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Measuring the thermal properties of anisotropic films of hybrid materials poses a challenge to existing metrology techniques. We have developed a new approach for measuring the volumetric heat capacity and anisotropic thermal conductivity of these systems using the 3ω method. While there exist many avenues for measuring the thermal properties of thin films, most carry with them difficult requirements such as smooth surfaces or advanced lithography. Here, we present measurements of a film's in-plane and cross-plane conductance and its volumetric heat capacity using relatively simple sample configurations, each requiring a single heater. For the measurement of volumetric heat capacity, we present a new model fitting method, relying on a standard film-on-substrate configuration. For the measurement of in-plane thermal conductance by 3ω, we have developed the use of an embedded micro-wire heater in suspended drop cast films, allowing for a 12 μm wide heater without the need for advanced lithography. We also expose the surprisingly significant effect of thermal radiation in the suspended film measurement and its associated error. Our measurements reveal a large anisotropy in the thermal conductivity of our test material, Te-PEDOT:PSS, of kin-plane/kcross-plane = 19, consistent with the nanoscale morphology of the material. [ABSTRACT FROM AUTHOR]

Thermal transport through various nanowires has attracted extensive attention in the past two decades. Nanowires provide an excellent platform to dissect phonon transport physics because one can change the wire size to impose systematically varying boundary conditions that can help to distinguish the contributions of various scattering mechanisms. Moreover, novel confinement phenomena beyond the classical size effect promise opportunities to achieve highly desirable properties. Based on a summary of research progresses in nanowire thermal properties, we discuss more intriguing observations due to the classical size effect, coupling between mechanical and thermal properties, and divergent thermal conductivity as a result of conversion from three-dimensional to one-dimensional phonon transport, showcasing the superdiffusive thermal transport phenomenon. We hope that these discussions could provide a new perspective on further exploring thermal transport in nanowires, which may eventually lead to breakthroughs such as achieving thermal conductivity values higher than that of any known materials. [ABSTRACT FROM AUTHOR]

Localization is a well-known wave phenomenon that significantly impedes transport, as uncovered by a pioneering work of Anderson. The localization of thermal phonons based on the phonon wave nature is widely represented in disordered atomic systems. Compared with electron and photon localization, the observations of phonon localization are much rarer, owning to the broadband nature of phonon thermal transport. In this Perspective, we summarize the experimental and theoretical evidences of phonon Anderson localization in disordered atomic systems from the aspects of vibrational spectroscopy, thermal conductivity measurement, phonon transmission, phonon wave packet, phonon participation ratio, and energy distribution. [ABSTRACT FROM AUTHOR]

Driven by the prospective application of thermoelectric (TE) materials, massive efforts have been devoted to improving its performance. However, strong-coupled thermal and electrical transport is still the largest block for the promotion of TE techniques. Here, we report a peak ZT over 1.2 at 400 K in an n-type Bi2Te2.7Se0.3 sample doped by 5 wt. % Sb under the spark plasma sintering method. This high performance is attributed to the synergistically optimized thermal and electrical transport properties. Sb nano-precipitates, which have been observed directly by spherical aberration-corrected transmission electron microscopy, substantially decrease the lattice thermal conductivity of the sample, leading to a low value of 0.35 W m−1 K−1. Meanwhile, band bending caused by the nano-precipitates significantly enhances the Seebeck coefficient, resulting in a high PF of 35 μW cm−1 K−2. The study about optimizing electrical and thermal properties simultaneously opens the door to the high performance of Bi2Te3-based materials. [ABSTRACT FROM AUTHOR]

High-performance thermoelectric (TE) properties of pristine Sn-based colusites are investigated theoretically. A recent experimental article [Bourgès et al., J. Am. Chem. Soc. 140, 2186 (2018)] showed how structural disordering reduced the lattice thermal conductivity in Cu 26 V 2 Sn 6 S 32 and improved the TE figure of merit (ZT). In this article, it is observed that low energy soft optical phonons and the vacancy defect play a crucial role in reducing thermal conductivity. An ultra-low lattice thermal conductivity 0.35 Wm − 1 K − 1 is observed in Cu 26 V 2 Sn 6 Se 32. It is seen that mass variance perturbation and number of vacancies are important to tune the thermal and electrical properties. Though the electrical conductivity decreases with the number of vacant sites, the Seebeck coefficient enhances due to the reduction in carrier concentration. The detailed study of thermoelectric properties of Cu 26 V 2 Sn 6 Se 32 with Se vacancies points to enhanced ZT values of 0.34 at 300 K, which is ∼ 15 times greater than ZT of Cu 26 V 2 Sn 6 S 32. A maximum ZT of 1.68 at 755 K is predicted for Cu 26 V 2 Sn 6 Se 32 with Se vacancies, which is the highest to date reported for Sn-based colusites. [ABSTRACT FROM AUTHOR]

Nanostructured semiconductors are promising candidates for thermoelectric materials owing to their superior thermal insulating properties over their bulk counterparts. In this study, a one-dimensional, crystalline nanostructure synthesized by sintering Si nanoparticles, called Nano Particle Chain (NPC) structures, is proposed. The structure is systematically analyzed for its thermal transport properties and compared with the nanowire counterparts. Both classical molecular dynamics and lattice dynamics tools were employed to evaluate lattice thermal conductivity (k) and to perform phonon mode level decomposition. A marked reduction in the phonon relaxation time of the NPC structure was observed indicating possible effects of phonon-boundary/constriction scatterings. This has resulted in a two-order reduction in k in NPC structures over bulk Si. Further, one order reduction of k of NPC structures was attained with respect to a nanowire of the same constriction size, indicating the effectiveness of the mismatch of particle and constriction diameters as an efficient thermal suppression mechanism. With the addition of a second material of different mass, the NPC structures can be further diversified to core/shell configurations. It was also identified that a non-monotonic variation of k exists, with a minimum in core/shell NPC structures. This effect is materialized by using a Ge-like fictitious material to coat the original Si nanoparticles, owing to competing effects of two phonon suppression mechanisms. Moreover, these core/shell NPC structures are compared with previously reported diameter modulated core/shell nanowire structures [E. Blandre et al., Phys. Rev. B, 91, 115404 (2015)] to highlight their capability to enhance the thermoelectric performance over conventional one-dimensional nanostructure configurations. [ABSTRACT FROM AUTHOR]

Conventional techniques of measuring thermal transport properties may be unreliable or unwieldy when applied to nanostructures. However, a simple, all-electrical technique is available for all samples featuring high-aspect-ratio: the 3 ω method. Nonetheless, its usual formulation relies on simple analytical results which may break down in real experimental conditions. In this work we clarify these limits and quantify them via adimensional numbers and present a more accurate, numerical solution to the 3 ω problem based on the Finite Element Method (FEM). Finally, we present a comparison of the two methods on experimental datasets from InAsSb nanostructures with different thermal transport properties, to stress the crucial need of a FEM counterpart to 3 ω measurements in nanostructures with low thermal conductivity. [ABSTRACT FROM AUTHOR]

