In order to expand the application prospects of SiCN ceramics in the field of microwave (MW) absorption materials, a series of Ni 3 Si embedded SiCN ceramic fibers composites (NSF) were prepared by controlling Ni conversion rate through the electrospinning technique and polymer derivation, with the intention of improving the impedance matching degree, enhancing the conductivity and polarization, and further promoting the dielectric loss ability and MW absorption performance of ceramic materials. The microstructure, phase composition, conductivity, MW absorption properties and mechanism of the material were analyzed by a variety of characterization methods. The results show that NSF exhibited high dielectric loss efficiency and desirable effective absorption bandwidth (EAB) when the conversion rate of Ni was 0.5 wt%: The MW of the entire Ku band (12–18 GHz, 6 GHz) could be effectively absorbed by the sample with a thickness of 2.64 mm, and its EAB could cover 6–18 GHz by adjusting its thickness from 1 mm to 5 mm, so its performance is significantly superior to a number of similar SiCN based composite ceramic materials previously reported. To sum up, the NSF prepared in this work exhibits suitable impedance matching degree, good conductivity, obvious polarization effect, excellent dielectric loss ability, and gratifying EAB in MW, and it is expected to become a powerful candidate in the field of broadband MW absorption materials in the future.
In this paper, the SiCN(Ni)/BN ceramic with excellent electromagnetic wave (EMW) absorption performance was successfully prepared. The Ni and Ni3Si were in situ formed by the introduction of nickel acetylacetonate (NA), which effectively improved the impedance matching performance of SiCN(Ni)/BN ceramics. The EMW absorption properties of the SiCN(Ni)/BN ceramics showed a trend of first increasing and then decreasing with the increase in content of NA. When the NA content reached 7 wt%, the impedance matching range of SiCN-7 was optimal. The minimum reflection loss (RLmin) of SiCN-7 reached −53.47 dB at 4.2 mm and the effective absorption bandwidth (EAB) was 2.32 GHz at 3.48 mm. Through the analysis of electrical conductivity, it was found that the proportion of polarization loss in dielectric loss was more than 99%. It is worth noting that the radar cross section (RCS) value of SiCN-7 absorber was lower than that of the perfect electrical conductor (PEC) plate in the range of −90–90°, and showed a larger coverage angle, indicating that it possessed a good practical application prospect in the field of electromagnetic wave absorption.
In recent years, electromagnetic wave (EMW) absorbing materials derived from biomass materials have been widely concerned because of their light weight and high efficiency. Here, Ni/PDCs/biomass ceramic composites absorbing material was prepared by a simple suspension impregnation-in-situ reduction carbonization process and polymer-derived ceramics (PDCs) with peanut shell as the absorbing matrix and NiO doped in polysiloxane as the precursor solution. The synergistic effect of Ni/PDCs could effectively adjust the impedance matching of the composite, and the BET results shown that the prepared Ni/PDCs/biomass ceramic composites had a hierarchical porous structure, which could not only provide a large number of heterogeneous interfaces, but also enhance the interface polarization, dipole polarization and multiple reflection loss of the absorbing material. The sample of NPP-1 possessed good EMW absorbing performance when the content of NiO was 1 % and the filler was 50 %, the minimum reflection loss (RL min ) reached − 66.38 dB at 1.74 mm, and the effective absorption bandwidth (EAB) was 3.54 GHz (14.46–18 GHz) at 1.45 mm. In this work, the electromagnetic parameters of biomass materials were adjusted by polymer conversion ceramics and metal oxides , which provided another feasible scheme for enhancing the absorbing properties of biomass materials.
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