into a crystal, it can undergo a high-frequency oscillation referred to as a local vibrational mode (LVM). A Fermi resonance may occur between the LVM and lower-frequency modes of the defect. The LVM may also interact with phonons or the electromagnetic field. Understanding these interactions can help model and control diffusion, defect reactions, and thermal conductivity. LVMs have been probed in semiconductors using pressure and alloying as experimental parameters, resulting in anticrossing between localized and extended vibrational modes. These types of vibrational interactions could play an important role in the stability and thermal properties of organic–inorganic hybrid semiconductors. The coupling between an LVM and electromagnetic wave yields an "LVM polariton," an excitation that has significant vibrational and electric-field amplitudes. [ABSTRACT FROM AUTHOR]

Time-domain thermoreflectance (TDTR) and frequency-domain thermoreflectance techniques have been widely used to measure thermal properties. However, the existence of the metal sensor brings some limitations to the experimental measurement, such as temperature limits, disability to measure low in-plane thermal conductivity, in situ measurement cannot be achieved, etc. This paper proposes a transducerless time-domain thermoreflectance method to measure in- and cross-plane thermal conductivity of nanofilms, in which the optical absorption depth and thermal conductivity tensor are considered to establish a new differential equation that can describe the heat conduction process in multilayer structures. This thermal model can also calculate the effects of spot ellipticity and spot offset distance. Then, the analytical solution and relative deviation of this new model and the surface heat flow boundary model used in conventional TDTR are compared by calculating the phase signals. In terms of experimental measurement, this model is successfully used to derive cross- and in-plane thermal conductivity of PdSi and IrNiTa amorphous alloy nanofilms without a metal sensor. [ABSTRACT FROM AUTHOR]

As the demand for computing applications capable of processing large datasets increases, there is a growing need for new in-memory computing technologies. Oxide-based resistive random-access memory (RRAM) devices are promising candidates for such applications because of their industry readiness, endurance, and switching ratio. These analog devices, however, suffer from poor linearity and asymmetry in their analog resistance change. Various reports have found that the temperature in RRAM devices increases locally by more than 1000 K during operation. Therefore, temperature control is of paramount importance for controlling their resistance. In this study, scanning thermal microscopy is used to map the temperature of Au/Ti/HfOx/Au devices at a steady power state and to measure temperature dynamics of the top electrode above the filament location during both resistive switching loops and voltage pulsing. These measurements are used to verify the thermal parameters of a multiphysics finite elements model. The model is then used to understand the impact of thermal conductivities and boundary conductances of constituent materials on resistance change during the first reset pulse in RRAM devices. It is found that the resistance change can be reduced significantly when the temperature in the titanium capping layer is reduced. We find that the greatest temperature reduction and, therefore, the lowest resistance change in the device are afforded by capping layers with increased thermal conductivities. This work links thermal properties to the resistance change in RRAM devices, providing critical insights into engineering devices with improved switching dynamics. [ABSTRACT FROM AUTHOR]

The suspension nanoparticles in non-Newtonian materials convey different applications in the thermal systems, engineering processes, industrial energy developments, extrusion systems, solar system, etc. It is commonly observed that the thermal properties in the various base materials fluctuated and cannot be assumed to be constants. A decomposition of nanofluids is fluctuated and cannot considered as a constant. The objective of this communication is to inspect the thermal mechanism of non-Newtonian nanofluids due to accelerated frame in view of variable thermal conductivity. The modified mathematical relations for Fourier and Fick theories are utilized to model the problem. The nanofluids contain the microorganisms to ensure the thermal stability. The problem is modeled in nonlinear partial differential system which is further communicated via HAM. The convergent analysis is ensured and later on physical illustrations to problem in view of parameters are discussed. It is observed that thermal phenomenon controls due to mixed convection parameter while increasing impact for Williamson fluid parameter is observed. The magnitude of oscillation of Nusselt number due to Prandtl number is enhanced without any phase difference. The obtained results may convey different engineering applications like extrusion systems, chemical processes, thermal management systems, heating and cooling application, plasma, manufacturing processes. [ABSTRACT FROM AUTHOR]

This study investigates the effect of positive temperature coefficient (PTC) fillers, i.e., barium strontium titanate (BST‐60) and nano hexagonal boron nitride (h‐BN) fillers, on thermal and dielectric insulation properties of epoxy (EP). The electrical resistivity, DC breakdown strength, space charge, thermal conductivity, thermogravimetric analysis, and glass transition temperature (Tg) of EP composites were measured. Results indicate that, below curie temperature, the EP composites containing 0.5 and 1 wt% of BST and 5 wt% of h‐BN have superior electrical resistivity, breakdown strength, and thermal conductivity. However, above curie temperature, the EP composites containing 2 and 2.5 wt% of BST and 5 wt% of h‐BN have superior insulation properties than the pure EP and other composites. While the thermal properties of EP improve with an increase in h‐BN loading to 10 wt%, its dielectric properties are slightly compromised due to the presence of tiny defects in the composite material. It is hypothesized that the BST‐60 suppresses the negative temperature coefficient effect (NTC) of EP by regulating the electrical resistivity above the curie point, whereas nano h‐BN enhances the thermal conductivity of EP by constructing a heat dissipation path. The proposed mechanism for charge dynamics along with heat conduction‐dissipation explains the fillers' behavior at different temperatures. Highlights: Analysis of epoxy composites with polydopamine‐modified BST and h‐BN fillers.PTC fillers are used to mitigate the negative temperature effect of epoxy.Optimal fillers wt% improves dielectric and thermal properties.This study shows that optimized epoxy composites can be used for packaging. [ABSTRACT FROM AUTHOR]

