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Latent Heat Storage (LHS) with Phase-Change Materials (PCMs) represents a high energy density storage technology which could be applied in a variety of applications such as waste heat recovery and integration of renewable energy technologies in energy systems. To increase the sustainability of these storage solutions, PCMs have to be developed with particular regard to bio-origin and biodegradability. Triglycerides represent an interesting class of esters as the main constituents of animal and vegetable fats, with attractive thermal properties. In order to be used as PCMs, the thermal behaviour of triglycerides has to be fully understood, as in some cases they have been reported to show polymorphism and supercooling. This study assesses the suitability of triglycerides as PCMs by reviewing the literature published so far on their behaviour and properties. In particular, melting points, enthalpies of fusion, polymorphism, thermal conductivities, heat capacities and thermal cycling stabilities are considered, with a focus on LHS and thermal energy storage applications. In addition, the efforts conducted regarding modelling and the prediction of melting points and enthalpies based on chemical structures are summarized and assessed.

Given their amphiphilic nature and chemical structure, phospholipids exhibit a strong thermotropic and lyotropic phase behaviour in an aqueous environment. Around the phase transition temperature, phospholipids transform from a gel-like state to a fluid crystalline structure. In this transition, many key characteristics of the lipid bilayers such as structure and thermal properties alter. In this study, we employed atomistic simulation techniques to study the structure and underlying mechanisms of heat transfer in dipalmitoylphosphatidylcholine (DPPC) lipid bilayers around the fluid-gel phase transformation. To investigate this phenomenon, we performed non-equilibrium molecular dynamics simulations for a range of different temperature gradients. The results show that the thermal properties of the DPPC bilayer are highly dependent on the temperature gradient. Higher temperature gradients cause an increase in the thermal conductivity of the DPPC lipid bilayer. We also found that the thermal conductivity of DPPC is lowest at the transition temperature whereby one lipid leaflet is in the gel phase and the other is in the liquid crystalline phase. This is essentially related to a growth in thermal resistance between the two leaflets of lipid at the transition temperature. These results provide significant new insights into developing new thermal insulation for engineering applications., (© 2017 The Authors.)

Bond line thickness (BLT) is an essential parameter of thermal conductive composite gels as the thermal interface material (TIM). Extensive research has been performed on designing next-generation TIMs with high thermal conductivity; however, it remains elusive how to link laboratory measurements and the theoretically predicted BLT. Here, we propose a new model to estimate BLT based on a rheological property, in which the TIM is assumed to be a simple power law fluid. To avoid the unrealistic situation of the BLT tending to zero, we introduce a decaying exponential function to describe the influence from fillers during the lid attach process and rebuild the force balance equation. Compared with previously reported models, the theoretical prediction BLT based on the proposed model is in good agreement with the experimental data. Our model has a guiding significance in predicting the BLT, which may help to optimize the thermal performance of TIMs. [ABSTRACT FROM AUTHOR]

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]

The continuous upgrading of electronic technology has facilitated the integration and miniaturization of electronic and electrical equipment, as well as putting great pressure on the multifunctional demand for internal materials. Developing insulating materials with both low permittivity and high thermal conductivity has become imperative. This perspective focuses on polyimide (PI), which is the top material of the polymer material pyramid, discusses the characteristic parameters that affect its dielectric property and thermal conductivity. A series of basic schemes to regulate the dielectric/thermal properties of PI are summarized, revealing the bottlenecks and drawbacks of the current research. Future development trends of PIs featured low permittivity-high thermal conductivity are anticipated, and novel ideas are proposed for the development of new generation of multifunctional PIs. [ABSTRACT FROM AUTHOR]

While improving the thermal conductivity of composites, single‐size carbon nanotubes (CNT) often degrade their mechanical properties due to the agglomerates. To overcome this limitation, this study reported thermoplastic resin matrix composites synergistically reinforced with small, medium, and large‐size carbon nanotubes (S‐CNT, M‐CNT, and L‐CNT). Using the thermal conductivity (λ) and mechanical properties (flexural strength [F], compressive strength [C] and tensile strength [T]) as the response values, we conducted 21 sets of mixing design experiments and developed the associated quadratic term models. Further multi‐objective optimization was carried out for the above response values. Optimized multiscale CNT synergistically modified composites (S‐CNT, M‐CNT, and L‐CNT contents of 1.25, 7.02, and 2.56 wt%) exhibited a λ value of 1.168 W/mK, which was 121% higher than that of pure composite and also superior to the same content of S‐CNT‐ (1.031 W/mK), M‐CNT‐ (1.016 W/mK), and L‐CNT‐modified composites (0.983 W/mK). Additionally, the optimized composite demonstrated excellent mechanical properties (F = 1482 MPa, C = 848 MPa, and T = 1759 MPa), which were 13%, 11%, and 13% higher than those of the pure composites, respectively, and also surpassed those of the S‐CNT‐, M‐CNT‐and L‐CNT‐modified composites. Highlights: Using three different scales of carbon nanotubes modified CF/PPBESK composites.Polynomial modeling of composite's thermal conductivity and mechanical properties.Synergistic interactions between carbon nanotubes to improve the composite's thermal conductivity and mechanical properties. [ABSTRACT FROM AUTHOR]

The relationship between interfacial structure and thermal conductivity in epoxy resin/Al2O3 composite is important but is still elusive. Here, we illuminate this issue by investigating the role of four silane coupling agents in thermal conductivity for epoxy resin/Al2O3 composites. The results show that 3‐glycidoxypropyltrimethoxysilane (KH560) is the best silane coupling agent to modify Al2O3, resulting in the lowest viscosity and the highest thermal conductivity of the epoxy resin/Al2O3‐KH560 composite compared with alternative systems. This is attributed to the strong interfacial interaction between Al2O3‐KH560 and epoxy resin, as confirmed by the Fowkes model and broadband dielectric spectroscopy. The interfacial thermal resistance between the epoxy resin and Al2O3 is also quantitatively measured via a photothermal radiometry technique. The epoxy resin/Al2O3‐KH560 also has the lowest interfacial thermal resistance (1.50 ± 0.02 × 10−6 m2 K W−1), compared with the other three systems. This study advances the understanding of the relationship between interfacial structure and thermal conductivity in polymer composites. Highlights: The relationship between interfacial structure and thermal conductivity in epoxy resin/Al2O3 composite is understood.The interfacial structure is characterized by broadband dielectric spectroscopy.The interfacial thermal resistance is quantitatively measured via a photothermal radiometry technique. [ABSTRACT FROM AUTHOR]

