Synthesis of a Lightweight Nanocomposite Based on Polyaniline 3D Hollow Spheres Integrated Milled Carbon Fibers for Efficient X-Band Microwave Absorption

3D lamellar skeletal network of porous carbon derived from hull of water chestnut with excellent microwave absorption properties

Biomass derived carbon has attracted extensive attention in the field of microwave absorption because of its sustainability and porous structure beneficial to microwave attenuation. In this study, 3D lamellar skeletal network porous carbon was successfully obtained from hull of water chestnut using biomass waste as raw material by controlling the ratio of KOH and precursors in a one-step carbonization process. The optimization of biomass carbon morphology was achieved and its microwave absorption properties were investigated. At the temperature of 600 °C, when the ratio of hull of water chestnut to KOH is 1:1, the porous carbon material with filling ratio of 35% can reach the effective absorption bandwidth (RL < -10 dB) of 6.0 GHz (12-18 GHz) at the matching thickness of 1.90 mm, covering the whole Ku band. When the thickness is 2.97 mm, the optimal reflection loss reaches -60.76 dB. The surface defects, interface polarization and dipole polarization of 3D porous skeleton network structure derived from hull of water chestnut contribute to the excellent reflection loss and bandwidth of porous carbon materials. The porous carbon with low density, low cost and simple preparation method has broad application prospects in the preparation of biomass-derived microwave absorbers.

Ultralight Hierarchically Structured RGO Composite Aerogels Embedded with MnO2/Ti3C2Tx for Efficient Microwave Absorption

Although intensive efforts have been devoted to fabricating Ti₃C₂T_x MXene composites for microwave absorption, it remains a great challenge to achieve excellent MA performance at low loading and thin thickness. Herein, a three-dimensional (3D) lightweight hierarchically structured MnO₂/Ti₃C₂T_x/RGO composite aerogel with abundant heterointerfaces was fabricated via a hydrothermal and chemical reduction self-assembly method. The RGO aerogel embedded with laminated MnO₂/Ti₃C₂T_x provides a lot of heterogeneous interfaces, 3D porous interconnected conductive networks, and reasonable combination of various loss materials for rich interfacial polarization, conductivity loss, multiple reflections and scattering, and good impedance matching. Benefiting from the synergy of different loss mechanisms, the maximum reflection loss (RL) is up to -66.5 dB (>99.9999% energy absorption) at only 10 wt % loading and 2.0 mm thickness, and even at only 1.5 mm thickness, the maximum RL value remains at -36 dB (>99.9% energy absorption). The work provides a promising route to construct 3D hierarchically heterogeneous composite aerogels for efficient MA at thin thickness and low loading.

Architecting functionalized carbon microtube/carrollite nanocomposite demonstrating significant microwave characteristics

Biomass-derived materials have recently received considerable attention as lightweight, low-cost, and green microwave absorbers. On the other hand, sulfide nanostructures due to their narrow band gaps have demonstrated significant microwave characteristics. In this research, carbon microtubes were fabricated using a biowaste and then functionalized by a novel complementary solvothermal and sonochemistry method. The functionalized carbon microtubes (FCMT) were ornamented by CuCo2S4 nanoparticles as a novel spinel sulfide microwave absorber. The prepared structures illustrated narrow energy band gap and deposition of the sulfide structures augmented the polarizability, desirable for dielectric loss and microwave attenuation. Eventually, the architected structures were blended by polyacrylonitrile (PAN) to estimate their microwave absorbing and antibacterial characteristics. The antibacterial properties against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) were scrupulously assessed. Noteworthy, the maximum reflection loss (RL) of the CuCo2S4/PAN with a thickness of 1.75 mm was 61.88 dB at 11.60 GHz, while the architected FCMT/PAN composite gained a broadband efficient bandwidth as wide as 7.91 GHz (RL > 10 dB) and 3.25 GHz (RL > 20 dB) with a thickness of 2.00 mm. More significantly, FCMT/CuCo2S4/PAN demonstrated an efficient bandwidth of 2.04 GHz (RL > 20 dB) with only 1.75 mm in thickness. Interestingly, FCMT/CuCo2S4/PAN and CuCo2S4/PAN composites demonstrated an electromagnetic interference shielding efficiency of more than 90 and 97% at the entire x and ku-band frequencies, respectively.