Epoxy resins (EPs) are highly coveted as insulating materials for engineering applications. However, their limited mechanical properties and inadequate thermal conductivity at cryogenic temperatures significantly restrict their range of applications. Herein, a novel approach was introduced for crafting EP composites infused with boron nitride (BN) using hyperbranched polymer (HBP) grafting. The resulting HBP‐BN was uniformly dispersed within the EP and securely bonded to the matrix through robust chemical interactions, significantly improving the property enhancement efficiency of HBP‐BN on EP. Thus, the mechanical strength of EP/HBP‐BN composites was significantly enhanced, with maximum tensile and impact strengths achieved at 6 and 4 wt% HBP‐BN content. These values exceeded those of pure EP by 47% and 22% at room temperature (RT) and increased even more substantially to 72% and 135% at 77 K. Moreover, the composite demonstrated a remarkable 430% improvement in thermal conductivity, reaching 1.1627 W·m−1·K−1, when the HBP‐BN content reached 40 wt%. Simultaneously, EP/HBP‐BN composites exhibit low dielectric permittivity and high volume resistivity, signifying exceptional electrical insulation properties. HBP‐BN substantially enhances the cryogenic properties of EP composites, offering an efficient pathway for the utilization of EPs in engineering applications. Highlights: A novel method to enhance the cryogenic properties of EP was introduced.HBP‐BN significantly improves the cryogenic properties in EP composites.The composites are of significant interest for various engineering applications. [ABSTRACT FROM AUTHOR]

By applying the high-entropy strategy, one can develop stable mixed oxide by populating a single sublattice with many distinct cations. Two kinds of rare-earth high-entropy hexaaluminates (La 1/5 Nd 1/5 Sm 1/5 Eu 1/5 Gd 1/5)MAl 11 O 19 (M = Mg and Zn) were successfully synthesized, and their mechanical and thermal properties were analyzed. We highlight that the Zn-containing sample displays a significant increase in fracture toughness (2.48 MPa m1/2) and a decrease in thermal conductivity (1500 °C, 1.2 W m−1 K−1) as compared to the Mg-containing sample. The diffusion of fine grains in platelet-like grains observed only in the Zn-containing sample is considered to be responsible for its outstanding mechanical properties. This work demonstrates the excellent thermal-mechanical properties of the Zn-containing sample and indicates the promising use of high-entropy hexaaluminate in the aerospace field acting as thermal barrier coating materials. [ABSTRACT FROM AUTHOR]

Strain provides an additional mechanism in tuning the thermal/electrical properties of nanostructures and therefore has triggered lots of interest in recent years. However, experimental research about the strain effect on the thermal conductivity of nanowires is still limited, especially in the low-temperature range, which is important in understanding the physics of strain-induced regulation in thermal conductivity. Here, we present thermal transport measurements of bent silicon carbide nanowires at temperatures ranging from 20 to 300 K. Reduction in thermal conductivity compared to their straight counterparts is observed. More specifically, the relative change is up to 55% at 20 K and descends with temperature, which is due to the inhomogeneous strain-induced phonon scattering. This study will deepen the understanding of thermal properties in nanostructures with strain. [ABSTRACT FROM AUTHOR]

Thermally conductive polymeric composites with low dielectric constant are highly promising for the packaging materials in the field of modern communication. Therefore, the synergistic improvement of low dielectric constant and high thermal conductivity has become a current research hotspot. In this work, we propose a one‐step alkylation of boron nitride nanosheet (BNNS) with ultrasonic stratification using 1‐hexanol, and then hot press the films to make Alkyl‐BNNSs orient in the fluorinated polyimide (f‐PI). The resulting Alkyl‐BNNS/f‐PI composite successfully realizes the synergistic improvement of thermal property and dielectric properties, exhibiting a high heat conductivity coefficient of 2.36 Wm−1 K−1 with a filler content of 4.99 wt.%. Moreover, the permittivity and dielectric loss of the film are as low as 1.76 and 0.0065 at 1 MHz, respectively. This work provides a facile strategy for breaking the bottleneck of making polyimide composites simultaneously with high thermal conduction and low dielectric performance. Highlights: The composite exhibits a high heat‐conducting coefficient of 2.36 Wm−1 K−1.Ultra‐low dielectric constant of 1.76 was achieved by the modification of film.Excellent breakdown resistance and flexibility were endowed with the composites. [ABSTRACT FROM AUTHOR]

The development of polymer‐based dielectric nanocomposites with superior dielectric properties, heat dissipation, and excellent thermal stability remains a significant challenge for advanced electronic and electrical systems. In this work, boron nitride nanosheets (BNNS) and MgAl layered double hydroxide nanosheets (MgAl LDHNS) were utilized as binary fillers and incorporated into polyetherimide (PEI) to fabricate BNNS‐MgAl LDHNS/PEI nanocomposite films by ball milling dispersion and solution casting method. Owing to the exceptional synergistic effect of BNNS with high thermal conductivity and large diameter, combined with MgAl LDHNS with high dielectric constant and small diameter, the dielectric constant and thermal conductivity of the nanocomposite film were enhanced while maintaining low dielectric loss and high breakdown strength. For the BNNS‐MgAl LDHNS/PEI nanocomposite films with filler loading of 12 wt%, the dielectric constant (6.47 at 100 Hz) increased by 73%, the in‐plane thermal conductivity (6.932 W/m·K) and through‐plane thermal conductivity (0.407 W/m·K) increased by 561% and 111%, respectively. And the breakdown strength of the nanocomposite film remains at 82.1 kV/mm. Simultaneously, the thermal stability and mechanical flexibility of the nanocomposite film were maintained. This work presents a promising PEI‐based composite material and offers new insights into the role of two‐dimensional binary fillers with varying sheet diameters in enhancing the properties of polymer‐based composites. Highlights: BNNS‐MgAl LDHNS/PEI nanocomposite film was prepared.The nanocomposite film has high dielectric and thermal properties.The interfacial polarization synergistic enhanced by the 2D binary fillers.A high thermal conductivity path was formed between 2D binary fillers. [ABSTRACT FROM AUTHOR]

This work describes the preparation and properties of a novel category of thermosetting microwave absorbing composite materials. The composites were prepared by a simple solution casting process, employing high temperature resistant polysilylaryl-enyne (abbreviated as PSAE) resin as matrix and perovskite CaMnO 3 (abbreviated as CMO) ceramic filler as absorbent filler. The microstructure, electromagnetic, wave absorbing and thermal properties of the CMO-PSAE composites were all examined. The results showed that the increasing fraction of CaMnO 3 filler not only densified the microstructure of the composites, but also greatly improved their temperature resistance, thermal conductivity and wave absorption properties. The CMO-PSAE composite doped with 50 vol% CaMnO 3 ceramic filler showed the strongest ability to absorb electromagnetic waves, with an effective absorption bandwidth (EAB) of 4.16 GHz and a minimum reflection loss is −53.01 dB. Besides, the thermal conductivity of the composite reached 1.106 W/(m·K). Furthermore, this composite material has exceptional thermal resistance, with the highest T d5 reaching 650 °C. Composites with varying doping levels can be used for specific performance needs in practical scenarios. Thus, such novel CMO-PSAE composites exhibit potential applications in the electromagnetic countermeasure field under high-temperature environments. [ABSTRACT FROM AUTHOR]

