Thermal Management Applications Research Articles

Advances in Liquid Crystal Epoxy: Molecular Structures, Thermal Conductivity, and Promising Applications in Thermal Management

Traditional heat conductive epoxy composites often fall short in meeting the escalating heat dissipation demands of large‐power, high‐frequency, and high‐voltage insulating packaging applications, due to the challenge of achieving high thermal conductivity (k), desirable dielectric performance, and robust thermomechanical properties simultaneously. Liquid crystal epoxy (LCE) emerges as a unique epoxy, exhibiting inherently high k achieved through the self‐assembly of mesogenic units into ordered structures. This characteristic enables liquid crystal epoxy to retain all the beneficial physical properties of pristine epoxy, while demonstrating a prominently enhanced k. As such, liquid crystal epoxy materials represent a promising solution for thermal management, with potential to tackle the critical issues and technical bottlenecks impeding the increasing miniaturization of microelectronic devices and electrical equipment. This article provides a comprehensive review on recent advances in liquid crystal epoxy, emphasizing the correlation between liquid crystal epoxy's microscopic arrangement, organized mesoscopic domain, k, and relevant physical properties. The impacts of LC units and curing agents on the development of ordered structure are discussed, alongside the consequent effects on the k, dielectric, thermal, and other properties. External processing factors such as temperature and pressure and their influence on the formation and organization of structured domains are also evaluated. Finally, potential applications that could benefit from the emergence of liquid crystal epoxy are reviewed.

Thermally Conductive and Electrically Insulating Polymer-Based Composites Heat Sinks Fabricated by Fusion Deposition Modeling.

This study explores the potential of novel boron nitride (BN) microplatelet composites with combined thermal conduction and electrical insulation properties. These composites are manufactured through Fusion Deposition Modeling (FDM), and their application for thermal management in electronic devices is demonstrated. The primary focus of this work is, therefore, the investigation of the thermoplastic composite properties to show the 3D printing of lightweight polymeric heat sinks with remarkable thermal performance. By comparing various microfillers, including BN and MgO particles, their effects on material properties and alignment within the polymer matrix during filament fabrication and FDM processing are analyzed. The characterization includes the evaluation of morphology, thermal conductivity, and mechanical and electrical properties. Particularly, a composite with 32 wt% of BN microplatelets shows an in-plane thermal conductivity of 1.97 W m-1 K-1, offering electrical insulation and excellent printability. To assess practical applications, lightweight pin fin heat sinks using these composites are designed and 3D printed. Their thermal performance is evaluated via thermography under different heating conditions. The findings are very promising for an efficient and cost-effective fabrication of thermal devices, which can be obtained through extrusion-based Additive Manufacturing (AM), such as FDM, and exploited as enhanced thermal management solutions in electronic devices.

Eco-Friendly Flame-Retardant Phase-Change Composite Films Based on Polyphosphazene/Phosphorene Hybrid Foam and Paraffin Wax for Light/Heat-Dual-Actuated Shape Memory.

Multiactuated shape memory materials are a class of promising intelligent materials that have received great interest in the fields of self-healing, anticounterfeiting, biomedical, soft robotic, and smart thermal management applications. To obtain a light/heat-dual-actuated shape memory material for thermal management applications in fire safety, we have designed a type of halogen-free flame-retardant phase-change composite film based on polyaryloxyphosphazene (PDAP)/phosphorene (PR) hybrid foam as a support material and paraffin wax (PW) as a phase-change material (PCM). PDAP was synthesized as a flexible foam matrix through the ring-opening polymerization of hexachlorocyclotriphosphazene, followed by a substitution reaction of aryloxy groups. The porosity of the PDAP foam is improved by introducing PR nanosheets, facilitating a high latent heat capacity of the PDAP-PR/PW composite films for thermal management applications. The PDAP-PR/PW composite films can implement rapid shape recovery within 65 s in the heating process, which is much shorter than that of the corresponding film without PR nanosheets (185 s). Furthermore, the PDAP-PR/PW composite films also exhibit light-actuated shape memory behavior thanks to their good solar-to-thermal energy absorption and conversion contributed by PR nanosheets as a highly effective photothermal material. More importantly, the presence of PR nanosheets imparts an excellent flame-retardant property to the PDAP-PR/PW composite films. The PDAP-PR/PW composite film can be self-extinguished within 2 s after the flame. Through an innovative integration of flexible polyphosphazene foam, PR nanosheets, and solid-liquid PCM to obtain a sensitive actuating response to light and heat, this study offers a new approach for developing multiactuated and eco-friendly flame-retardant shape memory materials to meet the requirement of applications with a requirement of fire safety in soft actuators, thermal therapy, control devices, and so on.

