SBIR-STTR Award

The critical technical issue in synthesizing bulk anisotropic interface-exchange-coupled magnets with magnetic performance superior to conventional magnets is to create a composite magnet microstructure in which a highly dispersed nanometer-sized magnetically soft phase, such as -Fe-or Fe-Co, is uniformly distributed in a nanograin magnetically hard phase, such as Nd-Fe-B or Sm-Co. Previously, sputtering, pulse laser deposition, electroless coating, and electrolyte coating were used to coat Nd-Fe-B or -Fe-or Fe-Co Sm-Co particles with thin layers followed by rapid inductive hot compaction and hot deformation. Bulk interface-exchange-coupled magnets synthesize using these technologies can have (BH)max = 45 - 55 MGOe. In order to accomplish better magnetic performance with (BH)max = 60 MGOe, technical problems associated with the above-mentioned powder coating technologies, such as low deposition rate, high processing cost, and high oxygen pickup, must be solved. In this proposed SBIR Phase I research project, innovative powder coating technologies will be studied and developed and their feasibility in crating the desired microstructure and in synthesizing high performance interface-exchange-coupled nanograin magnets will be demonstrated. The advantage of these technologies include high deposition rate, low processing cost, and low oxygen pickup.

Worldwide efforts to synthesize Nd-Fe-B or Sm-Co nanoparticles have been unsuccessful because of oxygen pickup. An alternative approach to synthesizing interface-exchange-coupled magnets with uncharted superior properties is to create a microstructure with highly dispersed soft phase (Fe or Fe-Co) embedded in the nanograin hard phase (Nd-Fe-B or Sm-Co). Coating micron-sized Nd-Fe-B particles with Fe or Fe-Co layers has proved to be practical for making such magnets in our previous efforts. Technologies including sputtering, pulsed laser deposition, and electroless and electrolytic coating were used followed by rapid inductive hot compaction and hot deformation. Such exchange-coupled magnets can have (BH)max greater than 45 MGOe. Coating Fe-based Nd-Fe-B particles with Fe or Fe-Co layers is a great challenge since the chemical potential difference between them is small. To accomplish (BH)max > 60 MGOe, in the proposed SBIR-II project innovative coating technologies will to be studied and developed to solve problems such as low deposition rate, non-uniform coating (due to loose bridging of particles), oxidation, and high cost. Applying the proposed innovative approach, the advantage of nanostructure is fully utilized, while the problems associated with synthesizing and handling nanoparticles, such as oxidation and agglomeration, are readily avoided.

Keywords:
Permanent Magnets, High-Energy Product, Nanocomposite, Exchange-Coupled Magnets, Innovative Coating On Powders Of Nanograins, Consolidation For Nanogr