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Lightweight, and broad and strong absorption are still a huge challenge for electromagnetic (EM) wave absorbers. Here, we propose a facile oxidative polymerization-carbonization strategy to synthesize O, S, N codoped carbon planar helixes for superior EM wave absorbers. The spiral cetyltrimethylammounium bromide crystallites act as a template for the in-situ oxidative polymerization of pyrroles into ordered PPy spiral nanowires. Sintering temperature (Ts) was used to adjust the defects, heteroatoms, graphitization degree, and properties of the carbonized products. With Ts varying from 400 °C to 800 °C, internal stress and heteroatom (N, O, S) content decreased, causing the decreased defect/dipole polarization and increased graphitization degree and conductivity loss. As a result, one broad high-frequency absorption band was exhibited by carbon planar helixes produced at 400 °C− 500 °C, two broad absorption bands were exhibited by those formed at 600 °C, and three absorption bands were exhibited by those formed at 700 °C − 800 °C. The carbon planar helix formed at 700 °C exhibited broader bandwidth (4.96 GHz), thinner sample thickness (1.4 mm), and stronger absorption (−35.44 dB) than those of other absorbers. The superior properties are attributed to a combination of dipole/defect polarization, interface polarization, conductivity loss, multiple scattering, and multiple LC-resonances generated from the unique planar helical structure, defects, heteroatoms, and local electric network.

A 3D thermal response model is developed to evaluate the thermal behavior of glass fiber/phenolic composite exposed to heat flux on one side. The model is built upon heat transfer and energy conservation equations in which the heat transfer is in the form of anisotropic heat conduction, absorption by matrix decomposition, and diffusion of gas. Arrhenius equation is used to characterize the pyrolysis reaction of the materials. The diffusion equation for the decomposition gas is included for mass conservation. The temperature, density, decomposition degree, and rate are extracted to analyze the process of material decomposition, which is implemented by using the UMATHT (User subroutine to define a material’s thermal behavior) and USDFLD (User subroutine to redefine field variables) subroutines via ABAQUS code. By comparing the analysis results with experimental data, it is found that the model is valid to simulate the evolution of a glass fiber/phenolic composite exposed to heat flux from one side. The comparison also shows that longer time is taken to complete the pyrolysis reaction with increasing depth for materials from the numerical simulation, and the char region and the pyrolysis reaction region enlarge further with increasing time. Furthermore, the decomposition degree and temperature are correlated with depths, as well as the peak value of decomposition rate and the time to reach the peak value.

High-performance absorbers are in urgent demand for dealing with the increasing electromagnetic wave (EMW) pollution caused by the rapid development of information technology. Herein, we developed a simple SDS/HCl-assisted oxidative polymerization method for the controllable synthesis of nanorod-coated PANI hierarchical microtubes as an efficient EMW absorber. The morphological evolution can be expediently achieved from hierarchical microtubes and solid nanofibers to nanorods by adjusting the HCl concentration. The formation of PANI hierarchical microtubes is caused by the cooperation of SDS and the minimum surface energy. What is more, morphology-dependent conductivity and EMW absorption properties were systematically investigated. Owing to the hierarchical 1D hollow structure and carrier concentration, the ultimate conductivity reached 0.08 S/cm at [HCl] = 7.5 mM. The corresponding HCl-doped PANI hierarchical microtubes exhibited superior EMW absorption properties (EMWAPs) with a large absorption of −43.6 dB and a wide absorption band of 5.84 GHz in relation to a 1.55 mm thick sample. The excellent EMWAPs are the consequence of the high conductivity and distinctive 1D, hierarchical, and hollow structure, which generate enhanced permittivity, multiple resonances, strong attenuation capability, multiple scattering, and EM radiation. Owing to their tunable morphology, tunable conductivity, and excellent EMWAPs, the PANI hierarchical microtubes offer great promise for fields such as sensors, electronics, optics, catalysis, energy storage, and EMW absorption and shielding.