Formation of nanocrystalline graphite in polymer-derived SiCN by polymer infiltration and pyrolysis at a low temperature  

作　　者：Mingxing LI Laifei CHENG Fang YE Conglin ZHANG Jie ZHOU 

机构地区：[1]Science and Technology on Thermostructural Composite Materials Laboratory,Northwestern Poly technical University,Xi'an 710072,China

出　　处：《Journal of Advanced Ceramics》2021年第6期1256-1272,共17页先进陶瓷（英文）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.51632007,51872229,and 52072304);National Science and Technology Major Project(Grant No.2017-VI-0007-0077).

摘　　要：The microstructure of polymer-derived ceramics(PDCs)was closely related to processing.This study demonstrated that SiCN matrix prepared by polymer infiltration and pyrolysis(PIP)at 900℃ inside a Si_(3)N_(4) whisker(Si_(3)N_(4w))preform with submicro-sized pores differed from its powder-consolidated analogue in both the content and structure of free carbon.Chemical analysis showed that PIP process had a higher free carbon yield.Raman spectroscopy and transmission electron microscopy(TEM)observation discovered a higher graphitization degree of free carbon and the existence of nanocrystalline graphite in SiCN matrix.Dielectric properties of Si_(3)N_(4w)/SiCN composites were greatly enhanced when volume fraction of SiCN matrix reached 24.5%due to dielectric percolation caused by highly-lossy free carbon.Reconsolidation of hydrocarbon released during pyrolysis by gas-state carbonization in Si_(3)N_(4) whisker preform was supposed to account for the high yield and graphitization degree of free carbon in PIP process.

关 键 词：polymer-derived ceramics(PDCs) silicon carbonitride(SiCN) free carbon CARBONIZATION dielectric property 

分 类 号：TQ174.1[化学工程—陶瓷工业]