INQUIRY 2001

E ver own an expensive wool suit that went out of style or got a little too small? Even though you can’t wear it, the price tag makes it too hard to part with. So, the suit hangs at the back of the closet, gathering dust, on the chance that you’ll drop some pounds or the fashion will come back into vogue.

In a way, that’s similar to the situation faced by manufacturers of high-energy neodymium-iron-boron magnets. These rare-earth magnets allow the production of smaller, more powerful and more efficient electric motors that are used to make everything from portable CD players to automotive power windows more compact, lighter in weight and easier on batteries.

Despite those good characteristics, the magnet material is brittle and processing it creates a larger than normal amount of machining waste. This leftover scrap can’t be reformed into magnets or easily recycled. But because it’s roughly 29 percent neodymium (by weight) that’s valued at $30 per kilogram — just slightly less per ounce than the price of silver — it’s worth too much to dispose of. So it’s been stockpiled on the chance that it might someday have a use.

"The neodymium-iron-boron material decomposes peritectically — it changes composition — when heated to its melting point," says Chumbley, lead researcher on the project. "So it can’t just be melted down and reused. But it’s too valuable to throw away, so there are literally warehouses full of 55-gallon drums of the stuff waiting to be recycled."

Until now, the best separation method available was to dissolve the neodymium-iron-boron scrap in acid, then perform a series of chemical extraction and reduction steps. However, the complexity and expense of such a method was impractical for large-scale, commercial recycling.

Building on research pioneered and patented by Ames Laboratory researchers Tim Ellis and Rick Schmidt in the mid-1990s, Chumbley focused on using molten magnesium to extract the neodymium from the magnet scrap. Neodymium is soluble in liquid magnesium. In fact, the magnesium-casting industry routinely adds neodymium and other rare-earth elements to make alloys that are corrosion-resistant and offer improved weldability.

The resulting alloy is roughly 30 percent neodymium, making it perfect for use as feed material for the magnesium-casting industry. And it should substantially lower the cost. Currently, a typical magnesium alloy casting contains only two percent neodymium by weight, yet the neodymium accounts for 40 percent of the raw materials cost.

"It would give them a product that is exactly what they’re already accustomed to using," Chumbley says. "They wouldn’t have to retool or change any of their processes."

Russell has fielded a number of inquiries about the process from metal producers and recyclers, but so far "no one seems to be on the verge of licensing the technology," he says. One company, a magnesium-casting firm, has requested samples of the magnet material to take a closer look at the process.

For more information:
Scott Chumbley, (515) 294-7903
chumbley @iastate.edu

Research funded by:
DOE Office of Basic Energy Sciences