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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.)

The thermal conductivity of glasses is well-known to be significantly harder to theoretically describe compared to crystalline materials. Because of this fact, the fundamental understanding of thermal conductivity in glasses remain extremely poor when moving beyond the case of simple glasses, e.g., glassy SiO2, and into so-called "modified" oxide glasses, that is, glasses where other oxides (e.g., alkali oxides) have been added to break up the network and alter, e.g., elastic and thermal properties. This lack of knowledge is apparent despite how modified glasses comprise the far majority of known glasses. In the present work, we study an archetypical series of sodium silicate [xNa2O–(100 − x)SiO2] glasses. Analyses of modal contributions reveal how increasing Na2O content induces increasing vibrational localization with a change of vibrations to be less ordered and a related general decrease in modal contributions to thermal conductivity. We find the vibrational phases (acoustic vs optical) of sodium vibrations to be relatively disordered compared to the network-forming silicon and oxygen species, explaining how increasing Na2O content decreases thermal conductivity. Our work sheds new light on the fundamentals of glassy heat transfer as well as the interplay between thermal conduction and modal characteristics in glasses. [ABSTRACT FROM AUTHOR]

Flexible electronic devices with skin-like properties are hailed as revolutionary for the development of next-generation electronic devices, such as electric-skin and humanoid robotics. Graphene is intrinsically flexible due to its structural thinness in nature and are considered next-generation materials for wearable electronics. These devices usually experience a large mechanical deformation in use so as to achieve intimate conformal contact with human skin and to coordinate complex human motions, while heat dissipation has been a major limitation when the device is under a large mechanical strain. Unlike the small deformation (<1%) induced by intrinsic material factors such as lattice mismatch between material components in devices, a large mechanical deformation (>1%) by an external loading condition could lead to apparent changes to global geometric shapes and significantly impact thermal transport. In this study, we investigated the thermal conductivities of graphene under several large mechanical strains: 2.9%, 4.3%, and 6.1%. We used a refined opto-thermal Raman technique to characterize the thermal transport properties and discovered the thermal conductivities to be 2092 ± 502, 972 ± 87, 348 ± 52, and 97 ± 13 W/(m K) for the relaxed state, 2.9%, 4.3%, and 6.1% tensile strain, respectively. Our results showed a significant decreasing trend in thermal conductivities with an increasing mechanical strain. The findings in this study reveal new thermal transport mechanisms in 2D materials and shed light on building novel flexible nanoelectronic devices with enhanced thermal management. [ABSTRACT FROM AUTHOR]

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]

To optimize the comprehensive performance of rare earth (RE) aluminates as thermal/environmental barrier coatings (T/EBCs), we engineered six kinds of novel high-entropy RE aluminate multiphase ceramics with the coexisting garnet and perovskite phases by regulating equivalent ionic radius of RE3+, and the relationship between the microstructure and thermal properties, as well as resistance to CMAS corrosion was investigated in-detail. The findings revealed that the garnet (5RE 0.2) 3 Al 5 O 12 content gradually decreased in multiphase ceramics with the increasing equivalent ionic radius of RE3+. The interaction between garnet and perovskite grains can decrease grain size, which in turn enhanced phonon scattering, thereby leading to the decrease in thermal conductivity. Moreover, the synergistic effect in the different dissolution rates of garnet and perovskite phases can form a dense garnet/apatite barrier layer at corrosion front, thereby contributing to CMAS corrosion resistance. These results provide a robust theoretical foundation for the advancement of next-generation T/EBCs. [ABSTRACT FROM AUTHOR]

Materials with a thermal expansion coefficient compatible with silicon carbide based ceramic matrix composites and low thermal conductivity at higher temperatures are crucial for developing environmental barrier coatings (EBCs) for aero-engines. Lately, high entropy silicate engineering has been a promising approach to develop optimized EBC materials. The solid solution reaction method was adopted for the fabrication of high entropy multicomponent (Dy 1/5 Er 1/5 Tm 1/5 Yb 1/5 Y 1/5) 2 SiO 5 or (5RE 1/5) 2 SiO 5 monosilicate. Scanning electron microscopy and X-ray diffraction show the homogenous distribution and a single-phase solution of (5RE 1/5) 2 SiO 5 monosilicate. Differential scanning calorimetry testing was done at 1450 °C which shows no exo/endothermic reaction has occurred. The value of the coefficient of thermal expansion (6 ppm/°C) up to temperature 1500 °C and low thermal conductivity values for (5RE 1/5) 2 SiO 5 monosilicate were observed (1.1–1.4 W/m°C) in the temperature range between 25 and 1500 °C. The water vapor corrosion resistance of (5RE 1/5) 2 SiO 5 monosilicate further confirms that the material is suitable for EBC applications due to the synergistic effect of different rare earth radii and stable crystal structure with a negligible weight loss value of 0.0005 mg/cm2 after 150 h corrosion time under 90 % H 2 O and 10 % O 2 at 1300 °C. The results of this work suggest that (5RE 1/5) 2 SiO 5 monosilicate can be used as a promising candidate for environmental barrier coatings. [ABSTRACT FROM AUTHOR]

With the development of electronic devices and wireless communication technology, the quality of human life has improved. However, shielding from electromagnetic interference (EMI) is required due to device malfunctions and harmful effects on human health. Polymer‐based shielding materials getting much attention due to their light weight, flexibility, good processability, and other desirable traits. However, achieving consistent dispersion of conductive fillers and optimizing the balance between electrical, mechanical, and thermal properties remain challenges despite the advantages of polymer‐based materials. Especially, epoxy resins are promising polymer materials for EMI shielding applications due to their excellent mechanical strength, chemical resistance, and excellent adhesive properties. Additionally, epoxy resin exhibits remarkable processability allowing for various fabrication techniques such as casting, molding, and three‐dimensional printing. However, one of the significant drawbacks of epoxy resin is the difficulty in achieving uniform dispersion of conductive fillers within the epoxy matrix. In this study, we propose an iron‐nickel alloy (FeNi) embedded in an epoxy matrix (FeNi/Epoxy) for EMI shielding material. It is manufactured by facile fabrication process due to the advantages of epoxy, which has excellent processability. EMI shielding effectiveness at 12 GHz is enhanced from 9.12 to 17.86 dB by the increase of FeNi concentrations. Furthermore, thermal and mechanical properties were improved by the increase of FeNi concentration. Thermal conductivity for efficient heat dissipation is increased from 0.63 to 1.49 Wm−1 K−1. Moreover, polydopamine (PDA) was employed as a surface coating material for FeNi to overcome the non‐uniform dispersion of FeNi particles in the epoxy matrix. Surface coating by PDA significantly enhanced the dispersion uniformity and strengthened the adhesion between the filler and matrix. Elastic modulus is greatly increased from 83.03 MPa to 1.29 GPa by the surface coating. The enhancement of mechanical properties is derived from the chemical bonds between the filler and matrix. [ABSTRACT FROM AUTHOR]