This study investigates spatially resolved phonon-mediated thermal transport across nano-sized grains and grain boundaries (GBs) in 3C-SiC using molecular dynamics (MD) simulations. This investigation involves controlling the complete range of inter-grain misorientation tilt angles (θ = 0°–90°) and nanoscale grain sizes (d = 2.18–130.77 nm). The grain boundary energy and interfacial thermal transport are found to be highly θ -sensitive and asymmetric with respect to θ = 45° due to the low symmetry associated with two interpenetrating diatomic SiC fcc lattices. When adjacent grains are tilted at θ = 14.25°, the interfacial heat conduction is highly suppressed compared to other θ values, especially for larger grains. The most stable atomic configuration of the GB region associated with the minimal GB energy results in the highest suppression of heat conduction across the GB interface. Spatially resolved thermal anisotropy reveals a strong GB-mediated nanoscale hydrodynamic phonon Poiseuille effect when heat flows parallel to the GB planes, as shown by our perturbed MD study. With the reduction of d , the intra-grain and inter-GB thermal conductivities decrease due to the enhanced phonon scattering from interfaces, but the difference between these conductivities becomes negligible for the heat flow normal to the GB planes. It is envisioned that nanoscale spatially resolved control of thermal energy will provide useful guidance to engineer nanocrystalline ceramics with tunable interfacial thermal properties. [ABSTRACT FROM AUTHOR]

Cu2Se‐based binary compounds have recently fetched the attention of researchers due to their remarkable electrical and extremely low thermal properties. In addition, Cu2Se‐based quaternary chalcogenides are expected to present exceptional thermoelectric performance. Cu2Se1−x−ySxTey‐like compounds are synthesized via microwave‐assisted hydrothermal method and their respective thermal and electrical transport properties are studied in this research work. The phase purity and homogeneity are examined by X‐ray diffraction and energy‐dispersive X‐ray spectrometry analysis. The introduction of S and Te elements into Cu2Se matrix enhances Seebeck coefficient resulting in improved electrical performance illustrating a maximum power factor of 989.4 μWK−2 m−1 at 673 K. Furthermore, S‐ and Te‐co‐doped samples exhibit reduced total thermal conductivity values with lowest value of 0.808 WK−1 m−1 for Cu2Se0.96S0.02Te0.02 sample in comparison to 1.18 WK−1 m−1 for the pristine sample. The simultaneous improvement in electrical and thermal properties results in enhanced figure of merit of 0.82 for Cu2Se0.96S0.02Te0.02 sample at 673 K. [ABSTRACT FROM AUTHOR]

[Display omitted] • CNTs-related composite PCMs are categorized in a new way: CNTs are usd as nanoadditives, porous supporters, and secondary network. • The research progress in the mechanism of heat transfer and phase transition of CNTs-related composite PCMs is introduced in detail. • In-depth insights into the micro-mechanism of heterogeneous interactions induced by CNTs are revealed. • The current challenges of designing CNTs-related composite PCMs are summarized. With the merits of inherent physicochemical properties of hollow structure, high mechanical strength, thermal stability, ultrahigh light absorption capacity, and ultrahigh thermal conductivity, carbon nanotubes (CNTs) are extensively used to enhance the thermal storage capabilities of solid–liquid phase change materials (PCMs). Interestingly, CNTs can act as thermally conductive additives and supporting skeletons when marring with PCMs. The state-of-the-art reviews on PCMs pay attention to carbon-based porous composite PCMs or nanoparticle dispersed PCMs, CNTs-derived PCMs only share a small part, lacking of a comprehensive review for multifunctional CNTs compounded PCMs. Herein, focusing on the enhancement effects of CNTs on PCMs, we retrospectively describe composite PCMs with a novel category way, by using CNTs as nanoadditives, porous supporters, and secondary network. We emphasize the micro-mechanism of heterogeneous interactions induced by CNTs: crystallization behavior, interfacial thermal resistance, thermal conductivity, phonon transport. Simultaneously, we provide in-depth insight into relationship between micro structural and thermal properties of CNT-derived PCMs. As a result, some different pathways of modern utilization based on the improved PCMs are presented. Finally, we outline the current challenges of designing CNTs to enable advanced functional thermal storage materials. The review aims to inspire clever use of CNTs into PCMs for targeted applications. [ABSTRACT FROM AUTHOR]

Thermally stable high-performance phenolic resin aerogels (PRAs) are of great interest for thermal insulation because of their light weight, fire retardancy and low thermal conductivity. However, the drawbacks of PRA synthesis, such as long processing time, inherent brittleness and significant shrinkage during drying, greatly restrict their wide applications. In this work, PRAs were synthesized at ambient pressure through a near-net shape manufacturing technique, where boron-containing thermosetting phenolic resin (BPR) was introduced into the conventional linear phenolic resin (LPR) to improve the pore characteristics, mechanical properties and thermal performances. Compared with the traditional LPR-synthesized aerogel, the processing time and the linear shrinkage rate during the drying of the PRAs could be significantly reduced, which was attributed to the enhanced rigidity and the unique bimodal pore size distribution. Furthermore, no catastrophic failure and almost no mechanical degradation were observed on the PRAs, even with a compressive strain of up to 60% at temperatures ranging from 25 to 200 °C, indicating low brittleness and excellent thermo-mechanical stability. The PRAs also showed outstanding fire retardancy. On the other hand, the PRAs with a density of 0.194 g/cm3 possessed a high Young's modulus of 12.85 MPa and a low thermal conductivity of 0.038 W/(m·K). [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation of nanocomposites composed of three ratios of epoxy/graphene nanoplatelets (GNPs) by weight. The 0.1, 0.2, and 0.3 wt.% specimens were carefully manufactured, and their mechanical and thermal conductivity properties were examined. The tensile strength and modulus of epoxy/GNPs were enhanced by the large surface area of graphene nanoplatelets, causing crack deflection that created new fracture fronts and friction because of the rough fracture surface. However, the compressive strength was gradually reduced as GNP loading percentages increased. This was probably due to severe plastic yielding on the epoxy, leading to catastrophic axial splitting caused by premature fractures. Furthermore, the highest thermal conductivity was 0.1283 W/m-K, representing a 20.92% improvement over neat epoxy (0.1061 W/m-K) when 0.3 wt.% GNPs were added to the epoxy. This was because of efficient heat propagation in the GNPs due to electron movement through percolative paths. The tensile failure mode in epoxy/GNP nanocomposites showed a few deflected and bifurcated rough cracks and brittle, dimple-like fractures. Contrarily, compressive failure mode in GNP-added epoxy showed plastic flexural buckling and brittle large-axial splitting. The epoxy/GNP nanocomposites were considered a damage-tolerant material. [ABSTRACT FROM AUTHOR]

