|Newly fabricated superstrong lumber gives a whole new meaning to
'hardwood'. This ultracompact wood is created by boiling a wood block in
a water-based solution of sodium hydroxide and sodium sulphite.
The chemicals partially strip the wood of substances called lignin and
hemicelluloses, which help give wood its structure and rigidity. Then the
block gets squeezed between metal plates heated to 100? Celsius at a
pressure of 5 megapascals - about 50 times the pressure of sea-level
atmosphere. That squashes the gaps between the cell walls in the wood,
shrinking the block to about 20% its original thickness and making it
three times denser.
Researchers from the University of Maryland in College Park found that
the densified wood could withstand being stretched or pulled 11.5 times
harder than its natural counterpart without breaking. That makes it
about as strong as steel, even though it's more lightweight. Stainless
steel pellets fired from an air gun and moving at 30 metres per second
easily busted through a typical wooden plank, but got lodged in a stack
of densified wood sheets with the same total thickness.
Chemicals used to process the wood work for various tree species and
don't pose any significant pollution concerns, according to the
researchers. So this condensed wood could provide an ecofriendly
alternative to steels or alloys for constructing buildings or bridges.
It could also be used to manufacture more lightweight, fuel-efficient
cars or trains.