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Silver nanowires find use in a myriad of applications, including communication systems, sensors, medical devices and electrical equipment. Temperature-dependent electrical and thermal properties of chemically derived silver nanowires are rarely explored. In the present work, seed-mediated synthesis of silver nanowires has been carried out, and their electrical and thermal conductivity at 300 K is found to be 1.848 × 107 S/m and 64.8 W/mK, respectively. A screen-printable ink of silver nanowires is formulated and printed on low-cost and widely used substrates like paper and cotton fabrics. Flexible printed electrodes could be made possible with uniform printed structures obtained in cotton fabric and paper substrate. The printed pattern exhibited sheet resistance of 0.7 Ω/sq. Screen-printed silver nanowires on paper show shielding efficiency of 99.9% in X band, which promotes them as excellent candidates in fabricating lightweight electronic devices by a one-step printing process. [ABSTRACT FROM AUTHOR]

In this paper, a novel composite phase change material (CPCM) is prepared with inorganic PCM through impregnation and dispersion method which can be used for thermal management applications. Inorganic PCMs have high latent heat and good thermal conductivity and are non-flammable, but there exist leakage (shape stability) and corrosion problems. To overcome these issues, a porous structured material is impregnated with the inorganic PCM (disodium hydrogen orthophosphate dodecahydrate). The CPCM is prepared by loading various wt% of expanded graphite and boron nitride nanoparticles with the PCM, and characterization is performed to find the thermal properties and stability. The findings from FTIR and XRD analyses validate both the chemical compatibility and crystalline nature of the samples. DSC thermographs reveal the CPCM5 sample has a latent heat value of 168.05 J/g during the heating process, an encapsulation efficiency of 78.8% and a thermal conductivity of 4.69 W/mK. The thermal stability and resistance to corrosion of the composite samples are also enhanced. The best composite PCM sample is then selected, and subsequently, the thermal performance of the heat sink is experimentally investigated. The thermal performance of rectangular cavity heat sink filled with CPCM5 is the highest for various power sources and temperatures with a maximum enhancement ratio of 6.57. [ABSTRACT FROM AUTHOR]

Organic phase change materials (PCMs) have received increasing attention for their applications in the fields such as solar energy storage and thermal management. Low thermal conductivity is a major key issue that hinders their practical applications. It has become a research hotspot to investigate the three-dimensional (3D) network method to improve the thermal performance of organic PCMs compared with the traditional blending method. Thermally conductive fillers form a 3D network in the resin matrix, which can enrich the thermal conductive pathway and effectively enhance the thermal conductivity. This paper mainly summarizes the research progress, preparation methods and influencing factors of composite PCMs, focusing on the methods of constructing 3D thermal conductivity network. It is hoped to provide reference or suggestion for the preparation of novel PCMs. [ABSTRACT FROM AUTHOR]

Carbon materials have excellent thermophysical properties, and different dimensions of carbon materials are attractive candidates for enhancing high-performance aluminum matrix composites for thermal management. This paper reviews the preparation processes of carbon/aluminum composite materials in various dimensions and summarizes the main factors affecting the thermal conductivity of carbon/aluminum composites from the perspectives of metal matrix, reinforcement, and interface. Finally, we summarize the experimental progress of interfacial modification of different carbon/aluminum composites and put forward the future research direction in this field. [ABSTRACT FROM AUTHOR]

As a typical representative of Ga-based III-V compound semiconductor material, the pressure-induced structural phase transition of gallium phosphide (GaP) has received more attention, while the present work explains the electronic structure and photoconductivity properties under high pressure, especially. The paper focuses on the high-pressure electronic structure and photoconductivity properties up to 50.0 GPa in GaP, along with the ZB (zinc-blende structure) to RS (rock salt structure) phase structural transition using enthalpy calculation. The discontinuous thermal expansion coefficient and unit cell volume collapse by 15.0–15.5% are observed at around 39.2 GPa due to reversible structural phase transition under compression and decompression conditions, which is also reflected in the measured discontinuous Hall coefficient and conductivity at approximately 39.0 GPa. The computed semiconductor-to-metal transition is determined to occur at 24.5 GPa by band-gap closure in good agreement with the experimentally determined transition pressure. The light illumination provides a potential way to reduce conductivity without effect on pressure of phase transition. [ABSTRACT FROM AUTHOR]

The material choice for electrical contacts fundamentally governs the breaking performance, safety, and reliability of electrical switches. In recent years, amid a rapid escalation in infrastructure development, an upsurge in living standards, and advancements in scientific and technological realms, there has been a burgeoning demand for increased load capacity within power distribution systems, thereby imposing novel demands on electrical contact materials. The advent of two-dimensional graphene, with its exceptional electrical conductivity, thermal conductivity, and mechanical attributes, has piqued the interest of researchers in the electrical contact field. This has spurred further research and development into innovative graphene-enhanced electrical contact materials. This paper presents a comprehensive review of the progression made in graphene-enhanced silver-based electrical contact materials over the recent years. It particularly delves into the application of graphene in silver-based contact substances, encompassing the most recent developments in graphene-enhanced contacts, the underlying principles and processes governing arc generation and erosion, the arc-resistant mechanisms inherent to graphene-enhanced contact materials, and provides a forward-looking perspective on the potential future of graphene-based contact materials. [ABSTRACT FROM AUTHOR]

Highly integrated and high-power devices place higher demands on the heat dissipation capability of heat sink components, and graphene meets the heat dissipation requirements due to its extremely high thermal conductivity of 5300 Wm−1 K−1 and good mechanical properties. Graphene by redox is one of the most promising methods for large-scale preparation of graphene; however, the quality of graphene prepared by different reduction processes varies. Herein, this paper presents a fast and efficient reduction process. Benzene was added as a reduction aid to increase the temperature from room to 2000 °C in 30 s and complete the reduction process. By this method, we obtained graphene with low defects and high thermal conductivity. The reduction process restored the lattice destroyed by the oxidation process, and the repaired material showed a higher crystallinity with a measured ID/IG of 0.18 (Ph-rGO-0, 0.58) and in-plane thermal conductivity of 510 ± 10 Wm−1 K−1. The in-plane thermal conductivity was increased by 262 Wm−1 K−1 compared with the film without benzene addition (Ph-rGO-0), which showed better homogeneous temperature performance and heat dissipation performance in practical applications. These results show the great potential for the application of graphene films prepared by this method in the field of heat dissipation materials. [ABSTRACT FROM AUTHOR]

