Role of in-situ formed free carbon on electromagnetic absorption properties of polymer-derived SiC ceramics
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ISSN 2226-4108 CN 10-1154/TQ
Research Article
Role of in-situ formed free carbon on electromagnetic absorption properties of polymer-derived SiC ceramics Zhaoju YUa,b,*, Xuan LVa, Kangwei MAOa, Yujing YANGa, Anhua LIUa,b,c,* a
College of Materials, Key Laboratory of High Performance Ceramic Fibers (Xiamen University), Ministry of Education, Xiamen 361005, China b College of Materials, Fujian Key Laboratory of Advanced Materials (Xiamen University), Xiamen 361005, China c Shenzhen Research Institute of Xiamen University, Shenzhen 518000, China Received: February 25, 2020; Revised: June 28, 2020; Accepted: June 30, 2020 © The Author(s) 2020.
Abstract: In order to enhance dielectric properties of polymer-derived SiC ceramics, a novel single-source-precursor was synthesized by the reaction of an allylhydrido polycarbosilane (AHPCS) and divinyl benzene (DVB) to form carbon-rich SiC. As expected, the free carbon contents of resultant SiC ceramics annealed at 1600 ℃ are significantly enhanced from 6.62 wt% to 44.67 wt%. After annealing at 900–1600 ℃, the obtained carbon-rich SiC ceramics undergo phase separation from amorphous to crystalline feature where superfine SiC nanocrystals and turbostratic carbon networks are dispersed in an amorphous SiC(O) matrix. The dielectric properties and electromagnetic (EM) absorption performance of as-synthesized carbon-rich SiC ceramics are significantly improved by increasing the structural order and content of free carbon. For the 1600 ℃ ceramics mixed with paraffin wax, the minimum reflection coefficient (RCmin) reaches –56.8 dB at 15.2 GHz with the thickness of 1.51 mm and a relatively broad effective bandwidth (the bandwidth of RC values lower than –10 dB) of 4.43 GHz, indicating the excellent EM absorption performance. The carbon-rich SiC ceramics have to be considered as harsh environmental EM absorbers with excellent chemical stability, high temperature, and oxidation and corrosion resistance. Keywords: polymer-derived ceramics (PDCs); microstructural evolution; dielectric properties; electromagnetic properties
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Introduction
Centimeter-wave frequency electromagnetic (EM) waves (2–18 GHz) are widely used in various environments, which require high efficient EM absorbing (EMA) materials due to the massive increasing use of high * Corresponding authors. E-mail: Z. Yu, [email protected]; A. Liu, [email protected]
operating frequencies and bandwidths in electronic systems [1–7]. Recently, polymer-derived ceramics (PDCs) attract great attention as EM absorbers since they possess tunable dielectric properties and conductivities, low density, excellent high-temperature mechanical properties, oxidation, and corrosion resistance as well as thermophysical and chemical stabilities [8,9]. However, due to their intrinsic low permittivity, high-temperature resistant ceramics including most PDCs in general cannot meet the basic requirements for the application as EMA materials [8].
www.springer.com/journal/40145
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J Adv Ceram 2020, 9(5): 617–628
Pristine PDCs without additional
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