25 research outputs found
Computational design of rare-earth reduced permanent magnets
Multiscale simulation is a key research tool in the quest for new permanent magnets. Starting with first principles methods, a sequence of simulation methods can be applied to calculate the maximum possible coercive field and expected energy density product of a magnet made from a novel magnetic material composition. Iron (Fe)-rich magnetic phases suitable for permanent magnets can be found by means of adaptive genetic algorithms. The intrinsic properties computed by ab intro simulations are used as input for micromagnetic simulations of the hysteresis properties of permanent magnets with a realistic structure. Using machine learning techniques, the magnet's structure can be optimized so that the upper limits for coercivity and energy density product for a given phase can be estimated. Structure property relations of synthetic permanent magnets were computed for several candidate hard magnetic phases. The following pairs (coercive field (T), energy density product (kJ.m(-3))) were obtained for iron-tin-antimony (Fe3Sn0.75Sb0.25): (0.49, 290), L1(0) -ordered iron-nickel (L1(0) FeNi): (1, 400), cobalt-iron-tantalum (CoFe6Ta): (0.87, 425), and manganese-aluminum (MnAl): (0.53, 80).Web of Science6215314
Simulation of magnetic active polymers for versatile microfluidic devices
We propose to use a compound of magnetic nanoparticles (20-100 nm) embedded
in a flexible polymer (Polydimethylsiloxane PDMS) to filter circulating tumor
cells (CTCs). The analysis of CTCs is an emerging tool for cancer biology
research and clinical cancer management including the detection, diagnosis and
monitoring of cancer. The combination of experiments and simulations lead to a
versatile microfluidic lab-on-chip device. Simulations are essential to
understand the influence of the embedded nanoparticles in the elastic PDMS when
applying a magnetic gradient field. It combines finite element calculations of
the polymer, magnetic simulations of the embedded nanoparticles and the fluid
dynamic calculations of blood plasma and blood cells. With the use of magnetic
active polymers a wide range of tunable microfluidic structures can be created.
The method can help to increase the yield of needed isolated CTCs
Self-organizing magnetic beads for biomedical applications
In the field of biomedicine magnetic beads are used for drug delivery and to
treat hyperthermia. Here we propose to use self-organized bead structures to
isolate circulating tumor cells using lab-on-chip technologies. Typically blood
flows past microposts functionalized with antibodies for circulating tumor
cells. Creating these microposts with interacting magnetic beads makes it
possible to tune the geometry in size, position and shape. We developed a
simulation tool that combines micromagnetics and discrete particle dynamics, in
order to design micropost arrays made of interacting beads. The simulation
takes into account the viscous drag of the blood flow, magnetostatic
interactions between the magnetic beads and gradient forces from external
aligned magnets. We developed a particle-particle particle-mesh method for
effective computation of the magnetic force and torque acting on the particles
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Automated meshing of electron backscatter diffraction data and application to finite element micromagnetics
This paper gives a procedure for automatically generating finite element meshes with an adaptive mesh size from Electron Backscatter Diffraction (EBSD) data. After describing the procedure in detail, including preliminary and image processing steps, an example application is given. The method was used to carry out finite element (FE) micromagnetic simulations based on real microstructures in the hard magnetic material, MnAl. A fast micromagnetic solver was used to compute hysteresis properties from the finite element mesh generated automatically from EBSD data. The visualization of the magnetization evolution showed that the reversal is governed by domain wall pinning at twin boundaries. The calculated coercive fields are very sensitive to changes of the Gilbert damping constant, even for low field rates. © 2019 The Author