RESEARCH
Wood that can cut like steel Hard materials are in high demand in engineering applications. Widely used hard materials, like alloys and ceramics, are often not renewable and expensive. Their production requires high energy consumption and often leads to negative environmental impacts. Scientists of the University of Maryland (UMD) now demonstrated a potential low-cost and sustainable hard material made from natural wood. The advantages of wood as a structural material are legion: renewable, lightweight, naturally durable and strong, and possessing a lower lifecycle cost than most other materials. Through a simple and effective approach, bulk natural wood can be processed into a hardened wood (HW) with a 23-fold increase in hardness. The trick is in optimizing the cellulose structure. Cellulose - the main component of wood - has a higher strength-to-density ratio than most engineering materials, such as ceramics, metals and polymers. But in ordinary wood, such as that used in construction, these possibilities are not exploited. That’s because wood only consists of about half of cellulose, the rest is binder, especially hemicellulose and lignin. The UMD researchers have now managed to remove the weaker components without destroying the cellulose skeleton. This is done in two steps. First, the lignin is removed by cooking the wood with chemicals. This leaves a flexible cellulose skeleton that is then hot pressed into a rock hard material. Finally, it is coated with mineral oil to extend its life.
Knife
To demonstrate the potential applications of HW, the UMD scientists demonstrated that an HW table knife can be made nearly three times sharper than commercial table knives. An HW nail can be as functional as a steel nail with comparable performance but is immune
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Illustration: UMD
from rusting, a key failure mechanism of steel nails. These encouraging applications suggest the promise of HW as a renewable and low-cost alternative for conventional hard materials with the potential to replace plastic table utensils and steel nails.
‘Hardened wood as a renewable alternative to steel and plastic’ door Bo Chen, Ulrich H.Leiste, William L. Fourney, Yu Liu, Qiongyu Chen and TengLi was published on 20 oktober in Cell. (DOI:https://doi.org/10.1016/j. matt.2021.09.020)
A mineral oil coating prevents water damage, making the knife a washable and reusable alternative to throwaway utensils. The material also has potential for hardwood flooring or wherever else super-tough wood is needed.
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