Gregor Vonbun-Feldbauer

Gregor Vonbun-Feldbauer
Technische Universität Hamburg | TUHH · Institute of Advanced Ceramics

Dipl.-Ing. Dr.techn

About

35
Publications
15,836
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322
Citations
Introduction
Gregor Feldbauer currently works at the Institute of Advanced Ceramics, Technische Universität Hamburg. Gregor does research in Computational Materials Science, Surface Science and Condensed Matter Physics. Currently, Gregor focuses on the study of adsorption phenomena at oxide and metallic surfaces using computational methods such as density functional theory.
Additional affiliations
September 2015 - present
Technische Universität Hamburg
Position
  • PostDoc Position
June 2015 - August 2015
TU Wien
Position
  • PostDoc Position
October 2011 - May 2015
TU Wien
Position
  • PhD Student

Publications

Publications (35)
Article
Full-text available
A fundamental knowledge of the interaction of carboxylic acids, such as formic acid, with magnetite surfaces is of prime importance for heterogeneous catalysis and the synthesis of novel materials. Despite this, little is known about the atomic scale adsorption mechanisms. Here we show by in-situ surface X-ray diffraction that the oxygen rich subsu...
Article
Full-text available
The ability to synthesize nanoparticles (NPs), here TiO2, of different shapes in a controlled and reproducible way is of high significance for a wide range of fields including catalysis and materials design. Different NP shapes exhibit variations of emerging facets, and processes such as adsorption, diffusion, and catalytic activity are, in general...
Article
Full-text available
Plasmonic photocatalysis via hot charge carriers suffers from their short lifetime compared with the sluggish kinetics of most reactions. To increase lifetime, adsorbates on the surface of a plasmonic metal may create preferential states for electrons to be excited from. We demonstrate this effect with O adsorbates on a nanoporous gold electrode. N...
Article
Full-text available
Magnetite shows enormous potential from biocompatible hybrid materials to heterogeneous catalysis. However, a detailed atomistic understanding of magnetite in complex nanostructures and at interfaces is required to unfold these potentials. Methods capable of treating (several) thousands of atoms and achieving an optimal balance between accuracy and...
Article
Full-text available
We report a novel heterogeneous adsorption mechanism of formic acid on the magnetite (111) surface. Our experimental results and density functional theory (DFT) calculations give evidence for dissociative adsorption of formic acid in quasibidentate and chelating geometries. The latter is induced by the presence of iron vacancies at the surface, mak...
Article
We report on differences in the magnetite (111) surface structure when treated in two different ways. Both preparations are done under UHV conditions at elevated temperatures, but in one case the sample is cooled down while keeping it in an oxygen atmosphere. Scanning tunneling microscopy after each of the preparations shows a different apparent mo...
Article
We present a combined experimental and computational investigation of phase stability and mechanical properties in the Al-Cu-Mg-Zn quaternary system. Samples containing different relative compositions were prepared using magnetron sputtering and investigated by electron microscopic and X-ray based methods. To classify the technical relevance of the...
Article
Full-text available
Magnesium is the lightest structural engineering material and bears high potential to manufacture automotive components, medical implants and energy storage systems. However, the practical use of untreated magnesium alloys is restricted as they are prone to corrosion. An essential prerequisite for the control or prevention of the degradation proces...
Article
Full-text available
Magnesium exhibits a high potential for a variety of applications in areas such as transport, energy and medicine. However, untreated magnesium alloys are prone to corrosion, restricting their practical application. Therefore, it is necessary to develop new approaches that can prevent or control corrosion and degradation processes in order to adapt...
Article
Full-text available
Acetone adsorbed on rutile TiO2 nanoparticles was investigated with respect to its energetic, vibrational, and chemical properties. Temperature-dependent ultrahigh-vacuum Fourier transform infrared spectroscopy measurements for different acetone dosages (4.5–900 L) give insights into the acetone adsorption behavior. Those experiments indicate therm...
Conference Paper
Palladium and Pd-based alloys exhibit a huge potential for widespread applications ranging from hydrogen storage to catalytic processes. Because of its ability to reversibly embed a significant amount of hydrogen into interstitial sites, palladium is often characterized as a "hydrogen sponge". With increasing amount of absorbed hydrogen, the mechan...
Data
Supplementary Data of the paper: "Suppression of Material Transfer at Contacting Surfaces: The Effect of Adsorbates on Al/TiN and Cu/diamond Interfaces from First-Principles Calculations" Citation: Gregor Feldbauer et al 2018 J. Phys.: Condens. Matter 30 105001 https://doi.org/10.1088/1361-648X/aaac91
Article
Full-text available
The effect of monolayers of oxygen (O) and hydrogen (H) on the possibility of material transfer at aluminum/titanium nitride (Al/TiN) and copper/diamond (Cu/C$_{\text{dia}}$) interfaces, respectively, were investigated within the framework of density functional theory (DFT). To this end the approach, contact, and subsequent separation of two atomic...