Strain-Driven High Thermal Conductivity in Hexagonal Boron Phosphide Monolayer.

Two-dimensional graphenelike material, hexagonal boron phosphide (h-BP), is a promising candidate for electronic and optoelectronic devices because of its suitable band gap and high carrier mobility. Especially from the ultrahigh lattice thermal conductivity (κl), it exhibits great potential to solve the challenges of future thermal management applications. Here, the excellent lattice thermal transport properties of the h-BP monolayer are systematically analyzed at the atomic level based on the first-principles method. The results show that the ultrahigh κl value of the h-BP monolayer is attributed to its high phonon group velocity and long phonon lifetime and the strong phonon hydrodynamic effect. We further explore the influence of the tensile strain on the thermal transport properties of the h-BP monolayer. As the strain increases from 0 to 8%, the κl value shows a trend of first increasing and then decreasing due to the coeffect of strain-driven changes for phonon harmonicity and anharmonicity. Under a strain of 6%, the κl value of the h-BP monolayer is as high as 795 W/mK at 300 K, which is about 2.22 times larger than that of 357 W/mK without strain. Such a significant increase in the κl value is mainly due to the increased phonon group velocity and decreased Grüneisen parameter caused by strain. This work is helpful to understand the critical role of tensile strain in lattice thermal transport of two-dimensional graphenelike materials. It is conducive to promoting the thermal management application of the h-BP monolayer.

Thermal transport in Yb-based 1-2-20 materials

Lattice thermal-transport properties of heavy-fermion YbT2Zn20-based (T = Co, Rh, and Ir) 1-2-20 compounds are calculated with the single-mode relaxation-time approximation and the full solution of the linearized phonon Boltzmann transport equation from first-principles anharmonic phonon calculations. We predict low lattice thermal conductivity κ L with a maximum value of ∼24.16 ·K at 85.14 K, 137.29 ·K at 9.67 K, and 23.55 ·K at 67.50 K and ∼12.02, 40.04, and 10.30 ·K at room temperature for YbCo2Zn20, YbRh2Zn20, and YbIr2Zn20, respectively. Based on the analysis of the cumulative κ L as a function of the phonon mean free path and the frequency-dependent joint density of states at various temperatures, we attribute the low κ L to a rattling mode with an average characteristic rattling frequency that enhanced phonon scattering processes, which reduced the phonon mean free paths, suppressed the phonon lifetime, and enhanced the probability of three-phonon scattering events. The predicted low κ L , especially in YbCo2Zn20 and YbIr2Zn20, makes them promising candidate materials for thermoelectric applications and thermal management.

Investigation of the mechanical, thermal and dielectric properties of electrical corrosion resistance glass reinforced polyimide-based composite produced by spark plasma sintering

Polyimide polymer matrix composites have gained numerous attentions in the design and fabrication of components for automobile, aerospace, and electronics applications as a result of their outstanding properties. Composites are currently replacing polymers as structural, insulation and dielectric materials, and the improvement of mechanical, thermal, and dielectric properties of polyimide (PI) becomes important. Thus, in this paper, the enhancement of the mechanical, thermal stability, and dielectric properties of PI composites with boron-free E-glass (electrical corrosion resistance (ECR) glass) reinforcements (0, 5, 10, and 15 wt%) using Spark Plasma Sintering (SPS) process is presented. X-ray diffractometer, scanning electron microscope (SEM), nanoindentation tests, thermogravimetric analyser, and LCR meter tester were used to investigate the morphology, mechanical, thermal, and dielectric properties of the developed composites, respectively. The SEM results revealed that the ECR-glass powder particles were well dispersed in the PI matrix. The introduction of the ECR into the PI matrix, improves its hardness, stiffness, and modulus. From the obtained results, a notable improvement in its hardness (9.36%), stiffness (30.77%), and modulus (43.58%) was revealed for ECR/PI loaded with 15 wt% ECR compared to pure PI. The thermal stability of the PI composites was observed to be improved with the incorporation of the ECR-glass particles. The heat resistance index of the PI was recorded to be improved by 3.8% at 15 wt% ECR incorporation. Furthermore, the composites depicted low dielectric constant and dissipation factor. In consideration, the obtained properties make the composites promising for mechanical load-bearing, thermal management and electronics applications.

