When we think of a knife, a sharp steel blade immediately comes to mind. And if someone says that a wooden knife can be up to three times sharper, possibly few people would believe it. But a new technology for hardening natural wood has made it possible to make knives that are sharper than stainless steel.
The technique, which makes wood 23 times harder, was developed by the team of Professor Teng Li, from the University of Maryland, USA, who had already created a wood as hard as titanium, in addition to wooden sponges and even made batteries. with wood and salt.
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In addition to cutting better than steel knives, wooden knives can be washed and reused normally, like any other household appliance, making them an alternative to steel, ceramic and plastic disposable knives.
Although it is widely used in civil construction and furniture joinery, wood has a lower strength than cellulose itself because wood is composed of only 40% to 50% cellulose, the rest being composed of hemicellulose and lignin, which act as binders.
“Cellulose, the main component of wood, has a higher strength/density ratio than most engineering materials such as ceramics, metals and polymers, but our current use of wood barely touches its full potential,” compared the teacher Li.
The team then set out to process the wood in order to remove its weaker components without destroying the cellulose skeleton.
“It’s a two-step process,” says Li. “In the first step, we partially delignify the wood. Normally, wood is very stiff, but once the lignin is removed, it becomes soft, pliable, and somewhat soft. In the second stage, we do a hot pressing, applying pressure and heat to the chemically processed wood, to densify it and remove water.”
After the hardened wood is processed and carved into the desired shape, it only needs a common coating, a mineral oil, the same product applied to meat boards, to extend its shelf life.
Cellulose tends to absorb water, so this coating preserves the knife edge during use and when washing in the sink or dishwasher.
The team also demonstrated that hardened wood can be used to produce wood nails as sharp as conventional steel nails – and unlike steel nails, wood nails are resistant to rust.
The researchers demonstrated the wooden nails by hammering them together to secure three small boards until it came out the other side, without showing any damage to its piercing tip.
Li hopes that, in the future, hardened wood can also be used to make wooden floors that are more resistant to scratches and wear.
The job now is to verify the economic viability of wood processing. The first step requires boiling the wood at 100°C in a bath of chemicals, which can be reused from batch to batch. For comparison, the process used to make ceramics requires heating materials to a few thousand degrees Celsius.
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