A novel surface modification technique for graphite films (GF) to improve the interface thermal resistance with epoxy resin was presented. By utilizing the self‐polymerization of dopamine (PDA), dopamine micro and nanoparticles were formed on the surface of the GF. Subsequently, the surface of the epoxy resin was functionalized with polydopamine (PDA) through grafting of the silane coupling agent 3‐glycidyl ether oxy‐propyl trimethoxy silane (GOPTS), enabling the introduction of epoxy resin groups onto the surface of the GF. Employing a simple folding technique, a three‐dimensional GF network (3DGF) was constructed, in which modified GF was successfully incorporated into the polymer matrix. The results showed that the 3DGF network further promoted the effective transfer of heat and electrons within the composite, leading to a significant improvement in thermal and electrothermal conversion performance. The prepared 3DGPGF/epoxy resin composite exhibits high thermal conductivity (7.14 W/mK) at a relatively low GF loading (31.9 wt%). Under a voltage of 12 V, the surface temperature of the sample rapidly rises from room temperature to 130°C within 200 s, and can completely melt ice cubes within 60 s. These results indicate that epoxy‐silane‐dopamine‐modified graphite film can be a promising candidate material, and this work provides a promising strategy for designing and manufacturing high‐performance composites with improved thermal properties. The developed method has the potential to be extended to other polymer matrices and fillers, and the prepared composites have enormous potential in various applications. [ABSTRACT FROM AUTHOR]

Passive cooling is a cooling technology that does not require external energy input, with most passive cooling strategies having high manufacturing difficulty and cost. In this study, we prepared lightweight aerogels (0.093 g/cm3) with high porosity (91.3%), directional pores, enhanced elastic recovery performance, and lower thermal conductivity (0.046 W/mK) through simple mixing, directional freezing, and freeze‐drying. The prepared samples have a reflectance of 87% in the ultraviolet—visible—near‐infrared (UV‐Vis‐NIR) range (0.2–2.5 μm) and an emissivity of 93.6% in the atmospheric transparency window. After covering the box with axial and transverse aerogel samples, the temperature inside the box relative to the uncovered sample box decreased by 12.9 and 13.4°C, respectively. This work provides a feasible method for the research of simply prepared passive cooling materials. [ABSTRACT FROM AUTHOR]

A coral-like network carbon aerogel was synthesized by introducing acid-modified carbon nanofibers (a-CNF) into phenolic (PR) aerogel through chemical grafting, followed by high-temperature carbonization. The bonding interaction between a-CNF and PR was analyzed by FT-IR spectroscopy. The microstructure of a-CNF/PR composite aerogel (a-CNF/PRA) was studied by SEM and pore structure analysis. The results showed that introducing 5 wt% of a-CNF was most favorable for forming a porous network of a-CNF/PRA. SEM photographs and pore structure analysis indicated that a-CNF/C composite aerogel (a-CNF/CA) developed a stable porous skeletal structure during carbonization. TEM images revealed that the complete porous skeleton consisted of a-CNF encapsulated by carbon layers. The carbonization shrinkage of a-CNF/CA was only 26.53% due to the presence of a-CNF as the skeleton support. Compared to carbon aerogel, a-CNF/CA exhibited lower density (0.072 g cm−3), thermal conductivity (0.0452 W m−1 K−1), and higher compressive strength (up to 3.26 MPa) up to 3.26 MPa than that of carbon aerogel (1.21 MPa). These findings confirmed the excellent mechanical and thermal insulation properties of a-CNF/CA. [ABSTRACT FROM AUTHOR]

The objective of this study is to synthesize hollow SiO2 nanospheres (HSNs), and to investigate the effect of varying divinylbenzene (DVB) amounts during synthesis on their morphology and pore structure. Additionally, it seeks to characterize the thermal conductivity of the synthesized HSNs and evaluate the impact of their incorporation on the thermal insulation properties of acrylic coatings. Single‐shell HSNs were synthesized using the Stöber method, which involved hydrolysis‐polycondensation of tetraethyl orthosilicate. The double‐shell HSNs were prepared using a stepwise wrapping synthesis method, with single‐shell HSNs as the core matrix and an appropriate amount of crosslinking agent added. The addition of DVB resulted in different morphologies, shell spacings, and specific surface areas for the double‐shell HSNs. The thermal conductivity of the double‐shell HSNs decreased significantly to as low as 0.0252 W·m1·K−1 with an increase in shell spacing. The shell spacing of double‐shell HSNs had doubled, resulting in a reduction of its thermal conductivity by approximately 18%. When the double‐shell HSN content reached 8%, the thermal conductivity decreased by 85% compared to that of the original acrylate coating. These results indicate that double‐shell HSNs can substantially decrease the thermal conductivity of the matrix material for thermal insulation applications. [ABSTRACT FROM AUTHOR]

Si3N4 ceramics with improved thermal conductivity and mechanical properties were prepared by carbothermal reduction and two‐step sintering. The addition of 2 wt% C led to the development of an intergranular phase YNSiO2 with reduced oxygen content. Notably, setting the pre‐sintering temperature at 1450°C promoted the formation of a rough bimodal morphology within the Si3N4 ceramics. Furthermore, an extended holding period at 1850°C resulted in additional grain growth and the elimination of intergranular phases. The Si3N4 specimens produced at 1450°C for 3 h followed by 1850°C for 8 h, incorporating 2 wt% C, exhibited a notable continuity between Si3N4 grains. The thickness of the grain boundary layer was only about 1 nm, and the N/O atomic ratio of the intergranular phase was measured to be 0.42. Consequently, the resulting thermal conductivity, flexural strength, and fracture toughness of Si3N4 specimens were found to be 101 W·m−1·K−1, 712 ± 29 MPa, and 7.7 ± 0.2 MPa·m1/2, respectively. Compared with samples without C additive and directly sintered at 1850°C for 8 h, the Si3N4 specimens produced in this work showed a significant increase of more than 50% in thermal conductivity and about 17% in fracture toughness. [ABSTRACT FROM AUTHOR]

