A tightening supply of rare-earth elements such as neodymium, samarium, and dysprosium used in permanent magnets, catalysts, glass, polishing, and a broad range of other applications has caught the attention of policymakers in Washington, stimulated efforts to tap rare-earth deposits in North America and Australia, and spurred R&D on alternative materials.
The US and the rest of the world have relied on China for nearly all of their rare-earth supplies. But China has been curtailing its exports in recent years, conserving the elements for its own manufacturers. That has prompted fears of an impending shortage in the West.
“There’s no reason to panic, but there’s every reason to be smart and serious as we plan for growing global demand for products that contain rare-earth metals and other strategic materials,” said the Department of Energy’s (DOE’s) David Sandalow, assistant secretary for policy and international affairs. “Strategies for addressing shortages of strategic resources are available, if we act wisely,” he told attendees at a March conference on rare earths. “We can invest in additional sources of supply. We can develop substitutes. We can reuse materials and find ways to use them more efficiently. We can consider use of stockpiles and strategic reserves.”
The Department of Defense (DOD) is currently assessing its dependence on foreign sources of rare-earth elements. In a 1 April briefing for the Senate Armed Services Committee, staff from the Government Accountability Office (GAO) noted that rare-earth elements are widely used in defense systems. Actuators for precision-guided munitions, for example, are specifically designed to the capabilities of Nd2Fe14B magnets, while the Aegis missile defense system’s radar, which is designed to last 35 years, has samarium-cobalt magnet components that will need to be replaced during that lifetime. A prototype hybrid-electric drive system for Aegis-class destroyers uses Nd2Fe14B magnets built in China, the GAO reported. The DOD’s internal assessment, which is to be completed by September, will include recommendations for mitigating possible interruptions in the rare-earths supply chain; stockpiling the materials could be one such option.
The White House Office of Science and Technology Policy has convened an interagency task force to monitor the supply situation and recommend actions, if any. Cyrus Wadia, a senior policy analyst with the OSTP, says a national strategy on rare earths may emerge from the process, but he cautions, “We don’t want to put the cart before the horse; we want to be thoughtful about how we are approaching this.”
The House Committee on Science and Technology, which held a hearing on the issue on 16 March, is mulling possible legislation to ensure US access to a broader list of critical materials, including rare earths.
A near monopoly
China currently is the source of more than 95% of the world’s supply of rare earths, a class of 17 metals that includes the lanthanides with atomic numbers 57–71, plus scandium (Z = 21) and yttrium (39). Since the 1970s, when its rare earths were exported mainly in concentrate form, China has moved up the value-added chain and now manufactures and exports rare-earth-containing products such as motors, computers, and batteries.
“What China is doing on rare-earth minerals mirrors what it is doing on a large number of other raw materials: reducing availability of supply for global customers and/or making purchases more expensive through the imposition of export duties, export licenses, et cetera,” Terence Stewart, an international trade lawyer, testified at the hearing. “The objective can be to encourage foreign investors to move investment to China to produce downstream products in the Middle Kingdom versus overseas, or to ensure low-priced supplies for sectors in China targeted for rapid industrial growth.”
Dudley Kingsnorth, a rare-earth industry analyst with Industrial Minerals Co of Australia Pty Ltd, estimates that Chinese production will total 110 000 to 130 000 metric tons of rare-earth oxides this year. Kingsnorth expects Chinese output to grow to between 170 000 and 185 000 tons in 2015. That’s well short of his forecast of global demand for that year, between 190 000 and 210 000 tons (see chart). The difference will have to come from other sources, given that Kingsnorth expects China to consume around 125 000 tons of its output in 2015.
China has been restricting rare-earth exports since 2006, and those quotas were tightened for the first half of 2010, to 5978 tons, down from the 6685-ton limit in place for the first half of 2009, Kingsnorth says. China also imposes a 25% tax on exports of rare earths, a trade practice that contravenes World Trade Organization rules. Kingsnorth forecasts that production of rare earths will satisfy global demand in 2015. But he cautions that supplies of neodymium, dysprosium, and terbium will be very tight.
Ideal for hybrid vehicles
Although applications of rare earths are numerous and diverse, their largest single use is in permanent magnets, in which neodymium is combined with iron and boron to form the strongest magnets known. Compared with ferrite or alnico-alloy permanent magnets, Nd2Fe14B versions offer weight savings, smaller size, and better performance at elevated operating temperatures. Those features make rare-earth magnets the choice for the electric motor-generators that propel today’s hybrid-electric vehicles. A Prius motor-generator, for example, contains a kilogram of neodymium, plus smaller amounts of other rare earths: praseodymium, dysprosium, and terbium (see diagram). In addition, some 10 kg of the rare earth lanthanum is contained in the nickel-metal hydride battery of a typical hybrid.
Many wind turbine generators use rare-earth magnets. In addition to reducing mass aloft, the rare-earth magnets are well-suited for generating electricity at the low revolutions per minute that are typical of windmills. Such direct-drive turbines eliminate the need for gearboxes, which reduces maintenance costs, noted Steven Boyd, an engineer in the Department of Energy’s office of energy efficiency and renewable energy.
