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KTH researcher develops first wood xerogel

Two researchers.
Professor Qi Zhou and postdoc Shennan Wang. Photo: KTH
Published Jun 13, 2023

Researchers at KTH have produced a xerogel made from wood – the material enables more energy-efficient production of high-quality transparent wood.
”The significant advance is that our mesoporous wood xerogel allowed infiltration of polymer resin at ambient condition without the use of solvent or vacuum,” says Qi Zhou, professor at the Division of Glycoscience.

Aerogel and xerogel are porous and solid gel materials with very low density. They are produced by drying wet gels while the solid structure is kept. The key difference between aerogel and xerogel is that aerogels form when the liquid from the gel is extracted at a supercritical state, whereas xerogels can be prepared by using common oven dryers or even by air drying. This means that xerogels have potentially no limitation in dimension and are scalable, according to Qi Zhou.

“The aim of our research in this project was to prepare highly mesoporous wood xerogel and demonstrate its application in fabrication of optically transparent wood composite with high wood volume fraction.”

Original material

Qi Zhou’s teams’ wood composites have a wood volume fraction as high as 50 percent and is original in terms of both material efficiency and high performance perspectives. Due to the highly porous nature of wood, transparent wood usually contains less than 10 percent wood mass, leaving the major component to be the polymer matrix.

“The optical property of the transparent wood composites is also significant. The high optical transmittance of the wood xerogel composites remained at high wood volume fractions, suggesting that aggregation of cellulose microfibrils was not induced by compression of the wood xerogel. In other words, the mesoporosity of wood cell wall was preserved upon mechanical compression of wood xerogel,” says Qi Zhou.

He thinks that wood xerogel will be a new material platform for development and fabrication of functional materials.

“We demonstrated its potential application in polymer composite materials. Other properties of wood xerogel including thermal, acoustic, fluidic and ionic properties are yet to be explored.”

Text: Jon Lindhe

For more information, contact Qi Zhou at 08 - 790 96 25 or qi@kth.se .

Fact box

  • Nanoporous materials have nanometer-sized holes (pores). The pores mean that the material has a very large surface that can be used for various chemical reactions. Mesoporous materials contain pores with diameters between 2 and 50 nm.
  • Aerogels are an extremely porous and light material that usually consists of an organic silicon compound that in solution can form a gel. Chemical bonds between the molecules cause a network to form, which forms the solid part of the gel. The solvent is enclosed in the network. By drying the gel at the supercritical point of the solvent, i.e. at the temperature and pressure at which it has gas properties, the structure is prevented from "collapsing" and the result is a material that for the most part, up to 98%, consists of air-filled pores. It becomes a transparent, slightly blue colored solid with a very large internal surface area. It does not burn and is excellent as thermal insulation.
  • Xerogels are a type of solid-formd gels, which are being prepared through drying slowly at the room temperature with an unconstrained shrinkage. Xerogels generally possess the properties of higher porosity and larger surface area together with very smaller pore sizes. 
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