Thermal metamaterials are typically achieved by mixing different natural materials to realize effective thermal conductivities (ETCs) that conventional materials do not possess. However, the necessity for multifunctional design of metamaterials, encompassing both thermal and mechanical functionalities, is somewhat overlooked, resulting in the fixation of mechanical properties in thermal metamaterials designed within current research endeavors. Thus far, conventional methods have faced challenges in designing thermal metamaterials with configurable mechanical properties because of intricate inherent relationships among the structural configuration, thermal and mechanical properties in metamaterials. Here, a data‐driven approach is proposed to design a thermal metamaterial capable of seamlessly achieving thermal functionalities and harnessing the advantages of microstructural diversity to configure its mechanical properties. The designed metamaterial possesses thermal cloaking functionality while exhibiting exceptional mechanical properties, such as load‐bearing capacity, shearing strength, and tensile resistance, thereby affording mechanical protection for the thermal metadevice. The proposed approach can generate numerous distinct inverse design candidate topological functional cells (TFCs), designing thermal metamaterials with dramatic improvements in mechanical properties compared to traditional ones, which sets up a novel paradigm for discovering thermal metamaterials with extraordinary mechanical structures. Furthermore, this approach also paves the way for investigating thermal metamaterials with additional physical properties. [ABSTRACT FROM AUTHOR]

Cordierite-mullite composite ceramics were prepared by solid-state method using Panzhihua low-grade Ti-rich clay, talc, and alumina. Influences of cordierite/mullite ratio, sintering temperature, and the chemical composition of clay on the phase composition, microstructure, physical properties, and thermal properties were investigated in detail. The results showed that the impurity oxides inside the Ti-rich clay had a great ability of forming liquid. Above 1300 °C, the reaction between TiO 2 of the clay and Al 2 O 3 produced stable Al 2 TiO 5 , which was conducive to decreasing the coefficient of thermal expansion (CTE). At 1300–1350 °C, the secondary mullitization caused the volumetric expansion, decreasing the bending strength and increasing the CTE. The optimum ratio of cordierite to mullite ranged from 90:10 to 80:20, and the sample fired at 1400 °C exhibited the lowest water absorption and porosity (0.64 % and 1.56 %, respectively), optimal bulk density, and bending strength (2.59 g cm−3 and 87.79 MPa), as well as better CTE, thermal conductivity, and thermal storage density (2.91 × 10−6 °C−1, 4.11 W/(m⋅K) (30 °C), and 1181 kJ kg−1, respectively). Compared with the reported values of cordierite-based thermal storage ceramics prepared by using the high-grade clay or minerals, the obtained samples showed the advantages such as lower costs for raw materials, higher bending strength, higher thermal conductivity (1.63–2 times higher), low CTE, and high thermal storage density. This study demonstrated that the low-grade Ti/Fe-rich clay has excellent cost-effective potential for the preparation of thermal storage ceramics. [ABSTRACT FROM AUTHOR]

In the domain of personal thermal protection, there is a growing demand for lightweight and efficient ceramic thermal insulation materials. However, conventional ceramic membranes face challenges such as brittleness, structural collapse, and pulverization, hindering their practical application. To address this issue, aluminum hydroxide-enhanced silica-zirconia ceramic membranes (SZ@ANFMs) have been successfully fabricated using electrospinning followed by subsequent calcination processes, and their properties have been comprehensively evaluated. The results demonstrate that SZ@ANFMs exhibit outstanding high-temperature resistance under an alcohol lamp, along with an extremely low thermal conductivity (only 0.041 W/m·K), excellent tensile strength (2.3 MPa), and flexible characteristics. This makes them highly promising in the domain of personal thermal protection. The study builds upon existing research in lightweight and efficient thermal insulation materials, offering improvements and robust support for the further development of personal thermal protection technology. [ABSTRACT FROM AUTHOR]

High‐density polyethylene (HDPE) nanocomposites containing different optimized fractions of carbon nanofiber (CNF) at 6 wt.%, polyethylene glycol (PEG) at 4 wt.%, and copper oxide (CuO) nanorods in concentration ranges of 0.15, 0.5, and 2 wt.% were successfully melt processed using corotating twin extrusion and compression molding technique. The effect of PEG and CuO nanofiller on the HDPE matrix were studied, particularly for the percolation threshold for electrical conductivity, structural morphology, and other properties including thermal stability, thermal conductivity (TC), dielectric, and UV protection properties. It is observed that PEG acts as a good compatibilizer, facilitating better interfacial connection between CNF and HDPE matrix. The optimized composite with 0.15 wt.% CuO nanorods (H/C6/P4/Cu0.15) shows a fine morphology and strong interfacial connections between fillers and the matrix, as observed in FE‐SEM micrographs. This optimized composite exhibits improved thermal stability, higher thermal conductivity (0.0404 W.K−1.m−1), increased dielectric constant, reduced electrical volume resistivity (from 2.1 × 1015 to 2.1 × 106 Ω.cm), and lower optical band gap value (2.74 eV). Additionally, all prepared nanocomposites offer approximately 100% Ultraviolet Protection Factor (UPF) rating for UV protection. Highlights: The transformation of insulating HDPE into conducting HDPE composites.The effect of CuO nanorods was investigated in compatibilized HDPE composites.A percolation is achieved in the HDPE composite at 0.15 wt.% of CuO nanorods.PEG and CuO nanorods improved the multifunctional properties of the composite. [ABSTRACT FROM AUTHOR]

