Using hardened wood, materials scientists at the University of Maryland have developed a new method of making sharp knives by making the wood 23 times harder .
This makes it possible, for example, to make knives almost three times sharper than a stainless steel table knife, or wooden nails as sharp as conventional steel nails (and also resistant to oxidation because they are made of wood).
Getting the most out of cellulose
While the method of producing hardened wood is new, wood processing in general has been around for centuries. What happens is that cellulose, the main component of wood, has a higher ratio of strength to density than most engineering materials, such as ceramics, metals and polymers, but our current use of wood is barely reaching its maximum. potential .
Although it is often used in construction, the resistance of wood is lower than that of cellulose. This is because wood is made up of only 40% – 50% cellulose, and the rest is made up of hemicellulose and lignin, which acts as a binder .
The process to create this superwood has two steps. The first step requires boiling the wood to 100 degrees Celsius in a chemical bath. In this way the wood is partially delignified. Wood is generally very stiff, but after removing the lignin, it becomes soft, pliable, and somewhat mushy.
In the second step , a hot pressing is done by applying pressure and heat to chemically processed wood to densify and remove water. Once the material is processed and carved into the desired shape, it is coated with mineral oil to extend its useful life. Cellulose tends to absorb water, which is why this coating preserves the sharpness of the knife during use and when washed in the sink or dishwasher.