Nanocrystalline Material and Fabrication Process for Advanced Magnetic Devices

August 17, 2019 by Paul Shepard

Magnetic components are essential to America's electricity delivery system, ultimately powering homes, businesses and more to drive the nation's economy and enhance quality of life. Converging societal trends — including the evolution of the nation's energy infrastructure, demand for more efficient electrical machinery and increasing electrification of transportation — have renewed interest in advanced power magnetics research aimed at developing more efficient, reliable and power-dense solutions.

The U.S. DoE's National Energy Technology Laboratory (NETL) is addressing these needs in collaboration with partners at Carnegie Mellon University, Metglas and Eaton. Researchers have developed two complementary technologies — a cobalt-based nanocrystalline alloy and an innovative strain anneal manufacturing process — that combine to produce inductive components with unprecedented magnetic capabilities for use in motors, electrical machinery and more.

These patented, market-ready technologies link atomic-level changes to grid-scale impacts, offering the possibility of customizing magnetic properties for superior performance in a broad range of specific applications.

The alloy itself is made primarily of cobalt, combined with lesser amounts of iron and other metals. Rapid solidification processes are used to synthesize metallic glass ribbons made of the finely tuned cobalt-rich alloy, producing thin sheets of metal several inches wide and miles in length.

During the in-line strain anneal manufacturing process, the alloy ribbon is held under tension as it travels through a furnace heated to temperatures of 500-600 degrees Celsius. The controlled heat treatment alters the material's crystalline makeup, transforming its structure from random to one composed of fine crystals embedded in a metallic glass. The result is a composite structure that can be tailored by controlling temperature, applied tension and more.

Using custom-developed machine controls, researchers can also grade permeability — the measure of a material's magnetic response to an applied field — from the inner to outer radius, which allows for simultaneous control of the magnetic and thermal properties of the component.

The alloy demonstrates superior mechanical properties, magnetic performance and responsiveness to the in-line strain annealing manufacturing process. The two technologies combined facilitate the manufacture of gapless inductors and other novel electrical tools that improve performance, boost efficiency and reduce peak temperature for next-generation power technologies.

To date, advanced magnetic core technology has already enabled researchers to advance combined solar photovoltaic and battery grid integration, motors for natural gas compressors and subsea electrification for oil and gas resource recovery.

Metglas Inc., the nation's only manufacturer of such metal ribbons, and Eaton Corporation, have accelerated commercialization efforts by bridging basic science to full-scale components and system-level demonstrations. Metglas completed the first successful scale-up cast of the cobalt-based metal ribbon and reproduced the permeability engineering approach using the team's custom-designed alloy to fabricate a full-scale prototype electromagnetic core designed and demonstrated in collaboration with Eaton.

Future energy systems will incorporate varied energy sources, multi-directional power flow and demand response to ensure efficient, cost-effective and reliable delivery. NETL's collaborative cobalt-based nanocrystalline alloy and strain anneal manufacturing technologies are critical achievements toward realizing that vision, as they support the development of solid-state transformers, grid-tied inverters, power flow controllers and more to revolutionize America's energy infrastructure and impact power delivery around the world.