With the innovation of microelectronics technology, the heat dissipation problem inside the device will face a severe test. In this work, cellulose aerogel (CA) with highly enhanced thermal conductivity (TC) in vertical planes was successfully obtained by constructing a vertically aligned silicon carbide nanowires (SiC NWs)/boron nitride (BN) network via the ice template-assisted strategy. The unique network structure of SiC NWs connected to BN ensures that the TC of the composite in the vertical direction reaches 2.21 W m-1 K-1 at a low hybrid filler loading of 16.69 wt%, which was increased by 890% compared to pure epoxy (EP). In addition, relying on unique porous network structure of CA, EP-based composite also showed higher TC than other comparative samples in the horizontal direction. Meanwhile, the composite exhibits good electrically insulating with a volume electrical resistivity about 2.35 × 1011 Ω cm and displays excellent electromagnetic wave absorption performance with a minimum reflection loss of - 21.5 dB and a wide effective absorption bandwidth (< - 10 dB) from 8.8 to 11.6 GHz. Therefore, this work provides a new strategy for manufacturing polymer-based composites with excellent multifunctional performances in microelectronic packaging applications. 

https://link.springer.com/content/pdf/10.1007/s40820-022-00863-z.pdf

Vertically Aligned Silicon Carbide Nanowires/Boron Nitride Cellulose Aerogel Networks Enhanced Thermal Conductivity and Electromagnetic Absorbing of Epoxy Composites

Electromagnetic absorption materials: current progress and new frontiers

With the rapid development of fifth-generation mobile communication technology and wearable electronic devices, electromagnetic interference and radiation pollution caused by electromagnetic waves have attracted worldwide attention. Therefore, the design and development of highly efficient EMI shielding materials are of great importance. In this work, the three-dimensional graphene oxide (GO) with regular honeycomb structure (GH) is firstly constructed by sacrificial template and freeze-drying methods. Then, the amino functionalized FeNi alloy particles (f-FeNi) are loaded on the GH skeleton followed by in-situ reduction to prepare rGH@FeNi aerogel. Finally, the rGH@FeNi/epoxy EMI shielding composites with regular honeycomb structure is obtained by vacuum-assisted impregnation of epoxy resin. Benefitting from the construction of regular honeycomb structure and electromagnetic synergistic effect, the rGH@FeNi/epoxy composites with a low rGH@FeNi mass fraction of 2.1 wt% (rGH and f-FeNi are 1.2 and 0.9 wt%, respectively) exhibit a high EMI shielding effectiveness (EMI SE) of 46 dB, which is 5.8 times of that (8 dB) for rGO/FeNi/epoxy composites with the same rGO/FeNi mass fraction. At the same time, the rGH@FeNi/epoxy composites also possess excellent thermal stability (heat-resistance index and temperature at the maximum decomposition rate are 179.1 and 389.0 °C respectively) and mechanical properties (storage modulus is 8296.2 MPa). 

/pdf/high-efficiency-electromagnetic-interference-shielding-of-3a08itbi.pdf

High-Efficiency Electromagnetic Interference Shielding of rGO@FeNi/Epoxy Composites with Regular Honeycomb Structures

/pdf/vertically-aligned-silicon-carbide-nanowires-boron-nitride-3c47jkzj.pdf

Multifunctional wearable electronic devices based on natural materials are highly desirable for versatile applications of energy conversion, electronic skin and artificial intelligence. Herein, multifunctional wearable silver nanowire decorated leather (AgNW/leather) nanocomposites with hierarchical structures for integrated visual Joule heating, electromagnetic interference (EMI) shielding and piezoresistive sensing are fabricated via the facile vacuum-assisted filtration process. The AgNWs penetrate the micro-nano porous structures in the corium side of leather constructing highly-efficient conductive networks. The resultant flexible and mechanically strong AgNW/leather nanocomposites exhibit extremely low sheet resistance of 0.8 Ω/sq, superior visual Joule heating temperatures up to 108°C at low supplied voltage of 2.0 V due to efficient energy conversion, excellent EMI shielding effectiveness (EMI SE) of ~55 dB and outstanding piezoresistive sensing ability in human motion detection. This work demonstrates the fabrication of multifunctional AgNW/leather nanocomposites for next-generation wearable electronic devices in energy conversion, electronic skin and artificial intelligence, etc . 