The effects of Ta doping on the thermal and electrical properties of SnO 2 varistors were researched. The results showed that the thermal conductivity is 2.01 WK−1m−1, the nonlinearity coefficient is 43, and the leakage current density is 0.7 μA/cm2 when the Ta doping level reaches 0.2 mol%. According to the measurement results of the EPR, SEM/EDS, and XRD, the Ta dopant can reduce the oxygen vacancy concentration, which was generated during the sintering. The decline of the oxygen vacancy concentration reduces the phonon scattering, then the thermal conductivity of the varistors is improved. On the other hand, the reduction of the oxygen vacancy concentration elevates the barrier height, so the nonlinearity coefficient is improved and the leakage current density is declined. [ABSTRACT FROM AUTHOR]

In present work, high entropy (MoTaTiVW)C X ceramics with different carbon stoichiometries (X = 3–6) were produced using spark plasma sintering. The microstructure, mechanical properties, and thermal properties of (MoTaTiVW)C X with different carbon stoichiometries were studied. At X = 3, the carbon deficiency resulted in a multiphase structure of the sample, (MoTaTiVW)C 3 with a Mo-rich carbide phase. At X = 3.5, the single-phase rock salt structure was formed despite carbon vacancies of up to 30 %. The relative density of (MoTaTiVW)C X gradually decreases as the carbon stoichiometry increases from X = 3 to X = 6. The concentration of carbon vacancies affects the sintering activation energy, which can enhance mass transfer and promote the densification process. The Vickers hardness of (MoTaTiVW)C X shows an overall decreasing trend as the carbon stoichiometry increases from X = 3.5 to X = 6, peaking at 20.4 ± 0.4 GPa at X = 3.5. The fracture toughness increases and then decreases, peaking at 4.4 ± 0.2 MPa m1/2 at X = 4. The thermal conductivity of (MoTaTiVW)C X gradually increases, then decreases and finally increases with the increase of carbon stoichiometry. At room temperature, the maximum value of thermal conductivity is 6.35 ± 0.29 W/m·K of (MoTaTiVW)C 5 and the minimum value is 5.32 ± 0.35 W/m·K of (MoTaTiVW)C 5.5. At 1000 °C, the thermal conductivity of (MoTaTiVW)C X ranges from 15.94 ± 0.37 W/m·K to 19.56 ± 0.45 W/m·K. As the concentration of carbon vacancies decreases, the decrease in point defect concentration will reduce the degree of lattice distortion, thereby reducing phonon scattering and affecting thermal conductivity. The study suggests that carbon stoichiometry can be used to adjust the microstructure, mechanical properties, and thermal properties of high entropy carbide ceramics. [ABSTRACT FROM AUTHOR]

The thermal barrier coatings (TBCs) system, a pivotal technology for advanced aviation engines and ground gas turbines, mitigates direct interaction between high-temperature gas and high-temperature alloy substrates. In this investigation, a series of high-entropy Eu 2 B 2 O 7 (where B = Y, Yb, Ce, Zr, Hf, Ta, and Nb) oxides were synthesized through solid-state reactions. By manipulating B-site cations and introducing substantial atomic size disparities, as well as mass and charge disorder, we synthesized a highly disordered high-entropy Eu 2 B 2 O 7 oxide. This oxide exhibits a disordered fluorite structure and commendable thermal insulation attributes. The observed thermal conductivity of Eu 2 (Y 0.2 Yb 0.2 Zr 0.2 Nb 0.2 Ta 0.2) 2 O 7 ranges from 0.94 to 1.13 W·m–1·K–1, which can be ascribed to amplified lattice anharmonicity and disorder causing supplementary phonon scattering. In addition, It also shows the thermal expansion coefficient of 10.52 × 10−6 K−1 and high-temperature stability. These results denote that the high-entropy Eu 2 B 2 O 7 oxide may become a prospective contender for thermal barrier coatings and thermal insulators. [ABSTRACT FROM AUTHOR]

Highlights Acrylonitrile butadiene styrene (ABS) polymer has received considerable attention due to its high versatility for applications, including additive manufacturing. However, its electrical and thermal transport properties limit its application potential. One route to enhance electrical and thermal conductivities is the development of ABS‐based composites by using carbonaceous fillers, which have exceptional mechanical properties and remarkable functional properties. Here, we testing the presence of carbonaceous fillers with different dimensionalities on the electrical and thermal conductivity of ABS composites. In particular, one dimensional (1D) carbon nanotubes (CNT), two dimensional (2D) reduced graphene oxide (rGO), and three dimensional (3D) carbon black (CB) have been used to develop ABS‐based composites with different filler contents. A similar trend exist for the electrical and thermal conductivity results, where the highest conductivity values (electrical conductivity 0.0305 S·cm−1 and thermal conductivity 0.56 W·mK−1) being achieved for ABS‐based composites with 2D rGO filler, highlighting the relevance of specific characteristics of the 2D type filler. In addition, electromagnetic interference (EMI) shielding effectiveness (SE) of the ABS‐based composites containing rGO was superior to other 1D and 3D fillers. The stated correlation between electrical and thermal properties and their dependence on carbonaceous filler dimensionality are essential to be taken into account for properly tailoring functional properties of ABS‐based composites. Carbonaceous fillers are used to tailor several properties of ABS composites Significant differences are established between filler type or content Electrical percolation threshold strongly depends on the dimensionally 2D rGO more effective to improve electrical/thermal conductivities 1D CNT and 2D rGO fillers exhibit best EMI shielding properties [ABSTRACT FROM AUTHOR]

Optimizing carrier concentration in PbTe materials can be achieved effectively through the chemical doping of sodium. Nevertheless, the valence balance can lead to the presence of "deleterious defects" in the PbTe matrix, resulting in low sodium solubility at room temperature. Herein, a strategy for fine‐tuning Pb vacancies to improve sodium solubility is developed. By a trace amount of Se‐doping, the solubility of Na in Pb0.99Te1‐xSex through the preservation of Pb vacancies in the matrix is substantially increased. Additionally, a large number of dense dislocations in the grains, which greatly reduced the lattice thermal conductivity is induced. A high power factor of ≈26 mW cm−1 K−2 and low lattice thermal conductivity of ≈0.43 W m−1 K−1 at 823 K in Pb0.95Na0.04Te0.97Se0.03 is achieved. Ultimately, a high figure of merit, ZT ≈2.2, is obtained at 823 K in quaternary PbTe compound. The current findings not only demonstrate that the introduction of trace amounts of Se and Pb vacancies in the PbTe matrix can effectively enhance Na solubility and minimize thermal conductivity, attaining synergistic improvement in electrical and thermal properties, but also indicate that the synergistic effect of Pb vacancies with a specific dopant is an alternative approach for enhancing ZT. [ABSTRACT FROM AUTHOR]

