Search

This study focuses on establishing and validating a method to accurately measure the in-plane thermal conductivity of very conductive thin films, such as single-crystal metals or semiconductors, 2D and nanostructured materials. By integrating both 2 ω and 3 ω measurements, the method is rendered insensitive to the superficial thermal boundary resistance of the insulating overlayer, enabling precise estimation of the in-plane thermal properties of conductive films grown on top of substrates or multilayer stacks. The proposed technique is applied to analyze the thermal conductivity of a silicon-on-insulator stack with a top layer consisting of a 340 nm thick film of monocrystalline silicon. Measurements are conducted within a temperature range spanning from 250 to 325 K. The results confirm the method's capability to correctly assess the thermal conductivity decrease of the silicon film compared to bulk value, demonstrating its reliability for the thermal characterization of conductive thin films. [ABSTRACT FROM AUTHOR]

As electronic devices continue to undergo miniaturization, the concomitant reduction in the size of semiconductor components presents significant challenges for thermal management at interfaces. Numerous studies have underscored graphene as an auspicious material for enhancing heat dissipation within integrated circuits, attributed primarily to its superior thermal conductivity. We have employed a molecular dynamics approach to examine the influence of various charge distributions on the thermal transport properties at the graphene–water interface. Specifically, this study explores how modifications in charge distribution at the interface impact thermal conductivity. The results show that comparing the interfacial graphene sheet modified with charge to the case without charge modification, the Kapitza resistance is significantly lower. In addition, the temperature difference at the graphene–water interface is smaller as the charge increases, and the thermal transport at the interface is easier. When the charge strengths of the modifications are the same, the thermal resistance of the diagonal distribution is smaller than that of the filled modification, and part of the reason for the ease of heat transport is due to the increase in interfacial mutual strength due to Coulomb forces. The other main reason is that when the charge reaches a certain strength (q = 0.8 e), an ordered water layer is created near the charge-modified graphene interface. Our study provides a method for designing solid–liquid interfacial heat transport properties by controlling and regulating the liquid stratification at the interface. [ABSTRACT FROM AUTHOR]

We study the effects of uniaxial pressure on the thermal conductivity between two nanoparticles using atomistic simulation. While the system is compressed, we analyze the evolution of contact area, the relative density, and the dislocation density. Lattice thermal conductivity is calculated by non-equilibrium molecular dynamics simulations at several stages of the compression. Despite the increment of dislocation defects, thermal conductivity increases with pressure due to the increase in relative density and contact radius. The behavior of the contact radius is compared with the Johnson–Kendall–Roberts (JKR) model. While there is good agreement at low strain, after significant plasticity, signaled by the emission of dislocations from the contact region, the discrepancy with JKR grows larger with the dislocation density. The results for thermal conductivity show good agreement with previous studies at zero strain, and a theoretical model is used to accurately explain its behavior vs strain-dependent contact radius. Both the Kapitza resistance and thermal resistance decrease with strain but with very different evolution. Simulations of a bulk sample under uniaxial strain were also carried out, allowing for a clear distinction between the role of compressive stress, which increases the conductivity, vs the role of dislocations, which decrease the conductivity. For the NP system, there is the additional role of contact area, which increases with stress and also modifies conductivity. An analytical model with a single free parameter allows for a description of all these effects and matches both our bulk and NP simulation results. [ABSTRACT FROM AUTHOR]

The document discusses the integration of machine learning (ML) into thermal transport research, highlighting its transformative impact on understanding and controlling heat transfer processes. It features 31 papers categorizing ML applications into machine learning potentials, predicting thermal properties, design and optimization, data analysis, and tutorials. ML has enabled accurate simulations, precise property predictions, innovative system designs, and efficient data analysis in thermal transport research, showcasing the potential for further advancements in the field. Despite challenges like model transferability, data scarcity, and interpretability, the document emphasizes the promising future of ML in advancing thermal science and engineering. [Extracted from the article]

Non-contact photothermal pump-probe methodologies such as Frequency-Domain Thermo-Reflectance (FDTR) systems facilitate the examination of thermal characteristics spanning semiconductor materials and their associated interfaces. We underscore the significance of meticulous measurements and precise error estimation attained through the analysis of both amplitude and phase data in Thermo-Reflectance (TR). The precision of the analytical estimation hinges greatly on the assumptions made before implementing the method and notably showcases a decrease in errors when both the amplitude and phase are incorporated as input parameters. We demonstrate that frequency-domain calculations can attain high precision in measurements, with error estimations in thermal conductivity (k), thermal boundary resistance (Rth), and thermal diffusivity (α) as low as approximately 2.4%, 2.5%, and 3.0%, respectively. At the outset, we evaluate the uncertainty arising from the existence of local minima when analyzing data acquired via FDTR, wherein both the phase and amplitude are concurrently utilized for the assessment of cross-plane thermal transport properties. Expanding upon data analysis techniques, particularly through advanced deep learning approaches, can significantly enhance the accuracy and precision of predictions when analyzing TR data across a spectrum of modulation frequencies. Deep learning models enhance the quality of fitting and improve the accuracy and precision of uncertainty estimation compared to traditional Monte Carlo simulations. This is achieved by providing suitable initial guesses for data fitting, thereby enhancing the overall performance of the analysis process. [ABSTRACT FROM AUTHOR]

A novel interfacial resistance-free (IRF) bifunctional camouflage (transparent and invisible) device is proposed in this paper. The thermal and electric conductivities of the shell and background are the same to eliminate the interfacial resistance. The IRF bifunctional camouflage device can operate in thermal–electric fields based on the neutral inclusion method. The distribution of isotherm and equipotential lines are studied quantitatively by the simulations. It is confirmed that the IRF bifunctional camouflage device with arbitrary natural materials can effectively achieve not only the invisible function but also the transparent function in thermal–electric fields. This method provides a window to the realization of bifunctions and the development of multi-physics fields. [ABSTRACT FROM AUTHOR]

