Preparation And Microwave Absorption Preformance Of SiC-based Core-shell Composites

Microwave absorbing materials play an important role in the field of aerospace due to their electromagnetic shielding function,and the conventional absorbing materials are easy to lose effectiveness in high temperature environment.The demand for high temperature absorbing materials is becoming stronger and stronger,and SiC based absorbing materials can show good dielectric relaxation properties under high temperature conditions.SiC based composite absorbing materials with strong absorption properties is designed by using SiC materials with dielectric loss and high temperature resistance as substrate,which is of great significance in the field of high temperature absorbing.In this paper,the following three aspects of SiC based absorbing materials are researched:（1）preparation of high temperature absorbing nanoparticles;（2）study of absorbing mechanism of microwave absorbing materials;and（3）broadband and strong absorption of absorbing materials.The specific results of the study are as follows:（1）Using different crystal forms and particle sizes of silicon carbide,nickel oxide can be successfully deposited on the surface of silicon carbide by redox deposition at a pH of 9-10,and the absorbing properties at this pH are also stronger than the reaction conditions of the original silicon carbide and weak acidity,the absorbing performance can reach-11 dB when the coating thickness is 5 mm,which meets the requirements of absorbing shielding.（2）NiO nanoparticle is deposited at different pH conditions with 50 nmβ-SiC as substrate by redox deposition.The results show that NiO can be successfully deposited on SiC surface at pH 9-10.The presence of NiO can be proved by XRD analysis,and its absorption performance is better than that of original SiC and weak acidic reaction.When the thickness of the sample is 5mm,the wave absorption performance can reach-11 dB,and the effective absorption band（RL≤-10 dB）is 7.0⁸.4GHz,meeting the requirements of wave absorption shielding.（3）SiC@SiO₂-NiO₂/rGO and SiC@SiO₂-Ni/rGO absorbing composites are successfully prepared by hydrothermal method and air and H₂/Ar treatment respectively.For SiC@SiO₂-NiO₂/rGO absorbing composites,the addition of nickel salt can effectively adjust the dielectric constant and magnetic permeability.With the increase of nickel salt,the absorbing performance is gradually improved.When the amount of nickel salt is 1.5 mmol,the absorbing property is the strongest,and the thickness is 5mm,the strongest absorbing value at 4.00 GHz reaches-29.80 dB.For the SiC@SiO₂-Ni/rGO absorbing composite,when the nickel salt is added in an amount of2 mmol,the thickness is 1.35 mm,which is the strongest at 14.5 GHz and absorbing value reaches-17.5 dB.Since the dielectric relaxation properties and magnetic permeability loss of SiC@SiO₂-NiO₂/rGO absorbing composites are better than SiC@SiO₂-Ni/rGO,the absorbing properties of SiC@SiO₂-NiO₂/rGO absorbing composites are obvious.Better than SiC@SiO₂-Ni/rGO.