Beyond Zapping The Leftovers

July 1, 1999

GAINESVILLE — One microwave in David Clark’s laboratory can top temperatures of 2,900 degrees Fahrenheit, while another can focus a beam of energy on a dime-sized target.

Clark, a materials science and engineering professor at the University of Florida, isn’t trying to come up with a faster way to make microwave popcorn — although that’s certainly a possibility. Instead, he and a half-dozen graduate students and staff are exploring what they view as the untapped potential for microwaves in industry, medicine and the home.

“Everyone thinks they understand microwaves because they have a microwave oven,” Clark said. “In fact, microwave energy is very poorly understood. We don’t know how microwaves interact with a whole range of materials, and we think there’s a lot of things you can do with microwave energy that people haven’t yet looked into.”

Over more than a decade of research, Clark and his students have come up with several new uses for microwaves, including making superconductors and removing precious and hazardous metals from old circuit boards. And that’s not all.

Mark Moore, a materials science and engineering doctoral student, said his area of research centers around using microwaves to process a ceramic called aluminum oxide for use as a supplement to Kevlar body armor. Manufacturers of the supplement, designed to stop armor-piercing bullets, currently use conventional ovens, but his research indicates microwave ovens could do the job more efficiently, he said.

“What we’ve determined is that it’s possible to process aluminum oxide to the same hardness and toughness at a lower temperature and with less-expensive insulation in the microwave oven,” he said. “Conventional firing requires 2,750 Fahrenheit while a microwave oven can do it using 2,550 Fahrenheit — a big difference on the industrial scale.”

Microwaves are a form of energy that travels at a high frequency in short wave lengths. More than a half-century ago, researchers recognized microwaves emitted at a certain frequency could boil water and so prove useful in cooking. The first microwave oven was patented in 1950, with the ovens reaching consumers in the early 1960s, Clark said.

Since then, researchers in industry and academia have discovered a handful of other applications, Clark said. For example, many rubber processing plants now use a combination of microwave and conventional ovens to cure rubber, he said. A Canadian company, meanwhile, is making construction beams out of wood chips and plastic using microwaves.

Several years ago, Clark and a UF graduate student patented a microwave-based process to make a ceramic superconductor. This high-tech ceramic, similar to conventionally made superconductors, was produced faster required much less energy to manufacture.

Under the supervision of Clark and George Wicks of Westinghouse Savannah River Co., a recent UF graduate developed a method of separating recoverable metals from waste metals in electronic circuit boards using microwaves. Rebecca Schulz’s research may reduce the amount of hazardous metals entering landfills while allowing industry to recover valuable metals such as gold, silver and copper, Clark said. The technology recently received a patent, and several related patents also are pending.

Clark said he is probing several other applications. Much of his research centers around using microwaves to manufacture ceramics, a process currently dominated by high temperature conventional ovens. Ceramics are used in a huge array of consumer and industrial products such as computer circuit boards, floor tiles and the blades of industrial cutting tools, and microwaves could make them cheaper and better, Clark says.

Diane Folz, a ceramic engineer in the research group, envisions many other uses for microwaves in the future. For example, she says it’s possible surgeons one day will train microwaves set at a certain frequency at a tumor to shrink or destroy it without affecting other tissues nearby. This could occur through tuning microwave frequencies to interact only with the tumor or with something injected into it, Folz said.

“I call this the tip-of-the-iceberg industry, because what we know about it is only about one-tenth what we don’t know about it,” Clark said.