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Critical Materials Problem Continues

Debate over use of and substitutions for rare-earth elements points out a need for much more research

by David J. Hanson
October 24, 2011 | A version of this story appeared in Volume 89, Issue 43

Credit: Molycorp
Molycorp’s Mountain Pass, Calif., mine will soon be producing rare-earth ores; it will be the only U.S. source of these materials.
Image of buildings, structures, and black hills at the Molycorp mine in Mountain Pass, California.
Credit: Molycorp
Molycorp’s Mountain Pass, Calif., mine will soon be producing rare-earth ores; it will be the only U.S. source of these materials.

Concern has been growing in the U.S. over the availability of rare-earth elements and other critical materials. Used in a range of products, from solar panels to catalytic converters to electronics, these minerals—which have properties that aren’t easily replicated—are essential to U.S. manufacturing, energy technology, and national security.

Credit: Shutterstock
The use of scarce materials such as gallium, indium, and tellurium in photovoltaic films has some developers worried about end-product costs.
Image of a stretch of solar panels in a field under a clouded blue sky.
Credit: Shutterstock
The use of scarce materials such as gallium, indium, and tellurium in photovoltaic films has some developers worried about end-product costs.
Credit: Dreamstime
Researchers have yet to find materials that can replace the expensive platinum and palladium used in automobile catalytic converters, which are often discarded after use.
Rusty pile of discarded automobile catalytic converters that are going to be recycled for their precious metal content.
Credit: Dreamstime
Researchers have yet to find materials that can replace the expensive platinum and palladium used in automobile catalytic converters, which are often discarded after use.

Currently, China holds a virtual monopoly on the mining and production of these rare earths (the 15 lanthanides plus scandium and yttrium) and other critical minerals such as rhenium, platinum, and iridium. China’s stronghold on this market—the nation produces 95% of the world’s supply of rare earths—has many in the U.S. government and industry worried about future access to these essential materials (C&EN, May 16, page 28).

Earlier this year, panic erupted when China announced it was severely restricting its exports of rare earths and keeping more production for its own domestic use. That fear has quieted as many in the field—including witnesses at a recent congressional hearing on these critical materials—are now focusing on the potential for future U.S. production. Likewise, a recent workshop held by the National Research Council (NRC) discussed research progress toward alternatives to these materials and their applications.

Congress last turned its attention to this issue on Sept. 21, when the House of Representatives Foreign Affairs Committee’s Subcommittee on Asia & the Pacific held a hearing on how to confront China’s rare-earths monopoly. This committee is interested in the topic because the situation has some serious implications for U.S. foreign policy in the arena of relations with China.

“China’s ability to dictate market terms to the rest of the world is particularly worrisome given its unwillingness to follow established international rules,” said subcommittee Chairman Donald A. Manzullo (R-Ill.) in opening the hearing. “The scope of the crisis is enormous, and only a concerted national effort will lead us out of this mess.” Manzullo is the cosponsor of legislation designed to streamline approval regulations for U.S. production of rare earths. It now can take as long as six to 10 years for a company to get the necessary permits to open a new mine.

Those testifying at the hearing agreed that there are things the government could do to help, but they also expressed optimism about what is already being done. “It is not very productive to spend time blaming China,” said Mark A. Smith, president and chief operating officer of Molycorp, the owner of the only U.S. rare-earth mining facility. He told the subcommittee that the U.S. needs to take a page from China’s book and use its own significant rare-earth mineral deposits to create new opportunities and jobs.

Smith also pointed out that the U.S. maintains an edge over its competitors with superior extraction and production technology. “The best thing Congress can do is to encourage continued technological innovation,” Smith said, “and key to that effort is maintaining robust research and development efforts in this area and strengthening the nation’s graduate and postgraduate programs.”

Other witnesses at the hearing concurred with Smith. John Galyen, president of Danfoss, a global manufacturer of heating, cooling, and other equipment that uses rare-earth metals, recommended that the federal government do more to level the playing field between China and the U.S. in the short term and fund research on the development of alternative materials as a long-term strategy.

And Christine Parthemore, a fellow at the Center for a New American Security, a nonpartisan research institution, told the panel that federal agencies need to “support research and development on the more efficient use of rare earths, rhenium, and lithium,” because of their increasing importance in weapons programs for U.S. defense.

Indeed, alternatives to critical materials and the more efficient use of these rare but economically important elements were the topic of a two-day workshop held at the end of last month by NCR’s Chemical Sciences Roundtable. The workshop included discussion of critical materials in catalysis and in electronic, energy, magnetic, and optical applications. It focused on both the current use of rare-earth metals and what researchers are doing to find alternatives to expensive materials like platinum and tellurium. Continued availability of critical materials was a recurring theme.

The industrial and academic researchers at the workshop emphasized that the issue of critical materials is broader than just the rare earths. In his overview of the situation, Roderick G. Eggert, of the Mineral & Energy Economics Program at Colorado School of Mines, said the whole periodic table is under siege. “The growing demand for complex materials is leading to exploding demand for elements that are now used in only small quantities,” Eggert said. And the limited availability of these materials, such as platinum, will be a constraint on development and diffusion of emerging technologies.

