Advanced magnetic materials for aircraft power applications

A multidisciplinary team of Carnegie Mellon University (CMU) researchers with substantial support from the public and private sectors was assembled to develop new materials with improved magnetic and mechanical properties at high temperature. The group worked on the refinement of existing soft bulk materials while conducting research on novel nanocrystalline magnets in parallel. The team also studied existing and new high temperature permanent magnetic materials for use in aircraft engine applications. A vigorous search for new magnetic materials, both hard and soft, was conducted. Prototypes for bulk soft magnets were Fe-Co alloys. The effects of alloy grain size, structural order, orientation, and texture were studied to maximize induction and permeability, and minimize hysteretic and eddy current losses at elevated temperatures. Investigation of nanocrystalline materials for soft magnetic applications proceeded on two fronts: plasma synthesis of magnetic nanoparticles followed by the use of compaction techniques to form dense magnets, and the nanocrystallization of amorphous precursors to produce exchange coupled magnetic nanocrystals. The first effort has led to the synthesis of metallic nanoparticles, of new core shell structures, and nanocrystalline ferrites. The second effort has led to the discovery of a new nanocrystalline soft magnetic material called HITPERM on which work continues to explore its use in power electronic applications. For hard magnetic materials capable of operating at up to 400 degrees, the team investigated Co-containing 2:17, 1:12, and 3:29-based permanent magnet materials. They investigated the fundamental properties of these alloy systems as well as processing protocols for engineering optimal microstructures for hard magnetic properties. Co-containing 3:29 phase magnets have extended the temperature range of these materials. Rapid solidification was used to tailor microstructure and harness anisotropy.