Highlights: Copolymer of divinylphenyl-acryloyl chloride copolymers (PDVB-co-PACl) is designed and synthesized to graft on the surface of aluminum nitride (AlN) to improve its hydrolysis resistance. AlN fillers functionalized by PDVB-co-PACl with the molecular weight of 5100 g mol-1 exhibits the highest hydrolysis resistance and the lowest interfacial thermal resistance. When the mass fraction of AlN@PDVB-co-PACl is 75 wt% and the grafting density of PDVB-co-PACl is 0.8 wt%, the λ for AlN@PDVB-co-PACl/PMHS composites is 1.14 W m-1 K-1 and maintains 99.1% after soaking in 90 °C deionized water for 80 h. A series of divinylphenyl-acryloyl chloride copolymers (PDVB-co-PACl) is synthesized via atom transfer radical polymerization employing tert-butyl acrylate and divinylbenzene as monomers. PDVB-co-PACl is utilized to graft on the surface of spherical aluminum nitride (AlN) to prepare functionalized AlN (AlN@PDVB-co-PACl). Polymethylhydrosiloxane (PMHS) is then used as the matrix to prepare thermally conductive AlN@PDVB-co-PACl/PMHS composites with AlN@PDVB-co-PACl as fillers through blending and curing. The grafting of PDVB-co-PACl synchronously enhances the hydrolysis resistance of AlN and its interfacial compatibility with PMHS matrix. When the molecular weight of PDVB-co-PACl is 5100 g mol−1 and the grafting density is 0.8 wt%, the composites containing 75 wt% of AlN@PDVB-co-PACl exhibit the optimal comprehensive performance. The thermal conductivity (λ) of the composite is 1.14 W m−1 K−1, which enhances by 20% and 420% compared to the λ of simply physically blended AlN/PMHS composite and pure PMHS, respectively. Meanwhile, AlN@PDVB-co-PACl/PMHS composites display remarkable hydrothermal aging resistance by retaining 99.1% of its λ after soaking in 90 °C deionized water for 80 h, whereas the λ of the blended AlN/PMHS composites decreases sharply to 93.7%. [ABSTRACT FROM AUTHOR]

Graphite (GR) is a commonly used two-dimensional filler with abundant sources and low cost. Its excellent electrical conductivity makes it widely used to prepare various conductive materials. However, its utilization in anti-corrosion materials is hindered by its extremely high conductivity, which pose significant challenges in material application. Nevertheless, its two-dimensional laminate structure serves as an effective filler for anti-corrosion applications. If the insulation properties of graphite can be enhanced, it will significantly broaden its applications in anti-corrosion coatings. The hydrolysis and condensation of tetraethyl orthosilicate (TEOS) and γ-methacryloxy propyl trimethoxy silane (MPS) were used to modify GR to improve its insulation. Additionally, this modification improved the compatibility between the filler and resin, reducing interfacial thermal resistance and thereby enhancing the thermal conductivity of the coating. The modified GR filler (SiO@GR) was added to epoxy resin (EPR) to prepare the composite coating (SiO@GR/EPR). When the SiO@GR content is 18 wt%, thermal conductivity can reach 0.67 W m−1K−1, and after soaking in 3.5 wt% NaCl solution for 7 days, the impedance modulus remains above 1.06 × 1011 Ω cm2. The synergistic effect of the physical barrier provided by two-dimensional fillers and the capacity enhancement of siloxane is thoroughly examined in relation to heat conduction and anticorrosive mechanisms. This study provides a simple approach to fabricating composite coatings with anti-corrosion and thermal conductivity performances. [ABSTRACT FROM AUTHOR]

With the miniaturization of electronic devices, thermal management has become a critical challenge, especially for high-power systems where efficient heat dissipation is essential. Polycrystalline diamond films, renowned for their exceptional thermal conductivity, offer a promising solution. However, the thermal boundary resistance (TBR) at the diamond/substrate interface remains a significant bottleneck, severely impacting heat dissipation efficiency. This study presents a measurement approach tailored for quantifying TBR in thick-film diamond heterostructures, focusing on diamond-on-silicon (Diamond-on-Si) systems with a silicon nitride barrier layer. Compared to conventional methods, such as transient thermoreflectance techniques, which often exhibit limited sensitivity for thick layers, this approach demonstrates greater reliability and applicability. The findings establish a foundation for advancing strategies to reduce TBR and improve the thermal management performance of diamond films in high-power electronic applications. [ABSTRACT FROM AUTHOR]

The physical/chemical properties undergo significant transformations in the different states arising from phase transition. However, due to the lack of a dynamic perspective, transitional mesophases are largely underexamined, constrained by the high resource burden of first principles. Here, using molecular dynamics (MD) simulations empowered by the machine-learning potential, we proffer an innovative paradigm for phase transition: regulating the thermal transport properties via the transitional mesophase triggered by a uniaxial force field. We investigate the mechanical, electrical, and thermal transport properties of the two-dimensional carbon allotrope of Janus-graphene with strain-engineered phase transition. Notably, we found that the transitional mesophase significantly suppresses the thermal conductivity and induces strong anisotropy near the phase transition point. Through machine-learning-driven MD simulations, we achieved high-precision atomic-level simulations of Janus-graphene. The results show that thermal vibration-induced intermediate amorphous or interfacial phases induce strong and anisotropic interfacial thermal resistance. The investigation not only endows us with a novel perspective on mesophases during phase transitions but also enhances our holistic comprehension of the evolution of material properties. [ABSTRACT FROM AUTHOR]

This paper provides a detailed examination of the anisotropic thermal conductivity of a two-phase layered composite material with an imperfect interface. The development of a closed-form solution focuses on using the variational asymptotic method (VAM). Highlighting the one-dimensional periodicity of the unit cell, the study includes reduced thermal conduction at the imperfect interface between the two layers of a laminate. In addition to the VAM approach, the research introduces the finite element method (FEM) for the one-dimensional periodicity of the unit cell, for the reduced thermal conduction at the imperfect interface. Validation of both the derived VAM-based closed-form analytical solutions and the FEM solutions, under identical imperfect interface conditions, has been conducted by comparing the results with those present in the literature. The results show satisfactory agreement. Furthermore, the VAM-based analytical solution is extended to unidirectional composites with similar imperfect interface conditions, predicting effective thermal conductivity. These predictions are validated against various literature models, showing significant agreement, especially with lower-bound models. As a practical application, the closed-form solution derived from VAM is used to investigate the influence of an imperfect interface on thermal conduction with changes in volume fraction, providing valuable insights for practical applications. [ABSTRACT FROM AUTHOR]

In this research, we have studied a self-heating effect in hybrid 2D-3D heterostructure diode, considering planar GaN-based structure of 1280 nm with n-type channel and donor concentration of 6·1017 cm-3. Two type c-plane substrate-based sapphire and GaN are considered in order to investigate heating effects in diode channel. Monolayer hexagonal boron nitride (h-BN) on the top of canal is considered as an element for thermal control of the diode. The model of a heating based on macroscopic thermal parameters of materials is used. The simulation of diode operation was carried out using the Ensemble Monte Carlo Technique selfconsistently with numerical solving of system of heat equations by full multigrid (FMG) method. Transport properties of diode is considered under condition of high electric fields and impact ionization. Characteristics of the diode with both h-BN monolayer and without one were obtained at DC applied voltage. A temperature distribution in diode is obtained with account of thermal boundary resistance at each interface, considering voltage range of 0-20 V. In strong electric field in anode, the heating rises maximal temperature in channel diode up to over 600 K. The h-BN was found to affect the temperature magnitudes and their redistribution in diode channel. Temperature decrease can achieve 3 % and increase in case of high temperature region. Role h-BN monolayer as a factor avoiding formation of localized overheating of a device is demonstrated. It is shown that, h-BN monolayer is effective in diode using the substrate with low thermal conductivity and can be applied for semiconductor devices with length of several micrometers. [ABSTRACT FROM AUTHOR]