High‐performance polypropylene (PP) foam is a vital polymer product in industrial areas. However, the poor melt strength of ordinary PP homopolymer limits its foaming molding. In this work, high melt strength polypropylene (HMSPP) is prepared by using styrene (St) and tripropylene glycol diacrylate (TPGDA) as comonomers, and then PP foams are prepared by mold foaming method. The results show that adding St in the grafting process of TPGDA will obviously improve the melt strength of the PP matrix, and its melt strength (28 184 Pa.s) is 7.4 times higher than that of pure PP. HMSPP foam has more regular and uniform cells and higher cell density, which significantly improves the sound and thermal insulation properties of PP foam. Compared with pure PP foam, the average sound transmission loss (52.9 dB) of HMSPP foam with a low foaming ratio increased by 64%, and the thermal conductivity (0.0867 W mK−1) decreased by 46%. Therefore, the obtained HMSPP foam can be used in sound insulation or thermal insulation area. This work provides an available route for the high‐performance utilization of PP foam. [ABSTRACT FROM AUTHOR]

Thermal interface materials (TIMs) with good thermal conductivity are paramount in mitigating the heat concentration challenges encountered during the operation of highly integrated components in sophisticated electronic devices. To optimize the comprehensive performance of TIMs, a balance must be struck: minimizing the filler concentration to attenuate materials hardness while maximizing filler content to bolster the thermal conduction pathway. Drawing inspiration from the orientation of tree branches passing through steppingstones in river, a method was proposed in this study. This method exploits the shear effect of carbon fiber (CF), owing to viscosity variances during diameter extrusion, and the differential flow velocity between CF and alumina to induce a significant degree of orientation. Combined with subsequent flipping and bonding, a TIM with vertically oriented CF was prepared. The TIM was obtained with a mere 12.1 wt% CF incorporation, the composite exhibits a through-plane thermal conductivity of 21.29 W/(m·K), representing an enhancement of two orders of magnitude relative to pristine silicone rubber, while retaining its flexibility and deformability. The orientation degree and high efficiency orientation effect of CF have been characterized via scanning electron microscopy (SEM), thermal conductivity test and light-emitting diode (LED) temperature rise test. [ABSTRACT FROM AUTHOR]

This study introduces transparent MgO ceramics produced via simply vacuum sintering at 1200–1500 °C by optimal incorporation of MgF 2 as a sintering additive. The effect of MgF 2 content and sintering temperature on the densification process, optical, and thermal properties of MgO ceramics is presented with emphasis on its function as a sintering aid and adverse effect of MgF 2 evaporation in the condition of high MgF 2 content or high sintering temperature. MgO ceramic with 1.0 mol% MgF 2 sintered at 1300 °C exhibits the highest relative density of 99.95% with average grain size of 17.46 μm. The in-line transmittance attains 60% at 1000 nm and >80% in the infrared range (3.8–6.8 μm), without absorption bands originated from the carbon contamination. The corresponding room-temperature thermal conductivity reaches 47.25 W/(m∙K). These results demonstrate that MgF 2 is an outstanding sintering additive for the preparation transparent MgO ceramics. [ABSTRACT FROM AUTHOR]

In Part 1 of this study, we investigated the macrokinetic parameters and phase formation mechanism in the combustion front of Zr–Nb–B mixtures. In the second part, we produced consolidated samples of solid solutions NbB 2 -(0.100%)ZrB 2 by hot pressing the combustion-derived powders at 1900 °C. By measuring the crystallographic parameters, mechanical and thermophysical properties of the produced bulk samples, we obtained valuable insights into the behavior of the solid solutions. Our results pave the way for the application-specific fine-tuning of the mechanical properties and thermal conductivity of diboride solid solutions in the Zr–Nb–B system for ultra-high temperature applications. Our findings have significant implications for the development of advanced materials with outstanding performance in extreme environments. [ABSTRACT FROM AUTHOR]

Improved mechanical and thermal properties are important characteristics for enhancing the performance of cast iron components that operate at elevated temperatures. Thermal conductivity defines the temperature distribution within the casting and influences the magnitude of the thermally induced tensile stresses. The microstructural features that increase the thermal conductivity have a negative impact on tensile strength. The results reported in this work show that there is a unique inverse relationship between thermal conductivity and tensile strength, valid for the whole range of cast iron alloys regardless of graphite form, solidification rates, carbon content and matrix constituents. The finding indicates the challenges for the simultaneous improvement of these properties, and it can be utilized as a guideline during the design of cast iron components for high temperature applications. [ABSTRACT FROM AUTHOR]

Hypereutectic Al-x(1.75Fe-1.25Ni) (x=1,2,4,6) alloys were designed and prepared by gravity casting in the present study. Both the microstructure and the thermophysical properties were investigated. The microstructure was significantly transformed from the eutectic phases to the coarse primary phases with the increase in alloying elements. The result of thermal analysis indicated that the solidification behaviors were modified by the increase in alloying elements, which was ascribed to the generation of different phases. The thermal conductivity and thermal expansion properties were also related to the alloy composition. From the variation in the ratio of thermal conductivity/electrical conductivity, it could be inferred the effective medium of heat conduction was changing, which decreased thermal conductivity due to the introduced defects that hindered the transport of electrons and low efficiency heat conducting medium of intermetallic. Meantime, the formation of bulk intermetallic with low thermal expansion coefficient and large volume fractions reduced effectively the thermal expansion of the alloy. The mathematical model was presented to quantify the influence of alloy content on thermophysical properties. [ABSTRACT FROM AUTHOR]

Non-edible oils hold great potential as a viable feedstock for bio-lubricant production. Among these oils, castor oil stands out due to its unique hydroxyl group structure. Castor oil finds applications in various fields such as lubrication, dielectrics, and heat transfer. This study focused on investigating the dynamic viscosity and thermal conductivity of castor oil and graphene nanoplatelets/castor oil nanofluids. The nanofluids were synthesized through a two-step process involving the combination of graphene nanoplatelets crystal powder with pure castor oil. Morphological and crystallographic analyses revealed platelet-shaped graphene nanoplatelets with a prominent (002) reflection. Dynamic viscosity measurements were performed using a rheometer at temperatures ranging from 40 °C to 100 °C, and thermal conductivity assessments were conducted using the Modified Transient Plane Source technique from 30 °C to 70 °C. Investigation revealed that as temperature increased, the nanofluids exhibited a significant decrease in dynamic viscosity. Conversely, the dynamic viscosity increased moderately with higher concentrations of graphene nanoplatelets. Importantly, the addition of graphene nanoplatelets did not disrupt the Newtonian flow behavior of castor oil. Furthermore, the study demonstrated a remarkable enhancement in thermal conductivity with increasing concentrations of graphene nanoplatelets. This enhancement can be attributed to the high conductivity of graphene nanoplatelets. Overall, biodegradable graphene nanoplatelets/castor oil nanofluid present promising prospects as an advanced lubricating oil with superior heat transfer properties. This research contributes to the understanding and utilization of nanofluids for effective thermal management applications. [ABSTRACT FROM AUTHOR]

