Full
ZHOU Wei (1986-), male, Ph.D.,Associate Professor.
Outline
To improve the microwave absorption properties of high-temperature resistance of Si3N4 based composites, four kinds of composites of Si3N4, Cf/Si3N4, SiCnf/Si3N4 and SiCnf-Cf/Si3N4 were prepared by a gel-casting and pressure less sintering process using Si3N4 ceramic as a substrate, and carbon fiber (Cf), SiC nanofibers (SiCnf) or SiC nanofibers coated carbon fiber (SiCnf-Cf), respectively, as an absorber. A comparative study on the microstructure, dielectric properties and microwave absorbing performance at room temperature and 800℃ of as-prepared Si3N4 based composites was conducted. The results show that the high-temperature chemical compatibility of Cf and Si3N4 is effectively improved by coating SiCnf on Cf , and Cf is well preserved in Si3N4 matrix and connected to each other into a conductive network, thus leading to the enhanced electron conduction and multiple relaxation phenomena in SiCn-Cf/Si3N4 composite. The SiCnf-Cf/Si3N4 composite exhibits the maximum dielectric loss value and the optimal microwave absorption performance both at room temperature and 800℃. At room temperature, the minimum reflection loss (RL) of SiCnf-Cf/Si3N4 composite is -15.2 dB at a thickness of 2.57 mm, and the effective absorption bandwidth (RL<-10 dB) is 1.9 GHz at a thickness of 2.30 mm. At 800℃, the minimum RL reaches -20.4 dB at a thickness of 2.0 mm, and the effective absorption bandwidth increases to 3 GHz at a thickness of 2.25 mm. The main absorbing mechanism of SiCnf-Cf/Si3N4 composite is multiple reflections and scattering, electrical conduction loss, electron polarization and multiple relaxations. At 800℃, the polarization and conduction of electrons are enhanced by the accelerated thermal motion of electrons, leading to a further enhancement in the microwave absorption performance. SiCnf-Cf/Si3N4 composite could be used as a high-performance microwave absorbing material for microwave absorption at a high temperature.
29
8
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
关闭全屏
No. 86 Xueyuan South Road, Haidian District, Beijing
010-62662699(Operation and Technical Support)
qkjq@cast.org.cn
Copyright © 2025 China Association for Science and Technology. All rights reserved. For all open access content, the relevant licensing terms apply.
Sponsored by the Office of the Leading Group for Cybersecurity and Informatization of CAST, and supported by Science and Technology Review Publishing House