Composites are popular in construction engineering due to their low water absorption, good chemical and corrosion resistance, lightweight, high specific strength, high specific modulus, and low thermal conductivity. The flame retardancy (FR) of composite materials has increasingly become the focus of attention in the field of construction engineering. With growing awareness of personal and property safety, a wide range of flame-retardant composites has been developed over the years through research and development. The FR of an unmodified polymer composite is not optimal, and therefore, many innovative methods for making more advanced flame-retardant materials have been developed. The aim of this review is to provide detailed literature on flame-retardant composites. The structure of this paper consists of evolution of flame-retardant materials, their manufacturing techniques, flame-retardant composites, their properties and characterization, applications, and challenges related to of FR composites. The primary focus of this review is to analyze the mechanism of fire retardancy and to summarize the preparation of flame-retardant polymer materials by adding various flame-retardant agents. [ABSTRACT FROM AUTHOR]

The 1045 steel is extensively heat treated because its mechanical properties can be easily improved by thermal processes. Reliable knowledge of the relationship between microscopic structure and thermal properties is essential for the thermal design of parts and tools. This paper reports on coupling microstructural aspects with the effects of tempering temperature on the temperature-dependent thermal properties of 1045 steel. Thermal conductivity (k) and specific heat (cp) were simultaneously estimated using inverse heat conduction analysis. The thermal characterization technique handled a simple and low-cost experimental setup, based on transient one-dimensional heat transfer on samples subjected to different heat-treatment conditions. The results, which were discussed in connection with the resulting microstructures, demonstrated that all quenching and tempering (Q&T) conditions led to lower values of both thermal properties throughout the temperature domain. The tempering temperature was found to impact k more substantially. The robustness of the results was ascertained by recovering the applied heat flux based on linear regression equations for k and cp and temperature measurements. Accuracy analysis indicated that the inverse approach provides estimates with an uncertainty close to 4%. [ABSTRACT FROM AUTHOR]

Coal combustion for energy has not only wasted the hydrogen-rich volatile matters but also results in CO2 emission causing serious environmental issues. An integrated coal pyrolysis and solvent extraction process under elevated temperatures in an inert atmosphere is implemented to convert as-mined coal from Wyoming Powder River Basin to functional carbon elements such as pyrolysis char (PC). This paper presents the development and fabrication of new carbon-based structural unit (CSU) using pulverized PC and two coal-derived pitches (mesophase pitch and tar pitch) to attain high compressive strength greater than 30 MPa, low thermal conductivity less than 0.30 W/m K, and low density less than 1.25 g/cm3. CSUs have the potential to overcome the current challenges with cement and concrete through pressurized fabrication followed by carbonization. This study aims to develop CSU with nearly 100% coal-derived carbon material for structural application in buildings. The effects of pressing pressures, carbonization temperatures, and binder contents on the density and mechanical and thermal properties of CSU samples are investigated. The study concludes that mesophase pitch produces a better performance of CSU samples, a combination of 100 MPa pressing pressure and carbonization temperature of 900 °C yields the highest compressive strength, and a 25% MP content is recommended for low-cost CSU fabrication. CSU has a much lower density, lower thermal conductivity, higher compressive strength, and higher strength-to-density ratio than normal concrete. [ABSTRACT FROM AUTHOR]

Recently, thermoelectric (TE) devices have attracted much attention because they have no moving parts, simple structures, high reliability, and environmental friendly, when compared to other green energy techniques. In this paper, we report a novel thermoelectric composite constructed one with a self-assembled highly oriented Sb doped Bi2Te3 and one without doping nanoflake layer deposited on regular vertically aligned checkerboard-patterned multi-walled carbon nanotube (MWCNT) arrays (500 nm squares and 1 µm pitch) on insulated SiO2/Si substrates. The height of Bi2Te3/Bi0.4Sb1.6Te3, MWCNTs and volumetric ratio of MWCNT to Bi2Te3/ Bi0.4Sb1.6Te3 are about 3 μm, 1.5 μm, and 25%, respectively. The blending of regular vertically aligned MWCNT patterns into Bi0.4Sb1.6Te3 results in a dramatically enhancement of Seebeck coefficient and electrical conductivity. The Seebeck coefficient and power factor of Bi0.4Sb1.6Te3-MWCNTs show a maximum value of 600 μV/K and 60 μW/cm-K2 at 160 K and gradually decrease to 409 μV/K, and about 14.1 μW/cm-K2 at 300 K, respectively. The significant records of the low temperature Seebeck coefficients and relative electrical properties are extremely important for the fundamental understanding of vertically aligned MWCNT embedded thermoelectric composites. [ABSTRACT FROM AUTHOR]

Simply filling the metal foam as a thermally conductive filler into the polymer matrix can improve the thermal conductivity of the polymer matrix, but it still cannot greatly improve the thermal conductivity of the composites. In this paper, the epoxy resin/copper foam-nickel (EP/CF-Ni) composite thermal conductive material was prepared by a combination of electroplating and vacuum liquid impregnation. The deposition of nickel increases the heat dissipation area of the copper foam and at the same time widens the heat conduction path of the materials. By comparing EP/CF with different pores and EP/CF-Ni with different deposition times, it was found that the thermal conductivity of EP/CF-Ni composites could reach 5.215 W/(mK) at 7.3 wt% nickel deposition, which enhanced 2507% and 75% compared to pure epoxy and copper foam matrix composites, respectively. The deposition of nickel further improves the wear resistance of the composite. This experiment reveals the synergistic effect of thermal conductivity of metallic Ni and 3D copper foam, and provides some reference opinions for the field of thermal conductivity of metallic foam. [ABSTRACT FROM AUTHOR]

New thermal interface materials (TIM) with liquid metal (LM) as the main component show many advantages in the field of thermal management. However, it is prone to leakage and causes electronic components to fail due to its fluidity, corrosiveness and difficulty in adsorption, thus limiting its applications. In this paper, based on the high thermal conductivity of LM, the composite material made of eutectic gallium indium alloy (EGaIn) and nickel-plated copper mesh (NPCM) was prepared, and the TIM with high thermal conductivity, stability and reliability was obtained. With surface plating, the plating on the copper surface achieves an area coverage of up to 97.7%, effectively preventing EGaIn corrosion. The complete wetting between materials can be achieved through surface modification of NPCM with an EGaIn oxide layer. The surface modification of NPCM with EGaIn oxide layer can achieve complete wetting between materials. The thermal conductivity of the composite is 26.4 W m−1 K−1. Compared to Nickel foams (NiF), NPCM/EGaIn composite exhibits a 22.4% increase in thermal conductivity. In addition, its thermal conductivity fluctuates in a range below 7 percent even after undergoing high-temperature aging and low-temperature cycling. The actual load test demonstrated that the use of EGaIn/NPCM resulted in an 18.0% reduction in CPU full load temperature and a 78.0% decrease in maximum throttling peak, as compared to conventional silicone grease. [ABSTRACT FROM AUTHOR]

