SiBCN metal-free ceramic wave-absorbing material obtained from cracking conversion of benzene ring-containing polymer and preparation method thereof

Abstract

The invention discloses a SiBCN metal-free ceramic wave-absorbing material obtained from cracking conversion of benzene ring-containing polymer and a preparation method thereof, wherein the preparation method includes synthesis of benzene ring-containing hyperbranched polyborosilazane and preparation of the SiBCN ceramic wave-absorbing material. The hyperbranched polyborosilazane is synthesized bymethyl dichlorodiphenylsilazane, dichlorosilazane, boron trichloride and hexamethyldisiliazide, then the hyperbranched polyborosilazane is crosslinked and tabletted into a blank body, and the blank body is cracked into the ceramic wave-absorbing material. Starting from the design of the structure of a ceramic polymer precursor, synthesis of a high ceramic yield polyborosilazane precursor and construction of a crosslinking topology system are performed, and the benzene ring is directly introduced into the structure of the polyborosilazane precursor, so that sp2 hybrid carbon atoms in the benzene ring directly form graphite carbon, carbon nanotubes and other structures in situ in cracking conversion process, the high temperature wave absorbent is uniformly dispersed in the structure of an amorphous low-loss carrier, and the metal-free ceramic based composite material with good wave absorbing properties is obtained.

Description

technical field [0001] The invention belongs to the technical field of wave-absorbing materials, and in particular relates to a SiBCN metal-free ceramic wave-absorbing material and a preparation method thereof. Background technique [0002] SiBCN composite ceramics can be obtained by pyrolysis of polyborosilazane precursor. Due to the introduction of boron, BN / B is formed during the ceramic conversion process. 4 Phase C, BN / B 4 The C phase itself has good high temperature resistance, and the high temperature resistance of the ceramic matrix can be greatly improved as a whole through the oxygen barrier protection effect and synergistic effect. According to Nature, SiBCN composite ceramics can reach a temperature resistance level above 2000 °C. Compared with single-phase SiC, Si 3 N 4 The matrix or multiphase SiCN ceramics, SiBCN multiphase ceramic matrix theoretically has higher high temperature resistance and better high temperature oxidation resistance, polyborosilazane ...

AI Technical Summary

Problems solved by technology

[0004] However, the existing polymer-based converted SiBCN ceramics need to add absorbing agents or transition metals to improve the absorbing performance, and the addition of transition metals has the following problems: (1) The application environment of high-temperature resistant absorbing materials is mainly long-term high-temperature conditions , for PDC ceramics, it is equivalent to being in a high-temperature annealing environment for a long time. The existence of transition metal elements will continue to catalyze the crystallization of the amorphous state inside the PDC ceramics. The increase of the crystalline high dielectric loss phase may cause impedance matching imbalance. , which is not conducive to the stability of the material's absorbing performance

(2) With the development of radar absorbing material technology, the integration of structure and function is the focus of future research on absorbing materials. Structural absorbing materials should have the dual functions of carrying and reducing the radar scattering cross section. However, the increase of crystal phase will The mechanical properties of ceramic materials are reduced, which is not conducive to the bearing capacity and practical application of ceramic materials.

Images