Comparison of polyelectrolyte and sodium dodecyl benzene sulfonate as dispersants for multiwalled carbon nanotubes on cotton fabrics for electromagnetic interference shielding

Natural wood templated hierarchically cellular NbC/Pyrolytic carbon foams as Stiff, lightweight and High-Performance electromagnetic shielding materials

Hierarchically cellular, stiff, and lightweight niobium carbide (NbC)-pyrolytic carbon (PyC) monolithic foam composites possessing excellent electromagnetic interference shielding effectiveness (EMI SE) were developed via a natural wood template-based method. Pyrolytic carbon derived from the decomposed cellulose in the wood worked as the carbon source for the growth of NbC phase, and the NbC-PyC heterogeneous nano-interface formed between the residual PyC and the freshly formed NbC. Multi-loss mechanisms (e.g. conductive loss, dipole polarization loss, and especially interface polarization loss) were established by controlling the NbC content and residual PyC phase in the NbC-PyC foams, which significantly improved the absorption capability. Compared to 28.0 dB of PyC monolith, the EMI SE of NbC-PyC foam can reach 54.8 dB when the thickness is 0.5 mm, which outperforms the other porous-based shielding materials. Due to the highly porous structure of pristine wood, the resulting NbC-PyC foam exhibited a low density of 0.48 g/cm³, which is ~ 1/16 of dense NbC (7.78 g/cm³). Generally, this work introduces innovative ideas for designing novel and advanced transition metal carbide-carbon composite materials.

Near-Instantaneously Self-Healing Coating toward Stable and Durable Electromagnetic Interference Shielding

Durable electromagnetic interference (EMI) shielding is highly desired, as electromagnetic pollution is a great concern for electronics' stable performance and human health. Although a superhydrophobic surface can extend the service lifespan of EMI shielding materials, degradation of its protection capability and insufficient self-healing are troublesome issues due to unavoidable physical/chemical damages under long-term application conditions. Here, we report, for the first time, an instantaneously self-healing approach via microwave heating to achieve durable shielding performance. First, a hydrophobic 1H,1H,2H,2H-perfluorooctyltriethoxysilane (POTS) layer was coated on a polypyrrole (PPy)-modified fabric (PPy@POTS), enabling protection against the invasion of water, salt solution, and corrosive acidic and basic solutions. Moreover, after being damaged, the POTS layer can, for the first time, be instantaneously self-healed via microwave heating for a very short time, i.e., 4 s, benefiting from the intense thermal energy generated by PPy under electromagnetic wave radiation. This self-healing ability is also repeatable even after intentionally severe plasma etching, which highlights the great potential to achieve robust and durable EMI shielding applications. Significantly, this approach can be extended to other EMI shielding materials where heat is a triggering stimulus for healing thin protection layers. We envision that this work could provide insights into fabricating EMI shielding materials with durable performance for portable and wearable devices, as well as for human health care.

Roll-to-roll layer-by-layer assembly bark-shaped carbon nanotube/Ti3C2Tx MXene textiles for wearable electronics

Smart wearable electronics have drawn increasing attention for their potential applications in personal thermal management, human health monitoring, portable energy conversion/storage, electronic skin and so on. However, it is still a critical challenge to fabricate the multifunctional textiles with tunable morphology and performance while performing well in flexibility, air permeability, wearing comfortability. Herein, we develop a novel roll-to-roll layer-by-layer assembly strategy to construct bark-shaped carbon nanotube (CNT)/Ti₃C₂T_x MXene composite film on the fiber surface. The fabricated bark-shaped CNT/MXene decorated fabrics (CMFs) exhibit good flexibility, air permeability and electrical conductivity (sheet resistance, 6.6 Ω/□). In addition, the CMFs demonstrate good electrothermal performance (70.9 °C, 5 V), electromagnetic interference (EMI) shielding performance (EMI shielding effectiveness, 30.0 dB under X-Brand), and high sensitivity as the flexible piezoresistive sensors for monitoring the human motions. Importantly, our CMFs show distinctive EMI shielding mechanism, where a great proportion of incident electromagnetic microwaves are reflected by the bark-shaped CNT/MXene films owing to the multi-interface scattering effects. This work may provide a new strategy for the fabrication of multifunctional textile-based electronics and pave the way for smart wearable electronics.

Facile Preparation of Continuous and Porous Polyimide Aerogel Fibers for Multifunctional Applications

High-performance aerogel fibers with high porosity, ultralow density and thermal conductivity, and good flexibility are attractive candidates for the next generation of effective thermal insulation, efficient personal thermal management, and other functional applications. However, most previously reported aerogel fibers suffered from either limited working temperatures, weak mechanical properties, or complex manufacturing processes. In the present work, a facile wet-spinning technique combined with freeze-drying was developed to fabricate strong polyimide aerogel fibers (PAFs) based on organo-soluble polyimide. Attributed to the unique "porous core-dense sheath" morphology, the PAFs exhibited excellent mechanical properties with an optimum tensile strength of 265 MPa and an initial modulus of 7.9 GPa at an ultimate elongation of 65%, representing the highest value for aerogel fibers reported so far. Moreover, the PAFs possess high porosity (>80%) and high specific surface area (464 m² g^-1), which render the woven PAF fabrics with excellent thermal insulation properties within a wide temperature range (-190 to 320 °C) and potential applications for thermal insulation under harsh environments. Additionally, a series of functionalized aerogel fibers or their fabrics based on PAFs, including phase-change fabrics with a thermoregulation function and electromagnetic shielding (EMI) textiles with a high EMI SE value, have been successfully fabricated for expanding their potential applications. Overall, this novel aerogel fiber sheds light on a promising direction for developing the next generation of high-performance thermal insulation and multifunctional fibers and textiles.