Cast-In-Situ, Large-Sized Monolithic Silica Xerogel Prepared in Aqueous System

Abstract

This paper reports the preparation of cast-in-situ, large-sized monolithic silica xerogels by a two-step acid–base catalyzed approach under ambient pressure drying. Low-cost industrial silica sol and deionized water were used as the silicon source and the solvent, respectively. Hexadecetyltrimethylammonium bromide (CTAB) was used as a modification agent. Different amounts of polyethylene glycol 400 (PEG400) was added as a pore-forming agent. The prepared silica xerogels under ambient pressure drying have a mesoporous structure with a low density of 221 mg·cm−3 and a thermal conductivity of 0.0428 W·m−1·K−1. The low-cost and facile preparation process, as well as the superior performance of the monolithic silica xerogels make it a promising candidate for industrial thermal insulation materials.

Comparative Study of the U(VI) Adsorption by Hybrid Silica-Hyperbranched Poly(ethylene imine) Nanoparticles and Xerogels

“…4 Pore diameter was determined from the pore size distribution (PSD) curve based on the DFT model (for the Non-Local Density Functional Theory (NLDFT) method, an equilibrium kernel for silica as an adsorbent and N 2 77 K as an adsorbate was used). Nano-silica composites-PEI 30% 104 [111] Nano-silica composites-PEI 60% 0.65 [111] Mesoporous silica microcapsules 514 [112] Silica xerogels 363.72 [113] Silica xerogels 335-850 [114] PEG-silica xerogels 19-127 [115] For the pore size distribution, the BJH (Barret, Joyner, and Halenda) [116] and NLDFT models were applied for the LN 2 isotherm desorption branch. The pore sizes were determined to be between 2 and 80 nm for all studied samples.…”

Sol-Gel Chemistry: From Molecule to Functional Materials

“…Large size silica aerogels with good thermal insulating properties were prepared using the sol-gel process in aqueous media by Shen et al [3]. In their paper, the authors described an easy and inexpensive synthesis of silica monoliths, as well as their textural characterization and thermal properties.…”

Preparation of Aerogel-like Silica Foam with the Hollow-Sphere-Based 3D Network Skeleton by the Cast-in Situ Method and Ambient Pressure Drying

“…10 However, the network framework of silica aerogel is composed of silica nanoparticles. Its slender skeleton is prone to collapse due to capillary forces during ambient pressure drying (APD), 11 thereby resulting in the spring-back effect, the dramatic volume contraction of the initial silica wet gel. Supercritical CO 2 drying, freeze-drying, and exchange solvent drying have been respectively adopted to overcome the structural damage of the silica aerogel by eliminating or weakening the gas−liquid interface and the interface tension.…”