Erythritol (ET) is a promising medium–low temperature organic phase change material. To solve the problems of supercooling, leakage, and low thermal conductivity, expanded graphite (EG) with four different particle sizes of 32 mesh, 50 mesh, 80 mesh, and 100 mesh was used as supporting material. A shape-stabilized composite phase change material (CPCM) with a mass ratio of EG to ET of 9:1 was prepared by the ultrasonic impregnation method. The properties were tested and analyzed by DSC, SEM, FTIR, XRD, and TGA. The experimental results showed that 50 mesh EG was more suitable as an adsorption carrier for erythritol among the four different particle sizes of EG. Compared with pure erythritol, the supercooling degree of 50 mesh EG/ET composite decreased by 35.2 %, the latent heat of solidification increased by 8 %, and the thermal conductivity increased by 250.8 %, which increased the heat storage and release capacity of the material by 19.2 %, and the 50 mesh EG/ET composite phase change material had good thermal stability. In this study, the relationship between the supercooling degree of EG/ET and EG particle size was analyzed, and EG/ET thermal storage materials with high thermal storage density and exothermic density were prepared. It helps to promote the application of EG-based composite thermal storage materials and the development of thermal storage technology. [ABSTRACT FROM AUTHOR]

Accurate temperature rise prediction of the gas‐insulated transmission lines (GIL) can help to lower the cost of equipment through optimization design. To investigate the temperature rise of GIL and the heat transfer efficiency of new eco‐friendly insulating gas, the electromagnetic‐thermal‐fluid field coupling method that considers the thermal properties of solid and gaseous media is proposed. The finite element method is applied to solve the eddy‐current field and obtain the Joule loss of the conductive rod and the enclosure accurately. The GIL temperature distribution of different insulating gases is computed based on their thermophysical parameters. The heat transfer efficiency is found to be positively correlated with gas density, constant pressure heat capacity and thermal conductivity. A parameter that characterizes the heat transfer efficiency of the insulating gas is defined, such that a larger value indicates a higher heat transfer efficiency. This parameter helps to quickly determine the heat transfer capacity of new eco‐friendly insulating gas, and facilitate the optimal design of GIL equipment. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In this study, we synthesize a porous silica nanoparticles (SiO 2) derived from recycled semi-conducting silica sludge via a conventional hydrothermal and microwave-assisted hydrothermal methods for flame-resistant applications. The corresponding thermal properties of as-synthesized SiO 2 nanoparticles are investigated. The effects of reaction temperature and urea concentration are investigated in terms of surface morphology and thermal conductivity. The results of thermal conductivity tests indicate that 180 °C reaction temperature for both conventional hydrothermal reaction and microwave-assisted hydrothermal reaction demonstrated the best thermal insulator performance. The thermal conductivities are determined to be 0.0193 W/m·K and 0.0192 W/m·K, respectively. For flame penetration and combustion tests, microwave-assisted one exhibits much better performance, maintaining a temperature of 34 °C after 600 s of combustion under a butane torch at nearly 800 °C. Furthermore, there is no deformation occurred when direct contact with the flame at a high temperature, proving that microwave-assisted hydrothermal reaction-synthesized silica is a potential candidate for thermal barrier applications. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, (20- x)MgO–20Al 2 O 3 –56SiO 2 –4B 2 O 3 - x CuO (x = 0, 0.25, 0.5, 0.75, 1, 1.25 mol%) glass-ceramics were synthesized by solid-state reaction method. The crystallization, microstructure, thermal and dielectric properties of (20- x)MgO–20Al 2 O 3 –56SiO 2 –4B 2 O 3 - x CuO glass-ceramics was discussed in detail. It was demonstrated that the CuO lowers the crystallization temperature of α-cordierite and promotes the crystallization process of MgO–Al 2 O 3 –SiO–B 2 O 3 glass-ceramics. Thus, the crystallization showed a substantial influence on the dielectric properties, as evidenced by an elevation in dielectric constant and a decrease in dielectric loss. Specifically, with the addition of 0.5 mol% CuO, the MgO–Al 2 O 3 –SiO–B 2 O 3 glass-ceramics sintered at 1050 °C shows excellent properties of: ε r = 5.04, tan δ = 2.2 × 10-4, κ = 3.4 W/mK and α = 1.75 × 10-6/°C. These works provide valuable insights into the design and development of (20- x)MgO–20Al 2 O 3 –56SiO 2 –4B 2 O 3 - x CuO glass-ceramics with tailored properties for structure/function integration in the electronics industry. [ABSTRACT FROM AUTHOR]

Layered materials exhibit competitively low thermal conductivity along the out-of-plane direction. The solution process is a promising method for preparing stacked structures. However, the thermal stability of the layered materials is poor after processing in solution, thus hindering their applications at high temperatures. One of the solutions to improve the thermal stability of layered structures is to expand the interlayer distance by inserting large-size metal ions. In this work, we studied the thermal properties of Cs+ intercalated layered niobate obtained by the ion-exchanged process. The layered structure of the Cs+ intercalated layered niobate survives after thermal treatment even at 1200 °C. The room temperature thermal conductivity of as prepared stacked Cs–HCa 2 Nb 3 O 10 is as low as 0.11 W m−1 k−1. Upon thermal annealing, the thermal conductivity increases. After annealing at 1200 °C, the value is 0.90 W m−1 k−1. The finding suggests Cs+ intercalated layered niobate is a promising material for high-temperature insulation applications. [ABSTRACT FROM AUTHOR]

Gas turbines efficiency growth is primarily associated with an increase in the operating temperature of the combustion chamber, which places new stringent requirements on the materials of thermal barrier coatings. Strontium cerate doped with tin SrCe 1- x Sn x O 3 where x = 0.1 ... 0.5, was proposed as a promising material. The research has shown that the lightly doped solid solution SrCe 1-x Sn x O 3 has an orthorhombic Pnma structure at x < 0.3, whereas at a high content of Sn4+ the monoclinic structure P2 1 /m becomes more favorable. Thermogravimetric analysis (TGA) in reducing atmosphere (5%H 2 in Ar) shows no mass lost as a result of unchangeable charge of Ce4+ and Sn4+. An increase in the distortion of the crystal lattice, due to the large difference in the ionic radii of Ce4+ and Sn4+, leads to a deterioration in the symmetry of the crystal lattice, a reduction of thermal conductivity (from 1.9 to 1.4 W m−1 K−1 at 1000 °C) and at the same time, growth of hardness and porosity. The increase in porosity, along with an increase in the required temperature of solid-state synthesis, indicates an enhancement in the melting point of the obtained materials. For the compounds with an orthorhombic structure, the thermal expansion coefficient increases with a growth in the Sn content, achieving a highest point 12.47·10−6 K−1 at 1100 °C for x = 0.3. The combination of the revealed properties and their comparison with advanced refractories makes the solid solution, primarily SrCe 0.5 Sn 0.5 O 3 , a promising material for application as thermal barrier coatings. [ABSTRACT FROM AUTHOR]

