This wooden knife is three times stronger and sharper than steel

Environmentally friendly, renewable and locally available, the woodwood it is definitely the MaterialMaterial fashionable. In particular, it is increasingly present in the construction industry, where projects for wooden houses and even skyscrapers are multiplying. A wooden satellite was even launched this year! University of Maryland researchers just found a new use for it: kitchen knives. By experimenting with different methods of working with wood, they created a natural material that can be shaped into knives three times sharper than wooden ones. steelsteeland can also be washed in the dishwasher.

A chemical bath followed by a thermal shock

Wood is a very resistant material by nature, thanks to the cellulosecellulose which represents 40% to 50% of its composition. Cellulose itself has a higher strength to density ratio than many metals, polymerspolymers OR ceramicceramic. The problem is that the rest of the wood, made up ofhemicellulosehemicellulose and of lignitelignite which act as a binder, weakens its overall strength and its own appapp possible. The researchers therefore decided to eliminate these two “annoying” components while preserving the cellulose structures.

A wooden nail to replace the metal.

Nails that don’t rust

At first, the ligninlignin and hemicellulose are decomposed in a hot bath at 100°C with the addition ofsodium hydroxidesodium hydroxide and sodium sulfite. ” Secondly, we cause a “thermal shock” by applying a strong one pressurepressure and some HeatHeat on the wood to remove the water and thicken it “explains Teng Li, lead author of the study published in the journal question. Once treated and carved into the desired shape, the wood is coated with mineral oil to extend its life durationduration of life and improve its waterproofing. This produces a knife three times stronger than steel and 23 times harder than raw wood. This “tempered wood” can also be shaped into nails, which have the advantage of not dulling, says Teng Li. “ This process also requires much less energy consumption than other materials. By comparison, ceramics must be fired at more than 1,000°C. »

Other methods of making wood super strong had already been tried. In 2021, another team from the University of Maryland managed to create bamboo six times stronger than steel by microwaving it, as well as wood capable of resisting to pistol bullets. ” But, in general, the material is very sensitive to the size and small defects in the wood, such as voids, channels or depressions.explains Teng Li. The two-step process we use eliminates virtually all water-carrying vessels at a microstructural level. »

Molded wood capable of supporting a 1.5 ton car

In a separate study, Liangbing Hu (also a researcher at the University of Maryland), used another method to create ultra-strong wooden structures. As in the previous case, the lignin and hemicellulose are degraded and the wood is dehydrated. But the material is then partially “swollen” by selectively reopening the vessels in the wood to form thin sheets that deform like an accordion, allowing them to be folded before they dry. Once solidified, honeycomb structures are obtained that are up to six times stronger than hardwood, thanks to the formation of hydrogen bondshydrogen bonds among the remaining cellulose fibers. A structure measuring 6.5cm x 6cm wide and 1.5cm high is therefore able to support the weight of a carcar 1.5 tons! ” Thanks to its low density, its high mechanical strength and its excellent plasticityplasticitythis shaped wood could have applications in construction, furniture or transport to replace aluminum alloys, which are much heavier and more polluting to produce “, argues Liangbing Hu.