The miniaturization, integration, and high data throughput of electronic chips present challenging demands on thermal management, especially concerning heat dissipation at interfaces, which is a fundamental scientific question as well as an engineering problem—a heat death problem called in semiconductor industry. A comprehensive examination of interfacial thermal resistance has been given from physics perspective in 2022 in Review of Modern Physics. Here, we provide a detailed overview from a materials perspective, focusing on the optimization of structure and compositions of thermal interface materials (TIMs) and the interact/contact with heat source and heat sink. First, we discuss the impact of thermal conductivity, bond line thickness, and contact resistance on the thermal resistance of TIMs. Second, it is pointed out that there are two major routes to improve heat transfer through the interface. One is to reduce the TIM's thermal resistance (RTIM) of the TIMs through strategies like incorporating thermal conductive fillers, enhancing interfacial structure and treatment techniques. The other is to reduce the contact thermal resistance (Rc) by improving effective interface contact, strengthening bonding, and utilizing mass gradient TIMs to alleviate vibrational mismatch between TIM and heat source/sink. Finally, such challenges as the fundamental theories, potential developments in sustainable TIMs, and the application of AI in TIMs design are also explored. [ABSTRACT FROM AUTHOR]

The continuous miniaturization and multi-function of electronic devices have put forward high requirements for the effective removal of the heat generated in the system. Developing thermally conductive polymer composite-based thermal interface materials is becoming the research hotspot. In addition to the usually concerned intrinsic thermal conductivity of the filler itself, surface modification is one of the important ways to form an effective heat conduction pathway and improve the overall thermal conductivity of materials. In this work, we used silicon rubber as the polymer matrix and achieved the thermal conductivity increment via various fillers with different shapes. The adopted fillers are spherical aluminum oxide (Al2O3), linear carbon fiber and boron nitride sheets, which can be considered as zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D) fillers respectively. We also prepared the silver-modified fillers and investigated the influence on the formation of heat conduction pathways and interfacial thermal resistance of different shaped fillers. An obvious increment in thermal conductivity of the composite with silver-modified fillers was observed compared to the composite with pristine fillers. Furthermore, through the practical thermal management performance investigation, we found the thermal conductivity increment did improve the actual heat transfer performance of composite elastomers functioning as thermal interface materials [ABSTRACT FROM AUTHOR]

Highlights Silicon carbide (SiC)/shape‐memory polyurethane (SMPU) soft robots possess programmable shapes and dual‐drive capabilities based on electrical and thermal methods. Enhancing the thermal conductivity (TC) of these composite materials effectively enhances the driving performance of the soft robots. In this study, we tune the interfacial thickness between SiC particles and the SMPU polymer matrix to regulate the TC of the composites. The optimized composite exhibits a 244% increase in the in‐plane TC and 153% increase in the out‐of‐plane TC. Furthermore, optimization significantly enhances the speed and efficiency of the soft robots. This study reveals that interfacial thickness is a key factor in regulating interfacial heat transfer, potentially introducing a new approach for reducing interfacial thermal resistance in composite materials. This study contributes to a deeper understanding of interfacial heat‐ transfer mechanisms and establishes a new theoretical framework for designing and fabricating advanced composite materials for soft robots. Interfacial heat‐ transfer mechanism was revealed. Interfacial thickness primarily controls interfacial heat transfer. The in‐plane and out‐of‐plane thermal conductivities of prepared composites were enhanced by 244% and 153%, respectively, by modifying the interfacial thickness. The multifunctional performance of the composites was improved due to microscale mechanisms. [ABSTRACT FROM AUTHOR]

Thermal transport properties for the isotropic and anisotropic characterization of nanolayers have been a significant gap in the research over the last decade. Multiple studies have been close to determining the thermal conductivity, diffusivity, and boundary resistance between the layers. The methods detailed in this work involve non-contact frequency domain pump-probe thermoreflectance (FDTR) and photothermal radiometry (PTR) methods for the ultraprecise determination of in-plane and cross-plane thermal transport properties. The motivation of one of the works is the advantage of the use of amplitude (TR signal) as one of the input parameters along with the phase for the determination of thermal parameters. In this article, we present a unique strategy for measuring the thermal transport parameters of thin films, including cross-plane thermal diffusivity, in-plane thermal conductivity, and thermal boundary resistance as a comprehensively reviewed article. The results obtained for organic and inorganic thin films are presented. Precise ranges for the thermal conductivity can be across confidence intervals for material measurements between 0.5 and 60 W/m-K for multiple nanolayers. The presented strategy is based on frequency-resolved methods, which, in contrast to time-resolved methods, make it possible to measure volumetric-specific heat. It is worth adding that the presented strategy allows for accurate (the signal in both methods depends on cross-plane thermal conductivity and thermal boundary resistance) and precise measurement. [ABSTRACT FROM AUTHOR]

With the rapid miniaturization and high degree of integration of modern electronic devices, there is an increasing demand for high-performance polymer-based thermal management materials. SiC nanowires (SiCNWs) are very promising fillers benefiting from their large aspect ratio and ease of constructing thermally conductive networks. However, the traditional random mixing method allows the SiCNWs to form a thermally conductive network only through physical overlap, resulting in a high interfacial thermal resistance. To address this problem, an innovative strategy for in-situ generating continuous network composed of SiCNWs was proposed in this study, in which the SiCNWs was formed through impregnation-sintering process using an inexpensive polyurethane (PU) sponge as a template. The porous skeletons were sintered by numerous SiCNWs, which not only conferred more thermally conductive pathways, but also solved the problem of weak bonding at the SiCNWs random lap interface. On this basis, the SiC skeletons were further used as reinforcement to prepare epoxy (EP)-based composites. Benefiting from the continuous thermally conductive networks composed of SiCNWs, the composites achieved a thermal conductivity (TC) of ∼1.17 W m−1 K−1 at a low volume fraction of 21.18 vol%, which was 548.7 % higher than that of pure EP. In addition, the unique SiCNWs skeletons also facilitated the enhancement of mechanical properties and thermal stability of the composites, providing new insight for the preparation of innovative thermal management materials. [ABSTRACT FROM AUTHOR]