The conventional approach to achieve desired effective thermal conductivity (ETC) of porous thermal interface materials (TIM) is processing-microstructure-properties forward analysis, which contains various trial-and-error cycles and is hence inefficient for materials development. Establishing the linkage from ETC to microstructure is essential; however, the recently developed methods including microstructure characterization and reconstruction are suffering from limited accuracy and computational efficiency. To address these problem, in this paper, generative artificial intelligence (AI) model was first implemented to design microstructure of porous TIM with desired ETC. Here, we introduced a representative porous TIM, sintered silver, and a typical kind of generative AI model, conditional generative adversarial network (CGAN), as an example for illustration. The CGAN model can efficiently generate sharp and crisp microstructures of sintered Ag with excellent morphology realism. Besides visual inspection, the ETC values of generated microstructures were evaluated by convolution neural network (CNN) model. It was found that the CGAN model also exhibits satisfactory performance in physical meaning, since the determination coefficient R2 between target ETC and CNN predicted ETC values is 0.985. These results confirm the effectiveness of generative AI model capable of synthesizing microstructure of porous TIM with desired ETC, and not limited to porous TIM, the approaches present here can also be generalized and applicable to design microstructure of other porous media and composites. [ABSTRACT FROM AUTHOR]

Boron nitride is a two-dimensional (2D) plate-like material with excellent thermal conductivity and lubricity. In this study, BN is introduced into Gutta-Percha (GP)/zinc oxide (ZnO) composites, and after orientation treatment, the GP@ZnO/BN composites with high TC and excellent fluidity are prepared. Moreover, the "skateboard effect" between BN plates and rod-like ZnO particles is proposed in this paper and confirmed, affording oriented GP@ZnO/5-BN lower shear viscosity (371.88 Pa·s) and higher thermal conductivity (1.65 Wm−1 K−1) than those of GP/ZnO composites. Specifically, in vitro experiments, with the assistance of the "skateboard effect," the lateral root canals filling depth (0.980 mm) of oriented GP@ZnO/5-BN composites exhibit 69.55, 49.62, and 49.16% deeper than that of commercial Bio Gutta-Percha points, MTWO Gutta-Percha points (VP), and PROTAPER universal Gutta-Percha points, respectively. Furthermore, the cytotoxicity level of the GP@ZnO/5-BN composites manifest 0–1 and the X-ray image of the GP@ZnO/5-BN composites depict similar radiopacity effect with DPP point, indicating that the oriented GP@ZnO/5-BN composites are safe and qualified as the commercial GP point materials. [ABSTRACT FROM AUTHOR]

The heat transfer performance of the graphene network in the polymer is not so satisfactory due to the high interfacial thermal resistance between layered graphene. This paper constructs partially stacked graphene sheets models with random vacancies by the molecular dynamics to investigate the effect of vacancy coverage rate, stacking length and stacking forms on the heat transfer coefficient. The results indicate that the heat transfer coefficient of the whole system mainly depends on the effective thermal conductivity of the stacking region. As the vacancy coverage rate increases, the effective thermal conductivity of the stacking region increases rapidly and then decreases slowly due to the synthetic effect of the interfacial thermal resistance and in-plane thermal resistance. Further studies reveal the positive correlation between the stacking length and the effective thermal conductivity of the stacking region. However, the effective thermal conductivities of models with different stacking lengths converge to a similar value approximately at a high vacancy coverage rate. Finally, the stacking form is proved to have a slight influence on the effective thermal conductivity. This work is of practical importance for the design and application of graphene networks in composites materials. [ABSTRACT FROM AUTHOR]

In this paper, an eco-friendly method of producing hybrid silica aerogels by freeze-drying method (FD) is proposed. In the freeze-drying system, deionized water was the only solvent, hybrid aerogels were prepared by acid–base catalysis and sol–gel method using methyltrimethoxysilane (MTMS) and water–glass as co-precursors. The microstructure, specific surface area, pore size distribution and thermal properties of the hybrid aerogels were characterized and analyzed. It was found that all samples exhibited the dual-mesoporous structures, and the molar ratio of co-precursors had a significant effect on the performance of aerogels. The tap density decreased and the porosity increased with the increase in the molar ratio of MTMS, while the thermal diffusion coefficient and thermal conductivity of aerogel decreased first and then increased. Especially when the molar ratio is 2.0, the hybrid aerogels exhibited excellent insulation performance, such as thermal diffusion coefficient of 0.0183 mm s−1, thermal conductivity of 0.0460 W(m k)−1 and great thermal stability up to 540 °C. It illustrates that hybrid aerogels have broad application prospects as insulation materials. [ABSTRACT FROM AUTHOR]

In this paper, graphite nanoplatelets (GNPs)-based polymer nanocomposites were reviewed. This review mainly discusses various synthesis techniques for making graphite nanoplatelets (GNPs) including dispersion of GNPs in polymers, functionalization and producing GNPs polymer nanocomposites. In addition, their critical morphology and rheological, mechanical, electrical, and thermal conductivity as well as gas barrier properties were explained. It was found that when GNPs were properly incorporated into the polymer matrix, they can enhance the properties of the host polymer at extreme conditions. Moreover, surface modification of GNPs by covalent and non-covalent functionalization has been explored as a new platform for realizing structure–property interactions of polymer nanocomposites. Proposed predictive modeling and analysis methods on the mechanical, electrical, and thermal conductivities and gas barrier properties of GNPs/polymer nanocomposites were also disclosed considering, in particular, GNPs geometry and orientation in polymers. It was concluded that GNPs added to thermoset and thermoplastic polymer nanocomposites exhibit conceivable developments in advanced engineering uses, including electronics, ultra-sensitive sensors, membranes, energy storage, wearable technology, aerospace and biomedical. [ABSTRACT FROM AUTHOR]

Thermal management is a crucial factor affecting the performance and lifetime in several applications, such as electronics, generators, and heat exchangers. Additive manufacturing (AM) techniques provide a new revolution in manufacturing by expanding freedom for design and fabrication for complex geometries. One way to overcome these problems is by developing novel polymer-based composite materials with improved thermal conductivity properties for AM technologies. In this review, the fundamental principles of designing high thermal conductive polymer nanocomposites are presented. High thermal conductive polymer nanocomposites generally consist of the base polymer and thermally conductive filler materials such as aluminum oxide or boron nitride which are reviewed in detail. The factors affecting the thermal conductivity of composites, such as the filler loading and overall composite structure, are also summarized. This article stands on statistical data from technical papers published during 2000–2020 about the topics of fused deposition modeling (FDM) polymers or their thermal conductive composites. Finally, the most critical factors affecting the thermal conductivity of polymer nanocomposites are described in detail. Nonetheless, various novel techniques show the potential abilities of thermal conductivity of polymer nanocomposites usage by AM technologies, enabling applications in LED devices, energy, and electronic packaging. [ABSTRACT FROM AUTHOR]

