Superhydrophobic silica aerogel microspheres from methyltrimethoxysilane: rapid synthesis via ambient pressure drying and excellent absorption properties

Abstract

Silica aerogels are nanostructured porous solids with an open pore structure, high surface area, high porosity, low bulk density, and low thermal/electrical conductivity, which have drawn great interest in both science and technology. Generally, silica aerogels are prepared via a sol-gel process with a subsequent drying step, in which a supercritical condition is usually employed to dry wet silica gels.However, the supercritical drying is a limiting factor for synthesis efficiency and cost. Ambient pressure drying (APD) is considered an alternative and more practical approach. However, the tedious surface modification and solvent exchange steps involved in conventional APD for the synthesis of silica aerogels (bead-or bulk-type) are still challenges. In this study, a novel APD method was successfully developed for the drying of precursor silica microspheres that were obtained via a waterin-oil (W/O) emulsion method using methyltrimethoxysilane (MTMS). The resultant silica aerogel microspheres were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and the Brunauer-Emmett-Teller (BET) method. The results indicate that silica aerogel microspheres possess similar characteristics to those aerogels prepared by supercritical drying. The silica aerogel microspheres have a mean diameter of approximately 300 mm, a bulk density as low as 0.08 g cm À3 , a specific surface area as high as 853 m 2 g À1 , a pore size distribution between 2 and 45 nm, and an average pore size of 16 nm. In addition, the aerogels are superhydrophobic with a contact angle as high as 172 , and they exhibit excellent absorption capability and recyclability for organic liquids and oils. A new production route for silica aerogel microspheres will greatly expand the commercial utilization of these materials.

Elastic silica aerogel using methyltrimethoxysilane precusor via ambient pressure drying

“…It is obvious that elastic aerogels with wonderful hydrophobicity and monolithic property are extremely important for long-term applications. Despite aerogels prepared through supercritical drying can meet requirements above and also maintain the integrity and high porosity of the structure [7][8][9][10], the process of synthesizing aerogels by supercritical drying has its own drawbacks. The large-scale commercial production of silica aerogels has been limited for the high cost and flammable solvents, which is risky at high temperatures (260°C) and high pressures (100 bars).…”

Characterization and comparison of uniform hydrophilic/hydrophobic transparent silica aerogel beads: skeleton strength and surface modification

“…Due to this silica aerogel beads are the small spheroid, solvent exchange process is much faster and 35 the beads are regularity and more convenient for application; this can considerably improve the product quality and reduce the production time and cost. Silica aerogel beads have recently been synthesized at ambient pressure, many researchers had made a great contribution [8][9][10][11] . Although these methods are much easier, 40 the key step to obtain the silica beads of synthesis path is tedious and unmanageable, and the solution is complex and difficult to recycle.…”

Continuous flow vortex fluidic synthesis of silica xerogel as a delivery vehicle for curcumin

“…39,40 Thermogravimetric analysis (TGA) gave 0.24% w/w curcumin present in the composite material (Fig. The concentration of the curcumin in the sample was determined using two different methods, uorescence spectroscopy and simultaneous thermal analyser (STA), to compare the integrity of the analysis results.…”