Thermal properties of poly(vinyl butyral)/iron oxide composite nanofibers

AbstractIn the present study, iron(II, III) oxide nanoparticles are added to the electrospinning solution of poly(vinyl butyral) in order to yield electrospun composite poly(vinyl butyral)/iron oxide nanofibers. Scanning electron microscopy, energy dispersive x‐ray spectroscopy, and Fourier transform infrared spectroscopy analyses confirm the successful incorporation of iron(II, III) oxide nanoparticles in the nanofibers. Differential scanning calorimetry results show a decrease of approximately 6 °C in the glass transition temperature of the nanofibers with the addition of 1.0 % iron(II, III) oxide nanoparticle compared to neat poly(vinyl butyral) nanofibers. The infrared thermograms suggest the formation of a thermally conductive network for poly(vinyl butyral)/iron oxide nanofibers with faster and more evenly heat dissipation compared to that of neat poly(vinyl butyral) nanofibers while thermal conductivity coefficient of the poly(vinyl butyral) nanofibers is found to increase by 57 % with 1.0 % of nano iron oxide loading. The increased thermal conductivity and thermal absorptivity values suggest the cooling effect of the poly(vinyl butyral)/iron oxide composite nanofibers, which are promising materials for thermal management applications.

MOF decorated boron nitride/natural rubber composites with heterostructure for thermal management application through dual passive cooling modes base on the improved thermal conductivity and water sorption-desorption process

Numerous researches have drawn on the polymer-based thermal conductive composites to cope with heat dissipation issue both in the integrated electronics and human body. However, the limited thermal conductivity and mono-cooling mode even in the high filler content are always restricted its further application. Currently, the use of latent heat from phase transition has aroused researchers’ appetite for the thermal management. Herein, inspired by the sweat modulating the body temperature, a passive dual thermal management strategy was proposed by taking advantage of high latent heat and the improved thermal conductivity, where the liquid-vapor phase transition of water inside the MOF coated on the polymer-based composites to form the heterogeneous composites. In the proof-of-concept test, the obtained MIL-101 (Cr) MOF as the sorbent owned the high specific surface area of 1850 cm3/g, cyclic water uptake of 1.18 g and phase change enthalpy of 1780 J/g, which promoted the well spontaneous adsorption and desorption ability of water. While sulfur surface modified boron nitride/natural rubber composites (BN-S/NR) exhibited the excellent anisotropic thermal conductivity (11.48 W m−1 K−1) in the through-plane direction at the filler loading of 70 wt%. After the MIL-101 (Cr) MOF coated composites (MOF-BN-S/NR) with heterogeneous structure, the composites with 0.07 g MOF possessed the pretty cooling performance and thermal stability to adjust temperature at a proper range both in electronics and human body because of the dual passive heat dissipation approach. Therefore, these findings provide the meaningful insight into research to fabricate composites with heterogeneous-assisted heat dissipation in thermal management.

Enhanced interface structure of electroformed copper/diamond composites for thermal management applications

Abstract As the power density of electronic devices increases, the requirement for heat sinks with enhanced thermal properties becomes imperative for advanced heat dissipation. Copper/diamond composites are next-generation heat dissipators with high thermal conductivities, yet fabrication of these composites requires high energy and complex instruments. In this study, copper/diamond composites are fabricated by electroforming. The sediment co-deposition process is modified to obtain uniform diamond particle distribution with tailorable volume fraction. Diamond particles were initially settled on the cathode surface outside the electrolyte, and then the setup was immersed in an acidic copper sulfate electroforming bath. Varying amounts (0–100 mg l−1) of thiourea are introduced to the electrolyte to enhance the matrix–particle interface. The gaps between diamond particles are filled with electrodeposited copper using optimized deposition conditions. The composite structure detaches from the cathode by itself after the production with desired shape and dimensions. The effect of operating conditions on cathodic polarization, composite microstructure, and thermal properties are investigated. Thermal conductivity of 49 vol.% diamond containing sample fabricated with optimized parameters exceeds 667 W m−1 K−1. The increase in thermal conductivity and enhanced interface structure is attributed to the excellent void-filling ability of the optimized electrolyte.

Enhancing the Thermal Conductivity of Epoxy Composites via Constructing Oriented ZnO Nanowire-Decorated Carbon Fibers Networks.

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.

