Abstract
Tannin-silica hybrid materials are expected to feature excellent mechanic-chemical stability, large surface areas, high porosity and possess, after carbothermal reduction, high thermal stability as well as high thermal conductivity. Typically, a commercially available tetraethoxysilane is used, but in this study, a more sustainable route was developed by using a glycol-based silica precursor, tetrakis(2-hydroxyethyl)orthosilicate (EGMS), which is highly water-soluble. In order to produce highly porous, homogeneous hybrid tannin-silica aerogels in a one-pot approach, a suitable crosslinker has to be used. It was found that an aldehyde-functionalized silane (triethoxysilylbutyraldehyde) enables the covalent bonding of tannin and silica. Solely by altering the processing parameters, distinctly different tannin-silica hybrid material properties could be achieved. In particular, the amount of crosslinker is a significant factor with respect to altering the materials’ properties, e.g., the specific surface area. Notably, 5 wt% of crosslinker presents an optimal percentage to obtain a sustainable tannin-silica hybrid system with high specific surface areas of roughly 800–900 m2 g−1 as well as a high mesopore volume. The synthesized tannin-silica hybrid aerogels permit the usage as green precursor for silicon carbide materials.
Highlights
A Systematic Study on Bio-Based Hybrid Aerogels Made of Tannin and SilicaMalfait 3, Thomas Sepperer 2,4 and Nicola Huesing 1,2,*
Porous materials, aerogels, became of great interest during the last decades since their first production in the 1930s by Kistler via supercritical fluid extraction
In order to investigate a wide range of TS gels, the pH value and the tannin/silica (T/S) weight ratio was varied while keeping the theoretical density of the batches constant
Summary
Malfait 3, Thomas Sepperer 2,4 and Nicola Huesing 1,2,*. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
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