Self-standing boron nitride bulks enabled by liquid metals for thermal management

Cation Bimetallic MOF Anchored Carbon Fiber for Highly Efficient Microwave Absorption

Carbon fiber (CF) is a potential microwave absorption (MA) material due to the strong dielectric loss. Nevertheless, owing to the high conductivity, poor impedance matching of carbon-based  materials results in limited MA performance. How to solve this problem and achieve excellent MA performance remains a principal challenge. Herein, taking full advantage of CF and excellent impedance matching of bimetallic metal-organic frameworks (MOF) derivatives layer, an excellent microwave absorber based on micron-scale 1D CF and NiCoMOF (CF@NiCoMOF-800) is developed. After adjusting the oxygen vacancies of the bimetallic MOF, the resultant microwave absorber presented excellent MA properties including the minimum reflection loss (RLmin) of -80.63 dB and wide effective absorption bandwidth (EAB) of 8.01 GHz when its mass percent is only 5 wt.% and the thickness is 2.59 mm. Simultaneously, the mechanical properties of the epoxy resin (EP)-based coating with this microwave absorber are effectively improved. The hardness (H), elastic modulus (E), bending strength, and compressive strength of CF@NiCoMOF-800/EP coating are 334 MPa, 5.56 GPa, 82.2 MPa, and 135.8 MPa, which is 38%, 15%, 106% and 53% higher than EP coating. This work provides a promising solution for carbon materials achieving excellent MA properties and mechanical properties.

Polymeric Nanocomposites of Boron Nitride Nanosheets for Enhanced Directional or Isotropic Thermal Transport Performance

Polymeric composites with boron nitride nanosheets (BNNs), which are thermally conductive yet electrically insulating, have been pursued for a variety of technological applications, especially those for thermal management in electronic devices and systems. Highlighted in this review are recent advances in the effort to improve in-plane thermal transport performance in polymer/BNNs composites and also the growing research activities aimed at composites of enhanced cross-plane or isotropic thermal conductivity, for which various filler alignment strategies during composite fabrication have been explored. Also highlighted and discussed are some significant challenges and major opportunities for further advances in the development of thermally conductive composite materials and their mechanistic understandings.

3D printed lightweight honeycomb vent structures with subsequent coating of silver nanowires for efficient electromagnetic interference (EMI) shielding

In light of the rapid advancements within the electronic industry, the urgent need for the development and implementation of advanced electromagnetic interference (EMI) shielding materials has become paramount. Herein a novel approach is presented for developing of lightweight honeycomb structures using 3D printing technology, combined with subsequent conductive spray coating, containing Silver Nanowires (AgNWs), to achieve effective EMI shielding as well as air vent functionality for thermal cooling. Using polyol method, AgNWs were synthesized having high aspect ratio and crystallinity for to be used as conductive coating on 3D printed structures. The EMI shielding results in X-band demonstrated that the developed structures exhibit promising EMI shielding properties, up to 35 dB attenuation with 2 mm honeycomb cell size, making them suitable for applications requiring EMI protection along with air venting. More importantly in all samples major contribution of the shielding efficiency comes from the absorption of the EM waves (up to 75 %) inside the structures which is helpful to reduce reflected EM noise. Effort was to effectively addresses the inherent limitations of conventional processing technology, by using additive manufacturing and material science to create structures for EMI shielding applications, bridging the gap between existing materials and desired components.

Shear-Induced Fabrication of Cellulose Nanofibril/Liquid Metal Nanocomposite Films for Flexible Electromagnetic Interference Shielding and Thermal Management

To address electromagnetic interference (EMI) pollution in modern society, the development of ultrathin, high-performance, and highly stable EMI shielding materials is highly desired. Liquid metal (LM) based conductive materials have received enormous amounts of attention. However, the processing approach of LM/polymer composites represents great challenges due to the high surface tension and cohesive energy of LMs. In this study, we develop a universal one-step fabrication strategy to directly process composites containing LMs and cellulose nanofibrils (CNFs) and successfully fabricate the ultrathin, flexible, and stable EMI shielding films with an average specific EMI shielding efficiency (EMI SE) value of 429 dB/mm and small thickness of only 70 μm in the wide frequency range of 8.2-18 GHz. In addition, the resulting films also exhibit excellent mechanical performance and flexibility, which endow the film with the ability to withstand repeated folding, bending, and folding into complex shapes without producing cracks or fractures. Besides, the resulting films display excellent thermal conductivity with a λ of 4.90 W/(m K) and an α of 3.17 mm2/s. Thus, the presented approach shows great potential in fabricating advanced materials for EMI shielding applications.

Peelable Microwave Absorption Coating with Reusable and Anticorrosion Merits

The peelable microwave absorption (MA) coating with reversible adhesion for stable presence on substrates and easy release without any residuals is highly desired in temporary electromagnetic protection, which can quickly enter and disengage the electromagnetic protection state according to the real-time changeable harsh surroundings. On the contrary, with the incorporation of abundant absorbent to achieve excellent MA ability, the tunable adhesion and sufficient cohesion are extremely challenging to fulfill the above requirement. The reported peelable coatings still have problems in controlling adhesion/cohesion strength and coating release, facing substantial residuals after peeling even using complex chemical modification or abundant additives. Herein, a peelable MA coating based on the block characteristics of polar and nonpolar segments of poly(styrene-(ethylene-co-butylene)-styrene) (SEBS) is successfully developed. The polyaniline-decorated carbon nanotube as a microwave absorber plays a positive influence on the adhesion/cohesion of the coating due to bonding interaction. The competitive effective absorption bandwidth (EAB) of 8.8 GHz and controllable yet reversible adhesion release on various substrates and complex surfaces have been achieved. The reusability endows peelable MA coating with 93% retention of EAB even after ten coating-peeling cycles. The coating with excellent chemical and adhesion stability can effectively protect substrates from salt/acid/alkali corrosion, showing over 98% retention of EAB even after 8 h of accelerated corrosion. Our peelable MA coating via a general yet reliable approach provides a prospect for temporary electromagnetic protection.