Significance of quadratic radiation and variable thermal conductivity on heat transfer of hybrid nanofluid using Xue model: A Legendre wavelet approach

Carbon nanotubes have a broad spectrum of applications in thermal management, enhanced cooling, lubricants, sensors and detections, environmental remediation, biomedical, and drug delivery. Motivated by its industrial applications, this work analyses the effects of nonuniform heat source/sink and quadratic thermal radiation on the thermal characteristics of hybrid nanofluid flow over a curved stretching sheet using the Legendre wavelet collocation technique (LWCT). The base fluid is found to be composed of ethylene glycol and water in the ratio of 30:70, and the nanoparticles are taken as single-wall carbon nanotube (SWCNT) and multi-wall carbon nanotube (MWCNT) in the ratio of 2% each. The thermal conductivity models, namely Xue, modified Maxwell and Hamilton-Crosser, are compared for heat transfer enhancement. From the results up to 5% volume fraction, the Xue model shows the maximum rate of heat transfer enhancement, while the above 5% Hamilton-Crosser model shows the maximum rate of heat transfer enhancement. The temperature profiles of existing hybrid nanofluid are increased with a heat source, radiation and variable thermal conductivity. Moreover, the graphs describing the local Nusselt number display the heat transfer rate depreciation with an increase in variable thermal conductivity and radiation parameters.

Synergistic phase change and heat conduction of low melting-point alloy microparticle additives in expanded graphite shape-stabilized organic phase change materials

Organic phase change materials (PCMs) have great potential for efficient thermal energy storage and passive thermal management applications due to their non-corrosiveness, high heat storage capacity and stable operating temperature. However, low thermal conductivity and easy leakage seriously restrict the actual application. Meanwhile, heat transfer enhancers typically have a serious negative effect on the heat storage capacity of the PCMs. In this paper, a novel strategy for preparing high performance shape-stable composite phase change materials (CPCMs) is reported, utilizing paraffin wax (PW) as the energy storage material and expanded graphite (EG) as heat transfer enhancers and supporting material, especially in which low melting-point alloy (LMA) micro particles having same phase change temperature as PW are employed with two purposes: one is to provide extra latent heat, and another is to construct a hybrid three-dimensional thermal conduction network in microscale to achieve synergistic thermal conduction with EG. The resulting CPCMs exhibit excellent characteristics in energy storage capacity, thermal conductivity, and thermal cycling stability. The thermal conductivity of ternary CPCM can reach 5.842 W m−1 K−1 when the LMA and EG loading are 4.55 wt% and 9 wt%, which is about 16.4 times higher than that of pure PW, with no obvious volumetric latent heat reduction. This work provides a novel and promising approach for the preparation of CPCMs with high and fast storage properties.

Catechol grafted rGO/MXene heterosheet structures for high performance electromagnetic interference shielding and thermal management applications

Two-dimensional MXenes have shown extraordinary potential in various scientific areas, including energy harvesting and microwave shielding. Despite their outstanding properties, MXene-based scaffolds suffer from vulnerable mechanical fragility and environmental instability, which reduces the operational life. Here, we used a nature-inspired strong surface adhesion to assemble a stacked heterosheet structure of reduced graphene oxide (rGO) and MXene (Ti3C2TX). Catechol bonding of self-triggered polydopamine between these two-dimensional nanofillers resulted in a dense and well-ordered structure, transforming their mechanical and electrical properties to those of a freestanding sheet. The simultaneous grafting of catechol and the formation of stacked heterosheets with rGO not only protects the MXene sheets from environmental oxidation but also preserves their intrinsic transportation properties. The resulting rGO/MXene composite sheet was ordered and dense, with a tensile strength of 86 MPa and toughness 118.2 MJm−3. The ultrathin, highly flexible, and conductive (26.5 Scm−1) composite sheet exhibited specific shielding effectiveness of 16340, 19136 and 21340 dBcm2g−1 in the X, Ku, and K bands, respectively. Additionally, it showed outstanding Joule-heating properties, with a rapid thermal response of approximately 2 s and the ability to reach a saturation temperature >120 °C at a relatively low supplied voltage of <7 V. The grafted rGO/MXene composite sheet maintained its transportation properties, electromagnetic interference shielding, and electrothermal properties even after 60days of continuous exposure to ambient by suppressing oxidation attacks. The synergistic enhancement of physical properties and environmental stability in the composite sheet suggest a great potential for high-performance, flexible shielding, and thermal management applications in aerospace and automobile electronics.