In a recent breakthrough in the field of two-dimensional (2D) nanomaterials, the first synthesis of a single-atom-thick gold lattice of goldene has been reported through an innovative wet chemical removal of Ti3C2 from the layered Ti3AuC2. Inspired by this advancement, in this communication and for the first time, a comprehensive first-principles investigation using a combination of density functional theory (DFT) and machine learning interatomic potential (MLIP) calculations has been conducted to delve into the stability, electronic, mechanical and thermal properties of the single-layer and free-standing goldene. The presented results confirm thermal stability at 700 K as well as remarkable dynamical stability of the stress-free and strained goldene monolayer. At the ground state, the elastic modulus and tensile strength of the goldene monolayer are predicted to be over 226 and 12 GPa, respectively. Through validated MLIP-based molecular dynamics calculations, it is found that at room temperature, the goldene nanosheet can exhibit anisotropic tensile strength over 9 GPa and a low lattice thermal conductivity around 10 ± 2 W/(m.K), respectively. We finally show that the native metallic nature of the goldene monolayer stays intact under large tensile strains. The combined insights from DFT and MLIP-based results provide a comprehensive understanding of the stability, mechanical, thermal and electronic properties of goldene nanosheets. [ABSTRACT FROM AUTHOR]

Ambient pressure drying (APD) of silica aerogels has emerged as an attractive method adapting to large-scale production. Spring-back is a unique phenomenon during APD of silica aerogels with volume expansion after its shrinkage under capillary force. We attribute the intense spring-back at elevated drying temperatures to a dense structure formed on the surface and the formation of positive internal pressure. Furthermore, an APD-assisted foaming method with an in situ introduction of NH4HCO3 was proposed. NH4HCO3 decomposing at drying temperatures hastened the emergence of positive pressure, thereby increasing the expansion volume. Compared to the previous method, the porosity of silica aerogel increased from 82.2% to 92.6%, and mesopore volume from 1.79 cm3 g−1 to 4.54 cm3 g−1. By adjusting the amount of the silicon source, silica aerogels prepared by the APD-assisted foaming method generated higher volume expansion and lower thermal conductivity. After calcination to remove undecomposed ammonium salts, the hydrophobic silica aerogel with a density of 0.112 g cm−3 reached a mesopore volume of 5.07 cm3 g−1 and a thermal conductivity of 18.9 mW m−1·K−1. This strategy not only improves the thermal insulation properties, but also offers a significant advancement in tailoring silica aerogels with specific porosity and mesopore volume for various applications. [ABSTRACT FROM AUTHOR]

In this study, a highly dense GdB 6 bulk ceramic material was fabricated using one-step in-situ reaction spark plasma sintering technology. The sample with a relative density of 96.7 % and a purity of 96.9 wt% was successfully obtained by sintering at 1800 °C for 30 min under a uniaxial pressure of 50 MPa. The Vickers hardness, elastic modulus and fracture toughness of the as-obtained GdB 6 bulk ceramics were 18.9 GPa, 209 GPa and 1.6 MPa·m1/2, respectively. The thermal conductivity of GdB 6 at room temperature was 28.68 W·m−1·K−1, 70 % of which was mainly attributed to phonon vibration, while the remaining 30 % to the electrical thermal conductivity. In addition, the as-obtained GdB 6 ceramics showed no phase transformation after heat treatment at a relatively high temperature of 2100 °C for 20 min in Ar atmosphere. The highly covalent octahedral boron framework played a critical role in maintaining the phase stability of the GdB 6 crystal lattice. This suggested that GdB 6 ceramics could be used as potential ultra-high temperature ceramics for aerospace applications and high-power vacuum electronic devices operated at high temperatures. [ABSTRACT FROM AUTHOR]

Rare earth compounds (RE 2 O 3), typically Eu 2 O 3 and Gd 2 O 3 , are considered as absorbing materials due to their long chain neutron absorbing ability and high efficiency of neutron absorption. In this paper, a specifically designed x Eu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 (x = 0.6, 0.7, 0.8, 0.85) composite ceramics with excellent thermal properties were synthesized through direct thermal decomposition reactions followed a high-temperature sintering method under vacuum conditions. X-ray diffraction (XRD) and Raman spectroscopy analysis indicated that the obtained ceramics consisted of monoclinic Eu 2 O 3 and fluorite Gd 2 Zr 2 O 7 phases. The hardness of x Eu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 ceramics (x = 0.8, 0.85) have no significantly changes in the test temperature range (25–350 °C). The thermal expansion coefficients (TECs) (7.3–10 ×10-6 K-1) are lower than Dy 2 TiO 5 (9.3–10.4 ×10-6 K-1), and the thermal expansion rate changes linearly with the increase of temperature, which indicates that the x Eu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 ceramics exhibit excellent high temperature phase stability. Furthermore, the range of thermal conductivities is from 0.96 W·m-1·K-1 to 2.02 W·m-1·K-1 (25–800 °C), which is higher than Dy 2 TiO 5 (0.27–0.55 W/m·K, 220–650 °C). Compared with the state-of-art Dy 2 TiO 5 ceramics, x Eu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 have superior thermal properties and are therefore expected to be the next generational of neutron absorbent materials used in ash rod. [ABSTRACT FROM AUTHOR]

