MPIE-Calendar 2021

January - Hydrogen Plasma Reduction of Iron Ore

Iron oxide sample partially reduced via the carbon-neutral hydrogen plasma-based reduction. EBSD map of iron drops embedded in a wüstite (FexO) matrix. The morphology in combination with the color code adopted to show the crystallographic orientations, resemble the surrealist paintings by Joan Miró.

February - Dewetting Pattern

Annealing a Co-Cu alloy film (orange) on a sapphire substrate below the melting temperature leads to solid state rupture of the film at energetically favorable sites. As a result, the sapphire is exposed (darker areas). Dewetting develops in the film through different mechanisms forming islands and particles. These particles can be applied in magnetic storage devices or as catalysts in electrochemistry.

March - Pure Iron Oxide Surface 

Light microscopy image of the surface of a pure iron sample. The sample underwent a heat treatment in which the atmosphere is set to be reducing at high temperature (here 700°C), but oxidizing during cooling, thus forming a thin oxide layer on the surface. Although the composition of the oxide is homogeneous, its color varies depending on its thickness and crystallographic orientation.

April - Nanoparticles for Oxygen Reduction Reaction

Colour coded scanning transmission electron microscopy image of alloy nanoparticles, which were formed during heating experiments of thin metallic films. The alloy particles are applicable in the oxygen reduction reaction, one of the most important reactions in e.g. energy systems.

May - Fermi Surface of Europium Compound

Momentum space surface separating occupied and unoccupied electron states (Fermi Surface) describing the interactions between lanthanide local moments that is mediated by conduction electrons. The Fermi Surface of a europium compound is shown, whose changing topology causes a giant magnetic discontinuity. This effect can be exploited in novel, environmentally friendly cooling technologies to combat climate change.

June - Dark Field Image of Silicon

Dark field image of the unpolished side of a (001) silicon substrate. The four-fold symmetry of the surface can be seen, which is an easy way to distinguish it from other orientations. Such Si substrates are used for epitaxial growth of thin films of semiconductors like GaN, which is used to make light emitting diodes (LEDs).

July - Helimagnetic States in Gadolinium-Cobalt

Fourier transformation of pairwise magnetic interactions of a hexagonal GdCo5 compound. Every point of the xy-plane cut in reciprocal space corresponds to a particular wave modulated helimagnetic state. The brighter the colour, the more stable the state is. Such rare-earth based compounds are important for permanent magnets, applicable in e.g. electric motors.

August - Hydrogen Induced Dislocation Structure

Microstructure evolution of the cross-section underneath nanoindentation imprints by S-TEM. The mechanical tests were conducted during hydrogen charging using an in-house built in-situ backside electrochemically charging set-up. More dislocations are generated after introducing hydrogen into the FeCr binary alloy, which leads to a hardening effect. This work reveals the hydrogen embrittlement mechanism.

September - Machine Learning for EBSD

Electron backscatter diffraction (EBSD) is a technique that provides the material’s crystal information. Using a machine learning algorithm, we are able to compress large information behind each EBSD pattern into two dimensions. The different colored dots represent simulation-, and red-colored dots are experimental patterns.

October - Electrochemical Oxidation

New ab initio enable precise simulations of electrochemical reactions under potential control. The figure shows an artistically enhanced snapshot of an ab initio molecular dynamics simulation, describing electrooxidation processes at the Ge(100) surface interfaced with liquid water. This method helps in understanding e.g. batteries, electrolysis and electrode degradation processes.

November - Machine Learning Potentials

Correlation of ab initio derived forces for bcc NbMoTaWV high entropy alloy at 3000 K versus a zero K harmonic approximation. Density is color-coded. Deviations from the dashed line indicate the breakdown of the harmonic approximation. Accurate high-temperature predictions have become possible by combining newly developed concepts from machine learning and ab initio calculations, paving the way to design novel alloys for high-temperatures

December - Hydrogen Enhanced Decohesion

Grain boundary κ-carbides as they appear on the intergranular fracture surface of a hydrogen charged high Mb lightweight steel tensile sample. This kind of precipitation promotes H enhanced decohesion along grain boundaries. Slip traces on the grain boundary form a tree-like structure with κ-carbides.

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