9 research outputs found
Microstructural Changes Influencing the Magnetoresistive Behavior of Bulk Nanocrystalline Materials
Bulk nanocrystalline materials of small and medium ferromagnetic content were
produced using severe plastic deformation by high-pressure torsion at
roomtemperature. Giant magnetoresistive behavior was found for as deformed
materials, which was further improved by adjusting the microstructure with
thermal treatments. The adequate range of annealing temperatures was assessed
with in-situ synchrotron diffraction measurements. Thermally treated CuCo
materials show larger giant magnetoresistance after annealing for 1 h at 300C,
while for CuFe this annealing temperature is too high and decreases the
magnetoresistive properties. The improvement of magnetoresistivity by thermal
treatments is discussed with respect to the microstructural evolution as
observed by electron microscopy and ex situ synchrotron diffraction
measurements
Tuneable Magneto-Resistance by Severe Plastic Deformation
Bulk metallic samples were synthesized from different binary powder mixtures
consisting of elemental Cu, Co, and Fe using severe plastic deformation. Small
particles of the ferromagnetic phase originate in the conductive Cu phase,
either by incomplete dissolution or by segregation phenomena during the
deformation process. These small particles are known to give rise to granular
giant magnetoresistance. Taking advantage of the simple production process, it
is possible to perform a systematic study on the influence of processing
parameters and material compositions on the magneto-resistance. Furthermore, it
is feasible to tune the magnetoresistive behavior as a function of the
specimens chemical composition. It was found that specimens of low
ferromagnetic content show an almost isotropic drop in resistance in a magnetic
field. With increasing ferromagnetic content, percolating ferromagnetic phases
cause an anisotropy of the magnetoresistance. By changing the parameters of the
high pressure torsion process, i.e., sample size, deformation temperature, and
strain rate, it is possible to tailor the magnitude of giant
magneto-resistance. A decrease in room temperature resistivity of approx. 3.5%
was found for a bulk specimen containing an approximately equiatomic fraction
of Co and Cu
Weakly Supervised Learning of Multi-Object 3D Scene Decompositions Using Deep Shape Priors
Representing scenes at the granularity of objects is a prerequisite for scene
understanding and decision making. We propose PriSMONet, a novel approach based
on Prior Shape knowledge for learning Multi-Object 3D scene decomposition and
representations from single images. Our approach learns to decompose images of
synthetic scenes with multiple objects on a planar surface into its constituent
scene objects and to infer their 3D properties from a single view. A recurrent
encoder regresses a latent representation of 3D shape, pose and texture of each
object from an input RGB image. By differentiable rendering, we train our model
to decompose scenes from RGB-D images in a self-supervised way. The 3D shapes
are represented continuously in function-space as signed distance functions
which we pre-train from example shapes in a supervised way. These shape priors
provide weak supervision signals to better condition the challenging overall
learning task. We evaluate the accuracy of our model in inferring 3D scene
layout, demonstrate its generative capabilities, assess its generalization to
real images, and point out benefits of the learned representation
Strain Induced Anisotropic Magnetic Behaviour and Exchange Coupling Effect in Fe-SmCo5 Permanent Magnets Generated by High Pressure Torsion
High-pressure torsion (HPT), a technique of severe plastic deformation (SPD), is shown as a promising processing method for exchange-spring magnetic materials in bulk form. Powder mixtures of Fe and SmCo are consolidated and deformed by HPT exhibiting sample dimensions of several millimetres, being essential for bulky magnetic applications. The structural evolution during HPT deformation of Fe-SmCo compounds at room- and elevated- temperatures of chemical compositions consisting of 87, 47, 24 and 10 wt.% Fe is studied and microstructurally analysed. Electron microscopy and synchrotron X-ray diffraction reveal a dual-phase nanostructured composite for the as-deformed samples with grain refinement after HPT deformation. SQUID magnetometry measurements show hysteresis curves of an exchange coupled nanocomposite at room temperature, while for low temperatures a decoupling of Fe and SmCo5 is observed. Furthermore, exchange interactions between the hard- and soft-magnetic phase can explain a shift of the hysteresis curve. Strong emphasis is devoted to the correlation between the magnetic properties and the evolving nano-structure during HPT deformation, which is conducted for a 1:1 composition ratio of Fe to SmCo. SQUID magnetometry measurements show an increasing saturation magnetisation for increasing strain γ and a maximum of the coercive field strength at a shear strain of γ = 75