α‐SiAlON is well known for its excellent mechanical properties, but its thermal properties are less investigated. In this work, we investigate the thermal conductivity of Ca α‐SiAlON ceramics with varying m and n values and prepared samples by spark plasma sintering (SPS) at 1600°C or gas pressure sintering (GPS) at 1800°C and 1900°C. The prepared Ca α‐SiAlON ceramics showed thermal conductivities ranging from 4.6 to 10.7 W/(mK) at 25°C. It was found that the thermal conductivity of the α‐SiAlON samples could be reduced by increasing either m or n or both. Besides, the samples prepared by SPS had lower thermal conductivity compared with those by GPS due to their smaller grain size, and the effect of m and n would be minor after m reached 2. These results provide basic knowledge for tuning α‐SiAlON's thermal conductivity for applications concerning thermal management. [ABSTRACT FROM AUTHOR]

Currently, Faraday isolators and rotators for high‐power lasers are popular research topics; therefore, finding magneto‐optical materials with excellent Verdet constants and thermal properties is crucial. In this study, novel holmium scandium aluminum garnet (HoSAG) magneto‐optical ceramics were fabricated using vacuum sintering. This study improved the traditional ball milling method and pre‐synthesized powders with great sinterability after secondary ball milling and sieving. Different pre‐synthesis temperatures were found to have significant effects on the particle size and micromorphology of the synthesized powders. HoSAG ceramics with 0.05 wt% MgO sintering aid and held at 1700°C for 30 h reached a transmittance of 76.7% at 1550 nm. Meanwhile, HoSAG transparent ceramics maintain higher transmittance in the infrared region (>1500 nm) than terbium gallium garnet (TGG) crystals, indicating better application prospects. The Verdet constants of HoSAG magneto‐optical ceramics at 405, 532, 808, and 1064 nm were −421.5, −181.2, −65, and −32.3 rad T−1 m−1, respectively, which are slightly less than those of TGG magneto‐optical ceramics. Moreover, the thermal conductivity of HoSAG ceramics at 300.00 K was 4.89 W m−1 K−1, which is comparable to that of the TGG ceramics. [ABSTRACT FROM AUTHOR]

High‐entropy single‐phase rare earth titanates (RE0.2Gd0.2Ho0.2Er0.2Yb0.2)2Ti2O7 (RE = Sm, Y, Lu) were designed and synthesized successfully, in which their lattice distortion was quantitatively described by mass disorder and size disorder. It is worth mentioning that (Y0.2Gd0.2Ho0.2Er0.2Yb0.2)2Ti2O7 could obtain the low thermal conductivity (1.51 W·m−1·K−1, 1500°C), high thermal expansion coefficient (average, 11.69×10−6 K−1, RT ∼1500°C) and excellent high‐temperature stability. In addition, the relationship between the microstructure and thermal transport behaviors has been studied at the atomic scale. Due to the disorder of A‐site ions, severe lattice distortion occurred in specific crystal planes, and the large mass difference between Y3+ and other RE3+ further causes mass fluctuation and results in lower thermal conductivity. Compared with YSZ, the high‐entropy rare earth titanate (Y0.2Gd0.2Ho0.2Er0.2Yb0.2)2Ti2O7 has lower thermal conductivity, higher thermal expansion coefficient, and excellent high‐temperature stability, which has great potential for application in the thermal protection field. [ABSTRACT FROM AUTHOR]

The thermal properties of soils can be influenced by additives of different origins (non-organic, organic and mineral) and roles in soil quality. This study aims to evaluate the effects of microplastics, vermicompost, and zeolite on the thermal properties of two soil types using a combination of experimental data and modeling approaches. Laboratory experiments were conducted using surface layer samples of a clay soil (Vertic Phaeozem) and a loam soil (Haplic Cambisol). Each additive was applied at a mass ratio of 10% to the soil samples. The thermal conductivity (λ), thermal diffusivity (D) and volumetric heat capacity (Cv) were measured with the SH1 sensor of a KD2Pro device during the drainage process of the soil samples at different matric potentials. The relationships between λ, Cv, D, gravimetric water content, and matric suction (h) were analyzed using linear and polynomial regression models (for Cv and D) and a closed-form equation (for λ). The fitted models exhibited small errors, such as a root mean square error (RMSE) of 0.03-0.06 W m-1 K-1, and high coefficient of determination R2>0.9. The effects of the different additives on water retention, λ, Cv and D were found to be specific to each soil type and depended on the properties of both the soil and the additives. These findings highlight the significance of additives in modifying soil thermal properties and emphasize the importance of considering the interactions between soil characteristics and additive properties. The combination of experimental data and modeling approaches provides valuable insights into understanding the complex dynamics of soil thermal properties and the potential impacts of additives on soil functionality and quality. [ABSTRACT FROM AUTHOR]

Inorganic aerogels have exhibited many superior characteristics with extensive applications, but are still plagued by a nearly century-old tradeoff between their mechanical and thermal properties. When reducing thermal conductivity by ultralow density, inorganic aerogels generally suffer from large fragility due to their brittle nature or weak joint crosslinking, while enhancing the mechanical robustness by material design and structural engineering, they easily sacrifice thermal insulation and stability. Here, we report a chemically bonded multi-nanolayer design and synthesis of a graphene/amorphous boron nitride aerogel to address this typical tradeoff to further enhance mechanical and thermal properties. Attributed to the chemically bonded interface and coupled toughening effect, our aerogels display a low density of 0.8 mg cm−3 with ultrahigh flexibility (elastic compressive strain up to 99% and bending strain up to 90%), and exceptional thermostability (strength degradation <3% after sharp thermal shocks), as well as the lowest thermal conductivities in a vacuum (only 1.57 mW m−1 K−1 at room temperature and 10.39 mW m−1 K−1 at 500°C) among solid materials to date. This unique combination of mechanical and thermal properties offers an attractive material system for thermal superinsulation at extreme conditions. [ABSTRACT FROM AUTHOR]

Anisotropic layered porous ceramics are crucial to satisfy the demand for devices with directional functions. However, challenges, such as complicated preparation processes and difficulties in regulating the oriented structure, severely limit their application. Here, multilayered mullite ceramics (MLMCs) with specific porosities and strongly anisotropy properties, were prepared by designing porous thin-layered units and an interlayer layout, in combination with a simple gel-casting. Benefiting from the suitable slurry properties, the samples did not show obvious defects, and a perfect bonding was observed between the layers. The optimized MLMCs exhibited a porosity of 65.12%, the differences in compressive and flexural strengths of 14 (± 0.7) and 5 (± 0.2) MPa in different pressure directions respectively, and the anisotropy factor of thermal conductivity up to 0.98, as well as exhibited good high temperature thermal insulation properties. Ultimately, the MLMCs formed transverse heat conductor and longitudinal heat insulation heat-transfer patterns, with promising applications in thermal insulation. [ABSTRACT FROM AUTHOR]

