Sustainability and Decarburization

Shaping our future in terms of sustainable technologies, new materials and industrial processes is one of the most important topics of our generation and we are in need of scientific and engineering answers. How can we avoid the use of carbon as energy and reductant carrier in the entire field of materials science and engineering? How can we make better and rare-earth free permanent magnets for electrical vehicles? How can we render alloys sustainable and improve recycling rates? Which are the novel materials that can withstand embrit­tlement caused by hydrogen? And what is the potential of new thermoelectric and so­lar cell absorber materials for green power generation? We have devoted our efforts to provide answers to these pressing ques­tions, showing you here some of our cur­rent research in the field of sustainability.

Advanced characterisation of nanostructured materials for photocatalytic <br />water splitting
The sunlight is capable of answering the global energy need. Semiconducting materials have been developed to convert solar radiation into fuels for energy storage and mobile applications. Electronic band alignment, carrier transport, and reaction kinetics at interfaces make the system optimization a joint adventure for physicists, materials scientists, and chemists. In our group, we apply structural and electrochemical characterization to study nanostructured materials and their stability. more
Alloy Design of WEC-resistant Bearing Steels using a Customized <br />Rolling Contact Fatigue Test Rig
The aim of the project is to elucidate the mechanism behind white etching crack (WEC) formation in bearing applications and to create materials that are resistant to this failure mechanism. The most prominent example for WEC failure are gear bearings of wind turbines. However, also many other applications from rails, over clutches to washing machines are concerned. more
Metals are ductile and ceramics are stiff. Ideally, these advantageous properties of each material class can be combined in one material. Examples are nanolaminated systems such as Mo2BC and Cr2AlC. In this project, we focus on the atomic level analysis of these materials using aberration corrected scanning transmission electron microscopy. more
The CarMON project, short for Carbon Metal-Oxide Nanohybrids, is performed by the INP - Leibniz Institute for Plasma Science and Technology (Greifswald), the INM - Leibniz Institute for New Materials (Saarbrücken) and our group. Novel materials are developed by combining metal oxides and carbonaceous materials for electrochemical energy storage and water desalination. Synergistic effects on the nanoscale between these two material types can lead to overall increased performance. more
In the light of growing energy needs, depleting fossil fuels, and the threatening global warming, alternative energy sources are needed. Chalcopyrite materials are suitable for renewable energy applications, for example solar cells, water splitting or photo catalysis. In our study, we synthesize copper indium disulfide films via a solvothermal procedure. The nanostructured films are crystalline even at temperatures below 200 °C as shown by electron microscopic techniques. more
<h4><span class="edit-container-element" data-url="/object/4200688/attribute/title/edit?type=multi_language" data-custom-direct-remote-link="true" data-remote="true" data-edit-label="Title">Development of Precipitation Strengthened CCAs in the AlCrFeNiTi system <br />for High Temperature Structural Applications</span></h4>
The need to make energy generation and conversion more sustainable and to reduce the emission of harmful gases requires the development of novel high temperature stable materials.  An alternative alloy development strategy searches the central regions of multicomponent phase space for multi-principle-element alloys that have been previously unexplored. Several of the resulting compositionally complex alloys (CCAs) have been shown to possess novel property combinations and, in some cases, exceptional mechanical properties. more
Because of their excellent corrosion resistance, high wear resistance and comparable low density, Fe–Al-based alloys are an interesting alternative for replacing stainless steels and possibly even Ni-base superalloys. Recent progress in increasing strength at high temperatures has evoked interest by industries to evaluate possibilities to employ Fe–Al-based alloys for various applications. These activities have matured to a point that industrial processing of parts is now investigated in more detail by considering economic aspects. more
<h4><span class="edit-container-element" data-url="/object/4200745/attribute/title/edit?type=multi_language" data-custom-direct-remote-link="true" data-remote="true" data-edit-label="Title">The effect of Mo and Nb additions on microstructure, thermal stability <br />and mechanical properties of Al-rich Ti-Al</span></h4>
TiAl-based alloys currently mature into application. Sufficient strength at high temperatures and ductility at ambient temperatures are crucial issues for these novel light-weight materials. By generation of two-phase lamellar TiAl + Ti3Al microstructures, these issues can be successfully solved. Because oxidation resistance at high temperatures is still a problem which could be improved by increasing the Al content, Al-rich TiAl alloys have recently come into focus. more
