Abstract
Microwave heating technology is known as an alternative to traditional gas and electric heating sources. In this work, mesoporous methylsilsesquioxane (MSQ) aerogels were prepared via a sol–gel process accompanied by microwave heating technology, and microwave heating was used in the gelation of sol and the drying of wet gels, respectively. The effects of hexadecyltrimethylammonium chloride (CTAC) as a surfactant and template, hydrochloric acid (HCl) as a catalyst, ethanol as a solvent, sodium hydroxide (NaOH) as a gelation agent, and microwave power on the pore structure of as-prepared MSQ aerogels were investigated in detail. Microwave heating at low power results in the acceleration of sol–gel transition and achieves the gelation within a few minutes. Appropriate amounts of chemical reagents and microwave heating at high power allow the preparation of mesoporous MSQ aerogels with a BET-specific surface area of 681.6 m2·g−1 and a mesopore size of 19 nm, and the resultant MSQ aerogel still has a BET specific surface area as high as 134 m2·g−1 after heat treatment at 600 °C for 2 h, showing high thermal stability. The MSQ aerogels/fibre composite possesses a low thermal conductivity of 0.039 W/(m·k)−1, displaying good thermal insulation. Microwave heating technology is a promising heating method for the preparation of other aerogels.
Highlights
Many studies have been reported about the optimization of synthesis process, pore structure, and properties of MSQ aerogels
Rao [13] reported the preparation of flexible MSQ aerogels by using trifunctional methyltrimethoxysilane (MTMS) as a precursor, oxalic acid as a catalyst, methanol as a solvent and ammonia as a gelation agent via supercritical drying
In this acid-base system, CTAC is firstly dissolved in a mixture of ethanol and hydrochloric acid, and the mixture is placed in ice bath until completely cooled
Summary
Methylsilsesquioxane (MSQ) aerogel is a methyl hybrid silica aerogel prepared by sol–gel reaction containing methyl siloxane [1,2,3,4]. Compared with conventional silica aerogels, there are mutually exclusive methyl groups in MSQ aerogel framework that can improve its mechanical and intrinsic hydrophobic properties to some extent. Many studies have been reported about the optimization of synthesis process, pore structure, and properties of MSQ aerogels. Rao [13] reported the preparation of flexible MSQ aerogels by using trifunctional methyltrimethoxysilane (MTMS) as a precursor, oxalic acid as a catalyst, methanol as a solvent and ammonia as a gelation agent via supercritical drying. Nadargi [14] prepared the MSQ aerogels by using MTES as a precursor with a two-stage acid-base catalyzed sol–gel process followed by supercritical drying
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