Soft Magnetic Nanocomposite for High-Temperature Applications

Commercial soft magnetic cores used in power electronics are limited by core loss and decreased ferromagnetism at high temperatures. Extending functional performance to high temperatures allows for increased power density in electric systems with fixed power output and elevated operating temperature. The innovators at Glenn developed a unique composition and process to improve the temperature capability of the material. Nanocomposite soft magnetic materials are typically comprised of a combination of raw materials including iron, silicon, niobium, boron, and copper. Instead of niobium, NASA's material utilizes small cobalt and tantalum additions. The raw materials are combined to form an amorphous precursor through melt spinning. NASA&#39s innovation with the fabrication lies in the thermal annealing step, which nucleates and crystallizes the precursor to form the composite structure of the material. By adjusting the temperature and magnetic field of the thermal annealing step, Glenn's process results in good coupling between the crystalline and amorphous matrix phases. Innovators at Glenn demonstrated the temperature robustness using small test cores of their material and are investigating additional quality attributes compared to other well-known soft magnetic materials (see two Figures below). Innovators at NASA's Glenn Research Center developed a novel nanocomposite soft magnetic material for use in power electronics. The material maintains near room-temperature attributes of available soft magnetics, such as Hitachi Metals' FINEMET®, while surpassing these materials in temperature capability. In the present state-of-the-art, soft magnetic nanocomposites have an upper temperature limit rating of 150°C before core loss occurs. By adjusting the composition and fabrication, innovators at Glenn increased the operating temperature range to 400°C with minimal increase in core loss. While operating at high temperatures, the material exhibits high permeability and saturation flux density desirable in soft magnetics. Test cores of the novel material show improved temperature performance compared to available materials. NASA's development expands the application of soft magnetic material, enabling efficient power electronics that are smaller and lighter due to the reduced need for cooling.