Foam-forming technique imparts ceramic fiber paper with excellent uniformity, low density, and high porosity, but its strength loss must be compensated. Herein, a flexible and rigid foam-formed ceramic fiber network was manufactured by using different strength improvement methods and simultaneously investigated their strength and thermal insulation properties. Sufficient strength (1136 kPa) was achieved by combining Polyvinyl alcohol (PVA) 2 % and Polyester (PET) 3 %. However, the tensile strength of fiber networks would decrease under the contribution of inter-fiber bonding area reduced when the fiber length was longer than 24 mm. Benefiting from the developed flocculation system (aluminum sol-anionic polyacrylamide-carboxymethylcellulose), the strength of the foam-formed ceramic fiber network was 20 kPa, the retention rate increased from 75 % to 88 %, and the average aggregation factor of fillers in the Z direction was 0.67. By adjusting the ratio and Z-directional distribution of functional fillers, the sintered foam-formed paper with a tensile strength of 1300 kPa and compressive strength of 1000 kPa could be obtained. The thermal insulation performance (thermal conductivity 0.03252 W/(m·K)) was similar to the quartz fiber paper reinforced silica airgel, and the flame resistance was better than the commercialized aluminum silicate wool board. [ABSTRACT FROM AUTHOR]

Ceramic thermal barrier coatings (TBCs) with high toughness and low thermal conductivity are important for developing aero engines with high thrust‐to‐weight ratio and thermal efficiency. In this work, the properties of tantalate Y1/6Yb5/6TaO4 (YYT) were optimized by introducing 8 wt.% yttria‐stabilized zirconia (8YSZ), synthesized using spark plasma sintering, as a second‐phase ceramic. The highest toughness (3.57 MPa m1/2) of the YYT/8YSZ composite ceramics was due to multiple toughening mechanisms. The underlying mechanisms of these processes were revealed based on the microstructures and residual stress of the YYT/8YSZ composite ceramics. A shift from an intergranular fracture to a transgranular fracture was caused by the difference between soft‐grain YYT and hard‐grain 8YSZ, which consumed the fracture energy. Furthermore, the formation of microcracks, crack deflection, bridging, and branching were analyzed based on the differences in Young's moduli and thermal expansion coefficients of YYT and 8YSZ. Internal defects and weak connections between the YYT and 8YSZ grains reduced the thermal conductivity of the composites until it reached its lowest value at 1.4 W m−1 K−1. The studied toughening mechanisms could be applied to various composites. Moreover, herein, we provide a new strategy to design and synthesize TBCs with enhanced performance. [ABSTRACT FROM AUTHOR]

The order-disorder transition (ODT) of RE zirconate (RE 2 Zr 2 O 7) has received much attention due to its potential applications in the design of thermal barrier coatings (TBCs). A series of high entropy RE zirconates (RE = La, Sm, Gd, Er and Lu) were designed and synthesized in order to regulate the fluorite-pyrochlore phases, and to investigate the effect of phase composition on the microstructures and performances. The results showed that the sintering temperature, as well as equivalent ion radius, played an important role in regulating the phase transformation of fluorite-pyrochlore. The coexistence of pyrochlore-fluorite phases not only can result in the decrease in grain size but also increased the lattice strain of each phase, thereby enhancing the phonon scattering and contributing to the reduction in the thermal conductivity. The CMAS corrosion resistance was mainly related to phase compositions, and the thicknesses of reaction layer decreased gradually with the increasing fluorite phase content. The results will provide theoretical guidance for the microstructural design of high entropy RE zirconates as next generation TBC materials in future. [ABSTRACT FROM AUTHOR]

Recent advances have shown the beneficial impact of adding nanoparticles to thermal oil. Diamond and boron nitride nanoparticles have superior thermal conductivity and excellent thermal and optical properties. In the current study, thermal conductivity, specific heat, and rheological behavior of diamond and boron nitride-based hybrid nanofluids in thermal oil are experimentally investigated for 0%, 0.2%, 0.4%, and 0.6% weight concentrations and a wide range of temperatures. The proportion between diamond and boron nitride utilized in the study is 1:1. A two-step method is applied to prepare stable hybrid nanofluids. The obtained data indicate that the hybrid nanofluids' thermal conductivity and specific heat enhance with increasing temperature and weight concentration. Almost 37.4% and 48.1% enhancement is observed in the thermal conductivity and specific heat, respectively, at 65 °C and 0.6% weight concentration. Thermal oil-based hybrid nanofluids display Newtonian behavior at low shear rates and an inverse relationship with temperature. Shear-thinning non-Newtonian behavior is observed at high shear rates and temperatures. A maximum increase in viscosity up to 22.0% is observed at 65 °C and 0.6% wt. concentration. The relative change indicates that all investigated properties have a significant impact, where the increasing trend of thermal conductivity and specific heat with increasing temperature and weight concentration of thermal oil-based hybrid nanofluids make them suitable for high-temperature heat transfer applications. [ABSTRACT FROM AUTHOR]