A silver metallic interlayer was inserted into a direct-bonded aluminum–copper (DBAC) substrate to inhibit the formation of aluminum–copper intermetallic compounds (IMCs) in the substrate. The Ag caused the dissolution of small quantities of Al and Cu to form a Ag(Al, Cu) metallic layer, which exhibited lower hardness (1.4 ± 0.2 GPa) and a lower elastic modulus (71.7 ± 12.8 GPa) than did Al–Cu IMCs (hardness/elastic modulus: 10.4 ± 0.9 GPa and 193.9 ± 7.2 GPa for Al4Cu9, 10.6 ± 0.3 GPa and 171.2 ± 10.7 GPa for Al–Cu, and 7.6 ± 1.5 GPa and 121.0 ± 8.4 GPa for Al2Cu, respectively). Moreover, the Ag(Al, Cu layer was able to withstand high stress caused by the coefficient of thermal expansion mismatch between Al, Ag, and Cu; thus, this layer prevented crack formation at the Al–Cu bonding interface. The shear strength of the Al–Cu bonding interface was originally 13.3 ± 3.4 MPa. This value then increased to 26.3 ± 3.6 MPa when a Ag metallic interlayer was inserted, and the shear strength was maintained at 21.9 ± 1.1 MPa during 500 thermal cycles between − 50 and 150 °C. At room temperature, the thermal conductivity of DBAC with a Ag metallic layer (280 W/mK) was higher than that of direct-bonded aluminum (233 W/mK) and DBAC without a Ag metallic layer (276 W/mK) because of the high thermal conductivity of Ag and the absence of Al–Cu IMCs in the DBAC with a Ag metallic layer. [ABSTRACT FROM AUTHOR]

UO2-BeO is an important composite nuclear fuel with high thermal conductivity. The impact of grain boundaries between UO2-UO2 and phase boundaries between UO2-BeO on the bubble evolution and the thermal conductivity in nuclear fuels is significant. In this study, we utilize a 3D phase field model to examine the influence of these boundaries on the nucleation and growth of bubbles in a bicrystalline UO2-BeO. Our simulations reveal that the diffusion of vacancies and gas atoms towards the phase boundaries results in bubbles preferentially forming at the phase boundaries. Intergranular bubbles possess an asymmetrical lectical shape due to the long-range diffusion-controlled boundary migration and the different defect production rate on the both sides. Spherical intragranular bubbles appear after the intergranular bubbles with high defects production rates and large grain size. The effective thermal conductivity decreases with the irradiation time and shows three distinct stages for systems that have both inter- and intragranular bubbles. [ABSTRACT FROM AUTHOR]

Polymeric heat exchangers (PHXs) have been used in applications involving weight restrictions, chemical compatibility, and fouling issues. Additive manufacturing (AM) or 3D printing provide new solutions to previously inaccessible combinations of properties and geometries. There are some advancements in the PHXs by AM; however, the process and the properties of materials still need further investigation to improve the overall performance. In this study, additively manufactured polyethylene terephthalate glycol (PETG) composites reinforced with graphite and pitch-based carbon fibers were evaluated for their potential application as PHXs. The thermal conductivity, volumetric heat capacity, coefficient of thermal expansion, creep behavior, and long-term performance were studied in detail. Our results reveal that the composites have an anisotropic thermal conductivity. The thermal conductivity along the printing direction is higher than the layer building direction due to the shear-induced alignment of the fillers. The printed composites achieve good thermal stability with 80% lower CTE at room temperature than neat PETG. Creep tests suggest the creep and creep recovery were highly temperature-dependent, and the deformation can be recovered when the temperature is below glass transition. These results suggest additive manufactured composites be potentially used for heat exchanger applications at low temperatures. [ABSTRACT FROM AUTHOR]

In recent decades, graphene has become a very promising thermal management material due to its excellent thermal performance and flexibility. The interaction between adjacent graphene nanosheets, on the other hand, is Van der Waals, limiting the improvement of thermal performance and flexibility of graphene-based heat-conducting films. In this work, a poly(ethylenimine) (PEI)/graphene oxide (GO) /carbon nanotubes (CNTs) heat-conducting film was fabricated, in which PEI acts as a cross-linking agent to form cross-links between GO nanosheets, followed by carbonization and graphitization. Further investigations illustrate that the graphitized PEI/GO/CNTs film has excellent mechanical properties with a tensile strength of 198.3 ± 15.6 MPa and excellent thermal performance with an in-plane thermal conductivity of 1038.4 ± 25.07 W m−1 K−1 and a through-plane thermal conductivity of 7.14 ± 0.25 W m−1 K−1. The graphene-based thermal conducting films have great potential in various fields, such as electronics, aerospace, 5G, etc. [ABSTRACT FROM AUTHOR]

Vitreous silica (v-silica) is a challenging material to characterize due to its disordered structure and thermal-history-dependent properties, which are not fully captured by classical potential models. In this study, we trained deep neural network (DNN) potentials with ab initio precision to describe the structure, dynamics, thermal conductivity, and densification of v-silica, comparing the performance of two exchange correlation functionals, BLYP and AM05. Our results demonstrate that the cooperative atomic movement within inner-tetrahedral and inter-tetrahedral SiO4 units plays a critical role in the volume-conservative "compaction" of v-silica, which in turn results in a "shrinking" of the vibrational density of state spectrum. We also found that the transition of coordination number is correlated with the minimum of longitudinal wave velocity. Moreover, our DNN model reveals that the long-range disorder changes linearly within the pressure range of 0–9 GPa. [ABSTRACT FROM AUTHOR]

Multi-material structures make it possible to obtain effective solutions to engineering problems by combining the benefits of different materials to meet the requirements of different working conditions. The aim of this multifunctional 420 stainless steel-copper structure is to create a hybrid solution in which copper acts as heat-transfer enhancer (through cooling channels) while maintaining the required mechanical properties of the steel matrix. This work focuses on a combined engineering process consisting of CNC machining through holes on a 420 stainless steel surface substrate and subsequent filling with copper by hot pressing. The influence of the copper filling on the physical, chemical, microstructural, mechanical, and thermal properties of this multi-material solution was analysed. The machined area (5% of the total surface area) consisted of nine holes with a diameter of approximately 1 mm. The multi-material samples showed high densification, homogeneous microstructures, and a well-defined and sharp interface between the two materials. The microhardness values measured for the 420 stainless steel and copper were 759 and 57 HV, respectively, and the thermal conductivity of the multi-material was ≅ 59% higher than the 420 stainless steel (39.74 and 16.40 W/m K, respectively). [ABSTRACT FROM AUTHOR]

The product of Hamiltonian and entropy as a new physical quantity is introduced to quantitatively explain the phenomenon that Co-doped crystals have lower thermal conductivities than single-doped crystals, because Hamiltonian does not characterize the disorder degree of Co-doped crystals. An application of the new quantity in combination with software VASP for Co-doped SrZrO 3 was given in this work. It is found that in terms of Co-doped with two species of rare earth elements, the combination of La and Eu element provides the optimal solution for most efficiently decreasing thermal conductivity of SrZrO 3 . In addition, all cases for the different number of substitutional elements were calculated. When the number of substitutional element species is 6, and the combination consists of La, Pr, Nd, Sm, Eu and Er, the combination can most efficiently decrease thermal conductivity of SrZrO 3 . Finally, the correctness of the model using the Slack's method was also certified. [ABSTRACT FROM AUTHOR]

