溶胶-凝胶法原位生成SiO2改性硅基耐烧蚀材料

建立了在硅基耐烧蚀材料中用溶胶-凝胶法原位生成SiO2的方法.首先将硅橡胶、气相白炭黑、纤维等原料混炼硫化制备出硫化胶.然后将硫化胶依次浸入四氢呋喃、原硅酸乙酯和正丁基胺水溶液中进行预溶胀处理、物理扩散和化学反应,得到原位生成SiO2.SEM照片显示,在硅基耐烧蚀材料中原位生成的SiO2颗粒呈球形,粒径在40~60 nm,但分布不均匀,在硫化胶表层存在富集现象.实验结果表明,原位生成SiO2平均含量增加,硅基耐烧蚀材料的抗拉强度增加,线烧蚀率下降;含13.7%原位生成SiO2硅基耐烧蚀材料抗拉强度为5.82 MPa,线烧蚀率为0.071 mm/s.

in situ SILICA PREPARATION IN SILICON-BASED ABLATION-RESISTANT MATERIAL BY SOL-GEL METHOD

A technique of in situ SiO_2 preparation in silicon-based ablation-resistant material by sol-gel method was established.The preparing processes were as follows:first,vulcanizates were prepared by mechanical mixing of silicone rubber,fumed silica and other fillers.Secondly,the vulcanizates were swelled in tetrahydrofuran(THF) at 30°C for 12 h,and subsequently subjected to soaking in the tetraethylorthosilicate(TEOS) for 24 h.Thirdly,the swollen vulcanizates were put into the aqueous solution of n-butylamine at 50°C for 48 h in order to conduct the hydrolysis and condensation reactions of TEOS.Finally,the resultant vulcanizates were dried for several days at 50°C under a reduced pressure.SEM photographs indicated that silicon dioxide particles prepared by sol-gel method were spherical,and the particle size distribution was in the range of 40～60 nm,but the in situ SiO_2 was dispersed differently in the vulcanizates,which was enriched in the surface than the inside.So the content of in situ SiO_2 was the average of the materials.Compared to the conventional silica-filled vulcanizates which were prepared by mechanical mixing of the silica particles,the new vulcanizates with the in situ SiO_2 showed better properties.The results showed that the tensile strength and the ablation rate were improved apparently when the average amount of in situ SiO_2 increased.The tensile strength of the silicon-based ablation-resistant material containsing 13.7% in situ SiO_2 was about 5.82 MPa,and the ablation rate was 0.071 mm/s.