Excellent Heat Dissipation Research Articles

Engineering of the Core-Shell Boron Nitride@Nitrogen-Doped Carbon Heterogeneous Interface for Efficient Heat Dissipation and Electromagnetic Wave Absorption.

The effective integration of multiple functions into electromagnetic wave-absorbing (EWA) materials is the future development direction but remains a huge challenge. A rational selection of components and the design of structures can make the material have excellent EWA performance and heat dissipation. Herein, the core-shell structured boron nitride@nitrogen-doped carbon (BN@NC) is prepared by using waterborne polyurethane (WPU) as the carbon source via a facile pyrolysis treatment process, where NC is used as the conductive loss shell, and BN serves as an impedance matching core and dominant heat transfer media. As a result, the BN@NC-900 filled with paraffin wax yields a minimum reflection loss of -42.2 dB at 2.2 mm and an effective absorbing bandwidth of 4.48 GHz at 1.8 mm, and its thermal conductivity reaches up to 0.92 W/m·K in epoxy resin. Most importantly, flexible BN@NC/WPU films are prepared and simultaneously achieve the dual-functional capability of efficiently dissipating heat and electromagnetic waves (-50.0 dB). Besides, an attractive multiband absorption feature (>99%) from C to Ku bands is realized and a strong absorbing over -27.0 dB at the S band (2.88 GHz) is even achieved. This study may pave a new route for the rational design of multifunctional EWA materials.

Fluorine-free and ultra-thin films prepared by RF-PECVD method for the anticorrosive applications

The high-reliability requirement of 5 G electronic products poses a higher challenge to its protective films, the high transmission quality of high-frequency signals, excellent heat dissipation and anticorrosive capability, which promotes the ultra-thin protective films with good adhesion and anticorrosion. In this work, a nanometer-scale p-HMDSO film was obtained on the Cu alloy with hexamethyldisiloxane (HMDSO) as the precursor by the low-temperature RF-PECVD method. Compared with Parylene and p-PFDA (1H, 1H, 2H, 2H-Perfluorodecyl acrylate) films, the p-HMDSO film possesses better hydrophobicity, mechanical stability and anticorrosive property. The corrosion inhibition efficiency of the p-HMDSO film reaches 99.95%. Meanwhile, it provides 3 orders of magnitude increment of charge-transfer impedance, a salt spray corrosion resistance for 24 h, and the protection of 10 days in the 3.5 wt% NaCl solution, which develops a better application prospect in the protection of integrated electronics.

Effects of pore structure on wide-frequency electromagnetic interference shielding performance of carbonized wood

Carbonized wood attracts widespread attention in the field of electromagnetic interference (EMI) shielding thanks to its layered porous structure and high electrical conductivity. Understanding the correlation between pore structure and shielding performance is crucial for constructing efficient EMI shielding materials. Herein, pore structures are monitored by changing the compression ratio during the hot pressing. Carbonized wood with a 40% compression ratio displays a superior EMI shielding effectiveness (SE) up to 71.69 dB in K-band, owing to the optimal structure. EMI shielding characteristics of carbonized wood in different frequency ranges are also studied. The effects of pore structure on the shielding performance are further illuminated by finite element analysis. After structure optimization, carbonized wood can demonstrate high EMI shielding performance, wide-frequency coverage, terahertz band use, and excellent heat dissipation. This work inspires the design of next-generation sustainable EMI shielding materials.

An analytical thermal model for the 3-D integrated circuit with new-type through silicon via

Through silicon via technology is a promising and preferred way to realize the reliable interconnection for 3-D integrated circuit (3-D IC), which can transfer heat from multiple dies to the heat sink in vertical direction. In this paper, a new gen?eral model of the through-silicon via (TSV) is proposed to investigate the thermal performance of the 3-D IC. The heat transfer characteristics of conical-annular TSV are studied for the first time. The impacts of different sidewall inclination angles and insulating layer thicknesses of TSV on the heat dissipation of 3-D IC were compared and analyzed in detail. As expected, our proposed model is in good agreement with the results of the existing models, which shows that the proposed model considering the lateral heat transfer and TSV structures can predict the distribution of temperature more efficiently and accurately. Furthermore, it is found that conical-annular TSV has more excellent heat dissipation performance.