Prefabricated vertical drains combined with heating is a new approach to improving the mechanical properties of soft clay foundations. Rising temperatures cause the formation of concentric and radially aligned soil regions with distinct heterogeneous characteristics. This results in incomplete contact between adjacent soil layers, with the water in the interstices impeding heat transfer and manifesting as a thermal resistance effect. Based on the theory of thermo-hydro-mechanical coupling, a two-dimensional dual-zone axisymmetric marine soft soil model improved by a prefabricated vertical thermo-drain has been established. A generalized incomplete thermal contact model has been proposed to describe the thermal resistance effect at the interface of concentric soil regions. The effectiveness of the numerical solution presented in this paper is verified by comparison with semi-analytical solutions and model experiments. The thermal consolidation characteristics of concentric regions of soil at various depths under different thermal contact models were discussed by comprehensively analyzing the effects of different parameters under various thermal contact models. The outcomes indicate that the generalized incomplete thermal contact model provides a more accurate description of the radial thermal consolidation characteristics of concentric regions of soil. The influence of the thermal conductivity coefficient on the consolidation characteristics of the concentric regions soil is related to the thermal resistance effect. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of this study is to further enhance the thermal storage and heat transfer performances of a low-melting-point quinary salt. The eutectic salt was prepared using LiNO3, NaNO3, KNO3, NaNO2, and KNO2 as raw materials, followed by the doping of nano-SiO2 and nano-MgO into the base salt using a microwave-assisted method. The thermal properties of the samples were analyzed using a Synchronous Thermal Analyzer and a Laser Flash Apparatus. The co-doping of two types of nanoparticles was found to significantly enhance the specific heat capacity of the base salt. The maximum specific heat reached 2.36 J/(g·K), showing a 50.4% increase compared to the base salt. The thermal conductivity of molten salts can be affected by nanoparticles. An observed sample demonstrated a thermal diffusivity of 0.286 mm2/s, indicating a 19.2% improvement over the base salt, which may be attributed to enhanced phonon thermal efficiency. In addition, this study revealed that while interfacial thermal resistance can enhance specific heat capacity, it can also lead to a decrease in the thermal conductivity efficiency of materials. This work can offer insights and references for the enhancement of molten salt properties. [ABSTRACT FROM AUTHOR]

The author has proposed a simple model to determine the effective thermal conductivity variance in nanomaterials with respect to size under Kapitza thermal resistance effect. The formulation is based on the relation of thermal conductivity with specific heat, sound velocity and mean free path in nanosolids. Using the Jiang's qualitative approach for melting temperature variation in nanomaterials with dimension and size;the thermal conductivity expression for nanosolids is formulated. Effective thermal conductivity of nanosolid is determined on the basis of effective medium approach. The results obtained from formulation depicts the increase in Effective thermal conductivity of nanomaterial with increase in its size. The present model results are seen in good consistency with the available data of previous workers and matches the variation trend as predicted previously. The exponential drop in thermal conductivity of nanomaterials with their size reduction to nanoscale make them efficient material to be use in thermoelectric devices because of their high figure of merit. [ABSTRACT FROM AUTHOR]

The increasing demand for effective thermal management has led to a growing need for composite coatings with high thermal conductivity (TC). In this work, we developed a novel approach to enhance the TC of polymer coatings by incorporating hybrid fillers composed of hexagonal boron nitride (h-BN) and graphitic carbon (GC). The process involved the creation of hybrid fibers through wet spinning, combining biomass polysaccharide sodium alginate with bulk h-BN, followed by controlled carbonization at varying temperatures. During carbonization, the in-situ generation of small-molecule compounds facilitated the preparation of BN nanosheets and the formation of a unique BN and graphitic carbon (BN-GC) preassembled heterostructure. By adjusting the carbonization temperature, the degree of graphitization was controlled in the hybrid fillers. Subsequently, these hybrid fillers were blended with a polymer matrix to create photocurable coatings. Leveraging the intrinsic high thermal conductivity of BN nanosheets and the low interfacial thermal resistance between BN and GC, our composite coatings demonstrated a remarkable enhancement in TC. Notably, with a filler content of 20 wt%, the resulting composite coating exhibited an impressive in-plane and out-of-plane TC of up to 2.34 and 0.41 W/(m K), respectively. This innovative approach holds significant promise for improving the thermal performance of polymer coatings in various applications. [ABSTRACT FROM AUTHOR]

Solid heterostructures composed of substrates and epitaxial films are extensively used in advanced technologies, and their thermophysical properties fundamentally determine the performance, efficiency, and reliability of the corresponding devices. However, an experimental method that is truly appropriate for the thermophysical property measurement of solid heterostructures is still lacking. To this end, a three-sensor 3ω-2ω method is proposed, which can simultaneously measure the thermal conductivities of the film and the substrate, along with the film-substrate thermal boundary resistance (TBR) in a single solid heterostructure without any reference samples, showing broad applicability for miscellaneous heterostructures with film thickness ranging from 100 nm to 10 μm. In this method, three parallel metal sensors with unequal widths and distances conforming to guidelines for the three-sensor layout design are fabricated on the sample surface, in which the two outer sensors serve as heaters and the middle sensor as a detector. The respective 3ω signals of the two heaters and the 2ω signal of the detector are measured, and then the thermophysical properties of the sample are fitted within 3D finite element simulations. To verify this method, two typical wide bandgap semiconductor heterojunctions, i.e., GaN on SiC (#SiC) and GaN on Si (#Si) with ∼2.3 μm GaN epilayers, are measured. The thermal conductivity of the GaN film, the thermal conductivities of the SiC and Si substrates, and the GaN/substrate TBRs are derived, exhibiting good agreement with the literature. The proposed method will provide a comprehensive solution for the thermophysical property measurements of various solid heterostructures. [ABSTRACT FROM AUTHOR]

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

With the continuous development of high‐end electronic information technologies such as 5G communications, thermal management is an urgent issue in the electronic and circuit industries due to the miniaturization, functionalization and integration. Recently, polymer‐based composites with the fillers of hexagonal boron nitride (h‐BN) have been regarded as promising candidates resulting from their excellent thermal conductivity (TC), good insulation and remarkable comprehensive properties. However, the high surface inertness of h‐BN itself, incompatibility with matrix and other fillers and mismatch of phonon‐spectrum will bring about the matrix/filler and filler/filler interfacial thermal resistance (ITR), which will greatly decline the TC of the composites, and limit their thermal management ability. Therefore, how to design, regulate and improve the interfacial states in composites and eventually enhance the TC is a current challenge. Researchers have made great effort to reduce the ITR of the composites to improve their TC. However, a comprehensive summary and analysis of researches on the improvement methods of the interface states in composites in the past 3 years is still lacking. In this work, the commonly used mechanism models, and simulation methods for calculating and predicting TC was summarized. From perspectives of Synthesis of h‐BNNs, modification, orientation, bridging and three‐dimensional structures construction, we reviewed strategies for improving the interface states in composites, and focused on the ITR regulation and TC improvement. The improvement effects of various methods on TC were compared. The development trend of high TC composite materials was prospected. Highlights: Crystallinity, defect, size, flatness, thickness of hexagonal boron nitride nanosheets (BNNSs) affect interfacial thermal resistance (ITR).Nature of interaction between adjacent layers of BNNS need exploited.Interface and defect are root cause of extra phonon scattering.Shape, density, surface area, distribution and compatibility reduce ITR.Theory, model, simulation methods need developed on different levels. [ABSTRACT FROM AUTHOR]