Influence of battery cell spacing on thermal performance of phase change material filled lithium-ion battery pack

The era of electric mobility has started, and petrol/diesel vehicles are being replaced by electric vehicles (EVs). The phase change material (PCM) is a trending field of research in its application of energy storage and thermal management. PCM-based thermal management method is found to be quite simple and effective for battery packs. However, its commercialization is difficult due to its low thermal conductivity and extra weight addition to the battery pack. Hence, the present research focuses on the battery performance with PCM. The experimental setup for a 48V, 25Ah battery pack is developed, and its performance is explored with and without PCM. The numerical model for same sized battery pack is developed, and validated with experimental results. The major objective of the present research is to find the optimal gap between two battery cells so that a sufficient amount of PCM can be filled inside the battery pack. Initially, inline and staggered cell arrangements are examined, and no significant difference in thermal performance is found. Further, cell spacing of 5 mm, 3 mm, and 1 mm are examined, and maximum temperature and temperature difference are compared along with the weight and volume of the battery pack. For a single charging process, 1 mm cell spacing is found sufficient, considering the weight of the battery pack and thermal performance. However, with 1 mm cell spacing, temperature increases significantly after each charging and discharging. At the same time, 3 mm and 5 mm are found as feasible solutions considering single and double charging-discharging cycles, respectively. 3 mm cell spacing is better option when weight is a critical issue, while 5 mm cell spacing is better when thermal performance is a critical issue. The current study offers guidance in the advancement of battery packs, particularly in cases where space constraints are a concern.

Flexible MXene-based Janus film with superior heat dissipation capability for ultra-efficient electromagnetic interference shielding and Joule heating

The incorporation of polymers into MXene-based functional materials has been proven to be an effective strategy for improving their flexibility and mechanical properties. However, insulating polymers inevitably sacrifice the conductivity of MXene, resulting in a deterioration of electromagnetic interference (EMI) shielding performance. In this work, inspired by Janus structure, an asymmetric flexible film composed of the carboxylated styrene-butadiene rubber (XSBR) with magnetic boron nitride nanosheets (mBNNS) layer and the MXene layer is developed through a casting plus spraying approach. The resulting mBNNS/XSBR@MXene (BXM) Janus film demonstrates the characteristic of “one side insulation, one side conductivity”, with the conductivity of 2746 S cm−1 on the MXene side and surface resistivity of 4.9 × 1013 Ω on the mBNNS/XSBR side. Profit from the designed Janus architecture, the EMI shielding effectiveness and in-plane thermal conductivity of the BXM Janus film reach 74.55 dB and 8.45 W m−1 K−1 when the total mass fraction of mBNNS and MXene is 50 wt%, which is 148 % and 43.46 % higher than that of the BXM blend film without Janus structure. Moreover, the BXM Janus film exhibits low applied voltage (∼3.0 V) driven Joule heating performance with a response time of less than 10 s, a saturation temperature of 133.7 °C, and long-term steady reliability. Meanwhile, the BXM Janus film possesses good mechanical properties and excellent EMI shielding stability. Therefore, this work provides an effective strategy to fabricate flexible MXene-based multifunctional film for EMI shielding, heat dissipation, and thermal management applications.

A nacre-inspired thermo conductive and healable nanocomposite captures extremely enhanced stiffness and toughness

Polymer-based nanocomposites that exhibit exceptional mechanical properties, rapid self-healing capability, high thermal conductivity, and superior electrical insulation are highly sought after for thermal management applications in modern electrical systems and electronic devices, owing to their versatility, ease of processing, and cost-effectiveness. However, traditional methods for enhancing thermal conductivity often compromise self-healing ability and mechanical and electrical properties. In this study, inspired by nacre, we propose an innovative approach to fabricating nanocomposites with a hierarchical architecture by incorporating boron nitride nanosheets (BNNSs) into a polyurethane matrix through a bottom-up assembly process and lamination technology. Leveraging the nacre-like layered structure and strong interfacial hydrogen bonding interactions, the nanocomposites were successfully transformed from exhibiting brittle fracture to displaying ductile fracture behavior, effectively reconciling the contradiction of high stiffness and toughness. The unique design of the nanocomposite leads to simultaneous enhancement in stiffness (5.3 times), strength (20.1 times), toughness (337.4 times), and fracture toughness (16.4 times) compared to those of the polyurethane matrix. Additionally, the resulting nanocomposites demonstrate excellent self-healing efficiency (∼98 %), high thermal conductivity (8.1 ± 0.3 W m−1 K−1) and superior electrical insulation property (>1012 Ω cm). Overall, our study provides a promising avenue for fabricating polymer-based nanocomposites for thermal management applications, which exhibit multifunctional properties without compromising on mechanical strength, electrical insulation, and self-healing capabilities.