Bidirectionally enhanced thermally conductive and mechanical properties MXene nanocomposite film via covalently bridged functionalized single-walled carbon nanotube

The development of thermal interface materials (TIMs) with excellent mechanical properties and efficient heat dissipation capability has become very necessary for the next generation of integrated electronics and flexible devices. Herein, a covalently cross-linked cellulose nanofiber/MXene/single-walled carbon nanotube (CNF/MXene/SWCNT-KH550, K-CMC) nanocomposite film was successfully fabricated by vacuum-assisted self-assembly method. This unique cross-linked ternary narce-like structure greatly promoted the load transfer and energy dissipation between the components, thereby improving the mechanical properties of K-CMC nanocomposite films. CNF/MXene/2wt%SWCNT-KH550(K-CMC2) nanocomposite film exhibits superior tensile strength of 255.1 MPa and satisfactory toughness of 3.9 MJ/m3. Additionally, strong covalent cross-linking network also effectively promotes the transfer of phonons between the components, notably in both vertical and horizontal directions. The K-CMC2 nanocomposite film exhibits in-plane thermal conductivity of 25.06 W m−1 K−1 and through-plane thermal conductivity of 1.64 W m−1 K−1, which enhanced 871% and 680% relative to the pure CNF film, respectively. The effective medium theory (EMT) proves that the formation of covalent cross-linked network effectively reduces the interfacial thermal resistance by 31.35%. These superior comprehensive properties endow the K-CMC nanocomposite films with great potential in the field of high power electronics.

Grid-type LED media façade with reflective walls for building-integrated photovoltaics with virtually no shading loss

Although anthropogenic climate change has demanded the development and use of building-integrated photovoltaics in zero energy building design, their poor aesthetic value has hindered their public acceptance. Accordingly, a grid-type LED display with reflective walls is herein proposed to bestow not only an aesthetic value to plain photovoltaic modules, but also an informative function as a media façade. Its lightweight, modular design enables it to be detachable and repairable. Upright flexible printed circuit boards embedded in the grid walls allow the use of wide copper electrodes and dual in-line package LEDs while casting virtually no shadows, leading to low resistive loss, excellent heat dissipation, and high luminance. The grid design exhibits a shading loss of only −3.67 %, which contributes to its superiority over conventional plane-type LED displays with a shading loss of −22.59 %. Reflective walls redirecting sunlight at solar incidence angles towards the photovoltaic modules lead to an average relative maximum power of 87.50 %, which is far higher than the 76.47 % achieved with opaque walls. The effective energy production simulations suggest that the grid-type LED displays can be run in a self-standing mode for up to 21.74 h per day. The presented grid-type LED display will contribute to the fast and wide adoption of building-integrated photovoltaics with increased public acceptance.

Soft and thermally conductive gels by introducing free-movable polymer chains into network

The rapid development of electronic devices has been putting forward requirements for higher thermal conductivity, softness, and stability of thermal interface materials. However, thermal interface materials simultaneously achieving softness, stability, and thermal conductivity is still challenging. Here, we propose a strategy of introducing free-movable polymer chains to prepare thermally conductive gels possessing high thermal conductivity (6.91 W m−1 K−1), good softness (Young's modulus ∼400 KPa, and stretchability increasing 262.4%). The high thermal conductivity is due to the high addition of microscale spherical Aluminum. The good softness is attributed to the free-movable poly (ethylene propylene diene), which reduces the interaction between polymer networks. When thermally conductive gels simulate practical applications, it shows excellent heat-dissipation ability and thermal stability after 1000 heating-cooling cycles. This work provides a simple strategy for constructing thermally conductive gels with high performance and promotes their potential applications in the thermal management of electronic devices.