The roasting process of Gari (Gelatinized cassava mash), a shelf-stable cassava product, is energy-intensive. Due to a lack of information on thermal characteristics and scarcity/rising energy costs, heat and mass transfer calculations are essential to optimizing the traditional gari procedure. The objective of this study was to determine the proximate, density, and thermal properties of traditionally processed de-watered cassava mash and gari at initial and final processing temperatures and moisture contents (MCwb). The density and thermal properties were determined using proximate composition-based predictive empirical models. The cassava mash had thermal conductivity, density, specific heat capacity, and diffusivity of 0.34 to 0.35 W m−1 °C−1, 1207.72 to 1223.09 kg m−3, 2849.95 to 2883.17 J kg−1 °C, and 9.62 × 10−8 to 9.76 × 10−8 m2 s−1, respectively, at fermentation temperatures and MCwb of 34.82 to 35.89 °C and 47.81 to 49%, respectively. The thermal conductivity, density, specific heat capacity and diffusivity of gari, ranged from 0.27 to 0.31 W m−1 °C−1, 1490.07 to 1511.11 kg m−3, 1827.71 to 1882.61 J kg−1 °C and 9.64 × 10−8 to 1.15 × 10−8 m2 s−1, respectively. Correlation of all the parameters was achieved, and the regression models developed showed good correlation to the published models developed based on measuring techniques. [ABSTRACT FROM AUTHOR]

The lattice thermal conductivity of graphene is evaluated using a microscopic model that takes into account the lattice's discrete nature and the phonon dispersion relation within the Brillouin zone. The Boltzmann transport equation is solved iteratively within the framework of three-phonon interactions without taking into account the four-phonon scattering process. The Umklapp and normal collisions are treated rigorously, thereby avoiding relaxation-time and long-wavelength approximations. The mechanisms of the failures of these approximations in predicting the thermal transport properties are discussed. Evaluation of the thermal conductivity is performed at different temperatures and frequencies and in different crystallite sizes. Reasonably good agreement with the experimental data is obtained. The calculation reveals a critical role of out-of-plane acoustic phonons in determining the thermal conductivity. The out-of-plane acoustic phonons contribute greatly and the longitudinal and transverse acoustic phonons make small contributions over a wide range of temperatures and frequencies. The out-of-plane acoustic phonons dominate the thermal conductivity due to their high density of states and restrictions governing the anharmonic phonon scattering. The selection rule severely restricts the phase space for out-of-plane phonon scattering due to reflection symmetry. The optical phonon contribution cannot be neglected at higher temperatures. Both Umklapp and normal processes must be taken into account in order to predict the phonon transport properties accurately. [ABSTRACT FROM AUTHOR]

The use of polylactic acid‐based composites as self‐fixing materials is a promising technology for various applications due to the shape memory effect of polylactide. In this study, hexagonal boron nitride (h‐BN) was mixed with polylactic acid (PLA) with concentrations of 0, 0.5, 1, 2, 5, and 10 wt% for subsequent film casting. The morphology, mechanical and thermal characteristics of the composite were investigated. With a high percentage of filler content, a decrease in thermal conductivity was observed. The recovery strain decreased with increasing the filler content. The amount of h‐BN had a mixed effect on the recovery stress of the composite. Thus, PLA/h‐BN composites represent a new research idea to study the influence of a heat‐conducting filler on a shape memory effect in polylactic acid. Highlights: Correlation between crystallinity, thermal and shape memory properties was describedDecrease in thermal conductivity was observed with the large percentage of fillingThe composite with 2 wt% of h‐BN exhibits optimal characteristics of SMERecovery strain decreased with the rise of filler contentAmount of h‐BN had a non‐trivial effect on the recovery stress of composite [ABSTRACT FROM AUTHOR]

Measurement of thermal properties of thin films is challenging. In particular, thermal characterization is very difficult in semi-transparent samples. Here, we use two photothermal methods to obtain information about the thermal diffusivity as well as thermal conductivity of azoheteroarene functionalized polymer thin layers. The photothermal beam deflection (PBD) method is employed to gather data directly on thermal conductivity and thermal diffusivity, while the thermal lens (TL) method is employed to measure the effective thermal diffusivity. Consequently, the thermal diffusivity of the layers is indirectly estimated from the effective thermal diffusivity using a well-established theoretical relationship. Despite the utilization of distinct methods, our study reveals a remarkable consistency in the highly accurate results obtained from both approaches. This remarkable agreement reaffirms the reliability and mutual compatibility of the employed methods, highlighting their shared ability to provide accurate and congruent outcomes. [ABSTRACT FROM AUTHOR]

At ultra-high temperatures, resilient, durable, stable material choices are limited. While Carbon/Carbon (C/C) composites (carbon fibers and carbon matrix phases) are currently the materials of choice, zirconium carbide (ZrC) provides an option in hypersonic environments and specifically in wing leading edge (WLE) applications. ZrC also offers an ultra-high melting point (3825 K), robust mechanical properties, better thermal conductivity, and potentially better chemical stability and oxidation resistance than C/C composites. In this review, we discuss the mechanisms behind ZrC mechanical, thermal, and chemical properties and evaluate: (a) mechanical properties: flexure strength, fracture toughness, and elastic modulus; (b) thermal properties: coefficient of thermal expansion (CTE), thermal conductivity, and melting temperature; (c) chemical properties: thermodynamic stability and reaction kinetics of oxidation. For WLE applications, ZrC physical properties require further improvements. We note that materials or processing solutions to increase its relative density through sintering aids can have deleterious effects on oxidation resistance. Therefore, improvements of key ZrC properties for WLE applications must not compromise other functional properties. We suggest that C/C-ZrC composites offer an engineering solution to reduce density (weight) for aerospace applications, improve fracture toughness and the mechanical response, while addressing chemical stability and stoichiometric concerns. Recommendations for future work are also given. [ABSTRACT FROM AUTHOR]

Complex thermoelectric materials composed of multiple phases with order/disorder mixing feature have drawn intense attention due to their high performance. However, some physical mechanisms relevant to thermoelectric properties including the relationship between carrier mobility and disorder extent in these materials are still elusive. Here, a phase‐dependent mobility edge in (Cu2Sn1‐yS3)0.85(CuGaS2)0.15 solid solutions is demonstrated. By control over the mobility edge in these solid solutions by increasing the ratio of tetragonal phase with less disorder, a weakened localization of electronic states and promoted carrier mobility are realized. Combined with reduced lattice thermal conductivity, a record high zT value of 1.22 is attained at 823 K for (Cu2Sn0.92S3)0.85(CuGaS2)0.15 with the lowered mobility edge. The findings shed light on a new route to tuning the electrical and thermal transport properties for complex thermoelectric materials with multiple phases. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents may develop a pivotal role in future technologies considering sustainability and safety as pivotal aspects for chemistry developments. The possible application of these fluids for heat transfer operations is of great relevance for which the knowledge of thermal properties such as thermal conductivity is required as well as inferring structure–property relationships which allow reverse design of the fluids according to the technological requirements. Considering the technological relevance of this property, the available literature on the thermal conductivity for deep eutectic solvents is critically discussed showing strengths and weaknesses. The analysis of the state-of-the-art shows the future needs in this research field considering the application of these solvents for thermal-related technologies. The review indicates the scarcity of reliable experimental data and the need of predictive methods, which could be used for process design and solvent screening purposes. Likewise, considering the relevance of developing predictive methods for in silico design of these fluids according to industrial needs, the available predictive theoretical approaches are analysed showing their reliability as well as future needs. Finally, considering the need of developing suitable and reliable structure–property relationship, the molecular level basis of thermal conductivity in deep eutectic solvents is discussed, showing the role of hydrogen bonding and the effects rising from the involved hydrogen bond donors and acceptors as well as the eutectic compositions. This work reports the first literature review and analysis on thermal conductivity for deep eutectic solvents considering an experimental and theoretical approach as well as providing support for the molecular basis of this technologically relevant property, thus contributing to the development of environmentally friendly materials for thermal-related technologies. [ABSTRACT FROM AUTHOR]