Highlights A fluorinated polyimide (PI‐FTD) was synthesized for preparing a thermally conductive PI matrix and composites. Additionally, surface‐treated boron nitride (BN) was incorporated into the PI‐FTD via the solution casting method to form efficient heat paths along the through‐plane direction. The resultant composite demonstrated remarkable characteristics, including an impressive through‐plane thermal conductivity of 3.6 W mK−1, a substantial tensile strength of 69.4 MPa, and excellent thermal stability. When this composite was applied to light‐emitting diodes, it effectively managed heat, reducing the operating temperature by 29°C. The PI‐FTD/BN‐OH composites can potentially improve thermal management in electronic devices. A novel fluorinated polyimide (PI‐FTD) was fabricated. Introducing CF3 functionalities in the PI‐FTD provides high thermal stability. BN‐OH reinforced the thermal and mechanical properties of the composites. The PI‐FTD/BN‐OH composites achieved excellent thermal management. [ABSTRACT FROM AUTHOR]

The strength of zirconium diboride ceramics was tested by three different methods, 3‐point flexure, 4‐point flexure, and compression. Nearly full‐density ceramics were obtained by hot pressing commercial ZrB2 powder with the addition of .5 wt.% carbon as a sintering aid. The thermal properties and hardness were studied for ZrB2 milled with ZrB2 and WC media. Based on phase purity and higher thermal conductivity, ZrB2 ceramics prepared from powders milled with ZrB2 media were selected for mechanical property studies. The strength in 3‐point flexure was 546 ± 55 MPa. The flexure strength was 476 ± 41 MPa in 4‐point bending, which was ∼20% higher than the previously reported value of 398 MPa for ZrB2 with similar grain sizes due to higher relative density and lower impurity contents. Compression testing was performed at room temperature, and the strength was 1110 ± 358 MPa. Finally, the fracture toughness of pure ZrB2 ceramics was determined by the chevron‐notched beam method to be 3.6 ± .7 MPa m1/2. The strength and fracture toughness values are higher than those previously published for ZrB2 ceramics and can be attributed to higher density and lower grain size. The strength‐limiting flaw sizes were comparable to the grain size, suggesting that porosity and impurity phases did not play a significant role in the strength of these ceramics. [ABSTRACT FROM AUTHOR]

In the context of ecological sustainability, this study focuses on the effect of variables of pasture fibers on the thermal properties of slag bricks made from a green recyclable material. This experiment uses slag as the binder, sand as the aggregate, and pasture fiber as an additive. The experimental variables include the additive content ratio of the pasture fiber, the size of the pasture fiber, and the type of pasture fiber. Significance analysis of the experimental results of the thermal performance tests is carried out using Minitab 18.1.0 software, and the optimal ratios for the thermal performance of the composite samples are derived from the response optimizer and conformity analysis. The results of the experiment's test analysis using Minitab 18 software indicate that, with an increase in pasture fiber content, the thermal performance of the composite samples initially decreases before increasing. Additionally, the lower the thermal conductivity of the composite sample, the lower the apparent density and the higher the porosity. Incorporating pasture fibers into slag bricks, as revealed in this study, reduces the waste of pasture resources in pastoral areas and promotes the development of sustainable building materials with favorable thermal properties. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC), as a third‐generation semiconductor material, has attracted significant research attention. Various empirical potentials and machine learning potentials have been developed, but there are few comparative studies on phonon and thermal properties. Herein, the Tersoff and Vashishta empirical potentials, as well as the Bayesian force field constructed by the FLARE framework using principled Gaussian process uncertainties (FLARE BFF), for a comparative study, are selected. The phonon dispersion relation, phonon density of states, Grüneisen constants, and the average phonon‐weighted Grüneisen constants are calculated using different potentials, and it is found that the FLARE BFF potential has the highest accuracy with respect to the first‐principles calculations. Furthermore, the thermal conductivity using molecular dynamics simulation with different potentials is calculated. The calculation results using the FLARE BFF potential closely match the experimental reports at high temperature, but the longest computing time is required. This study can facilitate the understanding of thermal properties of SiC. [ABSTRACT FROM AUTHOR]

In this study, De Gennes's scaling theory was developed to evaluate the variation of distance-dependent thermal properties inside the polymer/particle interphase region based on the molecular characteristics of the polymer matrix and surface adsorption energy. Accordingly, the average thermal conduction coefficient of the region was predicted and used to approximate the overall thermal conductivity of the nanocomposite system. The physical characteristics of the nanoparticle clusters (e.g., size and content) were defined using a specific strategy based on the equilibrium between dispersion and cohesion energies during the preparation of the nanocomposite samples, via melt mixing. Maxwell's model was also developed and used to predict the thermal conduction coefficient of the polymer/nanoparticle system considering the determinative impact of the polymer/particle interphase region and aggregation/agglomeration phenomenon. It was found that the scaling parameter, defining the polymer/particle interaction strength, increased by almost 50% by increasing the compatibility. This also increased the thermal conductivity of the interphase from 1.401 (W.m-1.K-1) to 3.028 (W.m-1.K-1) in the samples containing compatible nanoparticles. The thermal conductivity of nanoparticle clusters decreased exponentially with increasing the number of involved nanoparticles. The maximum prediction error of the proposed model (6.9%) was 12% less than that of the original Maxwell's model. [ABSTRACT FROM AUTHOR]

The advancement of implantable biomedical devices (IMDs) hinges on the development of biocompatible solid-state electrolytes with outstanding electrochemical performance, safety, and reliability for flexible solid-state supercapacitors. This study focuses on the development of gel polymer electrolytes (GPEs) using polyvinyl alcohol (PVA) and potassium chloride (KCl). The GPEs obtained were subjected to comprehensive characterization using a diverse range of techniques to evaluate their spectral features, morphological properties, thermal and mechanical performance, biocompatibility, ionic conductivity, and cyclic stability. What distinguishes our research is its comprehensive exploration of the profound impact of varying PVA molecular weights and PVA/KCl weight ratios on the ionic conductivity and thermal characteristics of these gels. Notably, we observed a decrease in ionic conductivity with increasing PVA molecular weight, whereas an increase in salt concentration under the same molecular weight led to higher ionic conductivity. In particular, the optimal gel electrolyte with a molecular weight (Mw) of 195,000 g/mol and a PVA/KCl weight ratio of 1/2 demonstrated a promising ionic conductivity of 3.48 ± 0.25 mS/cm. Even after 5000 cycles, it retained 88% of its initial specific capacitance. Our findings reveal that the GPEs exhibit remarkable mechanical robustness alongside unparalleled ionic conductivity, characterized by minimal interfacial resistance. Moreover, these gel electrolytes exhibit remarkable biocompatibility, evident in a cell viability test where 72.3% of cells remained unaffected after a 72-h exposure to PVA/KCl. These findings present a promising avenue towards the fabrication of stable and high-performance biocompatible gel polymer electrolytes which can be used in solid-state supercapacitors, thereby laying the foundation for their integration into flexible, safer, and wearable bio-electronics. [ABSTRACT FROM AUTHOR]