To improve the thermal stability of the explosive HMX (C4H8N8O8), in this study, different functional groups (hydroxyl, carboxyl and butyl) were grafted on the surface of graphene, and the corresponding thermal transport across graphene–HMX interface is studied by molecular dynamics simulations. The obtained results show that the covalent functionalization coverage rate of less than 7.5% is not beneficial for the interface heat transfer; however, further increasing the coverage rate significantly boosts the interfacial thermal conductance (ITC). Among the studied functional groups, butyl best enhances the ITC compared to hydroxyl and carboxyl groups, with an increase of 48.5% compared to that of the pristine graphene–HMX. Then, the obtained results from molecular dynamics simulations serve as input for the effective medium theory-based thermal conductivity prediction model, and the effective thermal conductivity of graphene–HMX composites were investigated. Meanwhile, the major factors that dominate the composite thermal conductivity were identified. Our investigation enriches the understanding of the physical mechanisms governing the heat transport in HMX composites with fillers and is instructive for the structural design of thermally conductive HMX-based explosives. [ABSTRACT FROM AUTHOR]

Improving solar energy conversion efficiency and salt resistance is particularly important for the practical application of green and sustainable solar steam generation technology. In this work, an interfacial evaporation polypyrrole-coated film was fabricated by the mixed-dimensional clay consisting of 1D palygorskite (Pal), 2D montmorillonite (Mt) and mica, etc., that was intercalated using polyaniline (PANI) and then introduced polyvinyl pyrrolidone (PVP) as pore-forming agent and polyvinylidene fluoride (PVDF) as a base film. The prepared film could efficiently convert light energy to heat under solar irradiation with excellent properties of self-desalination and photothermal conversion efficiency as well as superhydrophilicity and low thermal conductivity. The photothermal conversion efficiency achieved up to 93.6% under the simulated sunlight of 1 kW m−2. The evaporation rate in 15% NaCl brine differed very little from that in pure water, and 0.2 g of NaCl placed on the film would be eliminated in short time at room temperature, which demonstrated that the film had salt resistance and self-cleaning capability. In addition, the resulting film had low thermal conductivity (0.09994 W m−1 K−1) and good mechanical properties (tensile strength of 1.1 MPa) and exhibited superhydrophilicity (water contact angle ~ 0°) which could transport water molecules rapidly. [ABSTRACT FROM AUTHOR]

Thermal management has been increasingly recognized as a limiting factor for advanced high-power electronics. Diamond can offer unique technological opportunities in the field of thermal management due to a broad range of outstanding properties, such as exceptional high thermal conductivity, high radiation hardness, unique electronic, photonic and quantum characteristics, and outstanding mechanical behavior desirable for cutting-edge electronics, optics, and extreme mechanics. Diamond films have considerable applications for heat sink and high-power chips such as high-electron-mobility transistors and quantum devices where unique electronic or quantum properties, heat transfer, and structural stability are vital. The ever-growing miniaturization of electronics and the progresses in quantum sciences all call for diamond films with desired structures and properties. This review focuses on the thermal properties of chemical vapor deposited diamond thin films, including typical processing technologies, different techniques for thermal property measurement, in-plane and cross-plane thermal properties of various diamond thin films and associated interfacial thermal conductance in addition to highlights of diamond films for thermal management and other premier applications. [ABSTRACT FROM AUTHOR]

With the rapid evolvement of microelectronic devices, the accompanying high amount of heat should be transferred in time by the thermal management system to ensure the desired performance. The design of the thermal management system that possesses high thermal conductivity with flexibility is still a challenge that needs to be overcome. Here, we propose a two-step liquid-phase repairing method using hydriodic acid to remove the defects from large graphene oxide sheets produced by a modified Hummers method to make the structure intact. Compared to thermally reducing method, our method can work under much lower temperature so that it is easier to apply in mass production with much better energy conservation effects. In our research, transverse dimensions of the graphene oxide sheets with range from 50 to 270 μm were obtained by a modified Hummers method, which effectively reduces the interlayer thermal resistance; then flexible, highly thermally conductive graphene films can be developed by a two-step liquid-phase repairing method with hydriodic acid. This process produces a flat reduced graphene oxide film with a powder-free surface that is highly thermally conductive and flexible, can be folded at 180° for 1000 times without breaking and has a thermal diffusion coefficient of 1737 mm2 s−1. Multifunctional reduced graphene oxide graphene films can easily transfer large amount of heat from miniaturised, densely packed electronics for efficient thermal management. [ABSTRACT FROM AUTHOR]

Ultra-high temperature ceramics, especially di-borides, are regarded as potential candidates for thermal protection system in hypersonic vehicles by virtue of their high thermal conductivity. However, studies on thermal conductivity behaviour of ultra-high temperature ceramic di-borides exhibit scattered data at high temperatures. Herein, we report a systematic study of a range of di-boride compositions aiming at multiple aspects including the effect of temperature on thermal conductivity of monolithic di-borides (ZrB2 and HfB2), effect of SiC and carbon nanotubes (CNTs) addition on ZrB2 and HfB2 with increasing temperature till 1200 °C, and effect on thermal conductivity with systematic incorporation of ZrB2 and HfB2 into each another. Highest experimental thermal conductivity (63–83 W m−1 K−1) observed in 20 vol% SiC reinforced ZrB2 composite (in the temperature range of 50–1200 °C) witnessed crossover (and drop) than that of monolithic sample (above 900 °C) due to increased phonon–phonon scattering in SiC with the rise in temperature. Concurrently, agglomerated CNT reinforcement further decreased thermal conductivity due to increased inhomogeneity in solid solutioning and enhanced phonon scattering. [ABSTRACT FROM AUTHOR]

In this study, the diamond/SiC composites were fabricated by tape casting combined with Si vapor infiltration process and then heat-treated at 1500 °C in an argon atmosphere for 4, 8, 12 and 16 h, respectively. The effect of heat treatment on the microstructure evolution and thermal conductivity of diamond/SiC composites was investigated. Results showed that the SiC grain size in the matrix grows significantly, and the SiC particles are sintered to form a continuous network after heat treatment. And the growth of SiC grains is controlled by the diffusion and dissolution precipitation mechanism. The thermal conductivity of the composites increased significantly after heat treatment, reaching a maximum value of 423 W/mk after heat treatment at 1500 °C for 8 h, which is 40% higher compared with that without heat treatment. However, longer heat treatment time will lead to volatilization of residual silicon in the composites and reduce its densities and has a negative influence on the thermal conductivity of the composite. The increased thermal conductivity of the composite can be attributed to both the growth of SiC grains and the formation of continuous SiC heat transport channels. Heat treatment provides a new method for improving the thermal conductivity of diamond/SiC composite. [ABSTRACT FROM AUTHOR]