Thermal properties such as thermal conductivity, heat capacity, and thermal diffusivity and physical properties such as calorific value, density, and kinematic viscosity of liquid fuels play a significant role in the combustion process. These properties vary with the chemical structures and the fatty acid profiles of biodiesels. Making correlations for various properties with respect to fatty acid profile helps to analyze the combustion process. Most of the reported works generated correlations using data taken from the literature, and the correlations based on the fatty acid profile for thermal properties of biodiesel are unavailable. As coconut oil, sunflower oil, and palm oil have entirely different fatty acid profiles, in this study, biodiesels produced from these three waste cooking oils and their three hybrids (each in a 1:1 ratio) were used for biodiesel production, followed by correlation formulation. Higher thermal conductivity (0.2211 W mK−1) and thermal diffusivity (0.2459 mm2 s−1) and lower heat capacity (0.8993 MJ m−3 K−1), density (862.8 kg m−3), kinematic viscosity (2.71 cSt), and calorific value (36.73 cSt) were observed for coconut-based biodiesels compared with other biodiesels. The addition of coconut content to hybrid biodiesel enhanced thermal conductivity and thermal diffusivity and reduced heat capacity, density, and kinematic viscosity. From the experimental data of thermal conductivity, heat capacity, thermal diffusivity, density, kinematic viscosity, and calorific value, empirical correlations were proposed with the fatty acid profile. Good agreement was obtained between experimental and calculated values. [ABSTRACT FROM AUTHOR]

In this work, we study thermoelectric properties of GeTei-based alloys, doped with bismuth, with partial substitution of lead for germanium: Ge0.86Pb0.1Bi0.04Te. The aim of the study is to explore the possibility of increasing the thermoelectric efficiency of a compound by combining optimal doping and isovalent substitution to improve the electronic properties with a simultaneous decrease of the lattice thermal conductivity. We studied alloy samples prepared in two different research laboratories using similar, but not completely identical procedures. It is shown that the electronic (thermoelectric power and electrical conductivity) properties of the samples of the two groups are in good agreement with each other. The properties of alloys depend on the thermal history of the samples due to the presence at temperatures of 600–800 K of a phase transition from a low-temperature rhombohedral to a high-temperature cubic structural modification and missibility gap in GeTe–PbTe quasibinary system below 870 K. The thermoelectric figure of merit of alloys reaches a maximum value of 1.5 at a temperature of about 750 K. [ABSTRACT FROM AUTHOR]

First‐principles calculations are employed to explore the elastic anisotropy and thermal properties of Mg–Ti–O compounds (MgTiO3, MgTi2O5, and Mg2TiO4). The structure parameters used in this work are in good agreement with other theoretical and experimental results. The mechanical stability and ductile nature are demonstrated. The elastic anisotropy is characterized by different anisotropy indexes, three‐dimensional (3D) surface constructions, and two‐dimensional (2D) projections of Young's modulus. Besides, the sound velocities, Debye temperature, and minimum thermal conductivity are also investigated from the elastic modulus. The obtained results can provide references for future experimental investigations and engineering applications of these Mg–Ti–O compounds. [ABSTRACT FROM AUTHOR]

Terbium aluminum garnet (Tb3Al5O12, TAG) ceramics have become a promising magneto‐optical material owing to the outstanding comprehensive performance, including the magneto‐optical, thermal, and mechanical properties. Fine‐grained TAG ceramics with high optical quality and mechanical properties have attracted much attention. In this study, TAG ceramics with fine grains and high optical quality are fabricated successfully by a two‐step sintering method from co‐precipitated nano‐powders. After pre‐sintered at 1525°C in vacuum and hot isostatic pressed at 1600°C, the in‐line transmittance of TAG ceramics reaches 81.8% at 1064 nm, and the average grain size is 7.1 μm. The Verdet constant of TAG ceramics is −179.6 ± 4.8 rad T−1 m−1 at 633 nm and −52.1 ± 1.9 rad T−1 m−1 at 1064 nm, higher than that of commercial Tb3Ga5O12 crystals. The thermal conductivity of TAG ceramics is determined from 25 to 450°C, and the result is 5.12 W m−1 K−1 at 25°C and 3.61 W m−1 K−1 at 450°C. A comparison of mechanical properties between large‐ and fine‐grained TAG ceramics fabricated under different conditions is conducted. The fine‐grained TAG ceramics possess a bending strength of 226.3 ± 16.4 MPa, which is 9.7% higher than that of the large‐grained ceramics. These results indicate that reducing the grain size on the premise of high optical quality helps improve the comprehensive performance of TAG ceramics. [ABSTRACT FROM AUTHOR]

Aerogels, due to their unique features like lightweight, ultra-low thermal conductivity, and design variations, have gotten a lot of interest in thermal insulation, photocatalysis, and protective areas. Besides their superior thermal properties, aerogel thermal insulation and photocatalyst materials also possess many inherent flaws, such as handling issues, high manufacturing costs, and low strength as well as toughness. The most persuasive and successful ways to improve photocatalytic and thermal insulating qualities while lowering costs are composition optimization and microstructure reconstruction. Their high surface area and porosity make them ideal for enhancing the efficiency and capacity of these devices. Research may lead to more efficient and longer-lasting energy storage solutions. This review describes the characteristics, microstructural reconstruction, design variation, and properties of all aerogel fabrication techniques and provides a comprehensive overview of scientific achievements linked to them. The effectiveness of raw material compositions, properties, and mechanical parameters are also discussed. The major goal of this review is to highlight the aerogel-based materials and design variations and to explore the most potential development trends for photocatalysis and thermal applications. The industrial as well as technical applications of silica aerogels are also highlighted. This review highlights futuristic applications of aerogel-based textile materials to alleviate the CO2 burden on our atmosphere, either by providing next-level thermal insulation or by employing them in CO2 mitigating technologies such as CO2 capture. [ABSTRACT FROM AUTHOR]

This research paper presents the results and analysis obtained via the evaluation of calcium nitrate as an effective stabilizer to alter the thermal properties as well as improve the compressive strength of frost-susceptible soil. Two silty sand soils with 15% and 25% fines content that are categorized as high to very high frost-susceptible soil were considered and treated with varying dosages of calcium nitrate contents (1.5%, 3.0%, 4.5%, 10%, 15%, and 20% of soil weight). The thermal properties, including thermal hysteresis, thermal conductivity, specific heat capacity, freezing point depression, and phase changes (freezing and thawing point) were determined for the untreated and treated soil samples. It was observed that the treated samples' thermal properties were significantly altered with respect to untreated soils. The effects of fines content on the thermal properties were evaluated using a stabilizer–silt content ratio. The threshold calcium nitrate dosage content was established, and a new correlation was established to evaluate the freezing point and thawing point. The unconfined compressive strength (UCS) tests performed on the treated soils depicted a significant increase in compressive strength compared to the untreated soil. Further analysis showed that fines content has a significant role to play on the compressive strength of treated silty sand. A qualitative analysis performed on images from a scanning electron microscope (SEM) showed that increasing the calcium nitrate dosage reduced the pore size and improved the cementation between the sand and silt grains. [ABSTRACT FROM AUTHOR]