In view of the attention given the rare earths by the government and others, Eggert pointed out that time is an important component. “What is critical today may not be critical tomorrow,” he said. Short- and long-term adjustments will be made by industry and by emerging markets to deal with existing capacity, but those adjustments will require investment in scientific and technical innovations.

These adjustments include increased exploration for new deposits of rare earths and other valuable metals such as lithium. And more R&D for extraction technologies, manufacturing efficiency, and recycling is needed. In the longer term, Eggert sees the necessity for government stockpiles of critical materials, a more diversified supply chain, and element-for-element substitution.

Of particular interest to industry is the availability of platinum group metals, which although expensive are used as catalysts in many applications. James C. Stevens of Dow Chemical explained that use of platinum catalysts in chemical production is efficient and that developing and making the ligand for the catalyst often costs more than the platinum itself. He says the development of substitutes such as cobalt or iridium has stalled because of high costs of trying to separate the catalyst from the desired product.

The biggest use of platinum and palladium, however, is in automotive catalytic converters. Christine Lambert of Ford Motor Co. told the workshop that demand for platinum and palladium for auto catalysts is about 8.6 million oz per year compared with 3.0 million oz for jewelry and 4.1 million oz for industrial use. Most of the world use of rhenium is also for auto catalysts, she noted.

Research has yet to find substitutes for these metals in catalytic converters, she said. For example, gold and silver are not active or durable enough, and ruthenium, iridium, and osmium all form volatile oxides at 500 °C, the temperature at which catalytic converters operate. She said diesel engines, which require complicated multistage catalysts, are able to use iron to catalyze the reduction of nitrogen oxides (with the introduction of urea) but only because these engines operate at 200 °C.

One way to save on platinum and palladium costs is to reduce the amount used, said Jingguang G. Chen, a chemical engineering professor at the University of Delaware. He is making catalysts by putting a monolayer of platinum atoms on tungsten carbide, a combination that matches the hardness and stability of pure platinum but uses a fraction of the critical element.

R. Morris Bullock of Pacific Northwest National Laboratory is developing novel nickel complexes for use in low-temperature fuel cells. Finding “cheap metals for noble tasks”—that is, inexpensive, abundant metals such as iron, cobalt, copper, or chromium to replace rarer materials in catalysts and devices—is a major research goal. He said these replacements are often more environmentally benign, can be lost in industrial processes without the financial concern, and are less toxic to humans.

But as with most substitutions, there are problems. In Bullocks’ case, the problems include reduced scope of activity and much higher catalyst loading, as well as simply not knowing enough because of a lack of research on the replacement materials in fuel cells.

The availability of materials for production of solar panels is also a major concern. Ken Zweibel, director of George Washington University’s Solar Institute, said photovoltaics have tremendous potential to generate energy around the world, but the production of solar panels requires scarce materials such as gallium, tellurium, and indium.

One way to stretch supplies is to make the thin films even thinner, Zweibel said. “We need to undertake the research and development to get these films down to extremely small thicknesses,” he said, even down to about one-tenth their present thickness. He said there is a need for chemists to develop these films and to research the use of different materials such as molybdenum and ruthenium in solar panels.

Supply of another critical material used in energy technologies—lithium—was also discussed at the workshop. Lithium is widely used in batteries for everything from flashlights to vehicles as well as other energy storage systems, and some worry that access to it may become limited, thus driving up its price and the price of the products it’s used in. This fear, however, is overblown, explained several of the presenters.

Jay F. Whitacre, a battery researcher at Carnegie Mellon University, stated: “There is plenty of lithium in the world. Known resources can provide enough lithium to make more than 32 billion electric vehicles.” The real problem—and expense—in making these batteries includes factors such as the price of electrolytes, the need for very pure materials, and the requirement of a very dry manufacturing environment.

Likewise, David J. Bradwell, chief technology officer for Liquid Metal Battery Corp., said the struggle in developing any major energy system is going to be keeping costs down, not securing lithium. A number of alternatives to lithium exist for large-scale electricity storage such as for backing up the electrical grid, Bradwell said. He cited magnesium, zinc permanganate, and even lead acid batteries as prospects. But he pointed out that the challenges to using any of these materials include electrode cracking and deterioration, interfacial film growth, and dendrite formation. Research is needed in this area, he said, but not many academic scientists are pursuing it because most of the chemistry is considered unexciting.

Getting scientists to do new research on some of these older technologies is one of the barriers to progress, according to workshop participants. They cited researchers’ need to propose cutting-edge projects to successfully compete for federal grants and noted that, in the energy field, such research often involves using exotic metals and other materials, which are too expensive to ever be practical in a real-world energy device.

Workshop attendees also discussed ways the federal government can help improve access to rare earths and other critical materials. For example, the government could push for undistorted international trade in critical materials, improve the regulatory process for mining operations, and facilitate basic research in energy sciences.

Training of chemists in research and manufacturing using these critical materials was also a concern of the workshop participants. China is graduating many more Ph.D. chemists in the rare-earths field than is the U.S., they noted, and more U.S. chemists and chemical engineers are needed in the field of energy products such as photovoltaics. These remarks were corroborated by Dow’s Stevens, who said his company cannot get the academically trained chemists in the areas of catalysis or photovoltaics that it needs. “There are tremendous opportunities for scientists in these areas,” he said. ◾


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