Facile Synthesis of SnO2 Aerogel/Reduced Graphene Oxide Nanocomposites via in Situ Annealing for the Photocatalytic Degradation of Methyl Orange.

SnO2 aerogel/reduced graphene oxide (rGO) nanocomposites were synthesized using the sol⁻gel method. A homogeneous dispersion of graphene oxide (GO) flakes in a tin precursor solution was captured in a three-dimensional network SnO2 aerogel matrix and successively underwent supercritical alcohol drying followed by the in situ thermal reduction of GO, resulting in SnO2 aerogel/rGO nanocomposites. The chemical interaction between aerogel matrix and GO functional groups was confirmed by a peak shift in the Fourier transform infrared spectra and a change in the optical bandgap of the diffuse reflectance spectra. The role of rGO in 3D aerogel structure was studied in terms of photocatalytic activity with detailed mechanism of the enhancement such as electron transfer between the GO and SnO2. In addition, the photocatalytic activity of these nanocomposites in the methyl orange degradation varied depending on the amount of rGO loading in the SnO2 aerogel matrix; an appropriate amount of rGO was required for the highest enhancement in the photocatalytic activity of the SnO2 aerogel. The proposed nanocomposites could be a useful solution against water pollutants.

Polypropylene/Silica Aerogel Composite Incorporating a Conformal Coating of Methyltrimethoxysilane-Based Aerogel.

Silica aerogels possess low thermal conductivity but have a brittle nature, while their polymers tend to exhibit enhanced mechanical properties. In this study, we introduce a new approach to overcoming this brittle property of silica aerogels. Polypropylene/silica aerogel composites were prepared by thermally induced phase separation followed by a supercritical CO2 drying method. Silica aerogel was formed onto a polypropylene scaffold using a two-step sol-gel process with methyltrimethoxysilane as the silica precursor. Enhancement of the mechanical properties of the polypropylene/silica aerogel composite compared with a pristine methyltrimethoxysilane-based silica aerogel was observed. The effects of the latter on the microstructure and physical properties of the polypropylene/silica aerogel (hereafter referred to as the polymer matrix aerogel) composite were investigated. Compared with the polypropylene monolith, the polymer matrix aerogel composite demonstrated enhanced surface-chemical and microporous-structural properties such as higher hydrophobicity (135°), pore volume (0.18 cm³/g), average pore diameter (12.55 nm), and specific surface area (57.2 m²/g). This novel approach of incorporating methyltrimethoxysilane-based silica aerogel onto polypropylene when synthesizing the polymer matrix aerogel composite shows great potential as a durable superhydrophobic and corrosion resistant thermal insulating material.