Stretching as far back as the early Stone Age, and even beyond, wood has served many purposes - to generate warmth, as a weapon and for use in tools and construction. This makes wood one of the oldest and most enduringly popular materials known to humankind. No wonder, considering the immense potential of this renewable raw material. Having said that, wherever extreme stresses come into play, wood has always been outstripped by stable metal constructions. But all that looks set to change, thanks to a new method of treating wood that purportedly makes it harder than steel. The process developed by scientists at the University of Maryland first extracts lignin from the wood, which (among other things) is responsible for stabilizing the cell walls in it. This makes the wood extremely porous. Next, it is compressed at temperatures of around 100 degrees Celsius, which trebles its original density. What's more, the team says the wood's stiffness and specific rigidity are increased no less than tenfold.
"This kind of wood could find its way into cars, aircraft or buildings - anywhere that steel is currently used," claims Liangbing Hu in the article he recently co-authored with his colleague Teng Li for the science periodical Nature. "The wood is as strong as steel, but six times as light," Li explains. The researchers demonstrated the resilience of their high-tech wood by firing a projectile at it. While this passed straight through a block of untreated wood, it stuck fast in a comparable piece of the hardened wood. Although its stability is unaffected by ambient dampness, it is not yet entirely clear whether removing the lignin perhaps makes this hard wood susceptible to bacteria or fungi, as Peter Franzl from the Max Planck Institute of Colloids and Interfaces points out in a related article.
University of Maryland (US-College Park, MD 20742-2115)