Multifunctional Wearable Silver Nanowire Decorated Leather Nanocomposites for Joule Heating, Electromagnetic Interference Shielding and Piezoresistive Sensing

Highly thermal conductivity materials with excellent electromagnetic interference shielding and Joule heating performances are ideal for thermal management in the next generation of communication industry, artificial intelligence and wearable electronics. In this work, silver nanowires (AgNWs) are prepared using silver nitrate as the silver source and ethylene glycol as the solvent and reducing agent, and boron nitride (BN) is performed to prepare BN nanosheets (BNNS) with the help of isopropyl alcohol and ultrasonication-assisted peeling method, which are compounded with aramid nanofibers (ANF) prepared by chemical dissociation, respectively, and the (BNNS/ANF)-(AgNWs/ANF) thermal conductivity and electromagnetic interference shielding composite films with Janus structures are prepared by the “vacuum-assisted filtration and hot-pressing” method. Janus (BNNS/ANF)-(AgNWs/ANF) composite films exhibit “one side insulating, one side conducting” performance, the surface resistivity of the BNNS/ANF surface is 4.7 × 1013 Ω, while the conductivity of the AgNWs/ANF surface is 5,275 S/cm. And Janus (BNNS/ANF)-(AgNWs/ANF) composite film with thickness of 95 µm has a high in-plane thermal conductivity coefficient of 8.12 W/(m·K) and superior electromagnetic interference shielding effectiveness of 70 dB. The obtained composite film also has excellent tensile strength of 122.9 MPa and tensile modulus and 2.7 GPa. It also has good temperature-voltage response characteristics (high Joule heating temperature at low supply voltage (5 V, 215.0 °C), fast response time (10 s)), excellent electrical stability and reliability (stable and constant real-time relative resistance under up to 300 cycles and 1,500 s of tensile-bending fatigue work tests). 

https://link.springer.com/content/pdf/10.1007/s12274-022-4159-z.pdf

Janus (BNNS/ANF)-(AgNWs/ANF) thermal conductivity composite films with superior electromagnetic interference shielding and Joule heating performances

Flexible multifunctional polymer-based electromagnetic interference (EMI) shielding composite films have important application values in the fields of 5G communication technology, wearable electronic devices and artificial intelligence. In this work, Fe3O4/polyamic acid (PAA) nanofiber films are prepared by in-situ polymerization and electrospinning technology, and Ti3C2Tx nanosheets are deposited on the surface of the Fe3O4/PAA nanofiber films via vacuum-assisted filtration. Then, Janus Ti3C2Tx-(Fe3O4/polyimide (PI)) composite films are obtained by thermal imidization. The two sides of the Janus films exhibit completely different properties. The Fe3O4/PI side has excellent hydrophobicity and insulation property, and the Ti3C2Tx side has hydrophilicity and terrific conductivity. When the mass fraction of Ti3C2Tx is 80 wt.%, the Janus Ti3C2Tx-(Fe3O4/PI) composite film has excellent EMI shielding performances and mechanical properties, with EMI shielding effectiveness, tensile strength and Young’s modulus reaching 66 dB, 114.5 MPa and 5.8 GPa, respectively. At the same time, electromagnetic waves show different absorption shielding effectiveness (SEA) when incident from two sides of the Janus films. When the electromagnetic waves are incident from the Fe3O4/PI side, the SEA of the Janus film is 58 dB, much higher than that when the electromagnetic waves are incident from the Ti3C2Tx side (39 dB). In addition, the Ti3C2Tx side of the Janus Ti3C2Tx-(Fe3O4/PI) composite films also has excellent electrothermal and photothermal conversion performances. When the applied voltage is 4 V, the stable surface temperature reaches 108 °C; when it is irradiated by simulated sunlight with power density of 200 mW/cm2, the stable surface temperature reaches 95 °C. 

https://link.springer.com/content/pdf/10.1007/s12274-022-4358-7.pdf

Multifunctional Ti3C2Tx-(Fe3O4/polyimide) composite films with Janus structure for outstanding electromagnetic interference shielding and superior visual thermal management

The low thermal conductivity coefficient (λ) of polyimide (PI) films are limiting their application in high-power electronic equipment, and the disordered alignment of fillers discourage efficient improvement of λ for PI-based composite films. Herein, polyethylene glycol trimethylnonyl ether is used to perform liquid crystalline modification on graphene fluoride (LC-GeF) to achieve ordered alignment. Intrinsically thermally conductive liquid crystalline PI (LC-PI) matrix is utilized to fabricate thermally conductive LC-GeF/LC-PI composite films. In-plane λ (λ∥) and through-plane λ (λ⊥) of 15 wt % LC-GeF/LC-PI composite films reach 4.21 and 0.63 W/(m·K), 446.8% and 320.0% higher than λ∥ (0.77 W/(m·K)) and λ⊥ (0.15 W/(m·K)) of normal PI films, 99.5% and 96.9% higher than λ∥ (2.11 W/(m·K)) and λ⊥ (0.32 W/(m·K)) of LC-PI films, also higher than 15 wt % GeF/LC-PI composite films. Additionally, LC-GeF/LC-PI composite films possess more excellent insulating, mechanical, and thermal properties than GeF/LC-PI composite films. 

