先驱体转化法制备SiFeOC陶瓷及其吸波性能研究

Preparation of precursor derived SiFeOC ceramics and study on its electromagnetic wave absorption properties

摘要:

随着智能时代的快速发展，电磁污染已经成为继大气污染、水污染、噪音污染之后的第四大污染源，进而危害人体健康。开发轻质高效的电磁波吸收材料有望减少环境中的电磁污染，以及提高飞行器的雷达隐身功能，增强其安全服役。在此背景下，本研究以甲基三甲氧基硅烷、二甲基二甲氧基硅烷和硝酸铁为主要原料，以硝酸为催化剂，无水乙醇为溶剂，通过改变硝酸铁含量对SiOC陶瓷先驱体进行改性，采用溶剂热法合成SiFeOC陶瓷湿凝胶，经过老化、干燥等工艺形成SiFeOC陶瓷干凝胶，再经过高温处理获得SiFeOC陶瓷。主要研究了硝酸铁含量和热处理温度对SiFeOC陶瓷的物相组成和微观结构的影响，并表征了不同硝酸铁含量改性SiFeOC陶瓷的吸波性能，阐明了微观结构和物相对SiFeOC陶瓷吸波性能的影响。结果表明，由于硝酸铁的引入，促进非晶SiOC陶瓷基体中析出大量的SiC纳米晶和自由碳，形成丰富的异质界面。最后，由于SiC/SiOC、Cfree/SiOC等界面形成的界面极化、自由碳中的缺陷极化、SiC纳米晶的介电损耗和自由碳的导电损耗的协同作用，硝酸铁含量为3 wt.%的SiFeOC陶瓷具有最佳的吸波性能，当样品厚度为3.6 mm时，最小反射损耗值为-47.6 dB；而当样品厚度为4.5 mm时，最大有效吸波带宽达3.7 GHz。此外，由于硝酸铁的引入，SiOC陶瓷的非晶结构得以保留，其热稳定性能增强。本研究提供了一种新型SiOC陶瓷微结构调控策略，对高性能吸波材料的开发具有重要的指导意义。

Abstract:

With the rapid development of the intelligent era, electromagnetic wave pollution has become the fourth pollution source after air pollution, water pollution and noise pollution, which endangers human health. The development of efficient electromagnetic wave absorbing materials is expected to reduce electromagnetic pollution in the environment, as well as improve the radar stealth function of the aircraft, and enhance its safe service. In this study, methyl trimethoxysilane, dimethyl dimethoxysilane and ferric nitrate were used as the main raw materials, and nitric acid and anhydrous ethanol were used as catalyst and solvent. SiFeOC ceramic precursor was modified by ferric nitrate, SiFeOC ceramic wet gel was synthesized by solvothermal method, and SiFeOC ceramic dry gel was formed by aging and drying. And then the SiFeOC ceramic was obtained after heat treatment. The effects of ferric nitrate content and heat treatment temperature on phase composition and microstructure of SiFeOC ceramics were studied, and the electromagnetic wave absorption properties of SiFeOC ceramics were characterized. The influence of microstructure and material on the absorbing properties of SiFeOC ceramics was discussed. The results showed that the introduction of ferric nitrate promoted the precipitation of large amounts of SiC nanocrystals and free carbon in an amorphous SiOC ceramic matrix, forming a rich heterogeneous interface. Finally, owing to the synergistic effect of interface polarization formed by SiC/SiOC, Cfree/SiOC, defect polarization in free carbon, dielectric loss of SiC nanocrystals and conductive loss of free carbon, SiFeOC ceramics with 3 wt.% ferric nitrate exhibited the best electromagnetic wave absorption performance, when the sample thickness was 3.6 mm, the minimum reflection loss value was -47.6 dB; When the sample thickness was 4.5 mm, the maximum effective absorption bandwidth reached 3.7 GHz. In addition, due to the introduction of ferric nitrate, the amorphous structure of SiOC ceramics was preserved and its thermal stability was enhanced. This study provides a novel micro-structure control strategy for SiOC ceramics, which has important guiding significance for the development of high-performance absorbing materials.