As microelectronics technology advances towards miniaturization and higher integration, the imperative for developing high-performance thermal management materials has escalated. Thermal conductive polymer composites (TCPCs), which leverage the benefits of polymer matrices and the unique effects of nano-enhancers, are gaining focus as solutions to overheating due to their low density, ease of processing, and cost-effectiveness. However, these materials often face challenges such as thermal conductivities that are lower than expected, limiting their application in high-performance electronic devices. Despite these issues, TCPCs continue to demonstrate broad potential across various industrial sectors. This review comprehensively presents the progress in this field, detailing the mechanisms of thermal conductivity (TC) in these composites and discussing factors that influence thermal performance, such as the intrinsic properties of polymers, interfacial thermal resistance, and the thermal properties of fillers. Additionally, it categorizes and summarizes methods to enhance the TC of polymer composites. The review also highlights the applications of these materials in emerging areas such as flexible electronic devices, personal thermal management, and aerospace. Ultimately, by analyzing current challenges and opportunities, this review provides clear directions for future research and development. [ABSTRACT FROM AUTHOR]

The author has formulated a qualitative method to determine the effective thermal conductivity variation in nanomaterials with respect to their dimension and size. The model includes the impact of shape, size, dimension and increased phonon scattering in nanomaterial due to the thermal resistance. In the present work, Guisbier’s top-down approach is used to obtain the thermal conductivity expression in terms of size and shape factor. The effective thermal conductivity of the nanomaterial is deduced using the effective medium approach that help to find the thermal conductivity in nanomaterial based on Kapitza thermal resistance effect. The model approach predicts the increment in the thermal conductivity of nanomaterial with size increment. The Kapitza thermal resistance in nanosolids results in increase in Phonon scattering in nanosolids with size reduction to nanoregime. The effective thermal conductivity is determined in AlN, GaN, GaAs, InAs and ZnO semiconducting compounds with respect to size in spherical and tetrahedral nanoparticles; cylindrical and parallelopiped nanowires and nanofilms. The model results obtained are compared with available experimental and simulated data. Good consistency between the compared results is observed in graphical representations. The model shows a drastic drop in effective thermal conductivity in nanosolids with their size reduction that increases the figure of merit in nanomaterials for using them in thermoelectric devices. [ABSTRACT FROM AUTHOR]

With the rapid development of high-power-density electronic devices, interface thermal resistance has become a critical barrier for effective heat management in high-performance electronic products. Therefore, there is an urgent demand for advanced thermal interface materials (TIMs) with high cross-plane thermal conductivity and excellent compressibility to withstand increasingly complex operating conditions. To achieve this aim, a promising strategy involves vertically arranging highly thermoconductive graphene on polymers. However, with the currently available methods, achieving a balance between low interfacial thermal resistance, bidirectional high thermal conductivity, and large-scale production is challenging. Herein, we prepared a graphene framework with continuous filler structures in in-plane and cross-plane directions by bonding corrugated graphene to planar graphene paper. The interface interaction between the graphene paper framework and polymer matrix was enhanced via surface functionalization to reduce the interface thermal resistance. The resulting three-dimensional thermal framework endows the polymer composite material with a cross-plane thermal conductivity of 14.4 W·m−1·K−1 and in-plane thermal conductivity of 130 W·m−1·K−1 when the thermal filler loading is 10.1 wt%, with a thermal conductivity enhancement per 1 wt% filler loading of 831%, outperforming various graphene structures as fillers. Given its high thermal conductivity, low contact thermal resistance, and low compressive modulus, the developed highly thermoconductive composite material demonstrates superior performance in TIM testing compared with TFLEX-700, an advanced commercial TIM, effectively solving the interfacial heat transfer issues in electronic systems. This novel filler structure framework also provides a solution for achieving a balance between efficient thermal management and ease of processing. [ABSTRACT FROM AUTHOR]

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

Composite materials and structural optimization are important research topics in heat transfer enhancement. The current evaluation parameter for the conductive heat transfer capability of composites is effective thermal conductivity (ETC); however, this parameter has not been studied or analyzed for its applicability to different heat transfer models and composite structures. In addition, the optimized composite structures of a specific object will vary when different optimization methods and criteria are employed. Therefore, it is necessary to investigate a suitable method and parameter for evaluating the heat transfer capability of optimized composites under different heat transfer models. Therefore, this study analyzes and summarizes three typical conductive heat transfer models: surface-to-surface (S-to-S), volume-to-surface (V-to-S), and volume-to-volume (V-to-V) models. The equivalent thermal conductivity ( k eq ) is proposed to evaluate the conductive heat transfer capability of topology-optimized composite structures under the three models. A validated simulation method is used to obtain the key parameters for calculating k eq . The influences of the interfacial thermal resistance and size effect on k eq are considered. The results show that the composite structure optimized for the V-to-S and V-to-V models has a k eq value of only 79.4 W m−1 K−1 under the S-to-S model. However, the k eq values are 233.4 W m−1 K−1 and 240.3 W m−1 K−1 under the V-to-S and V-to-V models, respectively, which are approximately 41% greater than those of the in-parallel structure. It can be demonstrated that k eq is more suitable than the ETC for evaluating the V-to-S and V-to-V heat transfer capabilities of composite structures. The proposed k eq can serve as a characteristic parameter that is beneficial for heat transfer analysis and composite structural optimization. [ABSTRACT FROM AUTHOR]

Developing flexible thermal management materials is quite urgent for emerging flexible electronics and wearable devices. Here, a novel strategy is used to prepare hydroxyl-functionalized boron nitride@polyurethane (BNOH@PU) composites with desired BN orientation in the in-plane direction through the foaming process of PU and hot-pressing. BNOH flakes can react with isocyanates to form amido linkages, which is beneficial for reducing interfacial thermal resistance (ITR) between BNOH and PU. In addition, BNOH flakes will be rearranged along the direction of PU backbones through the volume compression of the foaming process and trend to be oriented in the in-plane direction after hot-pressing. The out-of-plane or in-plane thermal conductivities of the composites are 1.69 and 3.19 W m−1 K−1 at 30 wt% BNOH content, and the corresponding thermal conductivity enhancement (TCE) is 1986% and 3838%, respectively. Meanwhile, BNOH@PU exhibited low ITR between BNOH flakes (1.252 × 10−7 K m2/W), good flexibility and stretchability, which was a promising thermal management material for wearable devices. The interfacial thermal resistance (ITR) and the phonon scattering between fillers and polymer matrix could be reduced significantly via the hydroxyl functionalization of BN. In-plane thermal conductivity enhanced BNOH@PU composites with desired BN orientation in the in-plane direction through the foaming process of PU and hot-pressing. [ABSTRACT FROM AUTHOR]

