苯基硅橡胶／硅氮陶瓷前驱体复合绝热层烧蚀机理

摘要

Polymethylphenylsiloxane (PMPS) elastomer ablative composite filled with polysilazane, fumed silica and carbon fi⁃bers was prepared and tested using an oxyacetylene torch. After the ablation, the material structure, composition and thermal⁃oxida⁃tive properties of the composite were analyzed using the SEM, FT⁃IR, XRD and EDS. The results show that a silica layer, a ceram⁃ic layer, a pyrolysis layer and the matrix are formed in turn by decomposition, ceramization and oxidation reactions of the virgin ab⁃lative composite. Aromatic carbon is formed in the porous pyrolysis and ceramic layers by the degradation of the silicone rubber ma⁃trix, which transforms into inorganic carbon in the zone close to the ceramic layer. Silicon carbide crystallite is produced in the ce⁃ramic layer. Oxidation of the compounds in the ceramic layer yields a silica layer, which is primarily composed of silica. The thermo-oxidative stabilities of the ablative layers are better than that of the virgin material as a result of the formation of dense carbon layer structure.%采用甲基苯基聚硅氧烷（PMPS）与聚硅氮烷 PNS⁃3为复合基体，气相法白炭黑和炭纤维为填充材料，制备了有机硅耐烧蚀复合材料，并采用氧乙炔焰烧蚀实验的方法研究了材料的烧蚀性能。在对烧蚀后的材料形貌 SEM 分析和采用XRD、FT⁃IR、EDS 等方法进行了成分分析的基础上，发现加入聚硅氮烷后，苯基硅橡胶的烧蚀行为发生了变化，提出了氧化层、成炭层、陶瓷层、裂解层和基体五区域的新烧蚀模型，并对烧蚀机理进行了初步探讨。研究表明，绝热层在烧蚀过程中，氧化层主要组分是 SiO2，起到隔绝氧化性气氛渗入的作用；氧化层下是新生成的耐高温、耐氧化的 SiC 陶瓷；成炭层坚硬致密起到了热防护的作用。