Gadolinium Zirconate nanoparticles were synthesized by Co-precipitation and Ball milling techniques. In this study, the effect of the synthesis technique and calcination temperature on the structural, morphological and thermal properties were investigated. The thermal properties examined showed that the GZ nanoparticles obtained from CP technique suffered two-fold weight loss as compared to BM technique. The SEM results revealed the formation of agglomerated particles. However, TEM results confirms the formation of nanoparticles of 10.5 nm and 8 nm by BM and CP techniques respectively. GZ particles obtained through CP technique showed better uniformity of particle size over BM technique. The functional groups of the nanoparticle were studied using FT-IR spectroscopy analysis. The XRD results confirm the formation of defect-fluorite structure and pyrochlore structure for the samples calcined at 1100 °C and 1400 °C (BM) respectively. The formation of the corresponding structures was further confirmed by Raman Spectroscopy. The thermal conductivity of the nanoparticle produced by ball milling and co-precipitation technique is almost same. As compared to NiCrAlY and uncoated substrate materials, the micro hardness of the GZ coatings has the maximum hardness of 594.6 HV, indicating the improved hardness behavior of TBC system. [ABSTRACT FROM AUTHOR]

Cubic boron nitride (cBN) has been used as a tool material for several decades due to its high hardness and thermal stability. Various binders are commonly added to cBN to synthesise cBN composites for better cutting performance. However, most studies have only investigated properties such as hardness and bulk modulus, without comprehensively studying elastic properties through experiments. In this study, the sound velocities and elastic properties of cBN with AlN binder were determined by using the ultrasonic interferometry technique. The bulk and shear moduli with their pressure dependence were determined as B 0 = 351 (3) GPa, G 0 = 344 (3) GPa, B 0 ′ = 4.32 (4) and G 0 ′ = 1.74 (2) using the finite strain equation-of-state approaches. Elasticity-related thermal properties, such as Debye temperature, Grüneisen parameter, thermal conductivity and coefficient of thermal expansion were also estimated. The results show that the elastic properties of the cBN composite with vol. 8.8% AlN-binder are comparable to the pure cBN compact. Additionally, the thermal conductivity and coefficient of thermal expansion have little effect on cBN composite with AlN binder compared to pure cBN. [ABSTRACT FROM AUTHOR]

Rare earth silicates are promising environmental/thermal barrier coating (E/TBC) materials facing severe CMAS (CaO‐MgO‐Al2O3‐SiO2) corrosion. Previous studies mainly focused on the intrinsic properties of precorrosion coatings, but there were few studies on their CMAS corrosion products that play a crucial role in the performance of coatings in postservice stage. In this work, the mechanical and thermal properties of nine corrosion products between lutetium silicates and CMAS are studied using first‐principles calculations. Their differences of elastic stiffness are attributed to the different crystal structures and bonding strength. The T:O ratio is identified as a factor of the crystal structure for silicate products, and it has a good correlation with their elastic stiffness. Moreover, the divergences of thermal conductivity are dominated by three essential factors, that is, atomic vibration intensity, lattice vibrational anharmonicity, and complexity of crystal structure. Compared with rare earth silicates, six products, that is, the α‐CaSiO3, β‐CaSiO3, Ca2MgSi2O7, Ca2Al2SiO7, CaAl2Si2O8, and Ca2Lu8(SiO4)6O2, showing good damage tolerance and low thermal conductivities, are predicted to be advantageous to E/TBCs. These discoveries reveal the mechanical/thermal properties of corrosion products between lutetium silicates and CMAS and are expected to support the future researches on the performance of E/TBC in the postservice stage. [ABSTRACT FROM AUTHOR]

Tissue scaffold engineering technology can eliminate the impediments in revision surgery. A decent understanding of the mechanical compression properties of biomaterials is required for producing increasingly suitable materials for their use as tissue engineering scaffolds. The biomaterial must not only possess structural integrity but also appropriate biodegradability with sufficient sustainability. This study presents a numerical simulation method and the material behavior results that quantify the mechanical compression properties of a polycaprolactone (PCL) cube-cell model using the finite element method (FEM). The main interest of this study is to observe and quantify the quasi-static compression behavior and the effective thermal conductivity of the PCL scaffolds. It is modeled as such as it undergoes degradation due to surface erosion by the body fluid onto the scaffold. The effective elastic modulus, 0.2% offset yield stress, plateau stress and effective thermal conductivity were evaluated numerically. Results show a phenomenologically decreasing trend of these general properties for PCL scaffolds computed by numerical methods. The volumetric decrease in PCL promotes weakening of the scaffold at its strut causing failure under compression. The effective thermal conductivity decreases as the volume decreases due to the lower PCL substance possessed in the unit cell, which is naturally a thermal insulator. [ABSTRACT FROM AUTHOR]

Apparent thermal conductivity of soil (λ) as a function of soil water content (θ), i.e., λ(θ) is needed to determine the heat flow in soil. The function of λ(θ) can be used in heat and water flow models for simplicity. The objective of this study was to develop a sigmoidal model based on logistic equation for entire range of soil water contents and a wide range of soil textures that can be used in simulation of heat and water flow in respected modes. Further, performance of the developed sigmoidal model along with two other models in literature was evaluated. In the proposed sigmoidal model, the constants of this model are estimated based on empirical multivariate equations by using soil sand content and bulk density. The sigmoidal model was validated with good accuracy for a wide range of soil textures, as the relationship between the measured and predicted λ showed slope and intercept values of nearly 1.0 and 0.0, respectively. Comparison of the results obtained by sigmoidal model with those obtained from Johansen and Lu et al. models indicated that, the sigmoidal model was superior to the other two models in prediction of λ for a wide range of soil textures and soil water contents. Furthermore, comparison with a recently proposed model by Xiong et al. indicated that our sigmoidal model is superior. Therefore, our developed sigmoidal model can be used in heat and water flow models to predict the soil temperature and heat flow. [ABSTRACT FROM AUTHOR]