Factors influencing the thermoelectric characteristics of a thermoelectric generator with cold-side micro heat pipe arrays

The thermoelectric characteristics of a thermoelectric generator with cold-side micro heat pipe arrays are studied owing to their excellent heat dissipation performances. The influence of bending angle and vertical height of micro heat pipe arrays on the cold-side of a thermoelectric generator is examined. The bending angle influence factor is defined to analyze the changing law of thermoelectric characteristics. Three bending angles, five vertical heights, and nine temperature operating points are experimentally estimated with coupling parameters. The temperature difference, output power, and output current increase with increasing heat source temperature. Moreover, the growth trend of output characteristics does not show a significant slowdown over a period of time, indicating its reliability. The thermoelectric characteristics at a 130° bending angle are higher than those at other bending angles owing to the optimum capillary flow, condensation liquid backflow, and small evaporation thermal resistance of micro heat pipe arrays. The optimum vertical height changes as bending angle changes. Furthermore, the output power increases with increasing vertical height at a high heat source temperature. The innovative application of the micro heat pipe arrays in the cold-side heat dissipation of a thermoelectric module has great engineering significance for the optimal design of thermoelectric generators.

Novel in-situ constructing approach for vertically aligned AlN skeleton and its thermal conductivity enhancement effect on epoxy

As one of the key components of electronic devices, thermal management materials (TMMs) with high thermal conductivity are essential to ensure their safety and long service life. For polymer-based TMMs, AlN is one of the preferred fillers, but it has some drawbacks such as high cost and easy hydrolysis. Herein, a controllable and continuously oriented three-dimensional AlN skeleton (3D-AlNNS) was in-situ transformed from a low-cost 3D Al-containing skeleton (3D-AlNS) by combining the ice-templating and nitriding reaction sintering. Subsequently, AlN/epoxy composites were obtained by a vacuum infiltration. The composite containing 39.69 vol% AlN had the highest thermal conductivity of 4.29 W m−1·K−1, which was 21.45 times higher than that of pure epoxy. The composite substrates showed excellent heat dissipation performance in practical applications due to their high thermal conductivity. The continuous directional alignment of AlN powders in the 3D skeleton and intersection of AlN whiskers between the skeleton walls produced in-situ contributed to the formation of effective multichannel heat transferring paths and improvement in thermal conductivity. This novel approach has the advantages of low-cost, short processing time, simple operation and repeatability, and provides a new idea for developing heat-conducting polymer composites, which can also be extended to the preparation of similar TMMs.

Achieving highly anisotropic thermal and electrical conductivities via synergistic distribution of boron nitride and graphene nanosheets in multilayered composites

It has long been a challenging problem to fabricate polymeric composites that could combine high thermal conductivity, electrical insulating and anti-static capacity. Dirven by the fascinating features of multilayer structure in nature, here we report a series of multilayered boron nitride/graphene nanoplate (BN/GNP) composites by virtue of a sequentially layered assembly strategy, which is realized through unidirectional freezing drying followed by alternative compression molding. Due to the high orientation state, as well as the synergistic distribution of BN and GNP in multilayered pattern, the compositing BN/GNP film with optimized filler content displays a satisfying in-plane thermal conductivity of 21.9 W m−1 K−1, which is 6161 % and 669 % higher than that of pure CS and isotropic composite, respectively. Meanwhile, the qualification of such compositing film in factual dissipation of exhaust heat generated by complex electronic devices is further explored and demonstrated. Moreover, such compositing film possesses distinct anisotropic electrical performance, which could simultaneously satisfy the requirement of through-plane insulating and in-plane antistatic property. Given such superior performance, as well as the green and facile process, such work is believed to further inspire the design and fabrication of intelligent electronic device with excellent heat dissipation capacity.

Shape-stabilized low melting-point alloy/expanded graphite composite thermal pad with excellent chip heat dissipation performance