It is four decades that lanthanides are being doped into semiconductors as a way to realize light emitters. The most interesting feature of lanthanide emission is their very sharp luminescent lines. It enables them to be used in various applications such as TV displays and solid state lasers. This is due to 4f electrons being effectively shielded from the surrounding crystal field by the outer filled 5s and 5p shells. In fact, the 4f shell is not fully occupied which allows transitions to happen within the f orbital. more
The thermodynamic stability of computationally designed multicomponent compounds against decomposition into structures with less favorable properties is often unclear. In this project, we have used sophisticated finite temperature ab initio methods to determine the relative phase stabilities of promising Ce-Fe-Ti hard-magnetic materials. more
Understanding hydrogen-microstructure interactions in metallic alloys and composites is a key issue in the development of low-carbon-emission energy by e.g. fuel cells, or the prevention of detrimental phenomena such as hydrogen embrittlement. We develop and test infrastructure, through in-situ nanoindentation and related techniques, to study independently hydrogen absorption and further interaction with trap binding sites or defects and its effects on the mechanical behavior of metals. more
With the support of DFG, in this project the interaction of H with mechanical, chemical and electrochemical properties in ferritic Fe-based alloys is investigated by the means of in-situ nanoindentation, which can characterize the mechanical behavior of independent features within a material upon the simultaneous charge of H. more
Intelligent design of nanostructured materials forms the basis for high efficiencies in energy applications. 3D hierarchical niobium oxide nanostructures are investigated, as they form self-organized using a facile one-step synthesis approach. Electron microscopic investigations in combination with different spectroscopic methods are used to analyse these superstructures heading towards a better understanding of the forces involved in self-organization at the nanoscale. more
Microscopic understanding of the formation, reaction, and stability of <br />emerging functional nanomaterials
Understanding the atomic structure of functional nanomaterials and unraveling their impact on chemical reactions is important as it can provide guidelines for their improvement. In this study, low dimensional nanomaterials are synthesized using wet-chemical strategies and tested in various electrochemical reactions. Electron microscopy before and after the reactions allows to unravel the growth mechanism and the atomic arrangement as well as to identify degradation phenomena. more
The progressing climate change and our increasing demand of energy supply combined with a decreasing stock of natural resources constrain us to focus on alternative, renewable energy suppliers. One of the many viable solutions therefore are fuel cells (FCs) which are devices that enable us to convert the chemical energy of a fuel into electrical energy via catalyzed reactions on electrodes. This project focusses on high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). more
Multinary transition metal nanoparticles are promising candidates for energy applications. Our research is based on the synthesis and atomic-scale characterization of such multinary systems. The nanoparticles are prepared by sputtering of elements into ionic liquids. Depending on the synthesis conditions, they grow either in an amorphous or crystalline state. The amorphous particles can be transformed to different crystalline phases via electron beam bombardment or post annealing. more
Thermoelectric materials
Thermoelectrics have attracted increasing attention as a sustainable and flexible source of electricity able to meet a wide range of power requirements. Their application is wide as they could be used in automotive, aerospace and medical fields, and wherever temperature gradients exist. In this project we focus mostly on the ternary Ag–Sb–Te system as it is a promising thermoelectric material. The investigated compounds possess moderate to high ZT-values depending on their microstructure. more
TiO2 nanostructures are promising electrodes for dye or hybrid solar cells and are utilized as stable support for electrocatalyst. Among a great variety of nanostructures, single-crystalline TiO2 nanowires exhibit particularly interesting characteristics. In this project TiO2 nanowires are synthesized via a hydrothermal approach and analyzed using electron microscopy. The main focus is on the morphology changes during annealing and core etching which lead to better performance. more
Understanding the Excellent Rolling Contact Fatigue Durability of <br />High-Nitrogen Martensitic Bearing Steels
By characterizing the high N alloyed martensitic stainless bearing steel X30CrMoN15-1 in-depth, we rationalize the exceptional white etching crack resistance of this complex technical alloy in terms of the different grain boundary segregation behavior between nitrogen and carbon, the mechanical and thermodynamic stability of the precipitates, and the cleanliness of the steel. more
The unpredictable failure mechanism of White Etching Crack (WEC) formation in bearing steels urgently demands in-depth understanding of the underlying mechanisms in the microstructure. The first breakthrough was achieved by relating the formation of White Etching Areas (WEAs) to successive WEC movement. more
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