BioEd Online

A group of US researchers have petrified wood in record time, compressing a process that normally takes eons into a matter of days.

Yongsoon Shin and his colleagues at the Pacific Northwest National Laboratory in Richland, Washington, have developed a technique that converts an average two-by-four into a hard, fossil-like sponge in about five days.

By soaking everyday objects in solutions containing silica, otherwise known as sand, researchers have long been able to make fossils in a matter of months. That may seem counterintuitive, but even natural fossilization must begin within that time frame.

"The organic material must be stabilized within weeks to months, otherwise it decays," says Derek Briggs, a palaeontologist at Yale University in New Haven, Connecticut.

The silica permeates the organic material and hardens early in the process. This creates a structure that survives after the organic material rots away. By creating fossils in the lab, Briggs says, researchers can learn how the process alters organic matter, and where fossils might be found around the world.

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Shin accelerated the fossilization process by warming things up. He soaked wood in acid for two days, and in water and silica for another two. Then he fired the wood blocks in a furnace at 1,400 °C. The extreme temperatures bonded the silicon in the sand to the carbon in the wood, creating a silicon carbide 'fossil'. The work is published in Advanced Materials¹.

Technically, the wood is not really fossilized, says Briggs, because silicon and carbon never bond in normal fossilization. "I don't think this reaction happens in nature," he says. But, fossil or not, the wood makes an excellent sponge, according to Shin.

"This is a highly porous, very strong material," he says. Shin hopes that the wood might someday be used at the nearby Hanford Nuclear Reservation, where underground storage tanks hold some 200 million litres of radioactive material, some of which is boiling from the heat of radioactive decay.

If the pores in the wood could be made smaller and more regular, Shin believes that it could be used to sop up the boiling sludge, which is too hot to be handled by conventional clean-up techniques.

Shin thinks the wood has other properties that might make it useful. The silicon carbide structure can withstand temperatures of up to 1,500 °C. And it is very tough, something one laboratory assistant learned the hard way. "He broke two diamond blades trying to cut it," Shin says.