Effect of different silylation agents on the properties of ambient pressure dried and supercritically dried vinyl-modified silica aerogels

Optimization of Polyamide Pulp-Reinforced Silica Aerogel Composites for Thermal Protection Systems

“…However, these compounds (methanol and TMCS) represent more hazard for the operators and environment. The introduction of VTMS as a co-precursor leads to a slight increase in the surface area for S = 6 ( Table 2 ), and for S = 14 the values are much higher (~615 m 2 ·g −1 ), comparable with those for a similar TEOS/VTMS system [ 7 ]. The increase in surface area for the TEOS/VTMS-based aerogels may be explained by the higher amount of mesopores, since when vinyl groups were introduced in the aerogels, a reduction in the average pore diameter was observed ( Table 2 , Figure 5 ), probably due to more interaction between the KP and the organically modified matrix and to the higher shrinkage already discussed.…”

“…For all spectra ( Figure 3 ), the strong Si–O–Si vibration bands near 460 cm −1 (deformation), 788 cm −1 (symmetric stretching) and 1084 cm −1 (asymmetric stretching) confirm the SiO 2 network [ 25 ]. In Figure 3 B, the presence of VTMS was confirmed by the appearance of the following bands: (i) at 540 cm −1 , due to the twisting vibration of H derived from vinyl groups, (ii) at 1412 cm −1 , which corresponds to the deformation vibration of =C–H groups, (iii) at 1605 cm −1 from the stretching vibration of C=C, and (iv) between 3000 to 3070 cm −1 , attributed to the stretching of =C–H groups [ 7 , 25 ].…”

“…In addition to the referred reinforcement strategies, fibers can be incorporated into aerogels to increase their robustness [ 7 , 10 ]. The fiber web supports the aerogel and decreases the aerogel bulk size in the composite matrix, i.e., it becomes an aerogel consisting of small monolithic volumes filling the spaces of the fiber network.…”

“…The fiber web supports the aerogel and decreases the aerogel bulk size in the composite matrix, i.e., it becomes an aerogel consisting of small monolithic volumes filling the spaces of the fiber network. Some examples of fibers used for this reinforcement purpose include polymeric fibers, carbon nanofibers and glass fibers [ 5 , 7 , 10 ]; their addition leads to improvement of mechanical properties, while only slightly increasing bulk density and thermal conductivity [ 11 , 12 ]. The fibers can be added in different forms, for example original fibers, pre-processed fibers (e.g., cut or ground) or non-woven fiber felts [ 13 ], and should be introduced into the sol phase, so that the gel is already formed in their presence, resulting in a fiber-aerogel composite after drying.…”

Elastic methyltrimethoxysilane based silica aerogels reinforced with polyvinylmethyldimethoxysilane

“…The pore size distribution was derived from desorption branches of the isotherms by applying the Barrett-Joyner-Halenda (BJH) method. According to open literature, 26 the average pore size was calculated by eqn (1), and the pore volume (V pore ) was obtained by eqn (2). The skeleton density (r s ) of silica aerogels is 2.2 g cm À3 , which was obtained from reported work.…”