Highlights The development of epoxy resin (EP) potting material with high thermal conductivity (TC) and excellent electrical insulating properties plays an important role in the development of drive motors to high specific power and high voltage. In this study, a simple preparation method is presented to solve the problem of low content filler settling and low TC of EP. Firstly, small‐sized perfluoroalkyltrimethoxysilane surface‐treated nanodiamond (ND) and large‐sized hydroxylated boron nitride (BN) were adsorbed together using hydrogen bonding to construct “Sesame Cookie”‐like structures. The heterostructure filler with different “sesame” contents were obtained by modulating the ND:BN ratio, and were filled into high‐temperature resistant AG70 EP at a fixed mass ratio of 20 wt.%. By surface treatment, the dispersibility of fillers in EP was improved, and the settling problem of low content fillers was solved. Finally, when the ratio of ND: BN is 1:2, the TC value of EP composite reached 0.94 W·m−1·K−1, which was 348% higher than pure EP, and the composite possessed good electrical insulating properties. In addition, the heat‐resistance temperature of the composite exceeded 200°C, which ensured the stable operation of the drive motor. This study presents new ideas for the exploitation of EP potting materials with high TC and excellent electrical insulating properties. Heterostructure filler is constructed using hydrogen bonding. Dispersion of the filler in the EP is improved by surface treatment. The TC value of the EP composite increased by 348%. The heat‐resistant temperature of the EP composite is more than 200°C. The EP composite has excellent insulating properties. [ABSTRACT FROM AUTHOR]

This work created a fireproof sandwich structure in which the face sheets were made of expanded vermiculite and expanded perlite‐filled geopolymer composites and embedded basalt fiber mats and the core material was rock wool in designing the lightweight and cost‐effective fire‐resistant structure for steel bridges with excellent retardant and heat‐insulating performance. The effects of adding 5%, 10%, 15%, and 20% expanded vermiculite and expanded perlite to the geopolymer on mechanical properties and the thermal conductivity were investigated to obtain the optimized material mixtures for preparing the face‐sheets material of the sandwich panel. Then, the fireproof sandwich structures were fabricated and exposed to 800°C for 3 h to study the structural integrity, backfire side temperature, and mass loss ratio. The results indicated that adding 10 wt% expanded vermiculite and 10 wt% expanded perlite to the geopolymer achieved the retention of compressive strength of 66.5% after being exposed to 800°C, and the geopolymer mixtures showed a low thermal conductivity of 0.1942 W/(mK). The TOPSIS evaluation analysis reveals that the proposed fireproof sandwich panel had the highest integrated performance considering the structural weight, insulation properties, and cost. The findings of this work may provide some insights into fireproof and insulating applications in bridge engineering. [ABSTRACT FROM AUTHOR]

In this study, the molecular structure models of four ionic liquids were created, the reverse nonequilibrium molecular dynamics simulation (RNEMD) approach was used to predict their densities and viscosities, and their thermal conductivity was simulated using the non-equilibrium molecular dynamic simulation method (NEMD). The calculated results of ionic liquid densities were compared with the data in the literature; most of the variances are around 2.5%, and the maximum relative deviation was less than 6.27%; viscosity values were compared with the experimental data, with a maximum relative deviation of −8.96% and a minimum relative deviation of −2.72%. The simulated thermal conductivity has a good linear relationship with respect to temperature and pressure, which is in good agreement. This study provides a reference for molecular dynamics simulation to measure the physical properties of ionic liquids, which is important for the development of ionic liquids. [ABSTRACT FROM AUTHOR]

A high‐entropy rare‐earth disilicate (Er0.25Y0.25Ho0.25Yb0.25)2Si2O7 (hereinafter referred to as (EYHY)2Si2O7) ceramic was synthesized by a heat treatment process combined with spark plasma sintering. According to the experimental results, (EYHY)2Si2O7 presents good phase stability and low thermal conductivity ([1.48–2.35] W∙m−1∙K−1) from room temperature to 1200°C. Its coefficient of thermal expansion is (3.89–5.32) × 10−6 K−1 from 200 to 1400°C, similar to SiC‐based materials ([4.5–5.5] × 10−6 K−1). Due to the multiple doping effects, (EYHY)2Si2O7 exhibits outstanding corrosion resistance performance in water‐vapor corrosion tests. Its weight loss is 1.79 mg/cm2 after corrosion at 1600°C for 30 h in the presence of 50% H2O‐50% O2, which is lower than the corresponding four single components Re2Si2O7 (Er2Si2O7, Y2Si2O7, Ho2Si2O7, and Yb2Si2O7) under the same conditions. Therefore, high‐entropy (EYHY)2Si2O7 ceramics are regarded as potential environmental barrier coatings materials for SiC ceramic matrix composites. [ABSTRACT FROM AUTHOR]

In this study, composite phase change materials (CPCMs) comprising hexadecylamine (HDA) (C 16 H 35 N), disodium hydrogen phosphate dodecahydrate (DHPD) (Na 2 HPO 4 ·12H 2 O), and expanded graphite (EG) were prepared using the demulsification method. These CPCMs exhibit high latent heat and stable thermal properties. This approach effectively mitigates the issues of substantial supercooling and poor thermal conductivity commonly associated with DHPD and HDA. Additionally, the inclusion of EG imparts superior morphological stability to the CPCMs. The HDA/DHPD/EG CPCMs demonstrated robust thermal and morphological stability at temperatures below 100 °C. Their latent heat reached up to 221 J/g and remained stable at this value even after 50 cold-heat cycles, thereby indicating excellent cycling stability. When EG was incorporated at 2 wt%, the thermal conductivity of the HDA/DHPD/EG CPCMs increased to 0.751 W/(m·K), indicating that the three-dimensional network structure of EG facilitates heat conduction and offers exceptional photothermal conversion capabilities, with a photothermal conversion efficiency of up to 97.1 %. The aforementioned results highlight the promising potential of the prepared CPCMs for applications in low-temperature waste heat recovery. [ABSTRACT FROM AUTHOR]

BiCuSeO, an oxide thermoelectric material with a superlattice structure, presents the advantages of affordability, low toxicity, and environmental friendliness. However, its intrinsic low electrical conductivity has impeded its possible applications. To address this challenge, we put tiny PbZr 0.52 Ti 0.48 O 3 (PZT) with varying weight percentages (x = 0, 5, 7, 9, 11) into BiCuSeO (BCSO) to fabricate thermoelectric nanocomposites. Through the spark plasma sintering process, PZT particles underwent in-situ decomposition, generating nano-sized second phases such as PbO 2 , TiO 2 , and PbZrO 3 , which are homogenously distributed within BCSO matrix (validated by XRD and TEM). The introduced PbO 2 , TiO 2 , and PbZrO 3 second phases served a dual purpose: inhibiting the grain growth of BCSO and introducing additional nano-grain boundaries. This resulted in more effective phonon scattering sites, thereby reducing lattice thermal conductivity. Simultaneously, the Pb element derived from PZT decomposition was doped into the Bi site of the BCSO matrix, causing a reduction in the band gap of BCSO from 0.49 eV to 0.388 eV and a significant increase in carrier concentration. Consequently, this doping enhanced the electrical conductivity of BCSO-based composites, with the composite with 11 wt% PZT additive amount exhibiting a remarkable 318-fold increase, reaching 550 S/cm compared to pristine BCSO. Notably, the composite with 7 wt% PZT additive amount achieved an exceptionally low lattice thermal conductivity of 0.333 W m−1 K−1 at 823 K. Through the synergistic optimization of electrical and thermal transport properties, the BCSO-based composite with 7 wt% PZT additive amount obtained a ZT value of ∼0.9 at 873 K, representing a 2.45-fold increase compared to pristine BiCuSeO. This straightforward method presents a cost-effective and scalable approach to enhance the thermoelectric performance of various materials, opening new avenues for potential commercial applications. [ABSTRACT FROM AUTHOR]

