Dishes and cookware made from a newly developed ceramic material may soon enable faster and more energy-efficient microwaving, according to Sridhar Komarneni, a professor of clay mineralogy at Penn State University. Komarneni reports on the new material’s development in the July 11, 2008, online edition of Chemistry of Materials. “Currently, food heated in a microwave loses heat to the cold dish because the dishes are transparent to microwaves,” he says. “The plates are still cool when the cooking is completed.” He explains that microwave ovens have an alternating electric component that causes molecules with a positive charge at one end and a negative charge at the other – such as water molecules – to move back and forth, aligning themselves with the electrical field. The moving molecules bump into nearby molecules, causing them to move, too. This motion creates heat and, so, cooks food. Unlike food, however, microwave cookware does not become hot because its molecules are ”transparent” – or do not interact – with microwaves. This means food loses some of its heat to the cookware in which it is cooked, the researcher says.
Now, however, Komarneni has discovered a way to prevent this heat loss. Working in conjunction with Hiroaki Katsuki and Nobuaki Kamochi of Saga Ceramic Research Laboratory in Saga, Japan, he has developed a new ceramic material that can be directly heated by microwaves. Komarneni says the team took powdered petalite – a mineral containing lithium, aluminum and silicon – and mixed it with a small quantity of magnetic iron oxide. They then dried the powder and fired it in a kiln for five hours, before sintering it at 1250°C to create an iron oxide-petalite foam, suitable for use as a microwave ceramic. He explains that the iron oxide component interacts with the microwaves’ electric field and rapidly heats, while the insulating petalite component helps to retain the heat after the oven is turned off. He says the team tested the new ceramic material against standard porcelain ovenware in a 600-watt microwave oven. After 70 seconds of power, the porcelain had reached 50-60°C, but the new material’s temperature had increased to more than 200°C. The new material’s temperature continued to increase for 30 seconds after the oven was turned off, peaking at 294°C, he says. He also reports that, when he coated a plate made of the petalite-magnetite material with cooking oil and heated it for two minutes, 98 percent of the oil disappeared through decomposition. This makes Komarneni believe that the new material might also be used “in a closed system to decompose organic contaminants in soil or dirt.” The researcher says this would likely create less waste and utilize less energy than than that produced through existing remediation methods.