• A low melting point alloy/expanded graphite composite thermal pad is prepared. • The oxidation of the alloy is beneficial to its adsorption by expanded graphite. • The composite thermal pad possesses a high thermal conductivity of 26.94 W/m·K. • A very low thermal impedance of 0.42 K·cm 2 /W is achieved by the thermal pad. • The thermal pad shows higher heat dissipation efficiency than the commercial one. Thermal interface materials that possess high thermal conductivity and can reach low thermal impedance during service, are highly desirable for chip heat dissipation systems, especially when cooling high-power chips. Herein, a novel thermal pad was developed by combining low melting point alloy having metal-level thermal conductivity and liquid-like rheological property with expanded graphite possessing large pore volume and high thermal conductivity. Specifically, the alloy 62.5Ga21.5In16Sn was modified by the trace-oxidation method to obtain oxidized alloy, followed by adsorbing into expanded graphite and then molding and pressing to fabricate the thermal pad. It is found that the oxidation treatment resulted in the generation of refractory metal oxides Ga 2 O 3 and SnO 2 within the alloy, thereby preventing the leakage of the alloy from the composite thermal pad. Impressively, the optimal low melting point alloy/expanded graphite composite thermal pad, prepared at the oxidation duration of 24 min, expanded graphite mass fraction of 4 % and compact density of 3.125 g/cm 3 , reached a thermal conductivity of as high as 26.94 W/m·K and a thermal impedance of as low as 0.42 K·cm 2 /W, along with exhibiting a good shape-stability. More significantly, when employed into a simulative desktop CPU cooling system, this thermal pad exhibited 36.78 % higher cooling efficiency under the forced air convection, extended ten times in the time for the chip to reach the upper limit temperature (100 ℃) under the natural air cooling, and benefited to the chip to fight with the pulse-type instantaneous thermal shock, as compared to the commercial thermal pad. These excellent characteristics and good heat dissipation performance make the low melting point alloy/expanded graphite composite thermal pad show great potential for use in chip thermal management systems.

Improvement of 2.8 μm laser performance on LD side-pumped LuYSGG/Er:LuYSGG/LuYSGG bonding crystal

We demonstrate the laser performance of 970 nm LD side-pumped LuYSGG/Er:LuYSGG/LuYSGG bonding crystal in a frequency range of 50–800 Hz. The thermal distribution simulation implies that the bonded Er:LuYSGG crystal possesses a higher cooling efficiency compared with the un-bonded one. The maximum average power of 20.76 W is realized at a frequency of 150 Hz and a pulse width of 200 μs, corresponding to a slope efficiency of 23.94 % and optical-to-optical conversion efficiency of 19.22 %. A single laser wavelength of 2797.5 nm is observed. The M2 factors of the bonding rod are 6.80/6.74, indicating a relatively high beam quality. Therefore, the LuYSGG/Er:LuYSGG/LuYSGG bonding crystal exhibits an improvement of laser performance operated at 2.8 μm due to excellent heat dissipation ability, which is a promising gain element and can be applied to the harsh radiation environment.

Experimental and numerical study on the cooling performance of heat pipe assisted composite phase change material-based battery thermal management system

The phase change material (PCM) cooling system is considered a promising battery thermal management system due to its high energy conservation and simple structure. However, its development is restricted to the low thermal conductivity of PCM and the difficulty in heat dissipation over time. And the applicable border of the PCM cooling system is also unclear. This paper gives a comprehensive study and optimization design of a hybrid cooling system combining the composite PCM and flat heat pipe (composite PCM-HP) for the actual application. The thermal performance and applicable border of this hybrid system were investigated through orthogonal tests. The experimental results show that composite PCM (CPCM) system and composite PCM-HP hybrid system can control temperature rise and uniformity well. Compared to the thermal performance of the air-cooling system, the maximum temperature in the hybrid system is 22 °C lower when it is discharged at a 2C rate under 25 °C. The applicable border of the hybrid system is tested at a 2C discharge rate under 40 °C, where the maximum temperature exceeds the allowable temperature range. The flat heat pipe presents excellent auxiliary heat dissipation for CPCM in the cycling tests at 40 °C, which makes the maximum temperature 10 °C lower than the CPCM system and 15 °C lower than the air-cooling system. A lumped thermal model for the hybrid system was developed and validated and further analyzed the effects of the dimension size, the porosity of copper foam, and the convective heat transfer coefficient on thermal performance. In light of the permitted temperature range, volume energy density, cooling performance, and operational circumstance, the best designs for these criteria are recommended.