Ordered Alignment of Liquid Crystalline Graphene Fluoride for Significantly Enhancing Thermal Conductivities of Liquid Crystalline Polyimide Composite Films

Flexible multifunctional polymer‐based electromagnetic interference (EMI) shielding composite films have important applications in the fields of 5G communication technology, wearable electronic devices, and artificial intelligence. Based on the design of a porous/multilayered structure and using polyimide (PI) as the matrix and polymethyl methacrylate (PMMA) microspheres as the template, flexible (Fe3O4/PI)–Ti3C2Tx–(Fe3O4/PI) composite films with controllable pore sizes and distribution of Ti3C2Tx hollow microspheres are successfully prepared by sacrificial template method. Owing to the porous/multilayered structure, when the pore size of the Ti3C2Tx hollow microspheres is 10 µm and the mass ratio of PMMA/Ti3C2Tx is 2:1, the (Fe3O4/PI)–Ti3C2Tx–(Fe3O4/PI) composite film has the most excellent EMI shielding performance, with EMI shielding effectiveness (EMI SE) of 85 dB. It is further verified by finite element simulation that the composite film has an excellent shielding effect on electromagnetic waves. In addition, the composite film has good thermal conductivity (thermal conductivity coefficient of 3.49 W (m·K)−1) and mechanical properties (tensile strength of 65.3 MPa). This flexible (Fe3O4/PI)–Ti3C2Tx–(Fe3O4/PI) composite film with excellent EMI shielding performance, thermal conductivity, and mechanical properties has demonstrated great potential for applications in EMI shielding protection for high‐power, portable, and wearable flexible electronic devices.

Controlled Distributed Ti3C2Tx Hollow Microspheres on Thermally Conductive Polyimide Composite Films for Excellent Electromagnetic Interference Shielding

High integration development of electronics requires materials possessing excellent thermal conductivity, electromagnetic interference (EMI) shielding, and electrical insulation. In this work, Fe2O3 particles are deposited on carbon fibers (CF) and then utilized as fillers ([email protected]2O3) in boron nitride/silicone rubber (BN/SR) to fabricate sandwich structured [email protected]2O3/(BN/SR) composites, herein, BN/SR as top & substrate layer, and [email protected]2O3 as middle layer. Orientation of BN in [email protected]2O3/(BN/SR) composites realizes excellent in-plane thermal conductivity coefficient (λ∥), and the core-sheath structure of [email protected]2O3 achieves good EMI shielding performance by the “absorption-reflection (transmittance)-reabsorption” process of electromagnetic waves, insulation modification of CF and the sandwich structure strengthen the electrical insulation. When the amount of BN and [email protected]2O3 are 20.6 wt% and 45.5 wt%, respectively, the λ∥, EMI shielding effectiveness, volume resistance and breakdown strength of [email protected]2O3/(BN/SR) composites reach 3.86 W/(m·K), 37.7 dB, 6.2 × 1014 Ω cm and 26.8 kV/mm, respectively, which are all higher than those of commonly fabricated CF/(BN/SR) composites with same amount of BN and CF (3.83 W/(m·K), 19.4 dB, 8.6 × 1013 Ω cm and 21.4 kV/mm). [email protected]2O3/(BN/SR) composites possess better cooling effect (5.6 °C) than that of commercial silicon grease (QM850) on the testing platform of computer's central processing unit, whose functions are more abundant and have wide application prospects in electronics. 

Kun Ruan

Papers

Janus (BNNS/ANF)-(AgNWs/ANF) thermal conductivity composite films with superior electromagnetic interference shielding and Joule heating performances

Multifunctional Ti3C2Tx-(Fe3O4/polyimide) composite films with Janus structure for outstanding electromagnetic interference shielding and superior visual thermal management

Ordered Alignment of Liquid Crystalline Graphene Fluoride for Significantly Enhancing Thermal Conductivities of Liquid Crystalline Polyimide Composite Films

Controlled Distributed Ti3C2Tx Hollow Microspheres on Thermally Conductive Polyimide Composite Films for Excellent Electromagnetic Interference Shielding

Flexible and insulating silicone rubber composites with sandwich structure for thermal management and electromagnetic interference shielding