High-performance thermal protection materials(TPMs)for spacecraft are becoming current research hotspots.Lightweight polymer-based ablators are considered to be the most promising candidates for TPMs due to their exce...High-performance thermal protection materials(TPMs)for spacecraft are becoming current research hotspots.Lightweight polymer-based ablators are considered to be the most promising candidates for TPMs due to their excellent designability and versatility.In this study,a unique nano-TiO_(2) coated needled carbon fiber felt/phenolic resin aerogel composite(TiCF/PR)is reported.Wherein the anatase nano-TiO_(2) was in-situ coated on the surface of carbon fibers uniformly through the sol-gel and calcination method,then,the phenolic resin aerogel was in-situ synthesized in the nano-TiO_(2) coated needled carbon fiber felt(TiCF)preform through vacuum impregnation and solvothermal method.The as-prepared aerogel com-posite possesses a low density(0.30–0.32 g/cm^(3)),low thermal conductivity(0.034 and 0.312 W/(m K)in the z and xy directions),and excellent thermal stability with 13.86%residual weight at 1300℃ in air.It is worthwhile to note that the TiCF/PR composite exhibits excellent antioxidant ablation and infrared(IR)radiation shielding properties in a high-temperature heating environment.With an oxygen-acetylene blaze heating of 1.5 MW/m^(2) for 150 s,the linear ablation rates decreased by 13.4%,and the backside temperature reduced from 322.3 to 179.1℃ compared to that of the sample without nano-TiO_(2) coating.The experimental and theoretical analysis showed that the present TiCF/PR nanocomposite has competitive and potential application prospects in the field of future TPMs.展开更多
To improve the thermal insulation performance of SiO_(2)aerogels at high temperatures,SiO_(2)precursor solutions were prepared via a sol-gel two-step method.Fe_(2)O_(3)powder was extra added as an opacifier to the SiO...To improve the thermal insulation performance of SiO_(2)aerogels at high temperatures,SiO_(2)precursor solutions were prepared via a sol-gel two-step method.Fe_(2)O_(3)powder was extra added as an opacifier to the SiO_(2)precursor solutions with mass fractions of 0,0.2%,0.5%,1.0%,and 3.0%;and Fe_(2)O_(3)-SiO_(2)composite aerogels were fabricated using CO_(2)supercritical drying technology.The effects of the Fe_(2)O_(3)extra addition on the aerogels were investigated.The results show that:(1)Fe_(2)O_(3)doping does not alter the aerogel morphology;Fe_(2)O_(3)suppresses the mass loss at high temperatures and enhances the high-temperature stability of the composite;(2)below 800℃,the aerogel with 0.5%Fe_(2)O_(3)exhibits the lowest thermal conductivity and the best thermal insulation performance;at 800-1000℃,the aerogel with 1%Fe_(2)O_(3)exhibits the lowest thermal conductivity and a good nanoporous structure;(3)by adjusting the Fe_(2)O_(3)extra addition,composite aerogels suitable for different temperature ranges can be tailored.展开更多
基金We gratefully acknowledge the support from the National Nat-ural Science Foundation of China(Nos.51872066,52032003,and U20B2017).
文摘High-performance thermal protection materials(TPMs)for spacecraft are becoming current research hotspots.Lightweight polymer-based ablators are considered to be the most promising candidates for TPMs due to their excellent designability and versatility.In this study,a unique nano-TiO_(2) coated needled carbon fiber felt/phenolic resin aerogel composite(TiCF/PR)is reported.Wherein the anatase nano-TiO_(2) was in-situ coated on the surface of carbon fibers uniformly through the sol-gel and calcination method,then,the phenolic resin aerogel was in-situ synthesized in the nano-TiO_(2) coated needled carbon fiber felt(TiCF)preform through vacuum impregnation and solvothermal method.The as-prepared aerogel com-posite possesses a low density(0.30–0.32 g/cm^(3)),low thermal conductivity(0.034 and 0.312 W/(m K)in the z and xy directions),and excellent thermal stability with 13.86%residual weight at 1300℃ in air.It is worthwhile to note that the TiCF/PR composite exhibits excellent antioxidant ablation and infrared(IR)radiation shielding properties in a high-temperature heating environment.With an oxygen-acetylene blaze heating of 1.5 MW/m^(2) for 150 s,the linear ablation rates decreased by 13.4%,and the backside temperature reduced from 322.3 to 179.1℃ compared to that of the sample without nano-TiO_(2) coating.The experimental and theoretical analysis showed that the present TiCF/PR nanocomposite has competitive and potential application prospects in the field of future TPMs.
文摘To improve the thermal insulation performance of SiO_(2)aerogels at high temperatures,SiO_(2)precursor solutions were prepared via a sol-gel two-step method.Fe_(2)O_(3)powder was extra added as an opacifier to the SiO_(2)precursor solutions with mass fractions of 0,0.2%,0.5%,1.0%,and 3.0%;and Fe_(2)O_(3)-SiO_(2)composite aerogels were fabricated using CO_(2)supercritical drying technology.The effects of the Fe_(2)O_(3)extra addition on the aerogels were investigated.The results show that:(1)Fe_(2)O_(3)doping does not alter the aerogel morphology;Fe_(2)O_(3)suppresses the mass loss at high temperatures and enhances the high-temperature stability of the composite;(2)below 800℃,the aerogel with 0.5%Fe_(2)O_(3)exhibits the lowest thermal conductivity and the best thermal insulation performance;at 800-1000℃,the aerogel with 1%Fe_(2)O_(3)exhibits the lowest thermal conductivity and a good nanoporous structure;(3)by adjusting the Fe_(2)O_(3)extra addition,composite aerogels suitable for different temperature ranges can be tailored.