Nano silver-deposited cotton textile core with carbon nanostructure-filled shell for suppression of electromagnetic radiation via absorption-reflection-absorption

Modern communication technologies require new materials with uncompromising electromagnetic interference (EMI) shielding. To this end, dispersing nano-flakes of functional particles in a polymer matrix is not amenable to meeting the stringent requirements of EMI shielding. Hence, herein, a multilayered architecture is proposed with a unique strategy of the ‘absorbing-reflecting-absorbing’ approach. This offers enhanced attenuation with the right choice of the constituting layers. We report a smart textile consisting of a reflecting core made from ‘mussel-inspired’ seeding of silver nanoparticles on cotton fabric (Ag-CF) and an ‘absorbing shell’ made of a solvent-free coating consisting of carbonaceous nanoparticles like carbon nanofibers (CNF) and graphene nanoplatelets (GNP). The Ag-CF was prepared by polydopamine-assisted deposition-a green and safe method compared to the other existing methods. This work highlights the optimization of the deposition process for seeding time and the synergistic improvements in shielding effectiveness (SE) using CNF and GNP that give maximum EM attenuation. We observed both the Ag-CF and the CNF/GNP coating work to enhance thermal stability, ultraviolet (UV) blocking, and microwave shielding. The developed multifunctional textile showed a microwave SE of −50 dB, 99.99% UV blocking with exceptionally high values of UV protection factor (UPF) – 175, and a limiting oxygen index of 27%, demonstrating its high thermal stability. The developed hybrid textile shows excellent heat dissipation properties by cooling to 34 °C from 93 °C in just 60 s. It also proved to be a robust material showing no change in properties against washing-laundering cycles. To gain mechanistic insight into this approach, instead of seeding Ag on CF, it was seeded directly onto the carbon nanostructures (to yield Ag@CNF and Ag@GNP, respectively) and coated on the fabric. It was observed that layer positioning in the smart textile plays a crucial role in maximizing attenuation. The smart textile with an absorbing-reflecting-absorbing strategy attenuates the incoming EM radiation much more efficiently than dispersing the hybrid structures (like Ag@CNF and Ag@GNP) on the textile.

Visualization analysis of temperature distribution in the cavity of conventional PPS and high-thermal-conductivity PPS during the filling stage of injection molding

Abstract As a highly thermally conductive PPS that is lightweight and has excellent heat dissipation is expected to be applied in various products, its peculiar filling behavior can cause molding defects such as short shots and surface cracks. To address these challenges, it is important to elucidate the filling behavior and clarify the effects of cavity shape and molding conditions. Thus, we intend to visualize the filling behavior of the high-thermal-conductivity PPS. To achieve this goal, we develop an in-process visualization system to reveal both the thermal and kinetic behaviors of the resin while it fills the cavity. In the system, a sapphire prism glass is utilized in the mold for visualization because it exhibits high strength, high heat conduction, and high infrared transmittance. A high-speed visible camera for kinetic behavior and an infrared camera for thermal behavior are utilized. With the developed system, we successfully obtained for the first time the filling behavior of high-thermal-conductivity PPS. Visualization experiments prove that the temperature of the conventional PPS gradually decreases from the tip to the rear of the flow. However, the temperature of the high-thermal-conductivity PPS drops sharply from the tip of the flow to the rear, and breakage at the flow front near the cavity wall is generated. Our interpretation is that the flow front near the cavity wall can be easily broken when it is stretched, because the ductility of the high-thermal-conductivity PPS largely decreases because of the rapid temperature drop. To suppress the formation of this breakage, we modify the cavity shape and molding conditions, and verify its suppression effect.

Preparation of Graphene‐Based Hydrogel Thermal Interface Materials with Excellent Heat Dissipation and Mechanical Properties

AbstractHeat dissipation has become an essential factor affecting the performance and operating life of electronic devices as the development of modern electronic devices continues to miniaturize and integrate to increase power density. The development of new thermal interface materials has been the key solution to heat dissipation. Herein, a high thermal conductive graphene‐based hydrogel (G/PVP‐PVA) with an interpenetrating network is successfully constructed by physical cross‐linking combined with the freeze–thaw process. The effect of the preparation parameters on its all‐around performance is evaluated in detail. When the graphene dosage is 0.33%, the maximal tensile stress of the hydrogel is 322.4 kPa, the self‐recovery is 95.4%, and the thermal conductivity is as high as 1.486 W m−1 K−1. The cooling simulation experiment shows that the hydrogel can adhere closely to the wall to reduce the air thermal resistance effectively, and the cooling rate is as high as 5.04 °C min−1. The simulation experiment of the human body cooling shows that its cooling rate is 1.10 °C min−1, while that for a commercial hydrogel is 0.27 °C min−1. The G/PVP‐PVA can give a practically potential solution for the thermal management of flexible electronic products and provides a new material for an efficient medical cooling application.