This experimental study aimed to investigate the potential control of microstructural-mineralogical characteristics on thermal properties and its relation with the deformational behaviour in mild to high temperature (25°–800°C) regime of coal-bearing sandstone from an underground coal mine fire region. Barakar sandstone from Jharia Coalfield, India, one of the world's largest underground coal mine fire regions, was chosen. The thermal parameters and their relations to the mineralogical, microstructural, and damage characteristics of Barakar sandstone have been discussed. Thermal conductivity (λ), thermal diffusivity (κ), and specific heat capacity (Cp) of heat-treated samples were determined using the transient plane source method. Additionally, detailed petrography, scanning electron microscopy, and electron probe micro-analyser were used to understand the thermal effect on mineralogy and microstructures. The deformational behaviour with elevated temperature was investigated through the universal testing machine. The obtained results suggest three characteristic temperature regimes: mild temperature regime (25°–300°C), transitional temperature regime (300º–500°C) and high temperature regime (500º–800°C). Moreover, prediction models for thermal properties have also been developed using multi-gene genetic programming (MGGP), considering physical properties as input parameters. In view of experimental constraints to determine the thermos-elastic properties of a rock due to tedious experimental processes, the proposed prediction models shall be very useful to indirectly estimate the thermal properties of sandstone rocks using easily determined physical parameters. The outcome of the present study may be useful to understand the subsidence induced by underground coalmine fire, which is a distressing issue in the Jharia region due to persistent coalmine fire. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs-), graphene (GNs)-natural rubber (NR) composites were prepared by wet mixing process and dry mixing process, respectively. Thermal conductivity, 300% tensile stress, tear strength and elongation at break of the samples were measured experimentally. The effects of mixing process, carbon materials content and type on thermal properties and mechanical properties of composites were studied. The experimental results show that, the thermal conductivity of the mixed rubber, the 300% tensile stress and the tear strength of the vulcanizate all increase first and then decrease slightly with the increase of the carbon material content, regardless of the mixing process. However, the elongation at break of vulcanizate showed an opposite trend. When the carbon material content is 2.0% (w.t.%), thermal conductivity, 300% tensile stress and tear strength all reach their maximum, while elongation at break obtains minimum. Under the same amount of addition, GNs is more conducive to improving the thermal conductivity and elongation at break of composites, while CNTs are more conducive to improving the tensile strength and tear strength of composites. For CNTs-, GNs-NR composites, the wet mixing process can greatly improve the thermal conductivity, tensile strength and tear strength of composites, while the dry mixing process can greatly improve the elongation at break of composites. Therefore, when preparing CNTs-, GNs-NR composites, it is necessary to select a suitable mixing process according to the performance requirements of the final product. [ABSTRACT FROM AUTHOR]

Thermal transport properties of metallic nanowires are crucial to the near-junction heat dissipation of transistors. However, the understanding of the size-dependent thermal conductivity of these advanced interconnect metals is still limited. In this work, we select nine candidate metals and investigate the size effect on thermal transport properties by the mode-level first-principles method combining with the Boltzmann transport equation. Their thermal conductivity, the phonon contribution, and the Lorenz ratio in nanowires with characteristic size from 3 to 30 nm are analyzed. While all these metals have lower bulk thermal conductivity than Cu, we find some of these metals have larger thermal conductivity with characteristic size smaller than 10 nm. We identified that their smaller electron mean free path is the key factor. Moreover, the contribution of phonon thermal conductivity is smaller than 25% to total thermal conductivity. The Lorenz ratio is found to be slightly larger than the Sommerfeld value, mainly due to the phonon contribution. This work can provide important guidance for selecting advanced interconnects in the development of next-generation integrated circuits. [ABSTRACT FROM AUTHOR]

This paper describes the composites of silane cross-linked polyethylene (PEXb) mixed with four different fillers dedicated to improving thermal conductivity, such as multi-walled carbon nanotubes, graphite, boron nitride, and mineral filler. Using the mathematical modeling, the concentration of each filler was estimated to reach the value of 0.675 W m−1 K−1 suitable for the usage PEXb in the production of geothermal pipes. From tested fillers, all improve the thermal conductivity of pure PEXb; however, above the required value, only 28 mass% of boron nitride (0.937 W m−1 K−1). It was associated with its perfect dispersion and the highest gel content achieved, also resulting in the highest flexural modulus. Graphite at 5 mass% and mineral filler at 35 mass% allowed the thermal conductivity to equal 0.622 W m−1 K−1 and 0.624 W m−1 K−1, respectively, with a simultaneous medium effect on the mechanical properties. Carbon nanotubes increased PEX's conductivity to a small extent, due to their occurrence as agglomerates. [ABSTRACT FROM AUTHOR]

As one of the emerging nanomaterials, boron nitride nanotubes (BNNTs) provide promising opportunities for diverse applications due to their unique properties, such as high thermal conductivity, immense inertness, and high-temperature durability, while the instability of BNNTs due to their high surface induces agglomerates susceptible to the loss of their advantages. Therefore, the proper functionalization of BNNTs is crucial to highlight their fundamental characteristics. Herein, a simplistic low-cost approach of BNNT surface modification through catechol-polyamine (CAPA) interfacial polymerization is postulated to improve its dispersibility on the polymeric matrix. The modified BNNT was assimilated as a filler additive with AlN/Al2O3 filling materials in a PDMS polymeric matrix to prepare a thermal interface material (TIM). The resulting composite exhibits a heightened isotropic thermal conductivity of 8.10 W/mK, which is a ~47.27% increase compared to pristine composite 5.50 W/mK, and this can be ascribed to the improved BNNT dispersion forming interconnected phonon pathways and the thermal interface resistance reduction due to its augmented compatibility with the polymeric matrix. Moreover, the fabricated composite manifests a fire resistance improvement of ~10% in LOI relative to the neat composite sample, which can be correlated to the thermal stability shift in the TGA and DTA data. An enhancement in thermal permanence is stipulated due to a melting point (Tm) shift of ∼38.5 °C upon the integration of BNNT-CAPA. This improvement can be associated with the good distribution and adhesion of BNNT-CAPA in the polymeric matrix, integrated with its inherent thermal stability, good charring capability, and free radical scavenging effect due to the presence of CAPA on its surface. This study offers new insights into BNNT utilization and its corresponding incorporation into the polymeric matrix, which provides a prospective direction in the preparation of multifunctional materials for electric devices. [ABSTRACT FROM AUTHOR]

In the realm of thermal interface materials (TIMs), high thermal conductivity and low density are key for effective thermal management and are particularly vital due to the growing compactness and lightweight nature of electronic devices. Efficient directional arrangement is a key control strategy to significantly improve thermal conductivity and comprehensive properties of thermal interface materials. In the present work, drawing inspiration from natural leaf and branch structures, a simple-to-implement approach for fabricating oriented thermal conductivity composites is introduced. Utilizing carbon fibers (CFs), known for their ultra-high thermal conductivity, as branches, this design ensures robust thermal conduction channels. Concurrently, boron nitride (BN) platelets, characterized by their substantial in-plane thermal conductivity, act as leaves. These components not only support the branches but also serve as junctions in the thermal conduction network. Remarkably, the composite achieves a thermal conductivity of 11.08 W/(m·K) with just an 11.1 wt% CF content and a 1.86 g/cm3 density. This study expands the methodologies for achieving highly oriented configurations of fibrous and flake materials, which provides a new design idea for preparing high-thermal conductivity and low-density thermal interface materials. [ABSTRACT FROM AUTHOR]

