Nanolayering Improves Materials

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Nations worldwide are striving to replace traditional fossil fuels with cleaner, more abundant power sources. Recently, the Department of Energy concluded there is one common need to all future energy technologies: improved materials.

 

To meet that need, lightweight materials that resist corrosion, decay and failure—and that heal themselves—are being developed at Los Alamos National Laboratory (LANL).

 

These improved materials will also make our cars, airplanes, computers, and power transmission lines lighter, stronger and more damage-resistant. "Of course, if an aircraft or automobile is lighter, it will decrease fuel costs," says Amit Misra of the Center for Integrated Nanotechnologies (CINT) of the Lab’s Materials Physics and Applications (MPA) division.

 

Making Metals Thinner and Stronger

 

Misra, who recently won the LANL Fellows Prize for his research, is nanostructuring metals that are simultaneously stronger and damage-resistant. His team’s new technology combines two metals into a composite made up of ultra-thin layers; this nanolayering makes the composite extraordinarily strong and highly damage-resistant.

 

"The nanolayered composites have strengths that are over two orders of magnitude higher than high-purity metals in the single crystal form," Misra says.

 

In contrast to nanostructured materials, conventionally-engineered steel, aluminum, copper and other metals have low strengths and poor damage tolerance. In order to withstand high loads or extreme environments—high pressure, soaring temperature or long-term radiation—engineers must overdesign the structural components, for example, making a metal container thicker and heavier.

 

Making Power Plants Safer

 

Fossil fuels are scarce and efforts to curb greenhouse gases are increasing. Clean power sources such as nuclear power plants can help meet the world's future energy needs, but safety and economical concerns remain. According to the U.S. Nuclear Regulatory Commission, the 1986 accident at the nuclear power station in Chernobyl, Ukraine may ultimately cause approximately 4,000 radiation-related cancer deaths of its workers and residents.

 

In a nuclear power plant, constant exposure to radiation degrades the structural materials over time. For example, the metal containers used to hold nuclear fuel can experience radiation-induced swelling and creep (deformation). The swelling is caused when helium-filled cavities produced by radiation inflate inside the metal. Currently, engineers design around these limitations. The containers are made very thick, and the components are replaced frequently, making the process expensive and dangerous.

 

The Lab's research—which will help to design structural materials that better withstand the degrading effects of radiation—could help address those concerns.

Interfaces Protect Against Radiation Damage

 

The new nanolayered composites could dramatically improve the performance and reliability of materials in nuclear reactors. The key to damage resistance is the interface, or junction, between the layers in the composite. When the right kinds of metals are bonded, the interface between them has unprecedented, self-healing properties. The interfaces attract, absorb and annihilate radiation-induced defects.

 

Because the attraction of defects to interfaces only works when an interface is close to a damaged area, very thin nanolayers—just a few dozen atoms thick—must be used.

 

The right combination of metals is key. The combination of Copper and Niobium works well, Misra says; this combination produces the remarkable tolerance to radiation damage as well as the very high strength characteristics of nanolayered composites. "This is one combination, but is it the best one?" Misra says. "We don't know yet."

 

More research is needed to find the ideal materials that will help build tomorrow's power plants, cars, airplanes, computer components and electrical transmission lines, Misra says. The technology is still in the early development stages but the Laboratory is on the cutting edge for materials that enhance our lives.

 

Source: Los Alamos National Laboratory