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Research Projects
Atom Probe Tomography Group

Energy Materials

Enabling a ‘hydrogen economy’ requires developing fuel cells satisfying economic constraints, reasonable operating costs and long-term stability. The fuel cell is an electrochemical device that converts chemical energy into electricity by recombining water from H2 and O2, allowing to generate environmentally-friendly power for e.g. cars or houses. However, upscaling anion-exchange membrane fuel cells (AEMFCs) is hindered by the slow kinetics of hydrogen oxidation reaction (HOR) at the anode.
 
This project targets to exploit or develop new methodologies to not only visualize the 3D morphology but also measure chemical distribution of as-synthesized nanostructures using atom probe tomography.

More research topics

In collaboration with Dr. Edgar Rauch, SIMAP laboratory, Grenoble, and Dr. Wolfgang Ludwig, MATEIS, INSA Lyon, we are developing a correlative scanning precession electron diffraction and atom probe tomography method to access the three-dimensional (3D) crystallographic character and compositional information of nanomaterials with unprecedented spatial and chemical resolution.
Here, we aim to develop machine-learning enhanced atom probe tomography approaches to reveal chemical short/long-range order (S/LRO) in a series of metallic materials.
The structures of grain boundaries (GBs) have been investigated in great detail. However, much less is known about their chemical features, owing to the experimental difficulties to probe these features at the near-atomic scale inside bulk material specimens. Atom probe tomography (APT) is a tool capable of accomplishing this task, with an ability to quantify chemical characteristics at near-atomic scale.
This project is a joint project of the De Magnete group and the Atom Probe Tomography group, and was initiated  by MPIE’s participation in the CRC TR 270 HOMMAGE. We also benefit from additional collaborations with the “Machine-learning based data extraction from APT” project and the Defect Chemistry and Spectroscopy group.
This project is led by Felipe Morgado and Leigh Stephenson, and targets the analysis of single vacancies in nickel, but also their chemical neighborhood with tantalum, using Atom Probe Tomography, Field Ion Microscopy in conjunction with Time-of-Flight Mass Spectrometry, and Density-Functional Theory.
 In this project, we reveal the subtle yet important interplay between the faceting of grain boundaries and their chemical decoration with solutes in an engineering Al-Zn-Mg-Cu alloy. Previously, the interplay of chemistry and faceting was revealed for specific grain boundaries in well-defined bicrystals, which are realistically not encountered in engineering alloys.
Thermoelectric materials can be used to generate electricity from a heat source through the Seebeck effect, whereby a temperature difference leads to a difference in voltage for power generation. The opposite effect, known as the Peltier effect, is exploited for heating and cooling for instance. The efficiency of the conversion can be increased by introducing defects that efficiently scatter phonons, i.e. the carriers of lattice vibrations and hence heat, but do not affect much the movement of electrons so as to maintain good electrical conductivity.
 
This research focuses on studying the segregation behavior of solute atoms at defects like dislocations and grain boundaries (GBs). We aim at generating a connection between defect-related observations to mechanical properties. The outcome will provide input into the design of advanced alloys.
 
The Atom Probe Tomography group in the Microstructure Physics and Alloy Design department is developing integrated protocols for ultra-high vacuum cryogenic specimen transfer between platforms without exposure to atmospheric contamination.

Advanced APT Process Tools

Advanced microscopy and spectroscopy offer unique opportunities to study the structure, composition, and bonding state of individual atoms from within complex, engineering materials. Such information can be collected at a spatial resolution of as small as 0.1 nm with the help of aberration correction.
The project focuses on development and design of workflows, which enable advanced processing and analyses of various data obtained from different field ion emission microscope techniques such as field ion microscope (FIM), atom probe tomography (APT), electronic FIM (e-FIM) and time of flight enabled FIM (tof-FIM).

High Temperature Materials

Understanding the deformation mechanisms observed in high performance materials, such as superalloys, allows us to design strategies for the development of materials exhibiting enhanced performance. In this project, we focus on the combination of structural information gained from electron microscopy and compositional measurements from atom probe tomography (APT).
In this project we work on the fabrication and the thermodynamic and metallurgical basics associated with the additive manufacturing of dense Mo-Si-B-based alloys.
This project is part of Correlative atomic structural and compositional investigations on Co and CoNi-based superalloys as a part of SFB/Transregio 103 project “Superalloy Single Crystals”. This project deals with the identifying the local atomic diffusional mechanisms occurring during creep of new Co and Co/Ni based superalloys by correlative techniques.

Bio Materials

Atom probe tomography (APT) is predominantly used to study non-biological materials, in an ion-by-ion tomographic process. At MPIE, we are a part of a small cohort of research labs exploring the use of APT for biologically-relevant materials. This field of research takes on two streams within our research group: the study of materials for implants including bioresorbable ceramics and bioresorbable metals, and the study of frozen liquids that can be used as carry-media for hydrated biological materials.
In this project we try to expand the possibilities of using atom probe tomography (APT) to investigate proteins, their structures and binding to ligands. The project is funded by Volkswagenstiftung "Experiment" (Seeing atoms in biological materials - a new frontier for atomic-scale tomography)

Al & Ti based Alloys

CALPHAD-informed phase field modeling, scanning transmission electron microscopy and atom probe tomography have been used to study the segregation, precipitation, and solute distribution in high strength Aluminium alloys (7xxx).
The objective of the project is to investigate grain boundary precipitation in comparison to bulk precipitation in a model Al-Zn-Mg-Cu alloy during aging.

Finished projects

Materials used in catalytic reactions are exposed to conditions that inevitably lead to microstructural and chemical changes in the bulk and on the surface. To understand their complex interplay and influence on the catalyst´s performance, one requires spatially resolved methods that encompass surface and bulk sensitivity on the nanoscale, ideally in-operando.
In this project, we successfully developed a crystal-glass high-entropy nanocomposite in CrFeCoNi-based system. The microstructure, composition and deformation mechanism of the novel crystal-glass high-entropy nanocomposite was comprehensively studied using probe-corrected scanning transmission electron microscope and atom probe tomography. This crystal-glass nanocomposite design provides a route to develop advanced structural materials with an outstanding combination of strength and ductility.
In this project we work on the corelative characterization of the atomic structure and composition of water-splitting catalysts. We aim to better understand reaction and degradation mechanisms of Ir-based catalysts for the oxygen evolution reaction (OER) by establishing structure-function relationships at the atomic scale.
In this project we work on correlative atomic structural and compositional investigations on Co and CoNi-based superalloys as a part of SFB/Transregio 103 project “Superalloy Single Crystals”. The task is to image the boron segregation at grain boundaries in the Co-9Al-9W-0.005B alloy.
In this project, we directly image and characterize solute hydrogen and hydride by use of atom probe tomography combined with electron microscopy, with the aim to investigate H interaction with different phases and lattice defects (such as grain boundaries, dislocation, etc.) in a set of specimens of commercially pure Ti, model and commercial Ti-alloys.
Within this project we investigate chemical fluctuations at the nanometre scale in polycrystalline Cu(In,Ga)Se2 and CuInS2 thin-flims used as absorber material in solar cells.
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