Microwave heating has been applied to improve cement-based materials (CBMs) structures deicing efficiency, which reduce the effect of icing on their service life. Moreover, the enhanced thermal properties of CBMs can further improve their deicing efficiency. In this study, silicon carbide (SiC) ceramic particles with favorable thermal properties were used to prepare the SiC cement-based materials (SCBMs). The effect of SiC ceramic on the mechanical strength of CBMs was investigated. Next, the heat transfer and storage ability of CBMs were investigated to analyze the changes in their thermal-physical parameters. Then, the surface thermal responses of the CBMs during microwave heating and off were recorded to characterize their temperature evolution in a low-temperature condition. Furthermore, the deicing efficiency of CBMs was determined using the ice layer shedding time (ILST) as the index. The results show that the filling effect of SiC ceramic on CBMs improved their mechanical strength within a certain content range. However, a large content of SiC ceramic caused an increase in the weak area and porosity within the CBMs, further reducing their mechanical properties. The thermal-physical parameters of CBMs were improved after adding SiC ceramic. The thermal conductivity and thermal effusivity of SCBMs-100 were 13.17 W/(m·K) and 1.44 W/(mm2·K), respectively, 7.90 and 2.35 times higher than the control group. Due to the favorable thermal properties of SCBMs, their heating rate and surface temperature field distribution characteristics were further improved. Furthermore, with the increase of SiC ceramic content, the ILST of SCBMs was further reduced during microwave heating. Therefore, the SiC ceramic was a favorable material, improving the thermal properties and deicing efficiency of CBMs to a certain extent. However, considering its effect on the deterioration of the mechanical properties of CBMs, the optimal content of SiC ceramic might be 75%. [ABSTRACT FROM AUTHOR]

The rapid development of micro-electronics has a growing demand on the heat dissipation performance of devices, especially thermal management materials. However, recent researches focus on the improvement of single ability, such as thermal or mechanical properties. Herein, a strategy that simultaneously improves thermal and mechanical performance of thermal manager material was proposed, which was achieved by preparing Cu-SiC w composites via the co-electrodeposition technology. The influence of electroplating parameters, such as temperature, current density and reinforcement contents, on the microstructure evolution, mechanical and thermal conductivity were investigated systematically. The fabricated SiC w composite displayed excellent shear strength up to 420 MPa, which is resulted from the Orowan strengthening and load transferring. Additionally, the thermal conductivity of 340 W/(m·K) was obtained, owing to the uniform distribution of whiskers and good interface between the Cu matrix and whiskers. Therefore, the presented work provided an effective method for fabricating comprehensive thermal-mechanical properties and homogeneous heat dissipation capacity Cu-SiC w composites and paved the way for the practical application in the field of the connector between the power devices and heat sinks. [ABSTRACT FROM AUTHOR]

The application of nanotechnology in the field of Buildings and concrete Build is one of the main goals of this article because of the technology's role in enhances the properties of concrete and increasing the efficiency of building materials, as well as in preserving natural resources, reducing environmental pollutants, and increasing the attention that nanotechnology is currently receiving in various fields of science and engineering applications. By partially replacing cement with silica nanoparticles, the current research is focused on investigate the impact of silica nanoparticles (SiO2) on the concrete thermic properties, including specific heat capacity (SHC), thermic conductivity, and thermic diffusivity, in order to produce lightweight concrete with good thermal insulation capabilities. In order to replace a portion of the concrete's weight, nano-silica (NS) was added in percentages of 1%, 2%, and 3%. The results showed that the mixtures including nano-silica had lower thermic conductivity coefficient values, ranging from 0.5 to 0.92 W/m.°C. This indicates that the thermic insulation capacity of nano-concrete increased by 41.8 percent, 53.15 percent, and 65.57 percent, respectively. Furthermore, based on the data, Thermal conductivity coefficient's can be lowest value at a ratio of (3%). As a result, replacing concrete beyond this proportion will result in a reduction in its various qualities. Furthermore, a reduction in the specific thermic ability values was noted in contrast to traditional concrete. [ABSTRACT FROM AUTHOR]

Clinochlore is a major hydrous mineral in subduction zones, and its thermophysical properties at high temperature and pressure are critical to the thermal structures of subduction zones. Here, we used the pulse heating method to measure thermal diffusivity and thermal conductivity of clinochlore at 0.5-4.0 GPa and 298-1373 K. Our results indicate that upon heating, thermal diffusivity and thermal conductivity decrease from ~9.6 x 10-7 m² s-1 to 4.3 x 10-7 m² s-1 and from ~3.5 W m-1 K-1 to 1.9 W m-1 K-1, respectively, before dehydration, but this trend is reversed after dehydration. In general, the pressure derivatives for the thermal transport properties also decrease with temperature before dehydration. Lattice heat transfer is the dominant mechanism before dehydration, but fluid is involved after dehydration. Using our experimental data, we simulated the temperature distribution of subducting slabs containing clinochlore at volume fractions of 0%, 10%, 20%, 50%, and 100%. Our simulations showed that the heat insulation effect caused by the presence of clinochlore could result in an increase in temperature by 30-60 K for the upper part of the subducting slab. [ABSTRACT FROM AUTHOR]

