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
Intraocular lens(IOL)is a crucial implant for cataract therapy.Posterior capsule opacification(PCO)is the most common post-operative complication after IOL implantation,which is the abnormal hyperplasia of the residua...Intraocular lens(IOL)is a crucial implant for cataract therapy.Posterior capsule opacification(PCO)is the most common post-operative complication after IOL implantation,which is the abnormal hyperplasia of the residual lens epithelial cells(LECs)after IOL implantation in cataract surgery.It is reported that the cellular microenvironment in the lens capsule changes after surgery,such as the elevated secretion of matrix metalloproteinases(MMPs)and a decrease in pH due to undesired cell proliferation.In this study,MMP-2and pH-triggered drug delivery polysaccharide multilayer coating was designed and introduced onto the IOL surface for obtaining the cellular microenvironment-sensitive drug-eluting intraocular implant.The methacrylated heparin(HEP-MA)was synthesized and used to layer-by-layer self-assemble with the doxorubicin-loaded chitosan nanoparticles on the IOL surface.The matrix metalloproteinase-2(MMP-2)sensitive peptide with cysteine contained in both ends(GCRD-GPQGIWGQ-DRCG)was then used to crosslink the polysaccharide multilayer via the Michael addition reaction between sulfhydryl group in cysteines and double bonds in methacrylate groups.The multilayer construction and subsequent cross-linking were validated through ultraviolet-visible spectrophotometer(UV-Vis)and Fourier transform infrared spectroscopy(FTIR).After modification,the IOL material surface becomes more hydrophilic while the optical properties were well maintained.The MMP-2 and pH-sensitive drug sustained-release coating were successfully obtained on the IOL surface via such design.The enzyme-triggered cell proliferation inhibition was realized in the in vitro experiments.In an animal model,significant up-regulation of MMP-2 was observed in the aqueous humor after cataract surgery.The multi-functionalized polysaccharide-coated IOL implanted in the animal eye via cataract surgery effectively inhibits PCO formation while it keeps good in viuo biosafety.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.
基金financially supported by the Zhejiang Provincial Natural Science Foundation[LR23H180001]the Medical&Health Technology Program of Zhejiang Province[2022KY906].
文摘Intraocular lens(IOL)is a crucial implant for cataract therapy.Posterior capsule opacification(PCO)is the most common post-operative complication after IOL implantation,which is the abnormal hyperplasia of the residual lens epithelial cells(LECs)after IOL implantation in cataract surgery.It is reported that the cellular microenvironment in the lens capsule changes after surgery,such as the elevated secretion of matrix metalloproteinases(MMPs)and a decrease in pH due to undesired cell proliferation.In this study,MMP-2and pH-triggered drug delivery polysaccharide multilayer coating was designed and introduced onto the IOL surface for obtaining the cellular microenvironment-sensitive drug-eluting intraocular implant.The methacrylated heparin(HEP-MA)was synthesized and used to layer-by-layer self-assemble with the doxorubicin-loaded chitosan nanoparticles on the IOL surface.The matrix metalloproteinase-2(MMP-2)sensitive peptide with cysteine contained in both ends(GCRD-GPQGIWGQ-DRCG)was then used to crosslink the polysaccharide multilayer via the Michael addition reaction between sulfhydryl group in cysteines and double bonds in methacrylate groups.The multilayer construction and subsequent cross-linking were validated through ultraviolet-visible spectrophotometer(UV-Vis)and Fourier transform infrared spectroscopy(FTIR).After modification,the IOL material surface becomes more hydrophilic while the optical properties were well maintained.The MMP-2 and pH-sensitive drug sustained-release coating were successfully obtained on the IOL surface via such design.The enzyme-triggered cell proliferation inhibition was realized in the in vitro experiments.In an animal model,significant up-regulation of MMP-2 was observed in the aqueous humor after cataract surgery.The multi-functionalized polysaccharide-coated IOL implanted in the animal eye via cataract surgery effectively inhibits PCO formation while it keeps good in viuo biosafety.