Investigating how the thermal transport properties of iron change under extremely high pressure and temperature conditions, such as those found in the Earth's core, is a major experimental challenge. Over the past decade, there has been a great deal of discussion and debate surrounding the thermal conductivity of the iron-based Earth's core and its thermal evolution. One reason for this may be the variability in the experimentally obtained thermal conductivity of iron at high pressures and temperatures. In this study, we present the experimental results of measuring the thermal conductivity of hexagonal-closed-pack (hcp) iron over a wide pressure-temperature range up to 176 GPa and 2900 K using the pulsed light heating thermoreflectance technique in a laser-heated diamond anvil cell. Our findings indicate that the temperature derivative of the thermal conductivity of hcp iron undergoes a change from negative to positive above 74 GPa, potentially making hcp iron highly conductive at conditions similar to those observed in the Earth's core. This observation represents a notable example of a phenomenon where pressure appears to influence the sign of the temperature derivative of the thermal conductivity of an isostructural metal. [ABSTRACT FROM AUTHOR]

Among metal‐based phase change materials (PCMs), Al and its alloys have garnered significant attention due to their high latent heat and high thermal conductivity. However, challenges such as leakage, corrosion, and oxidation have limited their widespread application. Numerous researches have demonstrated that encapsulating Al and its alloy PCMs is one effective way to address these problems. This review provides a comprehensive overview of the characteristics, encapsulation strategies, and applications of Al and its alloy PCMs. First, the advantages and thermal properties of Al and its alloy PCMs are introduced, and their problems are then discussed. Subsequently, various encapsulation strategies that are expected to solve the above problems are summarized and compared. Additionally, the applications of Al and its alloy PCMs in solar thermal energy storage, catalysis, and electric vehicles are reviewed. Finally, current challenges, potential solutions, and the key direct of future study are presented. [ABSTRACT FROM AUTHOR]

The current market's imperative demand necessitates the research and development of advanced polymer composites, especially those incorporating nanofillers. Carbon nanotubes, in particular, have attracted significant attention within research and development for their potential in creating multifunctional composites. This study aims to evaluate the impact of incorporating carbon nanotube buckypapers (BP) on the thermal and electrical properties of poly (aryl ether ketone) (PAEK)/glass fiber (GF) composites. The BP was prepared through vacuum filtration and integrated into PAEK/GF composites with varying stacking sequences, followed by hot compression processing. The degradation behavior of the laminates was investigated using thermogravimetric analysis (TGA). The viscoelastic properties, evaluated by dynamic mechanical analysis (DMA), suggested an increase in stiffness with the inclusion of BP in two of the analyzed stacking sequences. Thermal conductivity, measured via the pulse laser method, showed results comparable to the base laminate (0.153 W/m·K). Meanwhile, electrical conductivity, assessed using the four‐point probe method in the in‐plane direction, revealed semiconductor properties, achieving a mean value of 3.162 S/cm for one of the samples, indicating electrical anisotropy within the multifunctional composite material. [ABSTRACT FROM AUTHOR]

Due to its high thermal conductivity, graphene finds extensive application in thermal composite materials. However, akin to polymer composites containing other fillers, the thermal resistance at the interface between graphene and the polymer matrix substantially impedes heat conduction. Thus, functionalizing graphene becomes imperative to enhance its dispersibility in polymers. In this study, we synthesized the imidazolyl ionic liquid 1‐methyl‐3‐triethoxysilpropyl imidazole chloride ([MTESiPIM]Cl). Ionic liquid complexes supported by graphene (G) were synthesized via a simple ultrasonic stripping method by combining electrochemical graphene (G) with [MTESiPIM]Cl (Si‐IL@G). The Si‐IL@G/LLDPE composite was formed by blending Si‐IL@G into the linear low‐density polyethylene (LLDPE) matrix using a melt blending technique. Upon adding 5% Si‐IL@G, the tensile strength and bending modulus of Si‐IL@G/LLDPE composite reached 13.5 MPa and 348.2 MPa, respectively, marking an increase of 20.67% and 57.79% over pure LLDPE. The Si‐IL@G/LLDPE composite exhibited a thermal conductivity of 0.49 W·m−1·K−1, 96.0% higher than that of pure LLDPE. Given its outstanding thermal conductivity and mechanical properties, Si‐IL@G holds great potential in producing composites with high thermal conductivity. Highlights: An ionic liquid with siloxanyl groups was synthesized using microwave assistance.The ionic liquid was modified onto graphene sheets using ultrasonic techniques.The study examined how ionic liquid‐modified graphene affects LLDPE structure.The thermal conductivity and mechanical properties of LLDPE were enhanced. [ABSTRACT FROM AUTHOR]

The present study investigated the use of expanded perlite (e‐perlite) as a sustainable and cost‐effective filler for EPDM (ethylene propylene diene monomer) rubber composites. Various amounts of e‐perlite were incorporated into EPDM to assess its impact on the composite properties, such as curing characteristics, physical and mechanical properties, crosslink density, thermal conductivity, thermal stability, surface roughness, and contact angle. The composite with 15 phr of e‐perlite exhibited approximately 20% higher crosslink density and a 12% increase in hardness, while slight decreases were observed in elongation at break and tensile strength. The FE‐SEM (field emission‐scanning electron microscopy), atomic force microscopy, and contact angle analysis have been performed to investigate the surface morphology and the hydrophobicity. The thermal properties of the composites were assessed through thermogravimetric analysis, thermal aging tests, and thermal conductivity measurements. The results showed that e‐perlite significantly improved the aging resistance and the thermal stability. The composites with 15 phr e‐perlite exhibited a 21% reduction in thermal conductivity and enhanced thermal isolation properties compared to the EPDM composite without e‐perlite. This work demonstrated the potential utilization of e‐perlite in EPDM as a green sustainable filler to enhance the thermal insulation and the stability properties of the composites, which may have practical applications in automotive, aerospace, construction, and electronic industries. Highlights: E‐perlite enhances the thermal insulation property of EPDM rubber composites.Higher e‐perlite content increases composite hardness and crosslink density.The thermal conductivity of EPDM is reduced by increasing e‐perlite content.EPDM/e‐perlite exhibits improved thermal stability and aging resistance.Potential uses in automotive, aerospace, construction, and defense industries. [ABSTRACT FROM AUTHOR]

