A team of researchers says it has created a way to incorporate nanoparticles into structural metal, creating the possibility of a strong but lightweight material for use in vehicles.

The research was conducted at the Henry Samueli School of Engineering and Applied Scientist at the University of California, Los Angeles. The findings were published in the journal Nature.

Researchers incorporated ceramic silicon carbide nanoparticles into magnesium. The resulting metal had high strength and a good stiffness-to-weight ratio. The team suggests that the lightweight metal could help improve fuel efficiency in vehicles, airplanes, and spacecraft and have applications in mobile electronics and biomedical devices.

"It's been proposed that nanoparticles could really enhance the strength of metals without damaging their plasticity, especially light metals like magnesium, but no groups have been able to disperse ceramic nanoparticles in molten metals until now," said Xiaochun Li, who is the Raytheon Chair in Manufacturing Engineering at UCLA and worked as the principal investigator on the research. "With an infusion of physics and materials processing, our method paves a new way to enhance the performance of many different kinds of metals by evenly infusing dense nanoparticles to enhance the performance of metals to meet energy and sustainability challenges in today's society."

Magnesium already offers the possibility to reduce weight when used as a structural material, since it is abundant on the planet and has two-thirds the density of aluminum. Silicon carbide is an extremely hard ceramic which is typically used in industrial cutting blades.

The researchers say that ceramics and nanoparticles have been considered as a way to increase the strength of a metal, but that certain challenges have prevented their implementation. Ceramics used on a microscopic scale increase a metal's strength but reduce its plasticity, or ability to be shaped. The use of nanoparticles can improve both strength and plasticity, but the particles tend to attract one another and clump together.

In order to create an even distribution of nanoparticles, researchers used a "nanoparticle self-stabilization mechanism" to add silicon carbide particles smaller than 100 nanometers into a molten alloy of magnesium and zinc. The method helped stabilize the distribution of particles and kept them from attracting one another.

Researchers also compressed the metal using a method called high-pressure torsion to further increase its strength. The resulting product exhibited a high level of specific strength, or ability to withstand weight before breaking. It also demonstrated significant stability at high temperatures as well as improved plasticity and stiffness-to-weight ratio.

The report says the product resulting from the process is a new metal, or a metal nanocomposite. It consists of about 86 percent magnesium and 14 percent silicon carbide nanoparticles.

"The results we obtained so far are just scratching the surface of the hidden treasure for a new class of metals with revolutionary properties and functionalities," said Li.

In addition to the UCLA researchers, authors contributing to the Nature paper hailed from Clemson University, North Carolina State University, the University of California – Riverside, and the Minneapolis-based nanomechanical test instrument company Hysitron Inc. Part of the research was funded by the National Institute of Standards and Technology.

Nanotechnology has been used or is being proposed for other automotive technologies as well. Michael Berger, writing for the nanotechnology educational portal Nanowerk, says the microscopic materials have the potential to improve fuel efficiency and engine performance, make parts more reliable and long-lasting, and reduce a vehicle's impact on the environment.

Paints with nanoparticles may help strengthen the paint's bond to the body and prevent the color from fading. In addition, they could be used to repel dirt, resist scratches, and create self-healing qualities to repair minor damage.

Lubricants with nanoparticles could help reduce friction in an engine's mechanical parts, thereby improving fuel economy. Nanotechnology might also be used to improve a battery's power and recharge time, reduce window glare and condensation through an ultrathin layer of nanoparticles on glass surfaces, and add small solar panels to the vehicle's exterior to collect energy from sunlight.

NanOpinion, a nanotechnology education and discussion resource funded by the European Commission, says nanoparticles developed for tires seek to reduce rolling resistance, improve air retention, improve the grip on the road, and enhance the overall strength of the tire.

These materials have also raised some health and safety concerns, particularly for particles smaller than 100 nanometers. Jim Novak, writing for the Canadian grounds maintenance publication Turf & Recreation, says some researchers have concluded that the long, thin shape of carbon nanotubes may have an effect on the lungs similar to that of asbestos. Novak says the possibility that the particles can lead to lung cancer is especially concerning since old tires are often recycled to provide surfaces for playgrounds and sports fields.