VOA常速英語：研究人員使木材比鋼更堅固

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COLLEGE PARK, MARYLAND — A new super-material — stronger, lighter and cheaper than steel — has emerged from scientists' labs.

It's not a high-tech nano-polymer or some new alloy.

It's wood.

With just some chemicals, heat and pressure, researchers at the University of Maryland have made wood three times denser and 10 times stronger. That means it competes with some of the toughest materials on the market, according to study co-author Liangbing Hu at the University of Maryland.

"We're interested in replacing steel and carbon fibers with strong wood structures," he said.

Strong and inexpensive

Since the process doesn't require any special raw material, the product will be relatively inexpensive, Hu said. "We can start with very cheap wood, and we can also start with very fancy, expensive wood. But in the end, ultimately we get very similar performance."

The key to what the researchers call "super wood" is partially removing a natural polymer called lignin.

"Lignin is like a binder to hold all the components together in natural wood," Hu explained. "In our process, we found out to be able to densify the wood completely, we have to remove some of these binders."

Caustic chemicals strip wood of about half its lignin. Then, after a day in a hot press, the wood is strong enough to build cars, airplanes, wind turbines and more with it, according to the researchers. Their findings are published in the journal Nature.

The researchers say super-strength wood would have less environmental impact than the steel or metal alloys it could replace. Their process is not pollution-free, however. It uses some of the same caustic chemicals involved in making paper.

Hu and his University of Maryland colleague Teng Li have found unusual uses for this extremely common material. They have made wood batteries. They made transparent wood and paper, removing the lignin and replacing it with a clear polymer.

Other scientists are finding remarkable uses for wood. Researchers at Sweden's KTH Royal Institute of Technology have made wood-based super-strong fibersfor clothing and other materials. Kyoto University scientists are making plastics with cellulose nanofibers derived from wood.

"The more we worked on this material, we realized, we have never fully exhausted the potential of this amazing material," Li said.