In recent years, the implementation of CO2 capture systems has increased. To reduce the costs and the footprint of the processes, different industrial wastes are successfully proposed for CO2 capture, such as gypsum from desulfurization units. This gypsum undergoes an aqueous carbonation process for CO2 capture, producing an added-value solid material that can be valorized. In this work, panels have been manufactured with a replacement of (5 and 20%) commercial gypsum and all the compositions kept the water/solid ratio constant (0.45). The density, surface hardness, resistance to compression, bending, and fire resistance of 2 cm thick panels have been determined. The addition of the waste after the CO2 capture diminishes the density and mechanical strength. However, it fulfills the requirements of the different European regulations and diminishes 56% of the thermal conductivity when 20%wt of waste is used. Although the CO2 waste is decomposed endothermically at 650 °C, the fire resistance decreases by 18% when 20%wt. is added, which allows us to establish that these wastes can be used in fire-resistant panels. An environmental life cycle assessment was conducted by analyzing a recycling case in Spain. The results indicate that the material with CO2 capture waste offers no environmental advantage over gypsum unless the production plant is located within 200 km of the waste source, with transportation being the key factor. [ABSTRACT FROM AUTHOR]

Improvement of thermal conductivity of polymer present a key to realizing efficient thermal transport used for various applications remains a long-standing challenge. In fact, we investigate the effect of TBPO-capped CdSe nanoparticles concentration on Thermal properties in Poly (3-hexylthiophene) (P3HT) thin films. We employed photothermal deflection technique PTD for thermal conductivity and diffusivity determination. Thermal conductivity and diffusivity were determined by fitting theoretical amplitude and phase of PTD signal to the experimental ones. We remark that thermal diffusivity D decreased for 3.52– 0.23 m2/s as function of CdSe nanoparticles concentration (NPs) in P3HT. However, thermal conductivity K increases for 1.78– 3.18 W/m.K as respect of CdSe nanoparticles concentration in P3HT. High thermal conductivity and lower thermal diffusivity are obtained for 40% TBPO-capped CdSe concentration in P3HT sample. [ABSTRACT FROM AUTHOR]

BiCuSeO is a promising oxygen‐containing thermoelectric material due to its intrinsically low lattice thermal conductivity and excellent service stability. However, the low electrical conductivity limits its thermoelectric performance. Aliovalent element doping can significantly improve their carrier concentration, but it may also impact carrier mobility and thermal transport properties. Considering the influence of graphene on carrier‐phonon decoupling, Bi0.88Pb0.06Ca0.06CuSeO (BPCCSO)‐graphene composites are designed. For further practical application, a rapid preparation method is employed, taking less than 1 h, which combines self‐propagating high‐temperature synthesis with spark plasma sintering. The incorporation of graphene simultaneously optimizes the electrical properties and thermal conductivity, yielding a high ratio of weighted mobility to lattice thermal conductivity (144 at 300 K and 95 at 923 K). Ultimately, BPCCSO‐graphene composites achieve exceptional thermoelectric performance with a ZT value of 1.6 at 923 K, bringing a ≈40% improvement over BPCCSO without graphene. This work further promotes the practical application of BiCuSeO‐based materials and this facile and effective strategy can also be extended to other thermoelectric systems. [ABSTRACT FROM AUTHOR]

This article presents a comprehensive review of the advancements in the use of Date Palm Fiber (DPF) reinforced composites, highlighting their mechanical, thermal, and morphological properties and the enhancements achieved through various modification techniques. Date palm fibers, a sustainable and biodegradable resource, have garnered significant interest due to their potential in reducing environmental impact across several key industries, including building and construction, automotive, and packaging. The review discusses the effects of hybrid approaches and physical and chemical treatments on the mechanical properties of DPF composites, demonstrating improvements in tensile strength, elasticity, and flexural strength through optimized fiber‐matrix bonding and reduced moisture absorption. Thermal behavior analyses through Thermogravimetric Analysis (TGA), Dynamic Mechanical Analysis (DMA), and thermal conductivity underscore the composites' suitability for applications requiring high thermal stability and conductivity for insulation applications. Morphological studies reveal that surface‐treated fibers integrate more effectively with various polymeric matrices, leading to enhanced composite performance. The practical applications of DPF composites are explored, emphasizing their role in promoting sustainable manufacturing practices. Challenges such as scalability, cost‐efficiency, and performance consistency are addressed, alongside future perspectives that suggest a promising direction for further research and technological development in the field of natural fiber composites. This review aims to solidify the foundation for ongoing advancements and increase the adoption of DPF composites in commercial applications. [ABSTRACT FROM AUTHOR]

Hybrid carbon nanotube (CNT) sheets were fabricated by mixing CNTs with silver nanowires (AgNWs) and MXene to study their electromagnetic-interference (EMI)-shielding properties. CNT/AgNW and CNT/MXene hybrid sheets were produced by ultrasonic homogenization and vacuum filtration, resulting in free-standing CNT sheets. Three different weight ratios of AgNW and MXene were added to the CNT dispersions to produce hybrid CNT sheets. Microstructure characterization was performed using scanning electron microscopy, and the Wiedemann–Franz law was used to characterize transport properties. The resulting hybrid sheets exhibited improved electrical conductivity, thermal conductivity, and EMI-shielding effectiveness compared to pristine CNT sheets. X-band EMI-shielding effectiveness improved by over 200%, while electrical conductivity improved by more than 1500% in the hybrid sheets due to a higher charge-carrier density and synergistic effects between nanomaterials. The addition of AgNW to CNT sheets resulted in a large improvement in electrical conductivity and EMI shielding; however, this may also result in increased weight and sample thickness. Similarly, the addition of MXene to CNT sheets may result in an increase in weight due to the presence of the denser MXene flakes. [ABSTRACT FROM AUTHOR]

