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Disruptive materials

Revolutionary advances in performance are needed to boost energy technologies and the economy

 

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A remarkable number of technologies are driven by advances in materials science. Breakthroughs in energy, computing, transportation and communication products often are rooted in improvements in the materials from which they are made. The more scientists know about the basic structure of materials, the more easily they can tailor those properties to specific needs.

Stronger materials, for example, result in safer cars. Photoelectric materials can boost the efficiency of solar panels, and lightweight materials improve the fuel efficiency of all kinds of vehicles.

"I think one of the laboratory's biggest challenges for the future is to develop what we call disruptive materials," ORNL Associate Laboratory Director Michelle Buchanan says. "I'm not talking about incremental changes; we're looking for quantum changes in the performance of materials that will help us greatly improve energy efficiency and achieve energy independence."

Focusing on disruptive materials is a natural evolution for ORNL, which not only supports one of the largest materials science programs in the world but also has a tradition of pairing basic and applied materials research that reaches back to the lab's World War II origins. Former lab director and Manhattan Project scientist Alvin Weinberg is generally credited with institutionalizing the coupling of "bench" science and practical applications at the laboratory. "Applied research done in a basic atmosphere has a sophistication that is hard to duplicate in a less scientific environment," Weinberg observed, "and … basic research done in an applied atmosphere has a kind of no-nonsense aggressiveness that is hard to duplicate when basic research is done entirely by itself."

Says Buchanan, "Emphasizing this scientifically inclusive approach to materials science is unique to Oak Ridge among all the other laboratories. It's one of the defining characteristics of our program."

Hidden potential

The ability to unlock the hidden potential of materials is one of the keys to developing game-changing applications. Some of the biggest opportunities for this exist in the areas outlined below.

Ultrastrong materials—Among the main attractions of developing stronger materials are their fringe benefits. For instance, if some of the steel parts in your car were replaced by a much stronger material, your car likely would be safer as a result of the sheer strength of the material. It also might be more durable because the stronger parts would last longer, and it almost certainly would be lighter because less material would be needed to produce the new parts. Finally, if your car were lighter, it would be more fuel efficient because less energy is needed to move a lighter vehicle.

Another attraction of pursuing ultrastrong materials is that there's plenty of room for improvement in material strength. Because of tiny defects throughout their structure, most materials used in manufacturing today only possess about 10 percent of their theoretical strength. Research at ORNL's Center for Defect Physics is gradually uncovering the reasons for this disparity and devising ways to take advantage of the 90 percent of the strength that seems to be unnecessarily lost.

"We are beginning to understand the 'why' part," Buchanan says. "We are using computational tools and our experimental expertise to analyze existing materials and understand how defects cause them to fail, as well as how to create new materials with fewer defects."

Energy storage—Another area ripe for disruption is the effort to increase the energy storage capacity of batteries. The electric and hybrid vehicle industries have great interest in storing more energy in smaller packages, since batteries account for 20 to 25 percent of each vehicle's weight. Laboratory researchers are exploring new ways to get battery electrodes to store more ions—the more ions, the more electricity. One way to squeeze more ions onto the electrodes is to make the electrodes out of a material that has lots of texture at the nanoscale.

"We have been experimenting with materials with small holes, called nanopores, on their surfaces," Buchanan says. "These holes are only a few thousandths of an inch in diameter, but because they are three-dimensional, rather than flat, they increase the surface area from which ions can come and go and greatly improve the battery's ability to store energy. We're in the early stages of this research, but if we can get these materials to perform as well as we think they can, it would be revolutionary."

Increased storage capacity would be a huge plus not only for electric vehicle batteries, but also for storing power on the grid. One of the reasons wind and solar power generation aren't more widespread is that they can provide power only when the wind is blowing or the sun is shining. These systems need a way to store large amounts of electricity when it's still and dark. Buchanan envisions new battery technology providing better storage options for individual homes or even neighborhoods. "Nobody wants to fill their basement with batteries," she says. "If we expect people to store power at home, we need to develop batteries the size of heat pumps that can sit outside their houses—reliable batteries that could be charged over and over for many years. We also envision larger batteries powering entire neighborhoods."

Separating materialsChelators are specialized molecules designed to chemically grab and separate very specific materials from a liquid mixture. This makes them handy for tasks such as environmental cleanup. A good example of chelation in action is an ORNL-developed system for separating radioactive cesium, a common environmental contaminant, from other waste products—a process that makes the remaining waste safer to handle. This process has been tested extensively and will be part of a $1.7 billion waste processing facility being built at the Department of Energy's Savannah River Site.

The success of the cesium-targeting chelator led its developers to apply the same kind of technology to the task of separating uranium from seawater for use as nuclear fuel. This development could have profound long-term impacts because there is much more uranium dissolved in seawater than there is on land.

Researchers have figured out how to attach a uranium-seeking chelator to points along the length of feather-like polymer fibers. They are planning to assemble these fibers into weighted nets and lower them into the ocean where the chelators will react with the uranium dissolved in seawater as it flows past. When the fibers are ready to harvest, workers just haul the net up and recover the uranium through a simple chemical process.

"The disruptive aspect of this technology is that it is much cheaper to extract uranium from seawater than it is to mine uranium," Buchanan explains. "There's only so much material you can mine easily and cheaply, and then you still have to worry about the environmental impact. Extracting uranium from the sea using chelation would avoid mining altogether."

Similar applications of this separation technology are being investigated for recycling materials that are vital to our nation's economy and come from discarded electronics, solar cells and magnets. These so-called "critical materials" include elements that possess unique magnetic, catalytic and luminescent properties needed to manufacture clean energy products, such as wind turbines, solar panels, electric vehicles and energy-efficient light fixtures.

"When it comes to critical materials," Buchanan says, "we have the ability to make every step of their lifecycle, from the mine to the recycling bin, more efficient. The Department of Energy's national laboratories, particularly those partnering in the new Critical Materials Institute, have all the components needed to make a lot of progress in this area. We have the expertise and the facilities, and we can apply computational tools to help us project what materials we should look at first."

Making an impact

"I think the laboratory is always going to be a leader in coming up with technologies that use basic science to solve practical energy-related problems," Buchanan observes. "Our goal is to meet the nation's future energy needs and spur economic growth. That's just what we have to do. Some of our technologies will be spun off into defense programs and health and all sorts of things, but we need to keep our eye on the ball. We want to serve the nation's needs in energy in general and its materials needs in particular."

Over the next few years, Buchanan expects the lab's materials science R&D program to have its biggest impacts in the area of extreme materials—structural elements that can hold their own under high levels of stress, strain and radiation better than conventional materials; functional materials like those found in batteries and solar cells; thermoelectrics—materials that turn waste heat into power; and polymer science—where ORNL's neutron science capabilities are spurring research in areas ranging from drug delivery to lightweight composite materials to carbon dioxide remediation.

"I think Alvin Weinberg would be very pleased with our progress," Buchanan says, "particularly with the way our basic and applied research programs support one another. We use the same philosophy in our unique user facilities like the Nanoscience Center, the ShaRE microscopy program and the Spallation Neutron Source. These facilities are making our scientific capabilities available to the entire scientific community and are helping to teach the next generation of scientists the skills of our trade." —Jim Pearce