Oxidation-Resistant MXene-Based Melamine Foam with Ultralow-Percolation Thresholds for Electromagnetic-Infrared Compatible Shielding

Abstract

To effectively avoid the drawbacks of conventional metal-based electromagnetic interference (EMI) shielding materials such as high density and susceptibility to corrosion, a multifunctional melamine foam (MF) consisting of MXene/polydimethylsiloxane (PDMS) layers with ultralow percolation thresholds was designed through the electrostatic self-assembly and impregnation strategies. The prepared lightweight foams simultaneously show multifunctional properties including EMI shielding, infrared (IR) stealth, oxidation-resistance, and compression stability. Typically, this multifunctional foam exhibits an excellent EMI shielding efficiency (EMI SE) of 45.2 dB at X-band (8.2–12.4 GHz) with only 1.131 vol % MXene filler. Moreover, the temperature difference between the upper and lower surfaces of the foam can be maintained at 45 °C due to its unique three-dimensional (3D) porous structure and low infrared emissivity. The MF skeleton with MXene/PDMS (MFMXP) displays high hydrophobicity, which remains stable in EMI SE after 60 days of exposure to air. Additionally, it shows outstanding mechanical stability after 100 cycles of compression experiments. The lightweight stealth nanocomposite foams can operate stably in complex environments and show high potential for applications in high-tech fields such as wearable electronics, the military, and semiconductors, etc.

3D Lightweight Interconnected Melamine Foam Modified with Hollow CoFe2O4/MXene toward Efficient Microwave Absorption

“…Because of the pretreatment to remove surface impurities, the MF had a smooth surface (Figure h) with a skeletal diameter of ∼6 μm and a pore diameter of ∼100 μm. As a lightweight porous 3D skeleton structural material, the continuous uniform network structure and surface hydrogen bonds of the MF provided conditions for subsequent material loading . In addition, the MF skeleton can effectively prevent volumetric shrinkage and structural cracking during freeze-drying.…”

Multifunctional Green Electromagnetic Interference Shielding Material for the Sub-6-GHz Band

“…In addition, the emissivity of ITO can be controlled by changing the ITO's value of square resistance. 41 In this work, the LIRL was constructed by the periodically arranged 6 ohm/ sq ITO etched on the PET substrate with a dielectric constant of 2.86 (1 − j0.053). The infrared emissivity of 6 ohm/sq ITO and PET are 0.1 and 0.9, respectively.…”

“…Fortunately, ITO has the property of visible transparency, and its inoxidized ability is much better than metals. In addition, the emissivity of ITO can be controlled by changing the ITO’s value of square resistance . In this work, the LIRL was constructed by the periodically arranged 6 ohm/sq ITO etched on the PET substrate with a dielectric constant of 2.86 (1 – j 0.053).…”

“…Zhang et al proposed a flexible and transparent material with a 90% absorption range in 7.7–18 GHz, and the emissivity about 0.23 . Nowadays, bispectrum (microwave and IR) shielding multifunctional materials, whether based on conventional materials or MMAs, still struggle to satisfy both ultralow IR emissivity, optical transparency, flexibility, g s ≥ 1, and SE R < 3.01 − in the sub-6G band.…”

Progression in the Oxidation Stability of MXenes

“…MXenes, a family of 2D materials composed of carbides, nitrides, and carbonitrides, are in the spotlight on account of their remarkable properties [1][2][3]. Since their discovery in 2011, many chemical configurations have been identified, with over 100 different stoichiometric compositions theoretically predicted and over 40 experimentally synthesized [4,5].…”