AbstractFunctionalization of graphene nanosheet (GNS) is found to be useful for improving the thermal property of materials. However, the mechanism responsible for the enhancement is still open. In this article, molecular dynamic simulation is adopted to investigate the effects of four functionalized groups, including -COOH, -NH2, -OH, and -CH3, on the adsorption and thermal properties of GNS/paraffin (PA) composites. The results show that it forms a spherical structure after GNS absorbs in PA. The loading rate of the systems follows the order: GNS-COOH/PA > GNS-NH2/PA > GNS-OH/PA > GNS-CH3/PA > GNS/PA, which is determined by the adsorption free energy. Due to the functionalization, the latent heats of the composites undergo a significant change and the thermal conductivities are significantly enhanced. GNS-OH/PA exhibits the most substantial improvement with the latent heat increasing by 11.2% and the thermal conductivity increasing by 107.4% compared to GNS/PA. The study demonstrates the potential of these composites for energy storage applications, highlighting the improved performance through functionalization. [ABSTRACT FROM AUTHOR]

Highlights This study explores the development of nanocomposites by incorporating multi‐walled carbon nanotubes (MWCNT), titanium nitride (TiN), and cubic boron nitride (c‐BN) nano powders into photo‐polymer epoxy resins for use in Stereolithography (SLA) additive manufacturing. Mechanical and thermal properties were systematically investigated to assess their performance. Initially, MWCNT, TiN, and c‐BN nano powders were homogeneously mixed with the resin to ensure uniformity. The resulting mixtures were then processed using SLA technology to evaluate production quality and material performance. The study revealed significant improvements in mechanical and thermal properties compared to pure resin, aligning with previous research outcomes. Specifically, the incorporation of MWCNT led to a notable enhancement in thermal conductivity, showing an increase of 24.21% as the thermal conductivity coefficient increased from 0.19 to 2.36 W/m·k. On the other hand, c‐BN significantly boosted mechanical strength, resulting in a substantial 20.45% increase as the shore D hardness went from 88.53 to 106.64. These findings highlight the promising potential of nanocomposites across various industries including electronics, aerospace, automotive, construction, medical devices, and manufacturing. Developed nanocomposites with MWCNT, TiN, and c‐BN in SLA resin. c‐BN increased hardness by 20.45%, proving its effectiveness in composites. MWCNT enhanced thermal conductivity by 24.21%, boosting material performance. Pioneering use of TiN and c‐BN in SLA, addressing gaps in existing research. Applications span electronics, aerospace, automotive and medical devices. [ABSTRACT FROM AUTHOR]

In this study, a silica boron modified phenolic resin foam (SiBPF) is prepared in a reactor under specific pressure and temperature and using supercritical CO2 (scCO2) as a physical foaming agent, to improve phenolic foam (PF) brittle and friable properties and avoid environmental pollution caused by conventional physical foaming. To determine the partially curing degree for foaming, the influence of partially curing time at partially curing degrees between 39.88% and 53.17% was studied. Further, through an orthogonal experimental method, the optimized foaming process parameters—partially curing time of 6 h, adsorption time of 9 h, foaming pressure of 1 MPa, and foaming temperature of 130°C—were determined. The SiBPF, thus prepared under the optimized conditions, exhibited a density of 0.2356 g/cm3, an average cell size of 86.66 μm, and a cell density of 7.10 × 106 cells/cm3. Its compressive strength was found to be 7.28 MPa, with a specific compressive strength of 30.90 MPa/g·cm−3. At 800°C, the carbon residue rate, thermal decomposition temperature T5%, and Tmax reached 77.61%, 355.21, and 702.70°C, respectively. The thermal conductivity of SiBPF was measured to be 0.0644 W/mK, with the rear temperature stabilizing at 60°C on a hot platform of 100°C. [ABSTRACT FROM AUTHOR]

It is well accepted that the intrinsic thermal conductivity is extremely important in achieving excellent thermal conductivity composite and can be improved via incorporation of mesogens. In this work, an azomethine type liquid crystal epoxy (LCE) with aliphatic ether was designed and synthesized with expected structure, and the liquid crystal epoxy resin (LCER), together with KH‐550‐modified boron nitride (K‐BN)/LCER composites, has been obtained. Results show an increase of 31.6% in the thermal conductivity of the matrix, which could result in an enhancement of 57.7% for the composites when compared with E‐51. Additionally, the coefficient of thermal expansion (CTE), dielectric properties, and shear strength of LCER and K‐BN/LCER composites were assessed across a broad temperature range. Remarkably, the 30 wt% K‐BN/LCER composites showed a maximum decrease of 37.8% in CTE, while maintaining adequate shear strength to fulfill the bonding requirement and high thermal conductivity at both RT and −196°C. [ABSTRACT FROM AUTHOR]

Highlights Increasing the thermal stability and thermal conductivity of polydimethylsiloxane (PDMS) is a crucial issue for thermal applications. This paper focuses on enhancing PDMS's thermal and structural properties by incorporating nanocomposite into the PDMS matrix. An investigation of the impact of rGO‐CaCO3 nanocomposite on the thermal and structural properties of PDMS was performed using Field Emission Scanning Electron Microscopy (FESEM), X‐ray diffraction (XRD), the thermogravimetric analysis and differential thermal analysis (TGA‐DTA), and thermal analyzer tests. It was observed that PDMS doped with rGO‐CaCO3 nanocomposite shows better thermal stability, thermal conductivity, and higher crystallinity. The thermal stability was enhanced significantly by adding a 5% rGO‐CaCO3 nanocomposite, and the initial and end degradation temperatures rose to 492°C and 605°C, respectively. The thermal conductivity of pure PDMS is approximately 0.17 W/mK, whereas a conductive elastomer filled with 5% rGO‐CaCO3 nanocomposite exhibits a thermal conductivity of 0.44 W/mK at a temperature of 20°C. In contrast, the thermal diffusivity is enhanced from 0.13 mm2/s to 0.366 mm2/s. Additionally, the Fourier Transform Infra‐Red (FTIR) spectrum at 1411 cm−1 becomes sharp and noisy, and an additional peak arises at 1398 cm−1, corresponding to the vibrational rocking of the CC bond and COC bond in CaCO3 and rGO. The manuscript focuses on the development of conductive elastomer by incorporating rGO‐CaCO3 doped and its effect on the morphology, structure, and thermal properties of PDMS. The variation in peak intensity observed in XRD attributed to disparities in the crystalline structure of PDMS due to the inclusion of nanocomposite. The thermal degradation range is observed to shift toward the upper end. The degradation temperature at the beginning and end of the process is observed to move to 492°C and 605°C, respectively, upon introducing a 5% rGO‐CaCO3 nanocomposite. The addition of 5% rGO‐CaCO3 filled conductive elastomers shows a significant improvement of approximately 2.6 times in heat conductivity than bare PDMS. [ABSTRACT FROM AUTHOR]

