Carbonized polyaniline bridging nanodiamond-graphene hybrids for enhanced microwave absorptions with ultrathin thickness

Design of Flexible Film-Forming Polydopamine/Polypyrrole/Nanodiamond Hierarchical Structure for Broadband Microwave Absorption

Microwave-absorbing materials are widely used in numerous fields, including the military, daily protection, etc. Currently, in addition to being lightweight and highly efficient, good film-forming processing characteristics and environmental stability are also required for the practical application of microwave-absorbing materials, which, in general, are difficult to make compatible. In this paper, a mulberry-like PDA/PPy/ND hierarchical structure was prepared by in situ polymerization. The hierarchical structure showed remarkably enhanced microwave absorption, as well as better flexible film-forming characteristics, thanks to the multiple roles PDA played in the system. The optimal RL peak for PDA/PPy/ND could reach −43.6 dB at 7.58 GHz, which is mainly attributed to the multiple dielectric loss paths and significantly improved impedance-matching characteristics. Furthermore, given the H-bond crosslink, the introduction of PDA also promoted the film formation and dispersion of PDA/PPy/ND in the PVA matrix, forming a water-resistant and flexible film. This work provides a referencing path for the design and practical applications of lightweight microwave-absorbing materials.

Functionalized carbonized monarch butterfly wing scales (FCBW) ornamented by β-Co(OH)2 nanoparticles: an investigation on its microwave, magnetic, and optical characteristics

In this research, a bioinspired carbon structure was applied as a novel, unique, green, affordable, light weight, thin, and broadband microwave absorbing material. Briefly, the monarch butterfly wing scales were pyrolyzed and then CBWs were functionalized using oxidative treatments, following that they were ornamented by hexagonal β-Co(OH)₂ nanoparticles to improve their microwave absorbing features based on an innovative complementary method by combining sonochemistry and hydrothermal routes. Noticeably, the polyacrylonitrile (PAN) was used as a practical medium to fabricate the microwave absorbers developing an integrated structure and augmenting the relaxation loss mechanism. Various analyses were applied to identify the prepared samples including x-ray powder diffraction, diffuse reflection spectroscopy, Fourier transform infrared, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), vibrating sample magnetometer, and vector network analyzer. The net-like morphology of FCBWs were fully coated by the hierarchical hexagonal β-Co(OH)₂ nanoparticles. FCBW illustrated a saturation magnetization of 0.06 emu g^-1 originated from its defects, distortions, dislocations, unique morphology, as well as folding, developing localized magnetic moments. Noticeably, inserting FCBWs narrow the energy bandgap of β-Co(OH)₂ nanoparticles, amplifying their light absorption and polarizability, desirable for the microwave attenuation. As revealed, FCBW/β-Co(OH)₂/PAN nanocomposite gained strong reflection loss (RL) of 68.41 at 9.08 GHz, while FCBW/PAN achieved broadband efficient bandwidth as wide as 7.97 GHz (RL > 10 dB) with a thickness of 2.00 mm. More significantly, β-Co(OH)₂/PAN nanocomposites demonstrated salient efficient bandwidth of 3.62 GHz (RL > 20 dB) with only 2.50 mm in thickness. Noteworthy, the eye-catching microwave absorptions were obtained by only filler loading of 10 Wt%. The remarkable microwave absorbing properties of the samples were generated from their microwave absorbing mechanisms which were scrupulously dissected. More significantly, the negative imaginary parts were obtained, originated from the produced secondary fields.