The long-term operation of motors induces substantial alterations in the surface conductivity and nonlinear coefficient of anti-corona paint, diminishing its efficacy and jeopardizing the longevity of large motors. Hence, the development of high-performance anti-corona paint holds paramount importance in ensuring motor safety. In this study, we integrate two nano-fillers, namely silicon carbide (SiC) and organic montmorillonite (O-MMT), into a composite matrix comprising micron silicon carbide and epoxy resin (SiC/EP). Subsequently, three distinct types of anti-corona paint are formulated: SiC/EP, Nano-SiC/EP, and O-MMT/SiC/EP. Remarkably, O-MMT/SiC/EP exhibits a glass transition temperature about 25 °C higher than that of SiC/EP, underscoring its superior thermal properties. Moreover, the introduction of nano-fillers markedly augments the surface conductivity of the anti-corona paint. Aging tests, conducted across varying temperatures, unveil a notable reduction in the fluctuation range of surface conductivity post-aging. Initially, the nonlinear coefficients exhibit a declining trend, succeeded by an ascending trajectory. The O-MMT/SiC/EP composite displays a maximum nonlinearity coefficient of 1.465 and a minimum of 1.382. Furthermore, the incorporation of nanofillers amplifies the dielectric thermal stability of epoxy resin composites, with O-MMT/SiC/EP showcasing the pinnacle of thermal endurance. Overall, our findings elucidate the efficacy of nano-fillers in enhancing the performance and longevity of anti-corona paint, particularly highlighting the exceptional attributes of the O-MMT/SiC/EP composite in bolstering motor safety through improved thermal stability and electrical properties. [ABSTRACT FROM AUTHOR]

Traditional thermally conductive materials are gradually losing their advantages as the electronics industry develops rapidly. Polymers are in urgent need of a material with high thermal conductivity, stable structure, good mechanical properties and oxidation resistance, which makes hexagonal boron nitride (h-BN) an excellent heat transfer filler for polymer composites. Boron nitride nanosheets (BNNS) are monolayers of hexagonal boron nitride, and theoretical studies have shown that BNNS have a higher thermal conductivity than h-BN (up to 400Wm-1K-1, in-plane). This paper provides a comprehensive review of various methods for preparing BNNS, including mechanical exfoliation, liquid phase sonication exfoliation and chemical vapor deposition (CVD). In addition, various factors affecting the thermal conductivity of BNNS, including grain boundary, grain size and defects, are also discussed. Then, the influence of BNNS as filler on the thermal conductivity of the polymer was further discussed. Finally, this paper summarizes the existing BNNS applications and lists the application scenarios of BNNS in various fields. The purpose of this review is to summarize the previous work and put forward the prospect and future development direction of preparing high thermal conductivity BNNS-included polymer composites, so as to stimulate the research and improvement of new preparation methods for BNNS and promote its practical application as heat transfer materials. [ABSTRACT FROM AUTHOR]

In the realm of high-tech materials and energy applications, accurately measuring the transient heat flow at media boundaries and the internal thermal conductivity of materials in harsh heat exchange environments poses a significant challenge when using conventional direct measurement methods. Consequently, the study of photothermal parameter reconstruction in translucent media, which relies on indirect measurement techniques, has crucial practical value. Current research on reconstructing photothermal properties within participating media typically focuses on single-objective or time-invariant properties. There is a pressing need to develop effective methods for the simultaneous reconstruction of time-varying thermal flow fields and internal thermal conductivity at the boundaries of participating media. This paper introduces a computational model based on the numerical simulation theory of internal heat transfer systems in participating media, stochastic particle swarm optimization algorithms, and Kalman filter technology. The model aims to enable the simultaneous reconstruction of various thermal parameters within the target medium. Our results demonstrate that under varying levels of measurement noise, the inversion results for different target parameters exhibit slight oscillations around the true values, leading to a reduction in reconstruction accuracy. However, overall, the model demonstrates robustness and accuracy in ideal conditions, validating its effectiveness. [ABSTRACT FROM AUTHOR]

Building materials are responsible for significant CO2 emissions and energy consumption, both during production and operational phases. Earth as a building material offers a valuable alternative to conventional materials, as it naturally provides high hygrothermal comfort and air quality even with passive conditioning systems. However, disadvantages related to high density, conductivity, and wall thickness prevent its effective inclusion in the mainstream. This research explores enhancing the thermophysical properties of compressed earth blocks (CEBs) by using locally sourced natural materials. The study is framed in the Portuguese context and the natural materials involved are wheat straw (WS) as a by-product of wheat harvesting, cork granules (CGs) from bottle caps, and ground olive stone (GOSs) residues from olive oil production. Blocks were produced with different mixtures of these materials and the thermal response was examined in a hot box apparatus. Best results include a 20 and 26% reduction in thermal conductivity for mixtures with 5v.% CG and 10v.% GOS, respectively, and an associated reduction in bulk density of 3.8 and 5.4%. The proposed approach therefore proves to be effective in improving the key thermophysical characteristics of CEBs. The article includes a comparative analysis of the experimental data from this study with those from the literature. The study contributes to the growing knowledge of sustainable materials, providing insights for researchers and practitioners looking for innovative solutions for low-carbon and energy-efficient materials. [ABSTRACT FROM AUTHOR]

The most important thermal and rheological properties of water-based CaCO3/SiO2 dual hybrid nanofluid (DHNF) at overall volumetric concentrations of the nanoparticles from 0.1 to 0.5 and different volume fractions at temperatures of 15–60 °C have been studied. Prepared DHNFs consisted using SDS and ultrasonic homogenizer. Stability analysis of the DHNFs performed by changing ultrasonication time and power. The optimum consistency conditions and volume fractions of the nanoparticles determined for the prepared DHNFs. Specific heat capacity, thermal conductivity and resistivity, usual viscosity and density of the DHNFs studied, experimentally, compared with preexisting models, and finally, theoretical models with 99% precisions suggested. Maximum augmentation in thermal conductivity attained to 21.8% for 80:20 corresponding volume ratio and 0.5 vol% total concentration. At these conditions, maximum reduction in heat capacity occurred as 1.08%, and the greatest reduction in thermal resistivity got about 22.2% at 60 °C. Usual viscosity and density increased as 36.9 and 1.2%, respectively. [ABSTRACT FROM AUTHOR]

The effect of defects on the thermal properties of Ψ-Graphene Nanotubes (Ψ-GNTs) is investigated in this study using Molecular Dynamics simulations. The results reveal that the thermal properties of Ψ-GNTs are profoundly impacted by the presence of defects. Specifically, a significant reduction in thermal conductivity is observed with increasing defect concentrations. This reduction is attributed to the scattering of phonons by the defects, which leads to increased phonon–phonon interactions and decreased thermal transport efficiency. Furthermore, the effect of temperature on the thermal properties of defective Ψ-GNTs is investigated. The findings demonstrate a nonlinear decrease in thermal conductivity with increasing temperature. [ABSTRACT FROM AUTHOR]