Highlights: A composite thermal interface material with three-dimensional hybrid carbon network-reinforced polydimethylsiloxane was proposed. The cooperative regulation of thermal conductivity and mechanical properties was achieved by controlling the assembly process of micro-nano scale unit carbon materials. The orthotropic continuous carbon structure endowed the composites with in-plane and out-of-plane thermal conductivities of up to 113.61 and 24.37 W m−1 K−1, respectively. The excellent compressibility and adhesion properties cooperatively improved the effective thermal conductivity by more than an order of magnitude. Vertically oriented carbon structures constructed from low-dimensional carbon materials are ideal frameworks for high-performance thermal interface materials (TIMs). However, improving the interfacial heat-transfer efficiency of vertically oriented carbon structures is a challenging task. Herein, an orthotropic three-dimensional (3D) hybrid carbon network (VSCG) is fabricated by depositing vertically aligned carbon nanotubes (VACNTs) on the surface of a horizontally oriented graphene film (HOGF). The interfacial interaction between the VACNTs and HOGF is then optimized through an annealing strategy. After regulating the orientation structure of the VACNTs and filling the VSCG with polydimethylsiloxane (PDMS), VSCG/PDMS composites with excellent 3D thermal conductive properties are obtained. The highest in-plane and through-plane thermal conductivities of the composites are 113.61 and 24.37 W m−1 K−1, respectively. The high contact area of HOGF and good compressibility of VACNTs imbue the VSCG/PDMS composite with low thermal resistance. In addition, the interfacial heat-transfer efficiency of VSCG/PDMS composite in the TIM performance was improved by 71.3% compared to that of a state-of-the-art thermal pad. This new structural design can potentially realize high-performance TIMs that meet the need for high thermal conductivity and low contact thermal resistance in interfacial heat-transfer processes. [ABSTRACT FROM AUTHOR]

A novel DC-assisted fast hot-pressing (FHP) powder sintering technique was utilized to prepare Al/Diamond composites. Three series of orthogonal experiments were designed and conducted to explore the effects of sintering temperature, sintering pressure, and holding time on the thermal conductivity (TC) and sintering mechanism of an Al-50Diamond composite. Improper sintering temperatures dramatically degraded the TC, as relatively low temperatures (≤520 °C) led to the retention of a large number of pores, while higher temperatures (≥600 °C) caused unavoidable debonding cracks. Excessive pressure (≥100 MPa) induced lattice distortion and the accumulation of dislocations, whereas a prolonged holding time (≥20 min) would most likely cause the Al phase to aggregate into clusters due to surface tension. The optimal process parameters for the preparation of Al-50diamond composites by the FHP method were 560 °C-80 MPa-10 min, corresponding to a density and TC of 3.09 g cm−3 and 527.8 W m−1 K−1, respectively. Structural defects such as pores, dislocations, debonding cracks, and agglomerations within the composite strongly enhance the interfacial thermal resistance (ITR), thereby deteriorating TC performance. Considering the ITR of the binary solid-phase composite, the Hasselman–Johnson model can more accurately predict the TC of Al-50diamond composites for FHP technology under an optimal process with a 3.4% error rate (509.6 W m−1 K−1 to 527.8 W m−1 K−1). The theoretical thermal conductivity of the binary composites estimated by data modeling (Hasselman–Johnson Model, etc.) matches well with the actual thermal conductivity of the sintered samples using the FHP method. [ABSTRACT FROM AUTHOR]

Because of their excellent insulation performance and processing properties, polymers are widely used in electrical and electronic applications. However, their further applications are severely constrained by their extremely low intrinsic thermal conductivity. Boron nitride (BN), which has high thermal conductivity and ideal insulation properties, is commonly used as a filler for improving the thermal conductivity of polymers. However, the high chemical inertia of the surface of BN makes it difficult to achieve an interconnection of BN sheets when building a three-dimensional (3D) BN skeleton in a polymer. In this study, urea melt pore preparation (UMPP) was used to fabricate a 3D BN skeleton. Urea was infiltrated into the BN skeleton to minimize the interfacial thermal resistance among the BN flakes and to join BNs. When the volume of a BN is 10 %, the thermal conductivity of the BN/epoxy composites is 3.15 W/(m·K). When the BN volume is 80 %, the thermal conductivity of BN/epoxy can reach 13.65 W/(m·K), which is 6500 % of pure epoxy resin. Additionally, the skeleton exhibits a remarkable mechanical strength capable of supporting weights up to 50,000 times its own, which facilitates easier handling and operation. The electrical resistivity volume of the UMPP composite is as high as that of the pure epoxy, whereas the dielectric loss is lower than that of pure epoxy. This study provides a new method for reducing internal interface thermal resistance of a skeleton formed by thermal conductive fillers with high chemical inertia such as boron nitride. [ABSTRACT FROM AUTHOR]

[AMIm]Cl@GNP/SBR composites were prepared by blending ionic liquid 1‐allyl‐3‐methylimidazolium chloride salt([AMIm]Cl) modified graphene nanoplatelets (GNP) and styrene‐butadiene rubber (SBR). The mechanical and thermal properties as well as the structure–activity relationship of the obtained composites based on the modified filler were investigated under the synergistic effect of non‐covalent and covalent bonding. The experimental results indicated that the modification of GNP by [AMIm]Cl occurred under mild conditions. The dispersibility of [AMIm]Cl@GNP in SBR was enhanced by its participation in vulcanization and the synergistic effect of non‐covalent and covalent cross‐linking networks such as cation‐π, π‐π, and hydrogen bonds. This improvement led to an increase in the interfacial bond strength of the composites and a reduction in the interfacial thermal resistance. These effects resulted in both reinforcement and thermal conductivity properties. The tensile strength and elongation at break of [AMIm]Cl@GNP/SBR composites increased from 18.2 to 22.9 MPa and from 737.9% to 923.5%, respectively, when the modification ratio of [AMIm]Cl was 1% and the loading of [AMIm]Cl@GNP was only 4 phr (mass ratio). At the same time, the thermal conductivity in the vertical direction of the composites increased from 0.25 to 0.44 W/(m·K), and the thermal conductivity in the horizontal direction increased from 0.27 to 0.81 W/(m·K). Highlights: Modified powder [AMIm]Cl@graphene nanoplatelets were prepared;[AMIm]Cl@graphene nanoplatelet/styrene‐butadiene rubber blend was prepared;Mechanical properties of blends significantly improved over blank;The horizontal thermal conductivity of the blends increases obviously;The vertical thermal conductivity of the blends was improved. [ABSTRACT FROM AUTHOR]

The effective thermal characteristics of composite materials used in the theory of solid-state cooling are studied. Two classes of composites are considered: layered structures consisting of a large number of nano-sized layers and two-phase granular composites. It is assumed that the interfaces between media are imperfect. The Kapitza temperature jump occurs at the interfaces. The effective characteristics of layered structures are obtained using the matrix homogenization method. The homogenization of the characteristics of granular composites is based on the Bruggeman approach. Formulas taking into account the influence of the interlayer Kapitza resistance on the homogenized thermal characteristics of the structure are obtained. Expressions for average values of heat sources are derived. [ABSTRACT FROM AUTHOR]