It was understood that various studies were carried out on the strength, permeability, durability, increasing the thermal performance of lightweight concrete facade panels, and sustainable and energy‐efficient concepts. It was observed that fiber was added to the mixture to improve the properties in question. However, it was determined that contradictory results were obtained due to the large number of active parameters and whether the fiber was distributed homogeneously in the matrix. In this study, the effects of fiber type, length and usage rate on the strength, energy absorption capacity, elasticity modulus, water absorption, and thermal performance of lightweight concrete mixtures were investigated. For this purpose, three different types of fibers of different lengths: polypropylene (3, 6, and 12 mm), glass (13 and 25 mm) and polyamide (6 and 12 mm) were used at 0%, 0.25%, 0.50%, and 0.75% of the total volume. It was determined that the mixture containing 0.25% polypropylene fiber with a length of 3 mm exhibited the best performance in terms of both mechanical and thermal properties. In terms of these features, it was understood that the mixtures with 12 mm polypropylene with a usage rate of 0.75% and 6 mm polyamide fibers with a usage rate of 0.50% had the weakest performance. [ABSTRACT FROM AUTHOR]

Glass foams and glass-ceramic foams exhibit great potential in thermal insulation of buildings, consequently reducing the necessity for heating or cooling, and ultimately contributing to energy saving. In this study, we prepared glass-ceramic foams utilizing silicate glass as starting material and CaCO 3 as foaming agent through a thermochemical process. Foams with varying degrees of relative crystallinity were produced by controlling temperature and duration of isothermal heat treatment. The foaming mechanism in the glass-ceramics was discussed by analyzing how the heat flow, mass, and volume evolve within the powder mixture during dynamic heating. The crystallization in glass did not show any clear trend on the compressive strength of glass foams. On the other hand, the thermal conductivity of the glass-ceramic foams increases with increasing relative crystallinity. The calculated solid thermal conductivity exhibited a minimum at low relative crystallinity (<20 %). These findings are crucial for designing high performance glass-ceramic foams for thermal insulation, potentially also for fabricating glass-ceramic foams using waste glasses. [ABSTRACT FROM AUTHOR]

Thermal protection was always a prominent issue in the aerospace industry. For vehicle safety, reliability and payload requirements, thermal protection materials were usually expected to possess low density, superior mechanical and thermal insulation properties. Here, lightweight and high-strength porous mullite-silica ceramics were manufactured using particle-stabilized foaming technique. The strength and thermal insulation properties of porous ceramics modified with hollow silica spheres were significantly enhanced. A 10 wt% hollow spheres addition achieved a 28.9 % increase in strength and a 33.4 % decrease in thermal conductivity with almost constant porosity (from 86.39 % to 87.04 %). Considering the characteristics of light weight, high compression strength and superior thermal insulation performance, porous ceramics could be applied as thermal protection materials in the aerospace sector. [ABSTRACT FROM AUTHOR]

Porous high-entropy transition metal compounds, an important type of ultra-high temperature material, have attracted increasing attention in the applications of extreme environments due to their low density, good thermal insulation and stable chemical properties. A robust, flame-retardant and high-temperature resistant high-entropy carbonitride (Ti 1/5 V 1/5 Mo 1/5 Nb 1/5 Ta 1/5)(C 0.55 N 0.45) (HECN) porous ceramic was synthesized and thoroughly characterized. It exhibited a porosity of 93.5 %, a compressive strength of 1.3 MPa and a good high-temperature stability up to 1673 K, which, along with its outstanding fire-retardancy, and low thermal conductivity (as low as 0.150 W m−1 K−1 at 298 K), made it a good candidate material for thermal insulation applications in ultra-high temperature environments. Moreover, the Density functional theory (DFT) calculations predict that the [N]/([C]+[N]) ratio in HECN foam affects its lattice thermal conductivity which is decreased by 67 % upon increasing the ratio from 0 to 1/2. [ABSTRACT FROM AUTHOR]

With the increasing development of productivity, new materials that allow for the efficient use of energy are slowly becoming a sought-after goal, as well as a challenge that is currently being faced. For this reason, we have made aerogels as the target of our research and prepared different series (CLPI (1–5)) of cross-linked polyimide aerogels by mixing and cross-linking the heat-insulating cross-linking agent 1,3,5-tris(4-aminobenzylamino)benzene (TAB) with polyamic acid solution. We created a three-dimensional spatial organization by using vacuum freeze-drying and programmed high-temperature drying, then controlled the concentration of the polyamidate solution to investigate the concentration and TAB's influence on aerogel-related properties. Among them, the shrinkage is reduced from 40% in CLPI-1 to 28% in CLPI-5, and it also shows excellent mechanical characteristics, the highest compression strength (CLPI-5) reaches 0.81 MPa and specific modulus reaches 41.95 KN m/Kg. In addition, adding TAB improves the aerogel thermal resistance, T5 in N2 from PI-2 519 °C to CLPI-2 556 °C. The three-dimensional network-type structure of the aerogel shows an excellent thermal insulation effect, where the thermal conductivity can be as low as 24.4 mWm−1 K−1. Compared with some protective materials, cross-linked polyimide aerogel presents better flame-retardant properties, greatly improving the scope of its application in the industrial protection. [ABSTRACT FROM AUTHOR]

Investment casting is a widely utilized casting technique that offers superior dimensional accuracy and surface quality. In this method, the wax patterns are employed in the layer-by-layer formation of a shell mold. As is customary, the patterns were created through the injection of molten or semi-solid wax into the die. The quality of the final casting is affected by the quality of the wax pattern. Furthermore, the filling of the die with wax can be associated with die-filling challenges, such as the formation of weld lines and misruns. In this study, the injection filling of the fluidity probe die with RG20, S1235, and S1135 pattern waxes was simulated using ProCast software. The thermal properties of the waxes, including thermal conductivity, heat capacity, and density across a wide temperature range, were determined with the assistance of a laser flash analyzer, a differential scanning calorimeter, and a dynamic mechanical analyzer. A favorable comparison of the acquired properties with those reported in the literature was observed. The Carreau model, which corresponds to non-Newtonian flow, was employed, and the parameters in the Carreau viscosity equation were determined as functions of temperature. Utilizing the thermal data associated with the wax patterns and the simulation outcomes, the interfacial heat transfer coefficients between the wax and the die were ascertained, yielding a value of 275–475 W/m2K. A strong correlation was observed between the experimental and simulated filling percentages of the fluidity probe across a wide range of injection temperatures and pressures. The analysis of the simulated temperature, fraction solid, viscosity, and shear rate in the wax pattern revealed that viscosity is a crucial factor influencing the wax fluidity. It was demonstrated that waxes with an initial high viscosity exhibit a low shear rate, which subsequently increases the viscosity, thereby hindering the wax flow. [ABSTRACT FROM AUTHOR]