Evolution of Gesn Lasers Towards Photonic Integration into Practical Applications

GeSn alloys have emerged as a promising material for group IV light sources because alloying Ge with Sn increases the directness of the bandstructure, thus improving the efficiency of light emission. Despite several years of progress in GeSn lasers, however, the integration of such lasers into practical applications still faces challenges such as high threshold, low operating temperature, and large device footprint. In this report, we address these challenges via each of the studies containing thermal management, defect reduction, and nanowire growth approach. First, we demonstrate improved lasing characteristics including reduced threshold and increased operating temperature in GeSn microdisks directly sitting on Si, which is allowed by the enhanced thermal management over the conventional suspended microdisks. Although there is a concern about poor optical confinement of the sitting approach, we confirm the simultaneous achievement of excellent heat dissipation and superior optical confinement from the microdisk released on Si through experiments and theoretical simulations. We also demonstrate a decreased threshold in microdisk lasers fabricated using a high-quality GeSn-on-insulator (GeSnOI) substrate. Photoluminescence measurements show that the reduction of defects in GeSnOI leads to enhancement of spontaneous emission and reduction of the lasing threshold. Lastly, we present the potential for GeSn nanowire lasers having smaller footprints by observing clear cavity resonances in a single nanowire grown by a bottom-up growth approach. Our demonstrations provide guiding principles to push the performance of GeSn lasers to the limit towards a realization of practical group IV light sources.

P‐8.9: Development of High‐reliability Glass Substrate MiniLED Direct Display Encapsulation Technology and Materials

Glass‐based mini‐LED has become the development direction of the next generation display technology with its advantages of low cost, low power consumption, high contrast and excellent heat dissipation after mass production. In this paper, in order to improve the reliability of glass‐based direct display mini‐LED, it was sealed with glue, and the moisture permeability of glue and the basic situation of the substrate after sealing were discussed.

Interfacial template-engineered eco-friendly nanocomposites towards rapid thermal conduction

Heat conductive polymer composites are widely applied in the thermal management of microelectronic devices, while most polymers as heat conductive composite substrates are difficult to degrade in natural conditions. To alleviate the increasingly severe environmental problems, herein, we elaborately design novel eco-friendly nanocomposites with high thermal conductivity through a facile interface-enhancement-template (IET) strategy, which was composited of poly (butylene succinate) (PBS) and chitosan-coated hexagonal boron nitride (CS/h-BN). The melt blending h-BN/PBS nanocomposites were only 1.40 W m−1 K−1 at 40 wt% in thermal conductivity, while the CS/h-BN/PBS-* nanocomposites prepared by the IET strategy can reach 2.72 W m−1 K−1 in the same loading. Besides, when pristine PBS was used as thermal interface material between LED chips and Cu heat sink, the run temperature of LED chips can reach 106.0 °C at 120 s. However, the CS/h-BN/PBS-* nanocomposites were only 47.3 °C under the same conditions, and the run temperature of LED chips remained relatively constant during the 8 cycles, exhibiting excellent sustained heat dissipation. This work provides a new strategy for the preparation of eco-friendly nanocomposites with high thermal conductivity.

Rhodium-Tellurium Nanorod Synthesis Using Galvanic Replacement-Polyol Regrowth for Thermo-Dynamic Dual-Modal Cancer Phototherapy.

Rh is a noble metal introduced in bioapplications, including diagnosis and therapy, in addition to its consolidated utilization in organic catalysis and electrocatalysis. Herein, we designed the synthesis of highly crystalline Rh nanocrystal-decorated Rh-Te nanorods (RhTeNRs) through galvanic replacement of sacrificial Te nanorod (TeNR) templates and subsequent polyol regrowth. The obtained RhTeNRs showed excellent colloidal stability and efficient heat dissipation and photocatalytic activity under various laser irradiation wavelengths. Based on the confirmed biocompatibility, RhTeNRs were introduced into in vitro and in vivo cancer phototherapies. The results confirmed the selective physical death of cancer cells in the local area through laser irradiation. While chemotherapy does not guarantee successful treatment due to side effects and resistance, phototherapy using heat and reactive oxygen species generation of RhTeNRs induces physical death.