This study compares the workability, mechanical, and thermal characteristics of structural self-compacting lightweight concrete (SCLWC) formulations using pumice aggregate (PA), expanded perlite aggregate (EPA), fly ash (FA), and silica fume (SF). FA and SF were used as partial substitutes for cement at a 10% ratio in various mixes, impacting different aspects: According to the obtained results, FA enhanced the workability but SF reduced it, while SF improved the compressive and splitting tensile strengths more than FA. EPA, used as a fine aggregate alongside PA, decreased the workability, compressive strength, and splitting tensile strength compared to the control mix (K0). The thermal properties were altered by FA and SF similarly, while EPA notably reduced the thermal conductivity coefficients. The thermal conductivity coefficients (TCCs) of the K0–K4 SCLWC mixtures ranged from 0.275 to 0.364 W/mK. K0 had a TCC of 0.364 W/mK. With 10% FA, K1 achieved 0.305 W/mK; K2 with 10% SF reached 0.325 W/mK. K3 and K4, using EPA instead of PA, showed significantly lower TCC values: 0.275 W/mK and 0.289 W/mK, respectively. FA and SF improved the thermal conductivity compared to K0, while EPA further reduced the TCC values in K3 and K4 compared to K1 and K2. The compressive strength (CS) values of the K0–K4 SCLWC mixtures at 7 and 28 days reveal notable trends. Using 10% FA in K1 decreased the CS at both 7 days (12.16 MPa) and 28 days (22.36 MPa), attributed to FA's gradual pozzolanic activity. Conversely, K2 with SF showed increased CS at 7 days (17.88 MPa) and 28 days (29.89 MPa) due to SF's rapid pozzolanic activity. Incorporating EPA into K3 and K4 reduced the CS values compared to PA, indicating EPA's lower strength contribution due to its porous structure. [ABSTRACT FROM AUTHOR]

In recent years, attention to the realization and characterization of wetsuits for scuba diving and other sea sports or activities has increased. The research has aimed to establish reliable and standardized measurement methods to objectively assess wetsuit quality, particularly focusing on their mechanical and thermal properties. In this work, we describe and compare two different measurement methods for the characterization of neoprene wetsuit thermal resistivity. The first method follows the existing regulations in the field, while the second one, which we are originally proposing in this paper, offers an alternative yet accurate way based on a simplified experimental set-up and easier measurements. In both cases, the wetsuit sample under testing was shaped in the form of a cylindrical sleeve of proper dimensions and wrapped around a phantom containing water at a higher temperature and surrounded by water at a lower temperature. The wetsuit's cylindrical surface allows heat flow from the warmer water on the inside to the colder water on the outside through the wetsuit area. In the first case, a thermal steady state was achieved, with constant heat flow from the phantom to the exterior. This was obtained with a power balance between two homogenous quantities. Electrically supplied thermal heating within the phantom was used to balance the thermal energy naturally flowing through the wetsuit's surface. In this first case, a stable and fixed temperature difference was obtained between the inner and the outer surfaces of the wetsuit sample. In the second case, a thermal transient was analyzed during the cooling process of the phantom, and the thermal time constant was measured, providing the sample thermal resistance once the phantom thermal capacity was known. In both cases and methods, the heat flow and thermal resistance of other elements than the wetsuit must be evaluated and compensated for if they are not negligible. Finally, the thermal resistivity per unit area of the wetsuit material was obtained with the product of the wetsuit sample's thermal resistance and the wetsuit area. The measurements, conducted until now by immersing the phantom in a free surface tank, show that both methods—under stationary and under transient temperature conditions—were valid to assess the wetsuit's thermal resistivity. The stationary method somehow provided better accuracy while involving less well-known parameters but at the expense of a more complicated experimental set-up and additional energy consumption. The transitory method, on the other hand, is quite easy to implement and, after careful characterization of the phantom's parameters, it provided similar results to the stationary one. An uncertainty budget was evaluated for both methods, and they did provide highly compatible measurement results, with resistivity values of 0.104(9) m2·K/W (stationary method) and 0.095(9) K·m2/W (transient method) for the same wetsuit sample under testing, which is also consistent with the values in the literature. We finally propose that the novel method is a valid alternative for characterization of the thermal insulation properties of a scuba diving wetsuit. [ABSTRACT FROM AUTHOR]

Here, we report the temperature-dependent electrical resistivity and thermopower of hole (Sr) and electron (Hf) doped LaCoO3 in the range of 303–753 K. With increasing temperature, the insulating behavior (303–503 K) with dominance of small polaron hopping to metallic transition (>503 K) is observed. The electron doped sample shows an insulating behavior (19.5 Ω cm) and positive thermopower (139 μV K−1) value due to the spin state blockade, i.e., electron hopping from high spin Co2+ to low spin Co3+ is strongly inhibited. The calculated weighted mobility ( μ W ) of 0.01 to 0.96 cm 2 V − 1 s − 1 validates the observed spin blockade mechanism in electron doped LaCoO3. The fluctuation of spin/orbital ordering and point defect scattering results in the low thermal conductivity of 0.5 W m − 1 K − 1 for Hf doped LaCoO3. The spin state blockade observed in the electrical resistivity and low lattice thermal conductivity reveals that spin state transition drives the thermoelectric response in Mott insulator LaCoO3. [ABSTRACT FROM AUTHOR]

The properties of rare-earth (RE) monosilicates can be regulated by solid solution engineering based on the mixture rule. The combination and number of RE principals are critical factors for better performances. In the present study, four single-phase equimolar multicomponent RE-monosilicate solid solutions including (Dy 1/3 Er 1/3 Yb 1/3) 2 SiO 5 , (Ho 1/3 Er 1/3 Yb 1/3) 2 SiO 5 , (Y 1/4 Er 1/4 Tm 1/4 Lu 1/4) 2 SiO 5 and (Dy 1/4 Er 1/4 Tm 1/4 Yb 1/4) 2 SiO 5 were synthesized by solid-state reaction and hot-pressing method. The microstructures, thermal and mechanical properties, and corrosion resistance to high-temperature water vapor were systematically investigated. Compared to the single-principal and ternary RE-monosilicates, the quaternary RE-monosilicates exhibited lower thermal conductivity of 1.32 Wm−1K−1 at 400 °C, matched thermal expansion coefficients (3.3 × 10−6/oC ∼ 5.8 × 10−6/oC from 200 °C to 1000 °C) with SiC, and much lower weight loss during water vapor corrosion. The results indicate that the increase of the RE element number can promote the grain growth, lower the thermal conductivity and thermal expansion coefficient, and enhance corrosion resistance. [ABSTRACT FROM AUTHOR]

