AMES, Iowa – The U.S. Department of Energy’s (DOE) Ames Laboratory is helping to develop magnesium-based alloys that could be used in rechargeable batteries for cellular phones, power tools and cars.
Under an $8.2-million project funded through the Advanced Technology Program of the National Institute of Standards, Ames Laboratory will be one of five entities collaborating in the development of a new generation of hydrogen-storage alloys that will be lighter, less expensive and store more hydrogen than current materials. The other four entities are Ovonic Battery Co., Crucible Research, Oak Ridge National Laboratory and the Colorado School of Mines.
As part of an agreement signed Monday (March 30), Ames Lab will receive $380,000 during the next two years to find the best method for processing the new alloys into high-quality, low-cost metal powders.
Project participants say the new hydrogen-storage materials could be used in rechargeable batteries that would be environmentally safer than the lead-acid batteries used in cars and the nickel-cadmium batteries in power tools, cellular phones and electronics. The special alloy powders could also be used in fuel cells for electric cars – a possibility that holds great promise because hydrogen is a clean, endless supply of energy that, when burned in an oxygen atmosphere, produces water rather than the carbon dioxide and other toxic emissions produced by gasoline-powered engines.
"If you think about the commercial applications of these alloys, the potential is almost limitless – it’s huge," says Vitalij Pecharsky, an associate scientist at Ames Lab and an associate professor of materials science and engineering at Iowa State University (ISU).
Certain metals and alloys form unstable hydrides, meaning that they can absorb hydrogen and then release it when heated. Rare earths, nickel, zirconium and titanium are the alloy components most commonly used in nickel metal-hydride (NiMH) batteries. But these alloys absorb only about 1 to 1.5 percent hydrogen by weight, Pecharsky says, meaning that storing 1 kilogram of hydrogen would require 99 kilograms of metal hydride material.
Pure magnesium, on the other hand, is a very lightweight metal that can store about 6.5 percent hydrogen by weight. Although magnesium won’t release hydrogen unless it is heated to 500-600 degrees Celsius (about 1000 degrees Fahrenheit), Pecharsky says project participants hope to overcome that problem by modifying the magnesium with other elements.
Ovonic Battery, a world leader in metal-hydride batteries, will concentrate on developing the new magnesium alloys. Ames Lab’s role will be to find the most effective way to turn the alloys into metal powder, which is the most versatile form of the material. Current powder production involves casting the molten alloy into ingots weighing several hundred pounds and then grinding them into powder. But it can take days to process the huge chunks of material and, because the metals within the ingot segregate during the solidification process, the resulting powder particles do not all have the same chemical composition. "It gives you inconsistent quality," Pecharsky says.
Pecharsky and Iver Anderson, director of the Lab’s Metallurgy and Ceramics program, believe the best way to process the magnesium alloys will be through a technique known as high-pressure gas atomization (HPGA).
In HPGA, a stream of molten material is converted into fine liquid particles that are blasted with very cold argon or helium gas at up to three times the speed of sound. The particles quickly solidify into nearly spherical powder particles that have virtually identical chemical compositions. Pecharsky says the homogeneity of the atomized powder is a big advantage over the powder made from crushed ingots.
"With HPGA, essentially 100 percent of the yield is the target alloy," Pecharsky says, noting that the resulting powder is also much cleaner because it doesn’t have to undergo any additional grinding.
A simpler processing technique will lower the cost of metal-hydride materials and the products in which they are used, Pecharsky says. This would allow manufacturers to offer consumers a more reasonably priced, environmentally safe alternative to lead-acid and nickel-cadmium batteries.
"Right now, a lead-acid car battery costs $40 to $50. If you wanted to replace it with a nickel metal-hydride battery, you would be looking at $300 to $400 and that would be a tough sell," Pecharsky says. "But if the cost of the battery could be reduced to around $100 per battery and it was smaller, much lighter, much safer and stored much more energy, people would start buying those batteries."
Adds Anderson, "Successful completion of our project can really affect the everyday lives of our children and future generations who will place ever-increasing reliance on electrically powered appliances, electronic devices and even electric cars that use the clean, quiet, portable power from batteries."
Ames Laboratory is operated for the DOE by ISU. The Lab conducts research into various areas of national concern, including energy resources, high-speed computer design, environmental cleanup and restoration, and the synthesis and study of new materials.
Release date: April 1, 1998
Contacts: Vitalij Pecharsky, (515) 294-8220 and Iver Anderson, (515) 294-4446
Last revision: 4/17/98 sd