Due to its mechanical, rheological, and chemical properties, high-density polyethylene (HDPE) is commonly used as a material for producing the pipes for transport of various media. Low thermal conductivity (0.4 W/mK) narrows down the usage of HDPE in the heat exchanger systems. The main goal of the work is to reduce the vertical depth of the HDPE pipe buried in the borehole by increasing the thermal conductivity of the material. This property can be improved by adding certain additives to the pure HDPE matrix. Composites made of HDPE with metallic and non-metallic additives show increased thermal conductivity several times compared to the thermal conductivity of pure HDPE. Those additives affect the mechanical properties too, by enhancing or degrading them. In this research, the thermal conductivity and tensile properties of composite made of HDPE matrix and two types of additives, expanded graphite (EG) and boron nitride (BN), were tested. Micro-sized particles of EG and two different sizes of BN particles, micro and nano, were used to produce composite. The objective behind utilizing composite materials featuring dual additives is twofold: firstly, to enhance thermal properties, and secondly, to improve mechanical properties when compared with the pure HDPE. As anticipated, the thermal conductivity of the composites exhibited an eightfold rise in comparison to the pure HDPE. The tensile modulus experienced augmentation across all variations of additive ratios within the composites, albeit with a marginal reduction in tensile strength. This implies that the composite retains a value similar to pure HDPE in terms of tensile strength. Apart from the enhancement observed in all the aforementioned properties, the most significant downside of these composites pertains to their strain at yield, which experienced a reduction, declining from the initial 8.5% found in pure HDPE to a range spanning from 6.6% to 1.8%, dependent upon the specific additive ratios and the size of the BN particles. [ABSTRACT FROM AUTHOR]

The 3ω method is a well-established thermal technique used to measure the thermal conductivity of materials and the thermal resistance of interfaces. It has significant advantages over other steady state and transient thermal techniques in its ability to provide spatially resolved thermal property measurements over a wide range of thermal conductivity. Despite its advantages, it has been restricted to lab-scale use because of the difficulty involved in sample preparation and sensor fabrication and is limited to non-metallic substrates. High-throughput 3ω measurements with reusable sensors have not been realized yet. In this work, we demonstrate a method of applying reusable 3ω sensors fabricated on flexible polyimide films to measure bulk and spatially resolved thermal properties. We establish the limits of thermal conductivity measurement with the method to be 1 to 200 W/mK, and within the measurement limit, we verify the method by comparing the measured thermal conductivities of standard samples with established values. From the 3ω measurements, we also determine the thermal resistance of an interlayer of thermal grease as a function of pressure and compare it against the resistance calculated from direct thickness measurements to demonstrate the ability of this method to provide spatially resolved subsurface information. The technique presented is general and applicable to both metallic and non-metallic substrates, providing a method for high-throughput 3ω measurements with reusable sensors and without considerable sample preparation. [ABSTRACT FROM AUTHOR]

The precise control of molten steel temperature in tundish is a key factor to ensure the quality of the cast billets, so it is important to develop permanent lining castables for tundish with low thermal conductivity and bulk density. In this work, the hydrophobic modification of pearlescent sand was carried out with hydrogen silicone oil, and 3% of modified pearlescent sand was added to mullite‐bauxite castable to realize its low thermal conductivity and light weight. It is found that modified pearlescent sand still has good hydrophobicity at 350°C, the addition of modified pearlescent sand effectively increases the apparent porosity and reduces the bulk density of the castable. At 1500°C, the bulk density of modified pearlescent sand‐castable is 25.54% less than that of conventional castable. Compared with conventional castable, the mechanical properties and thermal shock resistance of modified pearlescent sand castable are worse, but they are sufficient to meet the use conditions of tundish permanent lining castable. At 600–1000°C, the thermal conductivity of the modified pearlescent sand castable is about 30% lower than that of the conventional castable, which proves that the addition of modified pearlescent sand can significantly improve the thermal insulation performance of mullite‐bauxite castable. [ABSTRACT FROM AUTHOR]

• Molecular dynamics method was implemented. • Nano refrigerants include Freon-134a and Freon-407a as base fluids and Cu as nanoparticles. • The density, velocity, and temperature profiles are investigated. • Freon-407a base fluid shows a better thermal performance. • Nano-refrigerant with Freon-407a base fluid has more heat flux (1028 W/m2). Nano-refrigerants, which are the suspensions of nano-sized particles in a base fluid, were applied in many devices and systems to enhance thermal conductivity and improve heat transfer performance. This work studied the thermal and atomic behavior of two kinds of nano-refrigerants located inside an aluminum nanochannel for 5 ns. The molecular dynamics (simulation method simulated Nano-refrigerants, including R-134a and R-407A as base fluids and copper as nanoparticles. The density, velocity, and temperature profiles were studied to investigate the atomic behavior of the simulated sample. The thermal behavior of structures was studied by examining the phase transition rate, phase change time, thermal conductivity, and heat flux. The results show that R-407A base fluid showed better thermal behavior. The results show that in Cu/R-407A, the phase-changed particle reached 31% in 5 ns, and phase change time was estimated to be 3.91 ns. In contrast, in Cu/R-134a, the samples' phase changed particle and phase change time reached 26% and 4.06 ns. Moreover, the study of heat flux shows that nano-refrigerant with R-407A base fluid had more HF (1028 W/m2) than R-134a (654 W/m2). The results show that the thermal conductivity of R-407A and R-134a nano-refrigerant converged to 0.0975 and 0.0098 W/mK, respectively. [ABSTRACT FROM AUTHOR]

Novel bulk SiOC/spodumene composites have been developed by spark plasma sintering (SPS) at relatively low temperature (1200–1400 °C). Spodumene is a cheap and natural available lithium aluminosilicate mineral which acts as meltable/active filler. At 1300–1400 °C, the Al migrates toward the glassy matrix producing a Si-Al-O network and the crystallization of α-cristobalite. The C free phase also experiences a deep transformation. The epitaxial growth of few-layered graphene over SiC particles occurs at 1400 °C. An increase in the phonon transport is observed (36%, 1.28 – 2.14 Wm−1K−1) associated to the reduction of the interface resistance between the partially crystallized SiO 2 matrix and the SiC nano-wires/graphene-like carbon conductive phase. The electrical conductivity increases (1.14 ×10−2 – 8.1 Sm−1) due to the densification reached and an increasing ordering degree of the tortuous C free phase with a high quality of interconnection and crystallization. Raman parameters are determinant to understand the thermal and electrical response. • Spodumene was used for the first time to rise k and σ of SiOC/spodumene composites. • Raman parameters and densification are crucial to understand phonon/electron response. • The epitaxial growth of few-layered graphene over SiC particles occurs at 1400 ºC. • k boosts by the reduction of the interface resistance between SiO 2 /SiC nano-wires/C. • rises by densification and increasing ordering degree of the tortuous C free phase. [ABSTRACT FROM AUTHOR]