This study investigates the thermal conductivity (λ) and volumetric heat capacity (C) of sandy soil samples under a variety of conditions, including freeze-thaw cycles at temperatures both above and below zero and differing moisture levels. To estimate these thermal properties, a novel predictive model, EFAttNet, was developed, which utilizes custom-designed embedding and attention-based fusion networks. When compared to traditional de Vries empirical models and other baseline algorithms, EFAttNet demonstrated superior accuracy. Preliminary measurements showed that λ values increased linearly with moisture content but decreased with temperature, whereas C values exhibited a rising trend with both moisture content and freezing temperature. Following freeze-thaw cycles, both λ and C were positively influenced by moisture content and freezing temperature. The EFAttNet-based model proved highly accurate in predicting thermal properties, particularly effective at capturing nonlinear relationships among the influencing factors. Among these factors, the degree of saturation had the most significant impact, followed by the number of freeze-thaw cycles, subzero temperatures, porosity, and moisture content. Notably, dry density exerted minimal influence on thermal properties, likely due to the overriding effects of other factors or specific soil characteristics, such as particle size distribution or mineralogical composition. These findings have significant implications for construction and engineering projects, especially in terms of sustainability and energy efficiency. The demonstrated accuracy of the EFAttNet-based model in estimating thermal properties under various conditions holds promise for practical applications. Although focused on specific soil types and conditions, the insights gained can guide further research and development in managing soil thermal properties across diverse environments, thereby enhancing our understanding and application in this field. [ABSTRACT FROM AUTHOR]

γ-GeSe is a newly identified polymorph among group-IV monochalcogenides, characterized by a distinctive interatomic bonding configuration. Despite its promising applications in electrical and thermal domains, the experimental verification of its mechanical and thermal properties remains unreported. Here, we experimentally characterize the in-plane Young's modulus (E) and thermal conductivity () of γ-GeSe. The mechanical vibrational modes of freestanding γ-GeSe flakes are measured using optical interferometry. Nano-indentation via atomic force microscopy is also conducted to induce mechanical deformation and to extract the E. Comparison with finite-element simulations reveals that the E is 97.3 7.5 GPa as determined by optical interferometry and 109.4 13.5 GPa as established through the nano-indentation method. Additionally, optothermal Raman spectroscopy reveals that γ-GeSe has a lattice thermal conductivity of 2.3 0.4 Wm−1K−1 and a total thermal conductivity of 7.5 0.4 Wm−1K−1 in the in-plane direction at room temperature. The notably high ratio in γ-GeSe, compared to other layered materials, underscores its distinctive structural and dynamic characteristics. [ABSTRACT FROM AUTHOR]

Highlights Epoxy resin (EP) is widely employed in power systems and electronic devices due to its low cost and easy processing along with good insulative and adhesive properties. However, EP insulation properties are compromised at elevated frequencies and temperatures because of its negative temperature coefficient effect (NTC) and poor thermal characteristics. In this context, barium strontium titanate (BST‐60), a positive temperature coefficient (PTC) filler, and hexagonal boron nitride (h‐BN), a thermally conductive filler, both surface‐modified with dopamine, are added in EP to simultaneously improve thermal and dielectric insulation properties at high temperatures and high frequencies. This study finds that below the Curie point of BST, the insulating properties of h‐BN fillers significantly contributes to improving insulation properties. Conversely, above the Curie point, the insulating nature of BST fillers leads to an improvement in the insulation performance of composites. Furthermore, at elevated frequency and temperature, the nano h‐BN enhances thermal conductivity of EP by establishing a thermally conductive network, while micro‐BST suppresses the NTC effect of EP by regulating electrical resistivity above the Curie point. The Heywang model elucidates the PTC effect of BST fillers, while a proposed heat conduction‐dissipation mechanism explains the behavior of incorporated fillers at different temperatures. PDA‐modified Ba0.8Sr0.2TiO3 and h‐BN co‐doped epoxy composites are prepared. Negative temperature coefficient effect of epoxy is mitigated by PTC fillers. The optimal wt.% of filler enhances both dielectric and thermal properties. Dielectric properties are explored at high frequencies and temperatures. Optimized epoxy composites are suitable for high‐frequency applications. [ABSTRACT FROM AUTHOR]

Today's need of the growing industries is to get better products with long life which depends upon the production processes. This requires enhanced thermal properties of the fluid as well as the components surrounding to it. Therefore, this study reveals the flow of several water-based nanofluids past an expanding sheet. Oxide nanoparticles, such as Al2O3 and CuO, are considered in the base liquid water to show their behavior on the flow phenomena. Further, dissipative heat properties due to magnetization, i.e. Joule and viscous dissipation enrich the study. The novelty of this study is the consideration of KKL "(Koo–Kleinstreuer–Li) correlation" for the conductivity and viscosity plays its important role in which the influence of Brownian activity is vital. The utilization of similarity rules is beneficial for the transformation of the governing equations into non-dimensional form. Further, the shooting-based Runge–Kutta technique is useful for the solution of these set of equations. The characterization of diversified components likely the particle concentration, magnetic and buoyancy parameter on the velocity distribution along with the Eckert number, and thermal radiation on the energy profile is obtained and deliberated briefly. [ABSTRACT FROM AUTHOR]

In order to meet the requirements of practical applications, the comprehensive performance of thermally conductive high‐voltage insulating composites is worth evaluating. Guided by the particle packing theory, spherical alumina particles with different particle size distributions were compounded and filled into low‐density polyethylene (LDPE), and the thermal conductivity (TC) and mechanical breakdown of different compound systems were systematically investigated. The results show that the particle grading design of small‐particle filled composites has better comprehensive properties than that of single‐scale or large‐particle filled composites, which proves the superiority and feasibility of particle grading design. The 110–40 wt.% composite has a higher TC (0.47 W/(m K)) compared with LDPE, while maintaining excellent insulation properties (227 kV/mm) and mechanical properties (tensile strength of 10 MPa and elongation at break of 720%). Finally, studies on the application of composite materials in the field of thermal management and ice melting of steel‐core aluminum insulated wires were applied, and both studies show good prospects for the applications of Al2O3/LDPE thermal conductive high‐voltage insulation composites. [ABSTRACT FROM AUTHOR]

