Materials that are both strong and tough are difficult to find in nature, but a team from the University of Maryland has succeeded in ‘densifying’ wood to make it stronger than steel—but six times lighter.
The process involves boiling natural wood in sodium hydroxide and sodium sulphite, then heating and compressing it. This removes some of the polymers within the wood, allowing its internal structure to change, while retaining polymers that contribute to strength. The change in strength is largely due to the number of hydrogen atoms bonding with cellulose nanofibre within the wood.
In a study published in Nature in February, the researchers say this ‘super wood’ is 10 times stronger, and 12 times tougher, than natural wood. Projectiles fired at it did not pierce or shatter it, making it potentially useful for armour, buildings and vehicles.
“This could be a competitor to steel or even titanium alloy,” says senior researcher Liangbing Hu. “It’s also comparable to carbon fibre, but much less expensive.”