Majority of the modern electronics are made up of Si owing to a confluence of beneficial properties such as Earth-abundance, non-toxicity, light-weightedness, and versatile dopability. Yet, the thermoelectric performance of Si is not widely explored, due to the relatively high thermal conductivity of undoped Si. In this work, we devised a strategy combining light Ge alloying and B doping to simultaneously enhance the electronic properties and drastically reduce the thermal conductivity of Si. The phonon scattering brought about by Ge atoms, and optimal carrier concentration brought about by B dopant optimizes the thermal and electronic properties. Consequently, zT of 0.14 was achieved at 873 K for Si0.97Ge0.01B0.02, corresponding to 230% enhancement compared to pristine Si. The strategy reported in this work can be extended to the design of high thermoelectric performance in other Si-based compounds. [ABSTRACT FROM AUTHOR]

Lower thermal conductivity and improved mechanical properties at high temperatures have always been the principal focus of designing thermal barrier coating materials (TBCs). In the present study, layer-structured LaAl11O18 was introduced into 8 wt% yttria-stabilized zirconia (8YSZ) to further improve the thermal and mechanical properties of 8YSZ. Thus, a series of 8YSZ/LaAl11O18 composites were prepared by solid sintering at 1600 °C. The composition and microstructure analyses indicate excellent chemical compatibility between 8YSZ and LaAl11O18 at high temperatures. The composites demonstrate by ~ 61% reduction of total thermal conductivity at 1200 °C as compared to a single 8YSZ. The radiative heat transfer of composites decreases around ~ 96.3% due to substantial photon scattering, resulting from lower photon mean free paths. Meanwhile, relatively good fracture toughness and lower elastic modulus (about ~ 13.3%) are promising design features of the composites for engineering applications, such as TBCs. [ABSTRACT FROM AUTHOR]

In this work, new high-entropy RE2(Ce0.2Zr0.2Hf0.2Sn0.2Ti0.2)2O7 (RE2HE2O7, RE = La, Nd, Sm, Eu, Gd, Dy) ceramics were successfully prepared. RE2HE2O7 ceramics exhibited a pyrochlore–fluorite dual-phase structure. For Sm2HE2O7 ceramic, Ce4+ with larger ionic radius was enriched in the fluorite phase, Sn4+ and Ti4+ with smaller ionic radii were enriched in the pyrochlore phase, while Zr4+ and Hf4+ with medium ionic radii existed in both phases. Compared with YSZ materials, RE2HE2O7 ceramics exhibited a much lower glass-like thermal conductivity (1.19–1.68 W m−1 K−1, 100–900 °C) and comparable thermal expansion coefficients (8.67–10.85 × 10−6 K−1, 1200 °C). Furthermore, due to grain refinement caused by the competition of two phases, the Vickers hardness (10.29–13.85 GPa) of RE2HE2O7 ceramics is improved. The results indicate that dual-phase high-entropy RE2HE2O7 ceramics are promising candidate materials for the next generation of thermal barrier coatings. [ABSTRACT FROM AUTHOR]

Epoxy resins (ERs) are one of the main types of resins used as structural adhesives; however, they present some weakness, which are mostly related to their highly cross-linked network after the curing process. Low electrical and thermal conductivity and low fracture toughness are the major drawbacks of these type of materials, and several efforts have been made over the past few years to overcome them. A critical survey regarding the use of different fillers in ERs systems and the outcome is highlighted and discussed in the present review. The incorporation of fillers into ERs matrix is one of the most successfully explored alternatives to improve the properties of ERs. It is worth to mention that even though ER composites are a widely explored topic, few reports have been focused on a compilation of the most relevant fillers and the main changes on ERs composites performance. Therefore, the present review gives an overview of a vast selection of fillers—natural, metallic, carbon fillers—incorporated in ER matrices to enhance or to meet the requirements for a desired application, such as the increase in the final adhesive toughness. The combination of the top characteristics of fillers and polymers is accomplished, leading to high-performance composites. Among the most promising fillers, carbon nanomaterials, fiber-reinforced polymers, carbon fiber-reinforced polymers, biofillers and metallic and ceramic fillers are described which have the ones having higher application potential. The influence of the addition of these different types of fillers in ERs system properties such as flame retardancy, mechanical and thermal and electrical performance is discussed and reviewed in detail. [ABSTRACT FROM AUTHOR]

Thermal insulation materials with high mechanical strength and low thermal conductivity play an important role in the construction industry. In this study, a compound aerogel with stable performance, high strength, low density and good thermal insulation performance was successfully prepared by using gelatin as the base and layered bimetallic hydroxide (LDH) as the reinforcing phase. 3-aminopropyl triethoxylsilane was used to modify the surface of layered bimetallic hydroxide to enhance interfacial bonding. The results show that the gelatin/layered bimetallic hydroxide composite aerogel has high porosity (> 96%) and low thermal conductivity (0.034–0.037 W/(m K)), volume density as low as 0.035 g/cm3. The maximum compression strength and compression modulus are 1.05 Mpa and 9.82 Mpa, respectively. The improvement of the mechanical strength of the composite aerogel may be attributed to the two-dimensional layered nanosheets of LDH to construct the internal micro/nano structure of the composite aerogel. Outstanding mechanical and low thermal conductivity enable its application in high-performance thermal insulation materials. [ABSTRACT FROM AUTHOR]

High thermal conductivity graphite films (GFs) have been widely used in the field of heat dissipation. However, due to their extremely smooth surface and low surface energy, it is difficult for them to be used as the reinforcement of composites. In this study, hexagonal pits and channels were prepared on the surface of GFs by high-temperature air etching treatments. The morphology and reason of pits and channels prepared in the air were investigated. The pits and channels enable the mechanical interlocking effect between the GFs and the carbon matrix and enhance the mechanical and thermal properties of the carbon/carbon (C/C) composites. The GFs-reinforced C/C composites with high thermal conductivity were fabricated through impregnation-carbonization cycles. The results show that, with the increase in etched GFs volume fraction, the horizontal thermal conductivity was increased from 148 to 412 W/(m K). Moreover, compared with pristine GFs-reinforced C/C composites, etched GFs-reinforced C/C composites show an increase of 165% in flexural strength. Overall, etched GFs-reinforced C/C composites with superior properties have a broad prospect in the fields of heat dissipation. [ABSTRACT FROM AUTHOR]

