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Effects of thermal oxidation on microwave-absorbing and mechanical properties of SiC_f/SiC composites with PyC interphase

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Transactions of Nonferrous Metals Society of China 2015年第5期25卷 1484-1489页

作者：史毅敏罗发丁冬海穆阳周万城朱冬梅西北工业大学凝固技术国家重点实验室西安710072 西安建筑科技大学材料与矿资学院西安710055

The SiCf/SiC composites containing PyC interphase were prepared by chemical vapor infiltration process. The influences of thermal oxidation on the complex permittivity and microwave absorption properties of Si Cf/Si C composites were investigated in the frequency range of 8.2-12.4 GHz. Both the real and imaginary parts of the complex permittivity decreased after thermal oxidation. The composites after 100 h thermal oxidation showed that reflection loss exceeded-10 d B in the frequency of 9.7-11.9 GHz and the minimum value was-11.4 d B at 11.0 GHz. The flexural strength of composites decreased but fracture behavior was improved obviously after thermal oxidation. These results indicate that the SiCf/SiC composites containing PyC interphase after thermal oxidation possess good microwave absorbing property and fracture behavior.

关键词： SiCf/SiC composites thermal oxidation dielectric properties microwave absorbing mechanical properties

microwave absorption and thermal properties of coral-like SiC aerogel composites prepared by water glass as a silicon source

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International Journal of Minerals,Metallurgy and Materials 2023年第7期30卷 1375-1387页

作者： Xinyuan Zhang Chenkang Xia Weihai Liu Mingyuan Hao Yang Miao Feng Gao College of Materials Science and Engineering Taiyuan University of TechnologyTaiyuan 030024China

As a heat-resistant wave-absorbing material,silicon carbide(SiC)aerogel has become a research hotspot at ***,the most common silicon sources are organosilanes,which are costly and *** this work,SiC aerogels were successfully prepared by using water glass as the silicon ***,the microstructure and chemical composition of SiC aerogels were controlled by adjusting the Si to C molar ratio during the sol–gel process,and the effect on SiC aerogel microwave absorption properties was *** SiC aerogels prepared with Si:C molar ratio of 1:1 have an effective electromagnetic wave absorption capacity,with a minimum reflection loss value of-46.30 dB at 12.88 GHz and an effective frequency bandwidth of 4.02 *** also have good physical properties,such as the density of0.0444 g/cm^(3),the thermal conductivity of 0.0621 W/(m·K),and the specific surface area of 1099 m^(2)/*** lightweight composites with microwave-absorbing properties and low thermal conductivity can be used as thermal protection materials for space shuttles and reusable carriers.

关键词： water glass silicon carbide aerogel microwave absorbing thermal insulation performance

Designing Symmetric Gradient Honeycomb Structures with Carbon‑Coated Iron‑Based Composites for High‑Efficiency microwave Absorption

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Nano-Micro Letters 2024年第11期16卷 224-241页

作者： Yu Zhang Shu‑Hao Yang Yue Xin Bo Cai Peng‑Fei Hu Hai‑Yang Dai Chen‑Ming Liang Yun‑Tong Meng Ji‑Hao Su Xiao‑Juan Zhang Min Lu Guang‑Sheng Wang School of Chemistry Beihang UniversityBeijing 100191People’s Republic of China School of Electronics and Information Zhengzhou University of Light IndustryZhengzhou 450002People’s Republic of China School of Chemical Engineering Northeast Electric Power UniversityJilin 132000People’s Republic of China College of Chemistry and Materials Engineering Beijing Technology and Business UniversityBeijing 100048People’s Republic of China

The impedance matching of absorbers is a vital factor affecting their microwave absorption(MA)*** this work,we controllably synthesized Material of Institute Lavoisier 88C(MIL-88C)with varying aspect ratios(AR)as a precursor by regulating oil bath conditions,followed by one-step thermal decomposition to obtain carbon-coated iron-based *** the precursor MIL-88C(Fe)preparation conditions,such as the molar ratio between metal ions and organic ligands(M/O),oil bath temperature,and oil bath time,influenced the phases,graphitization degree,and AR of the derivatives,enabling low filler loading,achieving well-matched impedance,and ensuring outstanding MA *** MOF-derivatives 2(MD_(2))/polyvinylidene Difluoride(PVDF),MD_(3)/PVDF,and MD4/PVDF absorbers all exhibited excellent MA properties with optimal filler loadings below 20 wt%and as low as 5 wt%.The MD_(2)/PVDF(5 wt%)achieved a maximum effective absorption bandwidth(EAB)of 5.52 GHz(1.90 mm).The MD_(3)/PVDF(10 wt%)possessed a minimum reflection loss(RL_(min))value of−67.4 at 12.56 GHz(2.13 mm).A symmetric gradient honeycomb structure(SGHS)was constructed utilizing the high-frequency structure simulator(HFSS)to further extend the EAB,achieving an EAB of 14.6 GHz and a RL_(min) of−59.0 *** research offers a viable inspiration to creating structures or materials with high-efficiency MA properties.

