A Systematic Study on Bio-Based Hybrid Aerogels Made of Tannin and Silica

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...

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Published inMaterials Vol. 14; no. 18; p. 5231
Main Authors Koopmann, Ann-Kathrin, Malfait, Wim J., Sepperer, Thomas, Huesing, Nicola
Format Journal Article
LanguageEnglish
Published Basel MDPI AG 11.09.2021
MDPI
Subjects
aerogels
Aldehydes
Carbon
Crosslinking
Flavonoids
Hybrid systems
Lignin
Material properties
Mechanical properties
Porous materials
Precursors
Process parameters
silica
Silica aerogels
Silicon carbide
Silicon dioxide
Specific surface
Surface area
Surface stability
tannin
Tannins
Tetraethyl orthosilicate
Thermal conductivity
Thermal stability
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Summary: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.
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ISSN:1996-1944
1996-1944
DOI:10.3390/ma14185231