Magnetic-Polymer Composites for Bonding and 3D Printing of Permanent Magnets

Advanced manufacturing techniques using composite materials made of magnetic particles and polymers are attracting much interest for new routes of fabrication of more efficient and functional devices with complex shapes. The 3D printing and bonding technologies of a broad range of materials, such as NdFeB, improved ferrites, and Mn-based alloys, show up as alternatives to traditional fabrication techniques for a large range of permanent magnets' (PMs) applications. This paper focuses on the fabrication of magnetic products based on strontium ferrite and NdFeB by extrusion of magnetic-polymer composite materials. The composites have been extruded using different nozzles and optimizing the extrusion temperature for each of them, obtaining strips and filaments with rectangular and circular cross section, respectively. The morphological characterization of the strips and filaments has revealed that the polymer covers homogeneously the particles, obtaining continuous strips and filaments with a high filling factor. A decrease in the filling factor has been observed for the NdFeB-based strip and filament ascribed to the larger particle size compared to the Sr-ferrite particles. This paper opens a new path for fabricating PMs' materials as final products and for their use in advanced 3D printing technologies of elements and devices with no-restriction in composition, size, and shape.