Article
Full-text available
The lecture "Atomistic Materials Modeling" is a core qualification of the master program "materials science" at the Hamburg University of Technology (TUHH). Within the lecture, various modern methods for atomistic materials modeling are presented. Originally, the course was conceived as a traditional lecture. That didactic-methodical conception, ho...
Article
Density functional theory (DFT) has been applied to elucidate the adsorption structures and energetics of benzoic acid on TiO2 (110), (100), and (011) rutile surfaces. We demonstrate that ab initio calculations of interacting carboxylic acids require an exchange-correlation functional with van der Waals (vdW) correction to yield reliable results, e...
Article
We consider a nanomachining process of hard, abrasive particles grinding on the rough surface of a polycrystalline ferritic work piece. Using extensive large-scale molecular dynamics (MD) simulations, we show that the mode of thermostatting, i.e., the way that the heat generated through deformation and friction is removed from the system, has cruci...
Article
Full-text available
Using molecular dynamics, we simulate the abrasion process of an atomically rough Fe surface with multiple hard abrasive particles. By quantifying the nanoscopic wear depth in a time-resolved fashion, we show that Barwell’s macroscopic wear law can be applied at the atomic scale. We find that in this multiasperity contact system, the Bowden-Tabor t...
Article
Full-text available
We present an approach to determine the onset of contact between a tip and a surface. The real contact area depending on the distance is calculated using Bader's quantum theory of atoms in molecules. The jump to contact, which is often observed in atomic force microscopy experiments, is used as an indicator for the initial point of contact, which i...
Article
Full-text available
A series of density functional theory (DFT) simulations was performed to investigate the approach, contact, and subsequent separation of two atomically flat surfaces consisting of different materials. Aluminum (Al) and titanium nitride (TiN) slabs were chosen as a model system representing a metal-ceramic interface and the interaction between soft...
Article
Full-text available
While there are a number of models that tackle the problem of calculating friction forces on the atomic level, providing a completely parameter-free approach remains a challenge. Here we present a quasistatic model to obtain an approximation to the nanofrictional response of dry, wearless systems based on quantum-mechanical all-electron calculation...
Article
Full-text available
The presence of water in biofuels poses the question of how it affects the frictional performance of additives in fuels containing organic substances. To investigate the effect of water on the adsorption of molecules present in fuel and its additives we simulated within the framework of density functional theory the adsorption of ethanol, isooctane...
Presentation
Biofuels, especially ethanol mixed with standard gasoline or diesel, have become an important part of the worldwide motor fuel consumption. [1] Hence, the interaction of organic molecules constituting such biofuels with metallic surfaces is of high technological interest. In a combustion engine apart from organic molecules there are always other ch...
Article
Full-text available
Van der Waals (vdW) forces play a fundamental role in the structure and behavior of diverse systems. Thanks to development of functionals that include non-local correlation, it is possible to study the effects of vdW interactions in systems of industrial and tribological interest. Here we simulated within the framework of density functional theory...
Poster
Contacts of surfaces at the atomic length scale are crucial in many modern applications from experimental techniques such as nanoindentation or AFM/FFM to nanotechnologies applied in nano/micro-electromechanical-systems (NEMS/MEMS). Furthermore, detailed insights into such contacts are of fundamental interest also for a better understanding of trib...
Presentation
Accurate modelling of the energy dissipation in sliding friction with ab-initio methods in nanotribological systems poses a fundamental challenge in modern tribology. Here we present a quasi-static model to obtain the nanofrictional response of dry, wearless systems based on quantum mechanical all electron calculations. We propose a mechanism for e...
Presentation
Contacts of surfaces at the atomic scale are crucial in many modern applications from analytical techniques like indentation or AFM experiments to technologies such as nano- and micro-electro-mechanical-systems (N-/M-EMS). Furthermore, detailed insights into such contacts are fundamental for a better understanding of tribological processes like wea...
Poster
The interactions between organic molecules and metallic surfaces are crucial for various technological purposes. In particular the interplay between fuels or lubricants and iron based alloys is of high industrial interest. Van der Waals (vdW) interactions play a decisive role in such processes due to their long range nature together with their coll...
Article
Full-text available
The MedAustron medical synchrotron is based on the CERN-PIMMS design and its technical implementation by CNAO [1]. This document elaborates on studies performed on the baseline betatron-core driven extraction method and investigates the feasibility of alternative resonance driving mechanisms like RF-knockout, RF-noise and the lattice tune. Single p...

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