Experimental and Computational Evidence of Damped Axial Conduction with Reciprocating Flow

Abstract Axial conduction is a crucial performance deteriorating factor in miniaturized heat transfer devices, primarily due to the low fluid flow rates, high solid cross-sectional to free-flow area ratio, and use of high thermal conductivity materials. These causative factors, inherent to micro-scale systems, should be such that the axial conduction is minimum. The reciprocating flow of the convective fluid (instead of steady unidirectional flow) is proposed per se as an alternative, which directly alters the solid temperature profile, the root cause of axial conduction. An experimental setup is built as a proof of the concept. In the test rig, a double-acting reciprocating pump generates a fully reversing periodic flow of air through a flow channel carved into a steel block embedded with a heater. The experimental temperature profile in the solid at the cyclic steady state is bell-shaped, indicating a virtual adiabatic plane capable of restricting axial heat transfer. The experimental results are verified taking the help of an independent finite-element-based numerical analysis. Similarly, the non-dimensional interfacial flux ratio (?_0 ), integrally related to axial conduction, for unidirectional and reciprocating flow is significantly different. This ratio in the vicinity of the inlet is ~53% less with the reciprocating compared to the equivalent unidirectional flow. The optimal thermal performance with the reciprocating flow is correlated through a critical Strouhal number expression, Sr ≤ (pDh)/L. In thermal management applications employing reciprocating flow, the limiting relation can be used to determine flow parameters and optimum geometry design.

Honeycomb-like porous copper with pleated surface for supporting phase change material with enhanced thermal conductivity and solar thermal storage performance

Paraffin wax (PW) is concerned in the field of thermal storage because of its high thermal storage density, but it generally has problems such as low thermal conductivity, poor shape stability, and low solar absorption, which limit its application in solar thermal storage and thermal management. In this study, a honeycomb-like 3D porous Cu skeleton with a pleated surface was prepared by the salt template method, and the phase change composites (PCCs) were prepared using this 3D thermal conductive skeleton to support PW. The honeycomb-like porous structure with pleated surface has positive effects on the shape stability and solar-thermal conversion of PW. The thermal conductivity, leakage resistance, and solar-thermal conversion efficiency of the PCCs were significantly improved. Among them, the thermal conductivity of PW@PSHCPC2 reached 3.3 Wm−1 K−1, which was 16.5 times higher than that of PW, and the solar-thermal conversion efficiency reached 89.2 %, and a stable current of 61.8 mA was generated in the solar thermal power generation experiment. These results show that these PCCs have great potential for applications in several fields such as solar thermal storage, waste heat recovery, solar power generation, and electronic thermal management.

Phonon diffraction and interference using nanometric features

Phonon diffraction and interference patterns are observed at the atomic scale, using molecular dynamics simulations in systems containing crystalline silicon and nanometric obstacles, such as voids or amorphous inclusions. The diffraction patterns due to these nano-architectured systems of the same scale as the phonon wavelengths are similar to the ones predicted by the simple Fresnel–Kirchhoff integral. The few differences between the two approaches are attributed to the nature of the interface and the anisotropy of crystalline silicon. Based on the wave description of phonons, these findings can provide insights into the interaction of phonons with nano-objects and can have applications in smart thermal energy management.

A stable and visualized fatty acid-based phase transition material constructed by solid-phase molecular self-assembly for thermal management.

Fatty acids are excellent thermal management materials for thermal storage, release and preventing thermal runaway. However, the leakage of fatty acids leads to instability and prevents their application in thermal management. Herein, a stable and visualized fatty acid-based phase transition material P-S/PA was constructed through solid-state molecular self-assembly strategy from polydiallyldimethylammonium chloride (PDDA), sodium dodecyl benzene sulfonate (SDBS) and palmitic acid (PA). The electrostatic interaction between PDDA and SDBS and hydrophobic interaction between PA and SDBS can prevent PA leakage during phase transition, achieving stability. After 1000 cycles, the changes in the phase transition enthalpy (ΔH M, ΔH C) were less than 1%. The structural similarity also made P-S/PA phase transition visible, and the transmittance changed significantly from 0% to 68% during phase transition. In addition, P-S/PA can be remolded by hot-pressing without performance changes, showing temperature adjustability on varying the fatty acid carbon chain length. Thus, the stable and visualized P-S/PA fatty acid-based phase transition material constructed by solid-phase molecular self-assembly has promising application in thermal management.