Scientific Events

Conventional high-resolution imaging by electron microscopy plays an important role in the structural and compositional analysis of catalysts. However, since the observations are generally performed under vacuum and close to room temperature, the obtained atomistic details concern an equilibrium state that is of limited value when the active state of a catalyst is in the focus of the investigation. Since the early attempts of Ruska in 1942 [1], in situ microscopy has demonstrated its potential and, with the recent availability of commercial tools and instruments, led to a shift of the focus from ultimate spatial resolution towards observation of relevant dynamics. During the last couple of years we have implemented commercially available sample holders for in situ studies of catalysts in their reactive state inside a transmission electron microscope. In order to relate local processes that occur on the nanometer scale with collective processes that involve fast movement of large numbers of atoms, we have adapted an environmental scanning electron microscope (ESEM) for the investigation of surface dynamics on active catalysts. Using these two instruments, we are now able to cover a pressure range from 10^-4 to 10³ mbar and a spatial resolution ranging from the mm to the sub-nm scale. Presently we are investigating metal catalyzed CVD growth of graphene [2,3], as well as structural dynamics during oscillatory red-ox reactions on metal catalysts. The observations are performed in real-time and under conditions in which the active state of the catalyst can be monitored. The latter is of upmost importance, since the key requirement is to observe relevant processes and dynamics that are related to catalytic function. The ability to directly image the active catalyst and associated morphological changes at high spatial resolution enables us to refine the interpretation of spatially averaged spectroscopic data that was obtained under otherwise similar reaction conditions, for example during near-ambient-pressure in situ XPS measurements [4]. It will be shown that the ability of observing the adaption of an active surface to changes in the chemical potential of the surrounding gas phase in real-time potentially offers new and direct ways of optimizing catalysts and applied reaction conditions. References[1] E. Ruska, Kolloid-Zeitschrift, 100 (1942) 212-219[2] Z.-J. Wang et al., ACS Nano, 9 (2015) 1506–1519[3] Z.-J. Wang et al., Nat. Commun. 7 (2016) DOI:10.1038/ncomms13256[4] R. Blume et al., PhysChemChemPhys, 16 (2014) 25989 [more]

Publishing your research results is an integral – if not the most important – part of your research. In this talk, some insight in the publishing process at the inhouse editorial offices of the successful journal family of Advanced Materials will be given. I will clarify the workflow at a publishing house from the moment the manuscript arrives until it is published and emphasize the role of the editor in that process. In the second part, I concentrate specifically on the requirements for successful publication in our high-impact journals and explain our requirements for acceptable manuscripts in our journals – and which pit falls authors should avoid in the preparation and submission process. [more]

The Max-Planck-Institut für Eisenforschung GmbH in Düsseldorf is organizing the 3rd NRW-APT user meeting on May 16^th 2017 and we would like to invite you and your research colleagues to participate in this event. This meeting will bring together scientists from North Rhine-Westphalia dealing with APT technique or correlating APT with other techniques. We want to discuss problems and share knowledge regarding sample preparation, measurement conditions, data reconstruction & analysis, etc. If you and your colleagues would like to attend this event, then please register before May 2nd 2017. There are limited places only. We are looking forward to see you in Düsseldorf! [more]

The workshop is part of our series of one-day workshops "Frontiers in Material Science & Engineering", where we bring together leading experts from academia and industry in a workshop format that allows in-depth discussions of fundamental and applied research in this area. Places are limited to 50 participants. The workshop participation is free-of-charge and is sponsored by the MPIE. [more]

Nanoparticles, nanowires, and many other nanostructures are produced and investigated for applications for quite some time. The desired functionality is not easy to achieve in a reproducible way. Various methods will be presented how such structures can be produced in a well defined arrangement and well defined functionality. Nanoporous gold nanosponges will be presented and it will be shown how disorder can be used to obtain a robust and reproducible functionality, i.e. disorder can be used for precision.In addition, nanoporous nanostructures can be easily tuned for applications by advancing them to nanocomposites with desired functionality, which can be used in medicine, energy storage and conversion, photocatalysis and further applications. [more]

The processing of materials as well as their technologically important properties are controlled by a combination of thermodynamics--which determines equilibrium--and kinetics--how a material evolves. Mass transport in solids, where different chemical species diffuse in a material due to random motion with or without a driving force, is a fundamental kinetic process for a wide variety of materials problems: growth of precipitates in nearly every advanced structural alloy from steels to superalloys, fusing of powders to make advanced ceramics, degradation of materials from irradiation, permanent changes in shape of materials over long times at high temperatures, corrosion of materials in different chemical environments, charge/discharge cycles in batteries, migration of atoms in electric fields, and more. Mass transport is a fundamentally multiscale phenomenon driven by crystalline defects, where many individual defect displacements sum up to produce chemical distributions at larger length and time scales. State-of-the-art first principles methods make the computation of defect energies and transitions routine for crystalline systems, and upscaling from activation barriers to mesoscale mobilities requires the solution of the master equation for diffusivity. For all but the simplest cases of interstitial diffusivity, and particular approximations with vacancy-mediated diffusion on simple lattices, calculating diffusivity directly is a challenge. This leaves two choices: uncontrolled approximations to map the problem onto a simpler (solved) problem, or a stochastic method like kinetic Monte Carlo, which can be difficult to converge for cases of strong correlations. I will describe and demonstrate our new developments for direct and automated Green function solutions for transport that take full advantage of crystal symmetry. This approach has provided new predictions for light element diffusion in magnesium, "pipe diffusion" of hydrogen along dislocations cores in palladium, and the evolution of vacancies and silicon near a dislocation in nickel. I will also show our latest results for technologically relevant magnesium alloys with containing Al, Zn, and rare earth elements (Gd, Y, Nd, Ce and La), where prior theoretical models to predict diffusivity from atomic jump frequencies make uncontrolled approximations that impact their accuracy. The underlying automation also makes the extension of first-principles transport databases significantly more practical and eliminate uncontrolled approximations in the transport model. [more]

After a short introduction to thin film solar cells, I will review what we know about defects in Cu(InGa)Se2 (CIGS), where we found significant differences between Cu-rich and Cu-poor material. By photoluminescence we recently found fundamental differences between pure CIS and Ga containing CIGS: with Ga the recombination is higher in Cu-rich material. And high Ga content CIGS shows a deep defect which gets more and more shallow when we decrease the Ga content. Finally, I will show that we can use photoluminescence to characterise the tails states in kesterite. [more]