The escalating thermal power density in electronic devices necessitates advanced thermal management technologies. Polymer-based materials, prized for their electrical insulation, flexibility, light weight, and strength, are extensively used in this field. However, the inherent low thermal conductivity of polymers requires enhancement for effective heat dissipation. This work proposes a novel paradigm, emphasizing ordered structures with functional units, to create triple-level, ordered, low-filler loading of multi-walled carbon nanotube (MWCNT)/poly(vinyl alcohol)(PVA) nanofibrous films. By addressing interfacial thermal resistance through –OH groups, the coupling between polymer and MWCNT is strengthened. The triple-level ordered structure comprises aligned PVA chains, aligned MWCNTs, and aligned MWCNT/PVA composite fibers. Focusing on the filler's impact on thermal conductivity and chain orientation, the thermal transport mechanisms have been elucidated level by level. Our MWCNT/PVA composite, with lower filler loadings (10 wt.%), achieves a remarkable TC exceeding 35.4 W/(m·K), surpassing other PVA composites with filler loading below 50 wt.%. [ABSTRACT FROM AUTHOR]

Surface modification of a crystalline filler is a powerful method for increasing the thermal conductivity (κ) of filler-impregnated composites. Herein, boron nitride (BN) filler was functionalized with cationic molecules of different sizes to directly recognize the effect of an amorphous area on the filler-polymer matrix interface. Measured thermal conductivity and temperature rise for a polymer composite was up to 67.1 % and 15.3 % greater, respectively, in the sample to which the smallest molecule-modified BN was added, compared to the comparable sample with free BN. The smaller the size of the modifier molecule, the better it bonds with the resin and the smaller the non-crystalline area. Such changes improve the heat transfer at the interface by reducing interfacial thermal resistance. These findings can serve as a reference to develop alternative and effective strategies for filler modification, an alternative approach instead of focusing on functional groups and modifiers. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) reinforced polymer nanocomposites with high thermal conductivity show a promising prospect in thermal management of next‐generation electronic devices due to their excellent mechanical adaptability, outstanding processability, and superior flexibility. However, interfacial thermal resistance between individual CNT significantly hinders the further improvement in thermal conductivity of CNT‐reinforced nanocomposites. Herein, an interfacial welding strategy is reported to construct graphitic structure welded CNT (GS‐w‐CNT) networks. Notably, the obtained GS‐w‐CNT/polydimethylsiloxane (PDMS) nanocomposite with a GS loading of 4.75 wt% preserves a high thermal conductivity of 5.58 W m−1 K−1 with a 410% enhancement as compared to a pure CNT/PDMS nanocomposite. Molecular dynamics simulations are utilized to elucidate the effect of interfacial welding on the heat transfer behavior, revealing that the GS welding degree plays an important role in reducing both phonon scattering in the GS‐w‐CNT structure and interfacial thermal resistance at the interfaces between CNT. The unique welding strategy provides a new route to optimize the thermal transport performance in filler reinforced polymer nanocomposites, promoting their applications in next‐generation microelectronic devices. [ABSTRACT FROM AUTHOR]

High-temperature driven solid–solid reaction at coke (C)/calcium oxide (CaO) interfaces is attractive for industrial-scale production of calcium carbide (CaC2). However, the reaction rate limited by the low thermal conductivity (k) results from a high Kapitza thermal resistance (Rk) at C/CaO interfaces. Identifying various factors including temperature and absorbed moisture on the k of C/CaO pellets is significant for heat transfer enhancement. Here, we developed a modified effective medium assumption model considering the particle-packed configuration to predict the influence of temperature and moisture on the k of C/CaO pellets, in which the R k is evaluated by the non-equilibrium molecular dynamics. The results show that the k of C/CaO pellets increases from 0.48 to 0.55 W/(m K) when the temperature increases from 300 to 900 K, which is attributed to a 19.7% decrease in the R k of C/CaO interfaces caused by a rising temperature activated inelastic interfacial phonon scattering. Moreover, it is found that the k of C/CaO pellets decreases from 0.48 to 0.44 W/(m K) after inserting absorption water layers with a thickness of 0.5 nm at C/CaO interfaces. A further 38.4% degeneration in k is harvested when increasing the thickness of the absorption water layers from 0.5 to 1.3 nm. This work provides an overall insight into the interfacial effect on the k of C/CaO porous pellets and guides the heat transfer optimization for particle-packed systems. [ABSTRACT FROM AUTHOR]

We engineered the thermal conductivity of nano-grained Bi0.5Sb1.5Te3 (BST) by embedding SiO2 and diamond nanoparticles (NPs) with concentration ranging from 0.5 to 5 vol. %. The embedded NPs work as additional scattering centers for long mean free path phonons that are not effectively scattered by the grain boundaries. We found that both the SiO2 and diamond NPs materially reduced the lattice thermal conductivity (κ lat ) within the temperature range of 50–300 K, with stronger reduction occurring at a lower temperature. Furthermore, the diamond NPs were found to cause large reduction in κ lat compared to the SiO2 NPs at the same concentrations. Further theoretical analysis showed that the diamond NPs possess about tenfold higher interfacial thermal resistance with the BST matrix compared to that of SiO2 NPs, due to the larger acoustic mismatch between diamond and BST as compared to SiO2 and BST. As a result of the large reduction of κ lat , the thermoelectric figure of merit (ZT) was enhanced by 15% at room temperature with 0.5 vol. % diamond NP relative to the pristine nano-grained samples without the NPs. [ABSTRACT FROM AUTHOR]

With the miniaturization and high integration of electronic devices, high-performance thermally conductive composites have received increasing attention. The construction of hierarchical structures is an effective strategy to reduce interfacial thermal resistance and enhance composite thermal conductivity. In this study, by decorating carbon fibers (CF) with needle-like ZnO nanowires, hierarchical hybrid fillers (CF@ZnO) were rationally designed and synthesized using the hydrothermal method, which was further used to construct oriented aligned filler networks via the simple freeze-casting process. Subsequently, epoxy (EP)-based composites were prepared using the vacuum impregnation method. Compared with the pure CF, the CF@ZnO hybrid fillers led to a significant increase in thermal conductivity, which was mainly due to the fact that the ZnO nanowires could act as bridging links between CF to increase more thermally conductive pathways, which in turn reduced interfacial thermal resistance. In addition, the introduction of CF@ZnO fillers was also beneficial in improving the thermal stability of the EP-based composites, which was favorable for practical thermal management applications. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials have attracted more and more attention due to their excellent properties. In this work, we systematically explore the heat transport properties of Graphene-C3B (GRA-C3B) superlattices and van der Waals (vdW) heterostructures using molecular dynamics method. The effects of interface types and heat flow directions on the in-plane interfacial thermal resistance (ITRip) are analyzed. Obvious thermal rectification is detected in the more energy stable interface, GRA zigzag-C3B zigzag (ZZ) interface, which also has the minimum value of ITRip. The dependence of the superlattices thermal conductivity (k) of the ZZ interface on the period length (l p ) is investigated. The results show that when the l p is 3.5 nm, the k reaches a minimum value of 35.52 W m−1 K−1, indicating a transition stage from coherent phonon transport to incoherent phonon transport. Afterwards, the effects of system size, temperature, coupling strength and vacancy defect on the out-of-plane interfacial thermal resistance (ITRop) are evaluated. With the increase of temperature, coupling strength and vacancy defect, ITRop are found to reduce effectively due to the enhanced Umklapp phonon scattering and increased probability of energy transfer. Phonon density of states and phonon participation ratio is evaluated to reveal phonon behavior during heat transport. This work is expected to provide essential guidance for the thermal management of nanoelectronics based on 2D monolayer GRA and C3B. [ABSTRACT FROM AUTHOR]