The magnets in the largest windmills made today can weigh 2 tons, though only about 12% of that mass is rare earths.
Rare-earth magnets also have enabled the miniaturization of computer hard drives. Karl Gschneidner, professor of materials science at Iowa State University and an authority on rare earths, says today’s laptops would be double or triple in size without Nd2Fe14B magnets.
Peter Dent is vice president for business development at Electron Energy Corp in Landisville, Pennsylvania, the only remaining US manufacturer of rare-earth magnets that produces its alloys in-house. The company serves a niche market for permanent magnets, made with samarium instead of the more common neodymium, that are capable of operating at temperatures up to 550 °C. Dent acknowledged that he worries whether samarium will be available five years from now.
New mines opening
Several forces are at play that could ease concerns over supply. As the OSTP’s Wadia points out, there is a big difference between reserves and production. “If we went back 15 years, it was the US that had the dominant share [of output]. In fact, a third of the estimated reserves of rare-earth elements are in this country,” he says. The owners of one shuttered US rare-earth mine say they are on track to resume production in 2012, if the required financing can be obtained. Mark Smith, CEO of Molycorp, which owns the Mountain Pass mine in southern California, confessed that for years after the mine’s 2002 closure in the face of low-cost imported Chinese rare earths, “we sat and whined and cried.” But then, Smith told the House hearing, he and his co-owners got to work devising new processing technologies to reduce production costs. The firm plans to produce 20 000 tons per year of rare-earth oxides and to refine the material, provide alloying and magnet powder-metal manufacturing capabilities, and manufacture permanent magnets at the site.
But those ambitions highlight another problem caused by the Chinese monopoly: Little rare-earth expertise remains in the US. “I have 17 engineers and scientists competing with over 6000 scientists in China. And I can’t find any students from any university in the US that have any experience with a rare-earths curriculum today,” Smith lamented. Molycorp’s plans were set back early this year when DOE rejected the company’s request for a loan guarantee to help finance the project.
A newly developed mine at Mount Weld in Australia is scheduled to commence production next year at an annual rate of 10 500 tons. And other rare-earth deposits have been identified in the US, Canada, Australia, and Greenland. But their development could take as many as 10 years.
A search for alternatives
Concerns going forward about supplies of rare earths have spurred research to find alternative materials for magnets and other applications. But Gschneid-ner, who since the 1960s has conducted research with rare earths at Ames Laboratory, a DOE-owned facility on the Iowa State campus, says efforts to find substitutes have been under way for 20 years, to little avail.
Wadia is more hopeful. “There are known substitutes today and others that will be discovered in the future. In very few cases are we constrained to one singular material solution for a certain technological functionality.” Additional R&D funding for alternative materials might be warranted and pursued, he says, if the inter-agency task force now delving into the rare-earths issue makes that recommendation. The task force will also be looking more closely at some “high-growth scenarios, such as what the neodymium and boron demand could be if we plan to deploy, say, 30 gigawatts a year of wind generation,” he says. Wadia could provide no timetable for the completion of that exercise.
The vehicles technology program at DOE devotes about $3 million a year to R&D, mostly at Ames, on alternatives to rare-earth magnets, says Patrick Davis, a program manager. Researchers are exploring the potential for induction motors and switch-reluctance motors. But lower efficiencies and greater bulk will likely keep them at a disadvantage to permanent-magnet motors for hybrid cars. They could be more attractive in all-electric cars, where more space will be available under the hood, notes Boyd.
Finding new permanent-magnet materials is the goal of one of the first 37 research projects that were selected for funding by DOE’s Advanced Research Projects Agency-Energy. The ARPA-E program is reserved for high-risk research that could produce breakthroughs if successful. George Hadjipanayis, a University of Delaware physicist and principal investigator of the $4.5 million, three-year effort, says three approaches will be taken in a bid to find materials that can double the field strength of Nd2Fe14B. Both rare-earth-free magnets and magnets requiring smaller amounts of rare earths will be investigated. A team at the University of Nebraska will search for ways to improve the magnetic properties of iron-cobalt alloys. Hadjipanayis says some theoretical studies have hinted that the addition of tungsten could alter the molecular lattice of the iron-cobalt alloy, improving its anisotropy. A second approach, to be carried out at Ames, will evaluate a wide range of elements, including lithium, zinc, manganese, and selenium, for combination with rare earths and a transition metal. If successful, the newly discovered magnetic materials could require significantly less of the rare earths.
Hadjipanayis will lead a third, bottom-up approach to discover nanocomposites that offer a higher density of magnetic energy than Nd2Fe14B. Models have predicted that a combination of materials such as rare-earth compounds and materials like iron-cobalt should perform dramatically better if they can be manipulated at a scale of 20 to 30 nanometers, he says. “The first challenge is to make the magnetic nano-particles with a high coercivity. Challenge two is to make the iron-cobalt nanoparticles with high magnetization. And then we will try to assemble them in some two-dimensional and three-dimensional arrays and try to make a magnet out of them.”
