Net-shaped barium and strontium ferrites by 3D printing with enhanced magnetic performance from milled powders

• Published in: Journal of magnetism and magnetic materials 2020-01, Vol.493, p.165664, Article 165664
• Main Authors: Wei, Xiangxia, Liu, Yinhua, Zhao, Dongjie, Mao, Xuewei, Jiang, Wanyue, Ge, Shuzhi Sam
• Format: Article
• Language: English
• Subjects: 3-D printers; 3D printing; Barium; Coercivity; Extrusion; Ferrites; Ferromagnetism; Grain growth; Heat treatment; Hysteresis loops; Magnetic materials; Magnetic measurement; Magnetic properties; Magnetic saturation; Magnetic separation; Magnetism; Mechanical milling; Milled powders; Nanoparticles; Net-shaping without residues; Strontium; Three dimensional printing
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2019.165664

Net-shaped hexagonal barium and strontium ferrites with desirable shapes have been successfully fabricated by the extrusion-based three-dimensional (3D) printing. The influence of milling and calcination conditions on magnetic properties of as-printed hexaferrites are systematically investigated by vibrating sample magnetometry (VSM). The typical ferromagnetic hysteresis loops are observed, revealing that the resulting bulk ferrites derived from the preliminary milled powders are prefect hard magnetic materials. In particular, it is clear that the saturation magnetization is very close to the theoretical values after calcinations. Moreover, the coercivity can be effectively enhanced in the range of 4–6 kOe upon thermal treatment, which is a much higher value compared to ferrites prepared by the conventional ceramic processing. More importantly, the maximum energy product can be significantly improved to as high as around 2.5 MGOe for the 3D-printed strontium ferrites. This is attributed not only to fine precursor powders subjected to mechanical milling, but also to the optimized annealing for grain growth with sizes near the critical single domain limit. Overall, the fabrication of bulk ferrites derived from milled powders using the 3D printing is attractive for the large-scale applications, and may also pave the way for some specific applications, for instance, magnetic separation for nanoparticles.