Wood materials as strong as Steel
A group of scientists led by senior researcher, Liangbing Hu at the University of Maryland have developed a material as strong as steel, but six times lighter; a modification of the normal wood used in construction. Yes, from normal wood.
According to the researchers,
The wood is strong enough to build cars and airplanes, used in exterior walls and roof sheets and many more.
Teng Li, a colleague of Hu said: - "It is as strong as steel, but six times lighter. It takes 10 times more energy to fracture than natural wood. It can even be bent and moulded at the beginning of the process." - "The more we worked on this material, we realized, we have never fully exhausted the potential of this amazing material," Li said.
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Wood is basically made up of cellulose, lignin and hemicellulose. The basic structure has cellulose fibres embedded in a matrix of lignin (the natural glue that holds the cellulose molecules together including hemicellulose).
The modification involves a two phase process of removing about half of the lignin component present and then subjecting the wood to a heated compression method.
Hu said: - "We can start with either cheap wood or fancy, expensive wood. But in the end, we get very similar performance". - "In our process, we found out to be able to make the wood more densed, we have to remove some of these binders (lignin)."
First phase:
Natural wood is boiled in a mix of sodium hydroxide and sodium sulphite for seven hours. This removes some of the surrounding lignin but still leaves the starchy cellulose intact but loose in between the molecules.
Second phase:
The wood then goes through a compression phase to collapse the walls between individual cells. Heat of about 100°C plus a pressure of 5 MPa is added to encourage new chemical bonds while the wood continues to be compressed.
The strengthening ultimately comes from the large numbers of hydrogen atoms bonding to nanofibres of cellulose, already naturally in the structure of the wood.
The finished super wood is not only strong, tough and light, as already mentioned, but it's also impressively dense, resistant to compression, hard and scratch-resistant, and even inherently protected against moisture.
The researchers said the wood could reduce cooling energy requirements by 20 to 35 percent if used in constructing homes as they are able to absorb indoor heat and reflect sun rays. It would be best suited for areas that experience longer days of summer and short winters.
References:
- https://www.sciencealert.com/new-super-wood-stronger-than-steel/amp
- https://www.voanews.com/amp/researcher-make-wood-stronger-than-st/4270723.html
- https://www.google.com/amp/s/amp.iflscience.com/technology/scientists-discover-a-way-to-get-wood-as-hard-as-steel/
- https://www.newscientist.com/article/2204442-high-tech-wood-could-keep-homes-cool-by-reflecting-the-suns-rays/