Computational tools to study thermodynamic properties of magnetic materials have, until recently, been limited to phenomenological modeling or to small domain sizes limiting our mechanistic understanding of thermal transport in ferromagnets. Herein, we study the interplay of phonon and magnetic spin contributions to the thermal conductivity in α -iron utilizing non-equilibrium molecular dynamics simulations. It was observed that the magnetic spin contribution to the total thermal conductivity exceeds lattice transport for temperatures up to two-thirds of the Curie temperature after which only strongly coupled magnon-phonon modes become active heat carriers. Characterizations of the phonon and magnon spectra give a detailed insight into the coupling between these heat carriers, and the temperature sensitivity of these coupled systems. Comparisons to both experiments and ab initio data support our inferred electronic thermal conductivity, supporting the coupled molecular dynamics/spin dynamics framework as a viable method to extend the predictive capability for magnetic material properties. [ABSTRACT FROM AUTHOR]

Daytime radiative cooling is a burgeoning cooling technology that reflects solar irradiation and radiates heat to outer space (3 K) to cool down terrestrial objects without using external energy. However, previously reported radiative cooling materials require complex technology, expensive equipment, or harmful chemicals, most of which are easily contaminated during outdoor applications. In this work, we proposed a simple and eco-friendly method with water as template to fabricate robust superhydrophobic porous polydimethylsiloxane (PDMS) radiative cooling film. The film possesses strong reflectivity and emissivity which results in outstanding cooling performance with ambient temperature drop of 11.52 °C, and has a superhydrophobic property with water contact angle of 165.7° and a sliding angle of 2.1° which results in excellent self-cleaning function. In addition, the prepared film shows low thermal conductivity of 0.1063 W m−1 K−1 which efficiently suppresses the heat exchange because of the air-filled voids within the film. Combining the self-cleaning property to prevent the surface from outdoor contamination or wetting, the film is promising to be widely used for long-term cooling for outdoor applications. A superhydrophobic porous polydimethylsiloxane (S-P-PDMS) daytime radiative cooling film with high reflectivity and emissivity was prepared by a simple and eco-friendly template method, which achieved a cooling effect with sub-ambient temperature drop of 11.52 °C. [ABSTRACT FROM AUTHOR]

Effects of Si and Sr on solidification microstructure and thermal conductivity of Al–Si binary alloys and Al–9Si–Sr ternary were investigated, respectively, with a special focus on the relationship between solidification microstructure and thermal conductivity. It was found that (i) in Al–Si binary alloys, with increasing Si content, α-Al grain size increases and then decreases when Si content is over 7 wt%, while the percentage of eutectic Si continuously increases, which significantly decreases the thermal conductivity and electrical conductivity, and (ii) in Al–9Si–Sr ternary alloys, the presence of Sr has no significant effect on α-Al grain, but effectively modifies eutectic Si and significantly improves the thermal and electrical conductivity. On this basis, two theoretical calculation models [the Maxwell model and the Hashin–Shtrikman (H–S) model] were used to elucidate the relationship between solidification microstructure and thermal conductivity. Compared with the Maxwell model, the H–S model fits better with the measured values. The obtained results are very helpful to the precise composition control during alloy design and recycling of Al–Si-based alloys with the aim to further improve the thermal conductivity of Al–Si-based alloys. [ABSTRACT FROM AUTHOR]

With the extensive use of high-power electronic appliances, polymer-based thermal insulation composites with excellent thermal properties are utilized in the field of heat management with the aim of improving heat dissipation. Due to the high thermal conductivity and good electrical insulation, boron nitride (BN) is rendered as a superior candidate material for thermally conductive fillers. However, the thermal conduction of the composites is inevitably hampered by the interfacial resistance between BN and the polymer matrix. In this work, BN surface was modified by dopamine hydrochloride (PDA) and phenyltrimethoxysilane to enhance its interface compatibility with the polymer matrix. Meanwhile, by applying pressure to the composites during processing, BN grains inside the composite were well aligned to the direction parallel to the heat flow, thereby improving the through-plane thermal conductivity. When the filler content is fixed at 31 vol%, the thermal conductivity of the phenyl silicone rubber (PVMQ)-based composite prepared from modified BN (mark as M-BN/PVMQ) reaches 1.642 W/(m·K), nearly equal to nine times the value for the pure PVMQ matrix (0.18 W/(m·K)). Furthermore, in a nitrogen atmosphere, the initial decomposition temperature (T5%) reaches 512 °C, 172 °C higher than that of pure PVMQ (340 °C). The improved thermal stability of the composites prepared from modified BN resulted from the enhanced interfacial effect, which was analyzed by thermogravimetric infrared gas mass spectrometry system (TG-IR-GC/MS). The high thermal conductivity and stability enable the M-BN/PVMQ composite a promising material for thermal management. [ABSTRACT FROM AUTHOR]

Exfoliation of graphene nanoplatelets (GNP) in polymer melts is one of the key challenges when applying melt mixing for preparing polymer-based composite. And the GNP can be exfoliated better within the polymer matrix under the elongational flow field than under the shear flow field. Here, we design three extrusion dies with different convergent-divergent channels to explore the exfoliation mechanism of GNP in polymer melt under elongational flow. The flow field in the convergent-divergent channels is numerically simulated, and the results demonstrate that elongational flow plays a dominant role in the convergent-divergent channel when compared to shear flow. The exfoliation states of GNP in different channels are assessed by the thickness and interlayer space of GNP using analysis of scanning electron micrographs, transmission electron micrographs, and X-ray diagrams. And a significant enhancement (increased by 103%) in the in-plane thermal conductivity of PP (polypropylene)/GNP composites extruded by the designed convergent-divergent channel further demonstrates the GNP are exfoliated efficiently under the elongational flow. Furthermore, an exfoliation model is used to estimate the required stress and explore the exfoliation mechanism of GNP. And the exfoliation mechanism of GNP is associated with the applied stress and the angle between the applied stress and the normal direction of GNP. This work could provide experimental and theoretical guidance for the preparation of high-performance composite filled with layered nanosheets. [ABSTRACT FROM AUTHOR]

Spark plasma sintering (SPS) was a promising method for repairing refractory waste targets. In this study, Mo-10Nb powders and Mo-10Nb waste targets were joined at variable temperatures by SPS for 10 min. The effects of temperatures (1400–1650 °C) on the interfacial microstructure, thermal conductivity, and mechanical properties were studied. It was unveiled that more Nb dissolved into the Mo lattice as temperature raised and all interfaces were defect-free. The electron back-scattered diffraction images revealed that the grain size of the powder-sintered body at 1550 °C was close to the original waste target. Besides, "90°" junctions were formed on the interface at 1400 °C, part of "120°" configurations were formed at 1450–1500 °C, and the interface was fused at 1550–1650 °C. The evolution of the interface structure was related to the intrinsic diffusion coefficient (D ) of Mo-10Nb. The D calculated from SPS densification data verified that D increased with the increase in joining temperatures, which enhanced the atomic flux through the interface and facilitated the interface fusion. Additionally, the combination of effects (grain size and porosity) improved the thermal conductivity. Besides, the relative density and microhardness raised with increasing temperatures. The bending strength increased first and then declined at 1650 °C, and the failure position was also different. Based on the relevant analysis, it was determined that the optimum temperature for repairing the waste refractory Mo-10Nb target was 1550 °C. [ABSTRACT FROM AUTHOR]

