A team led by Sandia National Laboratories has developed a way to make a magnetic material that could lead to lighter and smaller, cheaper and better-performing high-frequency transformers, a requirement for more flexible energy storage systems and widespread adoption of renewable energy.

Transportable energy storage and power conversion systems, which could fit inside a single semi-trailer, would make it cost effective to rapidly install solar, wind and geothermal energy systems in even the most remote locations, the researchers say.

“Such modular systems could be deployed quickly to multiple sites with much less assembly and validation time,” says researcher Todd Monson of Sandia's Nanoscale Sciences Department, who led the team with Stan Atcitty, of Sandia’s Energy Storage Technology and Systems Department.

Sandia researcher Todd Monson says FAST manufacturing could shrink transformer size. Image credit: Randy Montoya.Sandia manufactures iron nitride (γ’-Fe4N) powders by ball-milling iron powders in liquid nitrogen followed by ammonia. The iron nitride powders are then consolidated through a low-temperature field-assisted sintering technique (FAST) that forms a solid material from loose powders through the application of heat and sometimes pressure.

The FAST manufacturing method enables the creation of transformer cores from raw starting materials in minutes, without decomposing the required iron nitrides, as could happen at the higher temperatures used in conventional sintering. Previously, the γ’ phase of iron nitride has only been synthesized in either thin-film form in high-vacuum environments or as inclusions in other materials—and never integrated into an actual device.

Monson says using this method could make transformers one-tenth the size that they are currently.

“FAST enables the net-shaping of parts, meaning that iron nitride powders can be sintered directly into perfectly sized parts, such as transformer cores, [that] don’t require any machining,” Monson adds.

Due to their magnetic properties, iron nitride transformers can be made much more compact and lighter than traditional transformers, with better power-handling capability and greater efficiency. According to Sandia, they will require only air cooling, another important space saver. Iron nitride also could serve as a more robust, high-performance transformer core material across the nation’s electrical grid.

So far, Monson and his colleagues have demonstrated the fabrication of iron nitride transformer cores with good physical and magnetic characteristics and now are refining their process and preparing to test the transformers in power conversion test beds.

“Advanced magnetic materials are critical for next-generation power conversion systems that use high-frequency linked converters and can complement Sandia efforts in ultra-wide-bandgap-device materials for improved power electronics systems," says Atcitty. "They can withstand higher frequencies and higher temperatures, which ultimately result in high power density designs.”

Team members from Sandia and the University of California, Irvine have filed a patent application for the materials synthesis process.