SiO2f/SiO2 composites were prepared by compression molding and sintering using short-cut quartz fibers as reinforcement. The effects of fiber volume fraction (15%∼35%) on bulk density, apparent porosity, and mechanical and thermal properties of the composites were investigated. The results indicated that the samples with 25% fiber volume fraction had the best comprehensive performance, with an apparent porosity and compressive strength of 36% and 46.3 MPa, respectively. The flexural strength of the samples was 13.9 MPa, which represented a 90% increase compared to the samples without fibers. It was attributed to the occurrence of fiber debonding and fiber pull-out in the porous matrix. Meanwhile, the residual strength ratio of the samples after 20 thermal shocks was 74.8%. In addition, the average coefficient of thermal expansion was 0.95 × 10− 6/℃ at 300 ℃∼700 ℃ and the thermal conductivity was 0.388 W·m− 1·K− 1 at 800 °C. This approach can satisfy the requirements of low cost, fast preparation of SiO2f/SiO2 composites, which offers the prospect of its application in the integration of load-bearing and thermal insulation. [ABSTRACT FROM AUTHOR]

This work evaluates the electrical, optical and thermal properties of Sn-doped GexSi1-xOy thin films for use as microbolometer sensing materials. The films were prepared using a combination of a radio frequency (RF) magnetron and direct current (DC) sputtering using a Kurt J Leskar Proline PVD-75 series sputtering machine. Thin films were deposited in an O2+Ar environment at a chamber pressure of 4 mTorr. The thicknesses of the thin films were varied between 300 nm–1.2 µm by varying the deposition time. The morphology and microstructure of thin films were investigated by atomic force microscope (AFM) imaging and X-ray diffraction (XRD), while the atomic composition was determined using the energy dispersive spectroscopy (EDS) function of a scanning electron microscope. The thin film with an atomic composition of Ge0.45Si0.05Sn0.15O0.35 was found to be amorphous. We used the Arrhenius relationship to determine the activation energy as well as temperature coefficient of resistance of the thin films, which were found to be 0.2529 eV and −3.26%/K, respectively. The noise voltage power spectral density (PSD) of the film was analyzed using a Primarius—9812DX noise analyzer using frequencies ranging from 2 Hz to 10 kHz. The noise voltage PSD of the film was found to be 1.76 × 10−11 V2/Hz and 2.78 × 10−14 V2/Hz at 2 Hz and 1 K H z frequencies, respectively. The optical constants were determined using the ellipsometry reflection data of samples using an RC2 and infrared (IR) VASE Mark-II ellipsometer from J A Woollam. Absorption, transmission and reflection data for a wavelength range of 900 nm–5000 nm were also determined. We also determined the optical constant values such as the real and imaginary parts of refractive index (n and k, respectively) and real and imaginary part of permittivity ( ε 1 and ε 2 , respectively) for wavelength ranges between 193 nm to 35 µm. An optical band gap of 1.03 eV was determined from absorption data and using Tauc's equation. In addition, the thermal conductivity of the film was analyzed using a Linseis thin film analyzer employing the 3ω method. The thermal conductivity of a 780 nm thick film was found to be 0.38 Wm−1K−1 at 300 K. From the data, the Ge-Si-Sn-O alloy was found to be a promising material for use as a sensing material for microbolometers. [ABSTRACT FROM AUTHOR]

Graphene foam prepared by the chemical vapor deposition method is a promising thermal interfacial material. However, the thermal properties of graphene foam highly depend on the experimental fabrication conditions during the chemical vapor deposition process. Aiming to reveal how to prepare the appropriate graphene foam for the various thermal management scenarios, the influence of experimental conditions on thermal properties of graphene foam was investigated. Furthermore, the contribution of thermal conductivity and thermal radiation to the effective thermal coefficient of graphene foam was carried out for comparison. The research results showed that the porosity and the cross-section shape of the struts of the growth template were two critical factors affecting the thermal transport of graphene foam, especially with the increase of temperature. In addition, the deposition time of graphene determined the wall thickness and affected the thermal conductivity directly. The thermal radiation contributed more than thermal conductivity when the temperature climbed continuously. Comparatively, the effective thermal coefficient of graphene foam composite with high porosity and circular-shape struts was much superior to that of others at high temperature. The research findings provide important guidance for graphene foam fabrication and its applications in the field of thermal management. [ABSTRACT FROM AUTHOR]

External pressure can significantly alter the transport coefficients, power factor, and figure of merit because of its direct influence on the electronic structure, electron–phonon, and phonon–phonon couplings. This study delves into the electronic and thermal transport properties of SnPS3${\rm SnPS}_3$ at external pressures up to 30 GPa using first‐principles calculations and Boltzmann transport theory. The electron–phonon relaxation time is computed within the electron–phonon‐averaged (EPA) approximation, enabling exploration beyond the constant relaxation time approximation. The first‐principles calculations reveal an indirect bandgap of 1.76 (without pressure) and 0.12 eV (30 GPa). The density functional perturbation theory calculations confirm the dynamic stability of SnPS3${\rm SnPS}_3$ at external pressure up to 30 GPa. The electronic transport properties are improved by more than one order of magnitude at 30 GPa, consistent with experimental observations. The Peierls–Boltzmann transport calculations demonstrate the room temperature lattice thermal conductivity of 0.22 (without pressure) and 7.4 Wm−1K−1${\rm Wm}^{-1}{\rm K}^{-1}$ (at 30 GPa). The results emanate that SnPS3${\rm SnPS}_3$ exhibits ZT$ZT$ of 0.71 at 900 K at a hole doping of 2×1020$\times 10^{20}$cm−3$\text{cm}^{-3}$ at zero pressure, which decreases with increasing pressure. The findings explore the effect of external pressure on both electronic and thermal transport properties of SnPS3${\rm SnPS}_3$, warranting further experimental exploration of thermal transport properties at higher pressures. [ABSTRACT FROM AUTHOR]

Lunar meteorites are the most diverse and readily available specimens for the direct laboratory study of lunar surface materials. In addition to informing us about the composition and heterogeneity of lunar material, measurements of their thermo‐physical properties provide data necessary to inform the models of the thermal evolution of the lunar surface and provide data on fundamental physical properties of the surface material for the design of exploration and resource extraction hardware. Low‐temperature data are particularly important for the exploration of low‐temperature environments of the lunar poles and permanently shadowed regions. We report low‐temperature‐specific heat capacity, thermal conductivity, and linear thermal expansion for six lunar meteorites: Northwest Africa [NWA] 5000, NWA 6950, NWA 8687, NWA 10678, NWA 11421, and NWA 11474, over the range 5 ≤ T ≤ 300 K. From these, we calculate thermal inertia and thermal diffusivity as functions of temperature. Additionally, heat capacities were measured for 15 other lunar meteorites, from which we calculate their Debye temperature and effective molar mass. [ABSTRACT FROM AUTHOR]