The Synthesis And Performance Of In-Situ Reinforced Silica Aerogel Derived From Crosslinking Of PTES And TEOS

In this work,we studied the design and synthesis of a SA composite reinforced with silica nanowires?SNW?by using two silicon sources: propyltriethoxysilane?PTES?and tetraethoxysilane?TEOS?.The samples were produced by two-step method,and dried under ambient pressure.The effects of factors in the synthesis process of both SA and SNW were explored carefully,then the varying SNW contents on the properties of the SA composites were studied and compared with those of neat SA under identical conditions.The structure and properties of composites were characterized by SEM,FT-IR,SSNMR,XRD,TGA,BET,etc.The results showed that the elastic aerogels were obtained when the molar ratio of TEOS:PTES=4:6.Furthermore,due to the hydrolysis rate of PTES is lower than TEOS,PTES was pre-hydrolyzed to solve this problem,CTAB was also used as a surfactant to avoid phase separation.The best molar ratio of Si : H2 O : Et OH : HCl : NH4 OH : CTAB was 1 : 4 : 7 : 10-3 : 0.06 : 0.05.After aging,solvent changing and drying,the obtained sample showed low density(0.158 g cm^-3),high surface area?487.34 ? g-1?,high porosity?92.8%?,and super hydrophobicity?the water contact angle reached 153o?without any surface modification.Besides,the cross-linked SA showed excellent mechanical behavior that the maximum completely recoverable compressive strain reached 50%.The addition of propyl groups not only provided mechanical robust to the SA but also the hydrophobicity,which reduced the time cost of the process.SNWs prepared by our method exhibited a draw ratio of 20 and a length over 4.5 ?m,then the different contents of SNWs were mixed with hybrid sol by ultrasonication and stirring.The SA composite reinforced by 15mg/ml SNW showed a 67% rise in elastic modulus over the pure SA sample?from 0.21 MPa to 0.35 MPa?and a 70% fracture threshold while the density just had a 9% rise,at the same time,the thermal stability and hydrophobic still maintained the good level.This could be concluded to the 3D structure established by SNWs and the well compatibility between SNWs and silica particles,which combined themselves in the similar scale.The SA composites with excellent properties were sent to test and the absorption performance for organic liquids.The results showed that,the highest absorption capacity was for DMF?10.2 times?within 5 minutes.The composites were added in PVB films to test the UV shielding.Just 5mass % SA could reduce the transmissivity?T?at UV region from 80% to under 50%.When the addition of SA reached 20 mass %,the T was as low as 17%.The excellent performance of the SNW/SA composite will enable its application in various fields.