Fe ions doped SnO2/MWCNTs composites with 48.8% Fe ions doping content showed the maximum reflection loss was −44.54 dB at 15.44 GHz, and the maximum absorption bandwidth of reflection loss below −10 dB was 4.5 GHz in the Ku band.

Ni-doped SnO2@MWCNTs composites were synthesized by a facile one-step hydrothermal method, and had a maximum reflection loss of −39.2 dB at 8.2 GHz and the absorption bandwidth of reflection loss lower than −10 dB was 3.6 GHz.

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Flame retardants endow epoxy resins (EP) with flame retardance, however, their introduction often lead to the decrease in the glass transition temperature (Tg), which is an important property for EP. Therefore, it is significant to design and synthesize a high‐efficiency flame retardant that enhances flame retardance and Tg of EP. To achieve this goal, a hyperbranched polyamide oligomer containing DOPO (HPD) was successfully synthesized by A4 + B2 polymerization and its structure was confirmed by FTIR, 1H NMR, and 30P NMR spectra and GPC. HPD was used as an additive flame retardant in epoxy resin, and its effect on the flame retardance and thermal properties of epoxy resin was studied. The epoxy resin with 7.5 wt% HPD reached UL‐94V‐0 rating and a higher LOI value of 29.6%, and its Tg was 176.2°C, which is higher than the pure epoxy resin. Moreover, the results of cone calorimetry testing (CCT) and TG‐FTIR analysis suggested that the gas‐phase and condensed‐phase flame‐retarded roles of HPD delayed the time to ignition, and reduced the value of relevant combustion parameters, including the peak of heat release rate, average of heat release rate, total heat release, smoke production rate, and total smoke production. The analysis results of Py‐GC/MS test of HPD further confirmed that HPD was able to play the flame‐retarded role in the gaseous and condensed phases.