A Rock-Hard Science -- Materials Science

By exploring basic molecular structure, scientists are developing new materials that mimic or build on what occurs in nature. "Ceramic wood," hard enough to withstand a foot-stomping, is one product of this developing science.

Who says tough guys don't dance?

Consider the University of Washington's Ilhan Aksay. The materials scientist has experimented with using the molecular structure of abalone shells to harden tank armor. He has pondered the advantages of violins made out of rock-hard ceramics.

And he's come up with wooden dance floor material impervious to spike heels, and tested it by having a cooperative high-heeled female jump on a test scrap with gusto.

Now that's tough.

Aksay, who works with the university's Washington Technology Center, has turned alder - the 97-pound weakling of the Northwest wood world - into material hard enough to flamenco on.

He does it by cooking silicon, the stuff of beach sand, into wood. The result is "ceramic wood," a material up to 2 1/2 times harder than conventional wood and twice as strong. It is also fire resistant and probably deters rot as well, though that remains to be tested.

Ceramic wood looks like wood, but is harder to scratch. It could be useful as wood flooring, counter or table tops, dock piers, or as acoustically superior material for violins and guitars.

Aksay's research is part of a revolution going on in materials science that is promising some astounding breakthroughs in the 1990s.

A generation ago, actor Dustin Hoffman was told in the movie "The Graduate" that he needed to know only one word as the key to the future: plastics.

If the movie were made today, that word might be ceramics.

Too brittle for many uses, ceramics are beginning to be combined with metal, wood or other materials to make super-strong hybrid materials. The result could be far lighter and more fuel-efficient automobile engines, as just one example.

Some scientists believe the secret to the superior sound of Stradivarius violins is the mineral content 18th-century craftsmen rubbed into them with abrasives. The Japanese have recently experimented with violins made entirely of ceramics, which reportedly have excellent acoustical properties.

The Japanese have also trooped to Aksay's office to examine his work.

Americans appear slower to recognize its potential significance. Weyerhaeuser, which financed the original research, has lost interest after a company shakeup that trimmed its research spending on futuristic wood substitutes.

"I really believe that in two years of research we pulled ahead of the Japanese in this field," said Aksay, who has been hired away by Princeton and will be going there in August. "Now it appears we are dropping the whole thing."

"The company changed its focus," explained Charlotte Taylor, manager of technology acquisition for Weyerhaeuser. "We reorganized to concentrate on the core of our business. While we are still interested in ceramic wood as a long-term possibility, we don't have the funds to continue with it."

Aksay is hoping another Northwest company will step forward to finance the ceramic wood team the UW has assembled.

It is an intriguing group that includes undergraduate Bud Hicks, a former logger who plunged into research after accidentally sawing his foot off in 1986. Scientists such as Aksay figure out what tasks to perform. Then Hicks goes to the lab and figures out a practical way to do them, using the tinkering ingenuity he learned to keep machines running in the forest.

The idea of combining wood and rock comes from nature. Teak, used for decking and railings on pleasure boats, gets its toughness by absorbing silica and other minerals through its roots and putting them in the walls of its cells. Bamboo does the same thing.

"The natural silicon in teak helps act as a preservative," said Don Dabbs, the laboratory manager.

The scientists are investigating whether other plants can be coached to do the same by feeding cherry trees a barium phosphate mixture. Another undergraduate is feeding a silica solution to grass.

Meanwhile, Aksay and his team have discovered a mechanical way to make wood far tougher than teak. Wood is placed in a sealed pressure container and injected with a liquid mixture of silica and alcohol. The process takes about 30 minutes.

For maximum hardness, the scientists can fill the hollow cellulose cells with ceramics. For more lightness and stability, the hollows can be left empty and the silicon shoved into the cell walls. For a completely ceramic product with the structure and appearance of wood, the wood itself can be burned away at temperatures of 500 degrees centigrade, leaving a honeycomb pattern of ceramics.

Aksay said the wood accepts stain well and remains easy to work.

Scientists also believe the wood would be cheap to produce. "The chemicals used to treat it are available in tank-car quantities," said David Treadwell, a chemist working on the project.

Copying the resiliency of teak and bamboo is not the only example of how materials scientists are learning from nature.

The new field is called biological mimicking, or in the latest jargon, "biomimetics." It has arisen because of the ability of scientists to analyze the structure of natural materials at the atomic and molecular scale, using microscopes so precise they can "see" the position of individual atoms, plus computers that can make models of how tough stuff is put together.

What they have discovered is fascinating ingenuity resulting from millions of years of evolution. For example, abalone shell gets its strength by laying a bricklike pattern of calcium carbonate crystals that use an adhesive called chitin as a mortar. Aksay has worked to synthesize this structure for use as an impact-resistant tank armor.

The result is a material twice as tough as present-day armor. It is being tested at Lawrence Livermore Laboratory in Berkeley, Calif., and at Los Alamos, N.M.

Other animals are also being examined. Scientists have discovered rats can gnaw through cans, thanks to teeth made of crossed rods of a calcium compound embedded in stringy collagen and reinforced with particles of the mineral titania.

The shells of beetles, the spines of sea urchins, and the stringy strength of human scar tissue are other promising materials. Beetle shells, for example, are being examined as possible models of complex molecular construction for aircraft wings that could withstand the stresses of a proposed plane that could jet from New York to Tokyo in two hours.

Aksay said tank armor is just one application of his abalone research. "I do it for biomedical reasons," he said. "I play the game (with the military) because they are a source of funding."

If humans can mimic nature's skill with abalone, the result could be the repair or replacement of bone and teeth. "We may actually grow bone or teeth on site," he said.

Aksay is collaborating with Clement Furlong of the UW's division of medical genetics to explore abalone further.

Furlong plans to begin work in May to identify the proteins that make up abalone shell. Using genetic engineering, he then hopes to insert genetic instructions in bacteria cells telling them to make the protein, and then see if the proteins will combine spontaneously to artificially build the shell structure. He calls this "bio-duplication."

Furlong said there are a host of materials in nature, such as deer antler, that could have uses in both healing or everyday materials.

This in turn could lead to techniques to treat or repair diseases that break down connective tissues.

Aksay said ceramic wood techniques could also be applied to make paper magnetic, useful for copying machines.

Other uses for new ceramic technology include filters, capacitators and material for submarine hydrophones.

Aksay thinks ceramic wood is too good an idea, both durable and cheap, to drop. "The silica needed to do this is the most abundant substance on Earth," he said.