Electromagnetic microwave absorption theory and recent achievements in microwave absorbers

New ultrathin and multifunctional electromagnetic interference (EMI) shielding materials are required for protecting electronics against electromagnetic pollution in the fifth-generation networks a...

/pdf/beyond-ti3c2tx-mxenes-for-electromagnetic-interference-17w8ppysey.pdf

Beyond Ti3C2Tx: MXenes for Electromagnetic Interference Shielding.

Renewable porous biochar and 2D MXene have attracted significant attention in high-end electromagnetic interference (EMI) shielding fields, due to unique orderly structures and excellent electrical conductivity (σ) value. In this work, the wood-derived porous carbon (WPC) skeleton from natural wood was performed as a template. And excellent conductive and ultra-light 3D MXene aerogel was then constructed to prepare the MXene aerogel/WPC composites, based on highly ordered honeycomb cells inner WPC as a microreactor. Higher carbonization temperature is more conducive to the graphitization degree of natural wood. MXene aerogel/WPC composites achieve the optimal EMI SE value of up to 71.3 dB at density as low as 0.197 g/cm3. Such wall-like “mortar-brick” structures (WPC skeleton as “mortar” and MXene aerogel as “brick”) not only effectively solve the unstable structure problem of MXene aerogel networks, but also greatly prolong the transmission paths of the electromagnetic waves and dissipate the incident electromagnetic waves in the form of heat and electric energy, thereby exhibiting the superior EMI shielding performance. In addition, MXene aerogel/WPC composites also exhibit good anisotropic compressive strength, excellent thermal insulation and flame retardant properties. Such ultra-light, green and efficient multi-functional bio-carbon-based composites have great application potential in the high-end EMI shielding fields of aerospace and national defence industry, etc.

Ultra-light MXene aerogel/wood-derived porous carbon composites with wall-like “mortar/brick” structures for electromagnetic interference shielding

Humans are undergoing a fateful transformation focusing on artificial intelligence, quantum information technology, virtual reality, etc., which is inseparable from intelligent nano-micro devices. However, the booming of "Big Data" brings about an even greater challenge by growing electromagnetic radiation. Herein, an innovative flexible multifunctional microsensor is proposed, opening up a new horizon for intelligent devices. It integrates "non-crosstalk" multiple perception and green electromagnetic interference shielding only in one pixel, with satisfactory sensitivity and fast information feedback. Importantly, beneficial by deep insight into the variable-temperature electromagnetic response, the microsensor tactfully transforms the urgent threat of electromagnetic radiation into "wealth," further integrating self-power. This result will refresh researchers' realization of next-generation devices, ushering in a new direction for aerospace engineering, remote sensing, communications, medical treatment, biomimetic robot, prosthetics, etc.

Variable-Temperature Electron Transport and Dipole Polarization Turning Flexible Multifunctional Microsensor beyond Electrical and Optical Energy.

Defect Engineering in Carbon‐Based Electrocatalysts: Insight into Intrinsic Carbon Defects

To guarantee the normal operation of next generation portable electronics and wearable devices, together with avoiding electromagnetic wave pollution, it is urgent to find a material possessing flexibility, ultrahigh conductive, and superb electromagnetic interference shielding effectiveness (EMI SE) simultaneously. In this work, inspired by a building bricks toy with the interlock system, we design and fabricate a copper/large flake size graphene (Cu/LG) composite thin film (≈8.8 μm) in the light of high temperature annealing of a large flake size graphene oxide film followed by magnetron sputtering of copper. The obtained Cu/LG thin-film shows ultrahigh thermal conductivity of over 1932.73 (±63.07) W m-1 K-1 and excellent electrical conductivity of 5.88 (±0.29) × 106 S m-1 . Significantly, it also exhibits a remarkably high EMI SE of over 52 dB at the frequency of 1-18 GHz. The largest EMI SE value of 63.29 dB, accorded at 1 GHz, is enough to obstruct and absorb 99.99995% of incident radiation. To the best of knowledge, this is the highest EMI SE performance reported so far in such thin thickness of graphene-based materials. These outstanding properties make Cu/LG film a promising alternative building block for power electronics, microprocessors, and flexible electronics.

Ultrahigh Conductive Copper/Large Flake Size Graphene Heterostructure Thin-Film with Remarkable Electromagnetic Interference Shielding Effectiveness.

Flexible graphite films with high conductivity for radio-frequency antennas

The use of advanced carbon nanomaterials for flexible antenna sensors has attracted great attention due to their outstanding electromechanical properties. However, carbon nanomaterial based composites have yet to overcome drawbacks, such as low conductivity and toughness. In this work, a flexible multi-layer graphene film (FGF) with a high conductivity of 106 S/m for antenna based wearable sensors is investigated. A 1.63 GHz FGF antenna sensor exhibits significantly high strain sensitivity of 9.8 for compressive bending and 9.36 for tensile bending, which is super than the copper antenna sensor (5.39 for compressive bending and 4.05 for tensile bending). Moreover, the FGF antenna sensor shows very good mechanical flexibility, reversible deformability and structure stability, and thus is well suited for applications like wearable devices and wireless strain sensing.

Highly sensitive wearable sensor based on a flexible multi-layer graphene film antenna

Herein, an efficient approach to prepare flexible, transparent, and lightweight films based on graphene nanosheets (GNS) and silver nanowires (AgNWs) for high electromagnetic interference (EMI) shielding effectiveness (SE) has been explained. High-conductive GNS were fabricated by liquid phase stripping and composited with AgNWs by a two-step spin-coating method. Owing to the high transparency, good conductivity, and homogeneous distribution of both GNS and AgNWs, the obtained GNS/AgNWs film exhibits superb EMI SE and light transmittance, yielding a significantly high EMI SE up to 26 dB in both Ku-band and K-band and light transmittance higher than 78.4%. Moreover, this GNS/AgNWs film shows good flexibility and excellent structural stability. The obtained flexible, light and transparent film could have a great potential for transparent EMI shielding and smart electronics.

Flexible and transparent graphene/silver-nanowires composite film for high electromagnetic interference shielding effectiveness

Graphene based antennas have attracted wide attention due to their low cost, high stability and well flexibility. However, the manufacturing process uses graphene based films to fabricate array antennas is few reports. In this paper, a unique process for fabricating microstrip 2×2 array antennas with flexible graphene based films is reported. The microstrip array antennas with the return loss of −40.28dB and the high gain of 6.78dB at 2.46GHz, which are as high as the identical copper antennas. Moreover, the graphene antennas have similar radiation patterns to the copper antennas, indicating that the graphene array antennas can be an ideal candidate for copper array antennas.

Zhi Wu

Papers

Ultrahigh Conductive Copper/Large Flake Size Graphene Heterostructure Thin-Film with Remarkable Electromagnetic Interference Shielding Effectiveness.

Flexible graphite films with high conductivity for radio-frequency antennas

Highly sensitive wearable sensor based on a flexible multi-layer graphene film antenna

Flexible and transparent graphene/silver-nanowires composite film for high electromagnetic interference shielding effectiveness

Flexible graphene based films for microstrip array antennas