The fabrication of high-entropy ceramics has recently expanded the pool of ultra-high temperature ceramics (UHTCs). To properly assess the suitability of these new types of ceramics for advanced aerospace applications, it is of vital interest to extend the characterizations beyond ambient conditions. Here, we have studied the thermal and ablation properties of a high-entropy diboride (HEB): (Hf 0.2 Zr 0.2 Ti 0.2 Ta 0.2 Nb 0.2)B 2. The thermal conductivity of the HEB increases as a function of temperature and becomes comparable to that of other UHTCs at high temperatures. The electron dominated thermal conductivity of HEB is also nearly isotropic along different crystallographic orientations. The temperature-dependent volumetric heat capacity of HEB is measured and found to remain in agreement with that of ZrB 2. Additionally, both material systems possess nearly the same ablation resistance. The multitudes of characterizations performed in this study establishes the suitability of HEB for high thermal load applications in extreme environments. [ABSTRACT FROM AUTHOR]

Polymers with high thermal conductivity (TC) and dielectric constant (ε) but low dielectric loss show enormously potential applications in electrical power systems. To enhance the ε and TC while significantly suppressing the loss of β‐silicon carbide whisker (β‐SiCw)/polyvinylidene fluoride (PVDF), in this study, SiO2 shells with different morphologies were constructed on the superficies of β‐SiCw via a facile oxidation method in air atmosphere. The SiO2 shell' morphology on the TC and dielectric performances of the β‐SiCw@SiO2/PVDF are systematically explored as a function of the frequency and filler loading. The β‐SiCw@SiO2/PVDF demonstrate astonishingly restricted loss and meliorative TC when compared to the β‐SiCw/PVDF because the SiO2 shell not only suppresses the β‐SiCw from direct contact with one another and impedes the long‐distance charges migration thereby resulting in rather low loss and leakage conductivity, but also restrains the thermal interfacial resistance via increased interfacial compatibility and interactions. The concurrent enhancement effect in the ε and TC but low loss of the composites is more evident in the crystalline SiO2 interlayer with a high TC compared with amorphous one. These results provide insight into the exploration of composite nanodielectrics with large TC and ε but low loss for applications in electrical power systems. Highlights: Core@shell structured β‐SiCw@SiO2/PVDF were obtained by a facile oxidation.The great reduction in both loss and conductivity is attributed to the SiO2 shell.Crystalline SiO2 shell can improve the composites' thermal conductivity.The SiO2 shell prevents long‐range carrier migration. [ABSTRACT FROM AUTHOR]

A new melt mixing and in‐situ exfoliation method based on the synergy of multi‐source pulsating flow and phase transition (MSPFPT) was reported. The corresponding device was also developed, and the structure and mixing process of the mixer were introduced in detail. High‐density polyethylene (HDPE)/expanded graphite (EG) composites were prepared via this new mixer, and microstructure and thermal properties of the composites were comprehensively investigated. Morphological analyses demonstrate that MSPFPT method promotes the efficient exfoliation and uniform dispersion of EG. The well‐exfoliated EG layers form more thermal conductive paths in the composites prepared by MSPFPT, increasing thermal conductivity from 0.47 of pure HDPE to 1.16 W/(m·K) with 9 wt.% EG. The crystallinity degree of HDPE is increased by 11.1%. The increment of crystallinity reduces phonon scattering, which further confirms that MSPFPT method can significantly improve the thermal performance. The research provides a practical strategy for fabricating high‐performance composites filled with layered fillers. [ABSTRACT FROM AUTHOR]

Copper (Cu) and tungsten (W) possess exceptional electrical and thermal conductivity properties, making them suitable candidates for applications such as interconnects and thermal conductivity enhancements. Solution-based additive manufacturing (SBAM) offers unique advantages, including patterning capabilities, cost-effectiveness, and scalability among the various methods for manufacturing Cu and W-based films and structures. In particular, SBAM material jetting techniques, such as inkjet printing (IJP), direct ink writing (DIW), and aerosol jet printing (AJP), present a promising approach for design freedom, low material wastes, and versatility as either stand-alone printers or integrated with powder bed-based metal additive manufacturing (MAM). Thus, this review summarizes recent advancements in solution-processed Cu and W, focusing on IJP, DIW, and AJP techniques. The discussion encompasses general aspects, current status, challenges, and recent research highlights. Furthermore, this paper addresses integrating material jetting techniques with powder bed-based MAM to fabricate functional alloys and multi-material structures. Finally, the factors influencing large-scale fabrication and potential prospects in this area are explored. [ABSTRACT FROM AUTHOR]

The structural, electronic, thermal and lattice thermal transport properties of the three hypothetical quaternary Heusler alloys FeRuTiX (X=Si, Ge, Sn) were investigated with the aid of first‐principles calculations. All compounds were found to be semiconducting with a small indirect band gap. Flat bands near the conduction band edge and degenerate multi‐bands near the valance band edge suggest that these systems should exhibit both large Seebeck coefficients and good electrical conductivity. The analysis of the calculated vibrational spectra showed that the three compounds are thermodynamically stable. The computed lattice thermal conductivity indicates that among the three compounds that of FeRuTiSn is rather low at high temperature. Indeed, a low lattice thermal conductivity (∼3.5 Wm−1 K−1 at 1000 K) together with a small electronic band gap (0.51 eV) with an appropriate electronic structure (disperse and flat bands) render FeRuTiSn a promising candidate as a high‐temperature thermoelectric material. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) is a promising material for thermoelectric power generation. The characterization of thermal transport properties is essential to understanding their applications in thermoelectric devices. The existence of stacking faults, which originate from the "wrong" stacking sequences of Si–C bilayers, is a general feature of SiC. However, the effects of stacking faults on the thermal properties of SiC are not well understood. In this study, we evaluated the accuracy of Tersoff, MEAM, and GW potentials in describing the thermal transport of SiC. Additionally, the thermal conductivity of 3C/4H-SiC nanowires was investigated using non-equilibrium molecular dynamics simulations (NEMD). Our results show that thermal conductivity exhibits an increase and then saturation as the total lengths of the 3C/4H-SiC nanowires vary from 23.9 nm to 95.6 nm, showing the size effect of molecular dynamics simulations of the thermal conductivity. There is a minimum thermal conductivity, as a function of uniform period length, of the 3C/4H-SiC nanowires. However, the thermal conductivities of nanowires weakly depend on the gradient period lengths and the ratio of 3C/4H. Additionally, the thermal conductivity of 3C/4H-SiC nanowires decreases continuously from compressive strain to tensile strain. The reduction in thermal conductivity suggests that 3C/4H-SiC nanowires have potential applications in advanced thermoelectric devices. Our study provides insights into the thermal transport properties of SiC nanowires and can guide the development of SiC-based thermoelectric materials. [ABSTRACT FROM AUTHOR]