Erich Schmid Institute of Materials Science

Abstract The magnetic rare-earth free α -MnBi phase has a high magnetic anisotropy and an increasing coercivity with increasing temperature. However, its use in practical applications is limited due to challenging manufacturing of bulk material. We introduced severe plastic deformation by high-pressure torsion as novel processing method to address this limitation. In this study, different processing parameters are evaluated and the upscaling potential of this method to obtain larger volumes of α -MnBi bulk magnets is demonstrated. The microstructural and magnetic characterization results confirm the formation of the magnetic rare-earth free α -MnBi phase in samples with a diameter of up to 30 mm. The bulk magnetic material possesses magnetic properties comparable to smaller material volumes processed with the same method.

• Nano-structuring metallic glass thin film triggers synergistic effect of enhanced plasticity without compromising strength. • Strong stress confinement to 100 nm revealed by 4D-STEM strain mapping. • Structural confinement of stress and enhanced plasticity were confirmed via MD simulations. • Plasticity improvement by designed microstructural features at the length scale of 100 nm. The deformation of metallic glasses (MGs) is characterized by strong strain localizations in shear bands and rapid propagation thereof, leading to brittle fracture. The incorporation of secondary phases or heterogeneities into the glassy structure has been shown to enhance ductility, resulting in the formation of metallic glass composites (MGCs). In this study, we examine the deformation behavior of MGCs composed of two distinct glassy phases applying in-situ deformation combined with 4D scanning transmission electron microscopy (4D-STEM). Local strain evolution was tracked during loading and revealed that nanolayered MGCs exhibit significantly enhanced plasticity compared to monolithic glasses. This improvement of ductility was attributed to a notable confinement of atomic strain in the soft layer, which is enabled by the layered architecture. Notably, confining stress within individual layers suppresses the development of mature shear bands and delays the onset of critical shear instabilities. Complementary molecular dynamics simulations support experimental results, clarifying how architectural confinement and phase synergy can be utilized to enhance the mechanical properties of two-phase glassy materials.

Abstract This study focuses on the synthesis and characterization of advanced polymeric composite electrospun nanofibers (NFs) containing magnetic oxide nanoparticles (NPs). By leveraging the method of electrospinning, the research aims to investigate polymer composites with enhanced interfacial properties, improved double-layer capacitance, and adequate biocompatibility. Electrospun polyacrylonitrile (PAN) NFs embedded with Fe₂O₃ and MnZn-Ferrite NPs were comprehensively characterized using advanced techniques, i.e., Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, high-resolution scanning electron microscopy, X-ray diffraction, and alternating gradient field magnetometry. The incorporation of metal oxide NPs led to significant changes in the thermal, spectroscopic, and morphological properties of the NFs. Spectroscopic analysis confirmed increased oxidation, graphitic carbon content, and the formation of new nitrogen functionalities after heat treatment. Furthermore, interactions between nitrile groups and metal ions were observed, indicating the influence of nanoparticles on surface chemistry. Magnetic characterization demonstrated the potential of these composite NFs to generate magnetic fields for biomedical manipulation. Cytocompatibility studies revealed no significant impact on the viability or morphology of human mesenchymal stromal cells, highlighting their biocompatibility. These findings suggest the promising use of PAN-magnetic NFs in applications including targeted drug administration, magnetic resonance imaging, and magnetic hyperthermia for cancer treatment. Graphical abstract