关键词： MIL-88C(Fe) Fe/Fe_(3)O_(4)/Fe_(3)C@C Controllable preparation Symmetric gradient honeycomb structure microwave absorbing

Toward high performance microwave absorber by implanting La_(0.8)CoO_(3)nanoparticles on rGO

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Journal of Materials Science & Technology 2024年第7期174卷 176-187页

作者： Li Chang Yu-Ze Wang Xin-Ci Zhang Lin Li Hua-Zhang Zhai Mao-Sheng Cao Key Laboratory for Photonic and Electronic Bandgap Materials Ministry of EducationSchool of Physics&Electronic EngineeringHarbin Normal UniversityHarbin 150025China School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China

The advent of“intelligent era”brings our life more convenience,but the electromagnetic radiation sur-rounding us not only greatly threatens human health,also makes information leakage and hidden trouble to national defense ***,it is very urgent to develop novel electromagnetic wave absorption materials with lightweight,strong absorption,tunable absorption frequency and broad band ***,a novel electromagnetic wave absorber is obtained by constructing La_(0.8)CoO_(3)-rGO nanocompos-ite,where La_(0.8)CoO_(3)nanoparticles are anchored on graphene nanosheets by the electrostatic interaction between GO and La_(0.8)CoO_(3).The effect of hybridization ratio of La_(0.8)CoO_(3)and rGO on microwave ab-sorption properties is carefully *** optimal reflection loss of La_(0.8)CoO_(3)-rGO nanocomposite can reach-62.34 dB with the maximum effective bandwidth of 6.08 GHz,presenting 48.78%and 245.45%increment compared to bare La_(0.8)CoO_(3)nanoparticles,*** effective absorption bandwidth covers a broad electromagnetic wave absorption band from Ku band to the C band by tailoring thickness of the absorbers from 2.4 mm to 4.4 *** fascinating electromagnetic wave absorption performance is attributed to the synergy effect of La_(0.8)CoO_(3)and rGO,which integrates magnetic and dielectric loss caused by resonance,conductance,relaxation,and scattering *** result confirms that La_(0.8)CoO_(3)-rGO nanocomposite is potential candidates toward high-efficiency microwave absorbers and provides a valuable pathway for designing high-performance microwave attenuation materials in the future.

关键词： Perovskite La_(0.8)CoO_(3)nanoparticles Graphene Nanocomposite microwave absorbing Broad band absorption

Preparation and microwave absorption performance of SiC aerogel via sol-gel and carbonization reduction process

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Defence Technology（防务技术） 2024年第12期42卷 73-82页

作者： Xinli Ye Pengyi Xu Hao Yu Shan Li Xiaomin Ma Wei Xu Junxiong Zhang School of Civil Aviation Northwestern Polytechnical UniversityXi'an 710072China Research&Development Institute of Northwestern Polytechnical University in Shenzhen Shenzhen 518057China Yangtze River Delta Research Institute of Northwestern Polytechnical University Suzhou 215400China National Equipment New Material&Technology(Jiangsu)Co. LtdSuzhou 215400China Xi'an Electronic Engineering Research Institute Xi'an 710100China School of Textile and Clothing Nantong UniversityNantong 226019China

SiC aerogel presents several advantageous features like lightweight and high temperature resistance when applied as microwave absorbing *** this paper,SiC aerogel was prepared eventually followed by the sol-gel and carbonization reduction *** results showed that the effective electromagnetic microwave absorption capacity of SiC aerogel was highly increased after being pyrolyzed at 1500℃,which presented a minimum reflection loss value of-57.80 dB at 3.10 mm and 9.86 ***,the electromagnetic parameters of SiC aerogel with different paraffin ratios were discussed as well as the varying electromagnetic microwave absorption *** minimum reflection loss value first rose then fell as the SiC/paraffin ratio increased,which demonstrated the importance of SiC *** study establishes the theoretical foundation for the subsequent functional application of SiC aerogel.

关键词： SiC aerogel microwave absorbing SiC/Paraffin ratio Functional applications

Synthesis and microwave Absorption Properties of BaTiO3-polypyrrole Composite

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Chinese Journal of Chemical Physics 2010年第5期23卷 603-607,622页

作者：李巧玲张存瑞李建强中北大学理学院化学系太原030051

BaTiO3 powders are prepared by sol-gel method by cotton template. Polypyrrole is prepared by chemical oxidation route in the emulsion polymerization system. Then BaTiO3- polypyrrole composites with different mixture ratios are prepared by as-prepared material. The structure, morphology, and properties of the composites are characterized with Infrared spectrum, X-ray diffraction, scanning electron microscope, and net-wok analyzer. The com- plex permittivity and reflection loss of the composites are measured at different microwave frequencies in S-band and C-band （0.03-6 GHz） employing vector network analyzer model PNA 3629D vector. The effect of the mass ratio of BaTiO3 to polypyrrole on the microwave loss properties of the composites is investigated. A possible microwave absorbing mechanism of BaTiOa-polypyrrole composite is proposed. The BaTiO3-polypyrrole composite can find applications in suppression of electromagnetic interference and reduction of radar signature.

关键词： BaTiO3 Polypyrrole microwave absorbing

A new electromagnetic functional material composed of metallic hollow micro-spheres

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Journal of Southeast University(English Edition) 2003年第1期19卷 8-11页

作者：徐鸿飞徐丽娜顾宁孙忠良东南大学毫米波国家重点实验室东南大学分子与生物分子电子学教育部重点实验室南京210096

This paper presents a new electromagnetic functional material developed byelectron-less nickel deposition technique, with a single hollow micro-sphere as the core templateand a thin nickel layer as the shell. The micrograph taken by a scanning electron microscope showsthe microstructures of the materials in detail. Scattering parameters of the waveguide sample holderfilled with the materials have been obtained over X band. The electromagnetic parameters computedfrom the measured S parameters show that the material with metallic hollow spheres has as highrelative permeability μ'_r as 19.0 with about 0.6 magnetic loss tangent over the whole *** to the material with non-metallic spheres, the permeability μ'_r and the magnetic losstangent μ'_r increase greatly, while the permittivity remains lower than 1.8.

关键词： electromagnetic functional material microwave absorbing electron-lessdeposition

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导电高分子复合材料的制备、性能及应用

导电高分子复合材料的制备、性能及应用