Microwave Bakes New Building Material
Some people put dinner into their microwave and end up with rock-hard sludge. Scientists at a government laboratory did it on purpose and ended up with a new building material.
But rather than using the latest gourmet frozen entree, researchers zapped tiny microbubbles of fly ash or glass in an ordinary kitchen microwave and found they could produce an incredibly hard, strong, featherweight foam that can be cut and sawed.
Like chefs, the scientists at Los Alamos National Laboratory in Los Alamos, N.M., are experimenting with many ingredients, but the best so far has been fly ash, the airborne ash that comes from coal-fired power plants.
“The strongest foams we’ve made have been out of fly ash, and also the lightest foams we’ve made have been out of fly ash,” said Tom Meeks, a ceramics engineer and section leader for the advanced ceramics project at Los Alamos.
Incredibly Strong
The fly ash foam weighs .012 ounces per cubic centimeter. It can hold up under 790 pounds per square inch, or 100,000 pounds per square foot. The tensile strength is about 50,000 pounds.
Sprayed-on concrete has a weight-bearing capacity of 300 to 400 pounds per square inch. Reinforced concrete, however, has a compressive strength of 3,000 to 4,000 pounds per square inch.
Meeks said the National Aeronautics and Space Administration has shown interest in the process. It may be possible one day for astronauts to place a bag of ceramic dust in a microwave aboard the space shuttle, zap the dust and use the resulting material to replace damaged tiles on their craft.
The process may be ideal for projects on a space station or lunar base, where moon dust could be used and thereby eliminate the need to transport raw materials from Earth.
It may also be useful as insulation or as material for buoys, he said.
Energy-Saving Process
The process could save energy in the making and transporting of building materials, but will it revolutionize the building industry?
“The jury’s out on that,” Meek said in a telephone interview. “What interests me and the people here is what we’re seeing with the microwave processing of this material. We’re seeing different kinds of chemistry going on that we don’t understand.
“I think it will take another five years to understand what’s going on with the reaction kinetics.”
It would be possible to do the same thing in a conventional oven, but the cost of reaching the necessary 2,700-degree temperature would be prohibitive.
The process relies on raw material in the form of tiny beads. Fly ash has this composition, but glass beads work also. The beads fuse under heat, forming foam.
Other researchers have been experimenting in the same area. A Canadian firm, Fiberglass Canada Ltd., patented a similar process but said it has not put it to use.
Meek began his own microwave research four years ago with a $250 table-top oven bought on sale. He started with glass beads, but a laboratory fellow, Haskell Sheinberg, suggested fly ash. He and Meek pursued the experiment with Rodger Blake, a technician.
As for what the other ingredients being investigated are, Meek isn’t saying. He admits, however, “we’ve only scratched the surface” in possibilities.