Heat management of high-performance secondary batteries, used in various applications that require high charging and discharging rates, such as electric vehicles and electronic devices, has recently been attracting increased attention. One of the most popular heat management technologies involves the use of thermal interface materials (TIMs) for heat dissipation. TIMs are composites of thermally conductive granulated fillers uniformly dispersed in a polymer matrix. In this study, the freeze granulation process is optimized to prepare MgO granules with high thermal conductivity as an alternative to commercial alumina fillers for TIMs. The heat dissipation characteristics of TIMs are directly related to their thermal properties, size distribution, shape, density, and filler content. Therefore, a suspension is optimized with high solid content and low viscosity for proper spraying. The size distribution and sintered granule density are analyzed for various spraying distances and pressures to optimize the process for producing high-quality TIMs. Finally, a TIM with MgO granules formed by freeze granulation dispersed in silicone-based resin is fabricated, with a high thermal conductivity exceeding 5.425 W/m∙K (with an interfacial thermal resistance of 0.343 K∙ cm2/W) and low density of 2.78 g/cm3. [ABSTRACT FROM AUTHOR]

Currently, there is rapid development of thermophysics of solids associated with the need to create models with a high degree of predictive reliability. This paper presents new approaches to solve relevant issues related to the study of heat transfer in semiconductors and dielectrics, mainly concerning nanostructures. The first of the considered tasks is the creation of a statistical model of the processes of interaction of heat carriers, phonons, with the rough surfaces of solids. For the first time, the authors propose a method based on the statistics of the slopes of the profile of a random surface. The calculation results are the mean free paths of phonon between the opposite boundaries of the sample, which are necessary for calculating the effective thermal conductivity in the ballistic and diffusion–ballistic regime of heat transfer, depending on the roughness parameters. The second task is to develop methods for calculating the processes of heat transfer through the contact surfaces of solids. We are able to show that, taking into account the phonon dispersion and the corresponding restrictions on the frequency values, the modified acoustic mismatch model for calculating Kapitza resistance can be extended to temperatures above 300 K. Previously, the limit of applicability of this method was considered to be a temperature of 30 K. Moreover, the proposed method is also generalized to the case of rough interfaces. The third task is a new approach to determine the thermal conductivity of solids. The authors develop a method of direct Monte Carlo simulation of phonon kinetics with strict consideration of their interaction due to the direct use of the laws of conservation of energy and quasi-momentum. The calculations of the thermal conductivity coefficient for pure silicon in the temperature range from 100 to 300 K show close agreement with the experiment and ab initio calculations of other authors, and also allow considering in details the kinetics of phonons. [ABSTRACT FROM AUTHOR]

Thermal transport properties in acceptor‐doped thiophene‐based polymer films such as poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) and poly[2,5‐bis(3‐tetradecylthiophen‐2‐yl)thieno[3,2‐b]thiophene] (PBTTT) are investigated using the cross‐plane 3‐omega method. A bilayer structure consisting of polymer semiconductors sequentially doped with 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ) and poly(methylmethacrylate) (PMMA) on a Si substrate is originally prepared by spin coating and employed to prevent leakage current from a heater wire during the 3‐omega measurements. Nondoped PBTTT thin film reveals an intrinsic cross‐plane thermal conductivity of 0.49 W m−1 K−1, which is higher than that for nondoped P3HT film (0.20 W m−1 K−1). X‐ray diffraction (XRD) analysis suggests that higher crystallinity of PBTTT films may result in higher thermal conductivity. The intrinsic thermal conductivity of P3HT and the interfacial thermal resistance between PMMA and P3HT are slightly increased at a low doping concentration (0.01 mg mL−1) and decreased at a higher doping concentration of 0.1 mg mL−1, whereas F4TCNQ doping reduces these values monotonously in the case of PBTTT layers. Furthermore, excess doping occurs only for P3HT and increments both intrinsic thermal conductivity and thermal resistance at PMMA/P3HT interface. The observed trend in the cross‐plane thermal transport caused by the sequential doping can be attributed to the differences between P3HT and PBTTT in their crystallinity and effective doping levels. [ABSTRACT FROM AUTHOR]

Polyimide-based composite films with high thermal conductivity, good mechanical property and electrical insulating performance are urgently needed in the electronics and microelectronics fields. As one of the key technical challenges to be solved, interfacial compatibility between filler and matrix plays an important role for composite film. Herein, boron nitride was modified by grafting polyimide brushes via a two-step method, and a series of thermally conductive polyimide/boron nitride composite films were prepared. Both characterization and performance results proved that the interfacial interaction and compatibility was greatly enhanced, resulting in a significant reduction in defects and interfacial thermal resistance. The interphase width of transition zone between two phases was also efficiently enlarged due to polyimide brushes grafted on filler surface. As a result, composite films based on polyimide-grafted boron nitride exhibited significantly improved properties compared with those based on pristine filler. Tensile strength can reach up to 80 MPa even if the filler content is as high as 50 wt%. The out-of-plane and in-plane thermal conductivity of composite film increased to 0.841 and 0.850 W·m−1·K−1, respectively. In addition, thermal and dielectric properties of composite films were also enhanced to some extent. The above results indicate that surface modification by chemically grafting polymer brushes is an effective method to improve two-phase interfacial compatibility so as to prepare composite film with enhanced properties. [ABSTRACT FROM AUTHOR]

Phase change memories (PCRAM) are often made of chalcogenide alloys in the form of multilayer systems (MLS). The mostly used alloys are Ge2Sb2Te5 and Ge‐rich Ge2Sb2Te5. The current article reports on the thermal characterization of very thin (<5 nm) Ge‐rich Ge2Sb2Te5/Ge2Sb2Te5 MLS by modulated photothermal radiometry (MPTR). The MPTR method allows for the investigation of such samples by determining, with an inverse method, the total thermal resistance of the stack deposited on the substrate. With the measurement of the total thermal resistance, it is possible to determine the thermal conductivity of the deposit and the interfacial thermal resistances between layers. The interfacial thermal resistance between Ge‐rich Ge2Sb2Te5/Ge2Sb2Te5 is characterized, which is an important parameter to reduce the energy cost of the PCRAM functioning. It is also possible to highlight a decrease in interface quality inside the MLS after the beginning of the phase transition around 250 °C. [ABSTRACT FROM AUTHOR]