Carbon fibers produced from mesophase pitch are superior in many properties such as high thermal conductivity and high tensile modulus, which originated from the high graphitizability and high carbon yield of the raw materials. Any variation in mesophase pitch microstructure will be inherited in derived carbon fibers. Herein, we monitored the microcrystal structure evolution of carbon fiber derived from thermal soaked mesophase pitch and the caused variation in mechanical properties. Results showed that mesophase pitch with prolonged soaking time from 1 to 12 h produced the carbon fibers with improved microcrystal structure, reduced diameter, and crack angle, contributing to an apparent increase in tensile strength from 1.70 to 2.72 GPa and tensile modulus from 152 to 246 GPa. Thermal soaking upon elevated temperature from 320 to 335 °C also contributes an improvement in microcrystalline development. However, the attendant increment in diameter and open crack angle lead to deterioration in tensile strength and modulus, the highest value of which is only 1.53 GPa and 190 GPa. This work provides useful information on thermal soaking parameter selection and is of particular interest for future optimization of carbon fiber production. [ABSTRACT FROM AUTHOR]

Silica ceramic nanofiber (SCNF) membranes with ultra-softness were fabricated by electrospinning and precursor derived ceramic technology. Firstly, the precursor fiber membrane was obtained by electrospinning from spinnable precursor sol, which was prepared by using silica sol as raw material and polyvinyl alcohol (PVA) as spinning aid, and after heat treatment, it was converted into the SCNF membrane composed of pure inorganic components, which had the ultra-softness to restore the original shape after arbitrary folding. Then the effects of different PVA dosages and heat treatment temperatures on the fiber morphology, thermal stability, mechanical properties, and thermal conductivity of SCNF membranes were investigated. Among all the membranes, the SCNF membrane that was made with a precursor sol of 5% PVA and sintered at 900 °C (Ss + PVA 5%-900 °C) showed the smoothest as well as the most uniform fiber morphology, with an average fiber diameter of 285.19 nm, a density of 0.106 g cm−3, the best mechanical properties (tensile strength of 4.145 MPa), and it also had the lowest thermal conductivity of 0.05285 Wm−1 K−1. The Ss + PVA 5%-900 °C SCNF membrane still maintained intact fiber morphology after being treated at 1200 °C. These excellent properties make the SCNF membrane have a potential application prospect as an insulation material in ultra-high temperature environments. [ABSTRACT FROM AUTHOR]

Novel materials with high thermal conductivity are urgently needed to solve the problem of thermal diffusion with the rapid development of science and technology. Experiments have been conducted to join polydopamine (PDA) with graphene (G) and carbon fibers (CF) using electrophoresis to form a G/PDA@CF material with ultrahigh thermal conductivity. The thermal conductivity has been improved by a factor of 6, which has ultrahigh thermally conductive properties. The composite doubled the tensile strength relative to the original material. Experiments were designed to test the thermal conductivity of G/PDA@CF. Scanning electron microscopy (SEM), X-ray diffraction pattern (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) analyses of the material were carried out to obtain the formation mechanism of G/PDA@CF. The SEM image shows that PDA and G formed a layered self-assembled structure on the CF surface. The XRD image shows the existence of G in G/PDA@CF. The XPS analysis obtained the bonding species between the G and PDA, CF and PDA. The phonon spectra were then calculated by microcanonical ensembles (NVE). The PDA has ultrahigh thermal conductivity due to the high overlap of its phonon spectrum with G, which leads to its high strength thermal conductivity of G/PDA@CF. G/PDA@CF material can be used for flexible screens, housings for wearable devices, and thermally conductive devices. [ABSTRACT FROM AUTHOR]

Thermal insulation composites are widely used in civil and military applications; however, it is difficult to achieve the synergy of multiple technical objectives such as lightweight, thermal insulation, high pressure resistance and high-temperature resistance by adopting traditional preparation techniques. In this study, a novel carbon-graphite thermal insulation material was rapidly prepared by exploiting the micro-thermal press additive manufacturing forming technology, and these multiple objectives were simultaneously achieved by introducing a large number of closed pores. It was found that the percentage of closed pores in the carbon-graphite insulation was increased by increasing the forming density or the amount of thermosetting phenolic resin added, but the thermal conductivity increased in parallel with the compressive strength, while the addition of pre-covered expandable graphite was able to achieve the synergy of high compressive strength and low thermal conductivity. When the content of thermosetting phenolic resin was 25 wt%, forming density was 1.2 g·cm−3, and expandable graphite was clad twice, the prepared carbon-graphite insulation exhibited a closed porosity/porosity ratio, compressive strength, and thermal conductivity of 48.92%, 16.432 MPa, and 0.743 W·m −1 K−1, which has the advantages of lightweight, high compressive strength, heat insulation and high-temperature resistance and has good prospects for industrial applications. [ABSTRACT FROM AUTHOR]

The development of materials with efficient heat dissipation capabilities and remarkable mechanical properties is essential for high-power integrated electronic devices and flexible smart devices. Herein, a flexible cellulose nanofibers (CNF)/nanodiamond (ND)/MXene (CNM) composite film with typical nacre-like structure is fabricated using a facile vacuum-assisted filtration approach. The composite film exhibits high thermal conductivity of 17.43 W m−1 K−1 at the thickness of 21 μm, which enhances 663% compared with CNF film. This is mainly due to the bridging effect of ND and the favorable orientation of MXene nanosheets. In addition, nacre-like structure and strong hydrogen bonding between MXene and CNF endow satisfactory mechanical properties (89.14 ± 3.61 MPa). Moreover, it is worth to note that the film exhibits improved electrical insulation (1.63 × 106 Ω cm) on account of the intervene of the insulating ND block the conductive path formed by MXene. Therefore, the CNM composite films provide a feasible choice of thermal management components for high-power flexible devices. [ABSTRACT FROM AUTHOR]

Currently, polymeric composites with good thermal conductivity and simple preparation method are in the rapid increment of demand. In this work, polypropylene/graphite/graphene films (PP/Gr/G-3, 8 layers) with high thermal conductivity were developed by a multi-folding and hot-pressing strategy. The PP/Gr/G-3 composite films exhibit highly in-plane thermal conductivity of 17.23 W m−1·K−1 (TCE = 99.19%, compared with the PP/Gr/G-0 films). This high thermal conductivity is mainly due to the well-oriented structure of fillers and tightly laminated microstructure in composite which are induced by the facile and scalable multi-folding method. Additionally, the PP/Gr/G-3 composite films demonstrate enhanced mechanical properties with the tensile strength of ~ 26.26 MPa and toughness of ~ 0.52 MJ m−3. The effective fabrication strategy proposed in this work could be valuable for improving the thermal management properties of polymeric composites. [ABSTRACT FROM AUTHOR]