Iron-gallium alloy shows promise as a power generation device

An alloy first manufactured nearly two decades ago by the US Navy could provide an efficient new way to generate electricity. The material, called Galfenol, consists of iron doped with metallic gallium. In new experiments, researchers at UCLA, the University of North Texas (UNT), and Air Force research labs have shown that galfenol can generate up to 80 megawatts of instantaneous power per meter square under strong impacts. The team describes the findings, which could lead to the development of wireless impact detectors and other applications, in an article published in the Journal of Applied Physics.

Galfenol is a magnetoelastic material, in which the state of magnetization can be changed by compressing, pushing or deforming the material. Conversely, when exposed to a magnetic field, magnetoelastic materials react by changing their shape. If the materials are prevented from deforming, for example by being held in a clamp, they will instead generate significant force.

“In general, this means that a magnetoelastic material can convert mechanical energy into magnetic energy, and vice versa,” explained John P. Domann, graduate student in mechanical engineering at UCLA and first author of the article. Galfenol converts energy with great efficiency; it is capable of transforming approximately 70 percent of an applied mechanical energy into magnetic energy, and vice versa. (A standard car, on the other hand, only converts about 15 to 30 percent of the energy stored in gasoline into useful motion.) Significantly, the magnetoelastic effect can be used to generate electricity. “If we wrap wires around the material, we can generate an electric current in the wire due to a change in magnetization,” said Domann.

As described in the new article, Domann and his colleagues, including his doctorate. advisor, Gregory P. Carman, professor of mechanical and aerospace engineering at UCLA, and Bradley E. Martin of the Air Force Research Laboratories at Eglin Air Force Base in Fla. – assessed the ability to generate energy of Galfenol in experiments using a device called a Split-Hopkinson pressure bar to generate high compressive stresses (eg, strong impacts). They discovered that when subjected to impacts, Galfenol generates up to 80 megawatts of instantaneous power per cubic meter.

For comparison, a device known as an explosive ferromagnetic pulse generator produces 500 megawatts of power per cubic meter. However, as the name suggests, such generators require an explosion, an explosion that destroys the ferromagnetic, even if it produces electricity. “Destroying a material takes a lot of wasted energy, only creating one-shot devices,” Domann said. “This waste of energy and destruction is not a problem in our method using galfenol, which means our devices can be used repeatedly and cyclically.”

Among the potential applications, devices powered by galfenol could be used as wireless impact detectors. “Essentially, we could make little devices that send out a detectable electromagnetic wave when a mechanical impulse passes through it,” Domann said. These devices could be embedded in vehicles – military or civilian – to detect collisions. Since electromagnetic waves travel three orders of magnitude faster than mechanical waves, information about the impact could be transmitted before the waves created by the impact. “This way we could wirelessly determine that an impact has occurred, before the majority of the vehicle (or passengers) even have time to feel it. This would allow a fast computer to take action. to mitigate damage or injury, “he added. .

Although the concept requires further analysis and testing, commercial technologies based on the idea could see the market in just a few years, the researchers said.