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二氧化硅气凝胶广泛用于各种航天器、飞行器的热防护中,添加遮光剂或纤维能大大改善其在高温下的隔热性能.本文通过计算辐射特性得到遮光剂和纤维不同温度下的最佳掺杂粒径,在复合材料等效热导率最小时得到最佳掺杂量,并应用优化结果设计了具有温度梯度的多层掺杂方案.研究发现:遮光颗粒和纤维的最佳掺杂直径随温度增加而减小,掺杂量随温度增加而增加,研究的4种遮光剂(碳黑、SiC、ZrO_2和TiO_2)中,碳黑具有最好遮光效果,但高温下会被氧化,SiC在高温下具有较好的遮光效果;石英纤维多层掺杂具有最小有效热导率,碳黑与SiC遮光剂和石英纤维共同掺杂对辐射传热的抑制最强.气凝胶复合材料背温实验结果有效证实了掺杂优化方法的正确性.
Silica airgel is widely used in thermal protection of various spacecraft and aircraft, adding sunscreen or fiber can greatly improve its heat insulation performance under high temperature.This paper obtains the sunscreen and fiber under different temperatures by calculating the radiation characteristics , The optimal doping amount is obtained when the equivalent thermal conductivity of the composite material is minimum, and the multi-layer doping scheme with temperature gradient is designed by using the optimization results. The best doping diameter decreases with increasing temperature, and the doping amount increases with the increase of temperature. Among the four sunscreens studied (carbon black, SiC, ZrO 2 and TiO 2), carbon black has the best shading effect, but under high temperature Is oxidized and SiC has good opacity at high temperature. The multi-layer doping of quartz fiber has the minimum effective thermal conductivity, and the co-doping of carbon black with SiC opacifier and quartz fiber has the strongest inhibition on radiation heat transfer. The experimental results of adhesive back temperature effectively confirmed the correctness of the doping optimization method.