SiBCN陶瓷前驱体高温裂解机理

doi:10.3724/SP.J.1077.2014.13278

无机材料学报 ›› 2014, Vol. 29 ›› Issue (3): 321-326.DOI: 10.3724/SP.J.1077.2014.13278 CSTR: 32189.14.SP.J.1077.2014.13278

SiBCN陶瓷前驱体高温裂解机理

李亚静, 张跃

(北京航空航天大学材料科学与工程学院, 空间材料与服役教育部重点实验室, 北京100191)

收稿日期:2013-05-24 修回日期:2013-07-24 出版日期:2014-03-20 网络出版日期:2014-02-18
作者简介:李亚静(1977-), 女, 博士研究生. E-mail: liyajinggz@163.com
基金资助:
国家自然科学基金(51072010 , 51272009) National Natural Science Foundation of China(51072010 , 51272009)

Pyrolysis Mechanism of SiBCN Polymer Precursor

LI Ya-Jing, ZHANG Yue

(Key Laboratory of Aerospace Materials and Performance of Ministry of Education, School of Materials Science and Engineering, Beihang University, Beijing 100191, China)

Received:2013-05-24 Revised:2013-07-24 Published:2014-03-20 Online:2014-02-18
About author:LI Ya-Jing. E-mail: liyajinggz@163.com

摘要/Abstract

摘要：

SiBCN是目前重要的高温非晶材料之一。非晶结构表征是研究非晶材料形成过程的关键。采用固态NMR和FT-IR为主要的研究手段研究聚硅硼碳氮烷的热稳定性和SiBCN陶瓷前驱体高温裂解机理。研究表明, 陶瓷化转变过程分为三个阶段, 第一阶段是产生引发剂, 即聚合物前驱体中的叔碳脱氢转化成季碳自由基; 第二阶段是链增长和链终止, 季碳自由基首先攻击碳甲基, 使甲基脱落生成新的自由基, 随着温度的升高, 自由基还会攻击硅甲基, 生成新的自由基。在生成新的自由基过程中使链增长。当自由基与自由基结合时, 链终止; 第三阶段是陶瓷化, 通过脱氢将已经无机化的中间产物转化成陶瓷, 形成无机三维连续非晶网络。第一、二阶段属于有机转变, 第三阶段属于无机转变。当转化成陶瓷时, 陶瓷内只含有Si、B、C和N四种元素, 端基完全脱落。

关键词: MNR, FT-IR, SiBCN, 聚硼硅氮烷

Abstract:

High temperature amorphous materials, mainly in the system of SiBCN, have aroused ever increasing attention. Effective methods should be used to study the structural changes in the process of fabrication. In this paper, the thermal stability of PBSZ and the pyrolysis mechanism of SiBCN polymer precursor were studied by SS-NMR and FT-IR. Polymer-to-ceramic transformation can be divided into three stages as follows. The first stage is the production of initiator in which, the tertiary carbon dehydrogenates to quaternary carbon free radical. The second stage is propagation and termination in which, quaternary carbon free radical attacks methyl group to turn the methyl group into new free radical. With increasing temperature, the free radical attacks Si-CH₃ and results in a new free radical. The propagation of the chain occurs when new free radicals are generated, while the termination occurs after the free radicals combination with each other. The third stage is polymer-to-ceramic transformation. Through dehydrogenation, ceramics are produced from the intermediate inorganic products, and amorphous continuous 3D mesh structures are formed. The first and second stages are organic transformations and the third stage is an inorganic transformation. There are four elements in the ceramic, including Si, B, C and N.

Key words: MNR, FT-IR, SiBCN, Polyborosilazane

中图分类号:

TB35

李亚静, 张跃. SiBCN陶瓷前驱体高温裂解机理[J]. 无机材料学报, 2014, 29(3): 321-326.

LI Ya-Jing, ZHANG Yue. Pyrolysis Mechanism of SiBCN Polymer Precursor[J]. Journal of Inorganic Materials, 2014, 29(3): 321-326.

图/表 8

图1 聚合物前驱体的合成路线

Fig. 1 Reaction paths presenting the synthesis of polymer precursor

图2 惰性气氛下陶瓷先驱体的TG和DSC曲线

Fig. 2 TGA/DSC curves for weight loss and heat flow of the preceramic polymer under inert atmosphere

图3 惰性气氛下陶瓷先驱体热解过程中气体放出情况

Fig. 3 Gas release situation of pyrolysis of the preceramic polymer under inert atmosphere

图4 SiBCN陶瓷前驱体热解不同阶段的13C-NMR图谱

Fig. 4 13C-NMR spectra of SiBCN ceramics at different pyrolysis temperatures

图5 SiBCN陶瓷前驱体热解不同阶段的11B-NMR图谱

Fig. 5 11B-NMR spectra of SiBCN ceramics at different pyrolysis temperatures

图6 SiBCN陶瓷前驱体热解不同阶段的29Si-NMR图谱

Fig. 6 29Si-NMR spectra of SiBCN ceramics at different pyrolysis temperatures

图7 陶瓷化过程试样不同温度段产物的FT-IR图谱

Fig. 7 FT-IR spectra of PBSZ-derived ceramic at different pyrolysis temperatures (a) Precursor; (b) 200℃; (c) 450℃; (d) 600℃; (e) 800℃; (f) Ceramic

表1 前驱体热解过程不同温度阶段的红外谱分析

Table 1 Analysis of FT-IR spectra of PBSZ-derived ceramics at different pyrolysis temperatures

	Precursor	200℃	450℃	600℃	800℃	Creamic
γN-H	3383	3444	3405	3444	3429	3447
γ_asCH₃	—	—	—	2973	—	—
γ_asCH₂	2925	—	—	2924	—	—
γ_sCH₂	2855	—	—	2854	—	—
δ_s(C-) CH₃, δ_sCH₂	1460	—	—	—	—	—
δ_as(C-) CH₃, δCH₂	1407	—	—	—	—	—
δ_s(C-) CH₃	1363	1389	1389	1388	—	—
γC-C	—	—	—	—	1369	1372
δ_s(Si-) CHX	1265	1269	1268	1276	—	—
γ B-C	1045	1038	1033	1041	1068	1082
γSi-N	926	883	879	—	—	897
γSi-C	783	779	779	775	794	801

参考文献 13

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SiBCN陶瓷前驱体高温裂解机理

Pyrolysis Mechanism of SiBCN Polymer Precursor

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