TY - JOUR AB - Magnetic nanoparticles can be embedded in electrospun nanofibers and other polymeric matrices to prepare magnetic composites with defined magnetic and mechanical properties. Metal-oxide nanoparticles, such as magnetite or nickel-ferrite, are of special interest since they do not need a coating to avoid oxidation. Like other nanoparticles, these metal-oxide nanoparticles tend to form agglomerations, in this way modifying the magnetic properties of the composites. After studying this effect for the magnetic elements Co, Fe, Ni as well as permalloy (Py) in a previous study, defining a new method to quantify the nanoparticle distribution in a polymer, here we concentrate on the influence of agglomerations on the magnetic properties of metal-oxide nanoparticles with different diameters in non-magnetic matrices. AU - Blachowicz, Tomasz AU - Grzybowski, Jacek AU - Ehrmann, Andrea ID - 2282 JF - Materials Today: Proceedings KW - Magnetic nanoparticles Electrospinning Magnetite Nickel-ferrite Maghemite SN - 22147853 TI - Influence of agglomerations on magnetic properties of polymer matrices filled with magnetic nanoparticles VL - 67 ER - TY - JOUR AB - Electrospinning can be used to produce nanofiber mats containing diverse nanoparticles for various purposes. Magnetic nanoparticles, such as magnetite (Fe3O4), can be introduced to produce magnetic nanofiber mats, e.g., for hyperthermia applications, but also for basic research of diluted magnetic systems. As the number of nanoparticles increases, however, the morphology and the mechanical properties of the nanofiber mats decrease, so that freestanding composite nanofiber mats with a high content of nanoparticles are hard to produce. Here we report on poly (acrylonitrile) (PAN) composite nanofiber mats, electrospun by a needle-based system, containing 50 wt% magnetite nanoparticles overall or in the shell of core–shell fibers, collected on a flat or a rotating collector. While the first nanofiber mats show an irregular morphology, the latter are quite regular and contain straight fibers without many beads or agglomerations. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) reveal agglomerations around the pure composite nanofibers and even, round core–shell fibers, the latter showing slightly increased fiber diameters. Energy dispersive X-ray spectroscopy (EDS) shows a regular distribution of the embedded magnetic nanoparticles. Dynamic mechanical analysis (DMA) reveals that mechanical properties are reduced as compared to nanofiber mats with smaller amounts of magnetic nanoparticles, but mats with 50 wt% magnetite are still freestanding. AU - Mamun, Al AU - Sabantina, Lilia AU - Klöcker, Michaela AU - Heide, Alexander AU - Blachowicz, Tomasz AU - Ehrmann, Andrea ID - 2041 IS - 3 JF - Polymers KW - freestanding nanofiber mats KW - magnetic nanoparticles KW - needle-based electrospinning KW - coaxial spinning KW - dynamic mechanical analysis (DMA) KW - atomic force microscopy (AFM) KW - scanning electron microscopy (SEM) TI - Electrospinning Nanofiber Mats with Magnetite Nanoparticles Using Various Needle-Based Techniques VL - 14 ER - TY - JOUR AB - Magnetic nanofibers are of great interest in basic research, as well as for possible applications in spintronics and neuromorphic computing. Here we report on the preparation of magnetic nanofiber mats by electrospinning polyacrylonitrile (PAN)/nanoparticle solutions, creating a network of arbitrarily oriented nanofibers with a high aspect ratio. Since PAN is a typical precursor for carbon, the magnetic nanofiber mats were stabilized and carbonized after electrospinning. The magnetic properties of nanofiber mats containing magnetite or nickel ferrite nanoparticles were found to depend on the nanoparticle diameters and the potential after-treatment, as compared with raw nanofiber mats. Micromagnetic simulations underlined the different properties of both magnetic materials. Atomic force microscopy and scanning electron microscopy images revealed nearly unchanged morphologies after stabilization without mechanical fixation, which is in strong contrast to pure PAN nanofiber mats. While carbonization at 500 °C left the morphology unaltered, as compared with the stabilized samples, stronger connections between adjacent fibers were formed during carbonization at 800 °C, which may be supportive of magnetic data transmission. AU - Fokin, Nadine AU - Grothe, Timo AU - Mamun, Al AU - Trabelsi, Marah AU - Klöcker, Michaela AU - Sabantina, Lilia AU - Döpke, Christoph AU - Blachowicz, Tomasz AU - Hütten, Andreas AU - Ehrmann, Andrea ID - 654 IS - 7 JF - Materials KW - ferrimagnetic materials KW - superparamagnetism KW - magnetic hysteresis KW - magnetic materials KW - magnetic nanoparticles KW - nanocomposites KW - nanowires SN - 1996-1944 TI - Magnetic Properties of Electrospun Magnetic Nanofiber Mats after Stabilization and Carbonization VL - 13 ER - TY - JOUR AB - One-dimensional materials, such as nanowires, nanotubes, or nanofibers, have attracted more and more attention recently due to their unique physical properties. Their large length-to-diameter ratio creates anisotropic material properties which could not be reached in bulk material. Especially one-dimensional magnetic structures are of high interest since the strong shape anisotropy reveals new magnetization reversal modes and possible applications. One possibility to create magnetic nanofibers in a relatively simple way is offered by electrospinning them from polymer solutions or melts with incorporated magnetic nanoparticles. This review gives an overview of most recent methods of electrospinning magnetic nanofibers, measuring their properties as well as possible applications from basic research to single-cell manipulation to microwave absorption. AU - Blachowicz, Tomasz AU - Ehrmann, Andrea ID - 639 JF - Journal of Engineered Fibers and Fabrics KW - Electrospinning KW - magnetic nanoparticles KW - nanofibers SN - 1558-9250 TI - Most recent developments in electrospun magnetic nanofibers: A review VL - 15 ER - TY - JOUR AB - Neuromorphic computing is assumed to be significantly more energy efficient than, and at the same time expected to outperform, conventional computers in several applications, such as data classification, since it overcomes the so-called von Neumann bottleneck. Artificial synapses and neurons can be implemented into conventional hardware using new software, but also be created by diverse spintronic devices and other elements to completely avoid the disadvantages of recent hardware architecture. Here, we report on diverse approaches to implement neuromorphic functionalities in novel hardware using magnetic elements, published during the last years. Magnetic elements play an important role in neuromorphic computing. While other approaches, such as optical and conductive elements, are also under investigation in many groups, magnetic nanostructures and generally magnetic materials offer large advantages, especially in terms of data storage, but they can also unambiguously be used for data transport, e.g., by propagation of skyrmions or domain walls. This review underlines the possible applications of magnetic materials and nanostructures in neuromorphic systems. AU - Blachowicz, Tomasz AU - Ehrmann, Andrea ID - 662 IS - 11 JF - Molecules KW - neuromorphic computing KW - adaptive computing KW - cognitive computing KW - magnetism KW - micromagnetic simulations KW - magnetic nanoparticles KW - neural network SN - 1420-3049 TI - Magnetic Elements for Neuromorphic Computing VL - 25 ER -