The increasing demand for high-performance materials has led to the development of natural fiber composites as an alternative to synthetic fiber composites. However, the low thermal conductivity of natural fibers limits their use in advanced applications. In this study, we have developed polyaniline-coated natural fiber composites to enhance their thermal properties. The methodology of this study involves the preparation of natural fiber composites using polyaniline-coated natural fibers as a reinforcement and a bio-based resin as a matrix. The composites were then coated with polyaniline, which was synthesized through chemical oxidation of aniline monomer. The coated composites were characterized using various analytical techniques such as Fourier-transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis to evaluate their structural, morphological, and thermal properties. The materials used in this study were natural fibers, bio-based resin, aniline monomer, ammonium persulfate, and hydrochloric acid. The gap identification of this study is the low thermal conductivity of natural fiber composites, which limits their application in advanced fields such as aerospace, automotive, and electronics. The problem identification is the lack of a cost-effective and eco-friendly method to enhance the thermal properties of natural fiber composites. The results of this study showed that the polyaniline-coated natural fiber composites exhibited enhanced thermal conductivity compared to the uncoated composites. The improvement in the properties of the composites was attributed to the high conductivity of polyaniline and its ability to form a continuous conductive network throughout the composite matrix. The development of polyaniline-coated natural fiber composites provides a cost-effective and eco-friendly approach to enhance the thermal properties of natural fiber composites. This approach has the potential to expand the use of natural fiber composites in advanced applications, leading to a sustainable and greener future. [ABSTRACT FROM AUTHOR]

Highlights The impact of carbon fiber (CF) composites sizing with graphene oxide (GO) to form brick‐and‐mortar structures on their mechanical properties and thermal conductivity has not been closely examined. This study systematically investigates the effect of GO sheet size on the interfacial properties and thermal conductivity of CF composites. Three sizes of GO—small (0.11 μm), medium (0.33 μm), and large (0.97 μm)—were used to modify CF surfaces via layer‐by‐layer self‐assembly, forming the brick‐and‐mortar structures. The mechanical properties were assessed through flexural tests, interlaminar shear strength (ILSS) tests and tensile tests, while thermal conductivity was measured using a thermal constant analyzer. The results revealed that medium‐sized GO (GO‐M) significantly enhanced the interfacial strength and toughness of the composites. This improvement is attributed to the orderly arrangement of GO‐M on the CF surface, which enhances stress transfer between the fiber and the matrix. In contrast, small‐sized GO (GO‐S) tended to scatter, resulting in less effective reinforcement, while large‐sized GO (GO‐L) exhibited stacking and agglomeration, limiting its reinforcement effectiveness. However, GO‐L provided the highest thermal conductivity due to the formation of continuous heat conduction pathways. These findings suggest that GO‐M offers a balanced improvement in mechanical properties, whereas GO‐L is more suitable for applications requiring high thermal conductivity. This work underscores the importance of selecting the appropriate GO sheet size to optimize the interfacial properties and thermal conductivity of CF composites, which is crucial for enhancing their performance in high‐end engineering applications, such as aerospace, automotive, and marine industries. Modification of CF composites by GO‐M sheets significantly improved toughness and strength. GO‐L sheets formed an effective heat transfer channel with the highest thermal conductivity. The study emphasized the critical role of selecting the appropriate GO sheet size to optimize the mechanical and thermal properties of CF composites. [ABSTRACT FROM AUTHOR]

Diurnal and seasonal variations in soil and surface temperature measured with the HP3 ${\mathrm{H}\mathrm{P}}^{3}$ thermal probe and radiometer of NASA's InSight Mars mission are reported. At a representative depth of 10–20 cm, an average temperature of 217.5 K was found, varying by 5.3–6.7 K during a sol and by 13.3 K during the seasons. From the damping of the temperature variation with depth and the phase shift, a thermal diffusivity of (3.93 ± $\pm $ 0.39) × 10−8 ${10}^{-8}$m2 ${\mathrm{m}}^{2}$/s was derived for the upper ∼ ${\sim} $10 cm from the diurnal temperature variation and of (3.63 ± $\pm $ 0.53) × 10−8 ${10}^{-8}$m2 ${\mathrm{m}}^{2}$/s for the ∼ ${\sim} $40 cm depth range of the mole from the annual temperature variation. Using published thermal conductivity and inertia values together with the diffusivities, soil densities of 1,470 and 1,730 kg/m3 ${m}^{3}$ were derived for these depths. The temperatures allow the deliquescence of thin films of brine, the efflorescence of which may explain the cemented duricrust observed. Plain Language Summary: Temperature is an important factor in understanding the physical properties of Martian soil. It determines how quickly physical processes and chemical reactions occur, including the transport of heat and materials. Temperature is crucial to astrobiology because it affects the habitability of the soil and the potential for water or brine to support microbial life. We measured the temperature in the soil during several Martian days and over a Martian year using the NASA InSight Mars mission's Heat Flow and Physical Properties Package. The average temperature was −56°C (217.5 K) over the depth extent of the thermal probe, which was about 40 cm. The temperature varied by 5–7° during the day, which is only a tenth of the daily surface temperature variation. It varied by 13° during the seasons. The temperature is subfreezing for water, but it allows the formation of thin films of salty brine for 10 hr or more during a Martian day. The solidification of the brine is a likely explanation for the observed few tens of centimeters thick duricrust, a layer of consolidated, cohesive sand, which is thought to have hampered the penetration to greater depth of the mission's thermal probe. Key Points: We measured the temperature and its diurnal and annual variations in the top 40 cm of the Martian soil at the InSight landing siteThe soil thermal diffusivity was calculated from the diurnal and seasonal surface and soil temperature variationsThe soil temperature allows the formation of thin films of brine; their efflorescence may explain the formation of the observed duricrust [ABSTRACT FROM AUTHOR]