Abstract: Elektronen bewegen sich im feldfreien Raum immer gleichförmig geradlinig, so steht es in den Lehrbüchern. Falsch, sagen wir. Elektronen lassen sich zu Tornados formen, die theoretisch Nanopartikel zerreißen können. In der Elektronenmikroskopie eingesetzt, versprechen sie neue Erkenntnisse in der Festkörperphysik.

Abstract: In this study, the effect of a stress aging process on the microstructure and martensitic phase transformation of NiTi shape memory alloy has been investigated. NiTi samples were aged at 450 degrees C for 1 h and 5 h under different levels of external tensile stress of 15, 60 and 150 MPa. Transmission electron microscopy (TEM) was used to characterize different variants and morphology of precipitates. The results show that application of all stress levels restricts the formation of precipitates variants in the microstructure after I h stress aging process. However, all variants can be detected by prolonging aging time to 5 h at 15 MPa stress level and the variants formation is again restricted by increasing the stress level. Moreover, the stress aging process resulted in changing the shape of precipitates in comparison with that of the stress-free aged samples. Coffee-bean shaped morphologies were detected for precipitates in all stress levels. According to the Differential Scanning Calorimetry (DSC) results, the martensite start temperature (M-s) on cooling shifts to higher temperatures with increasing the tensile stress during the aging process. This can be related to the change ofaustenite to martensite interface energy due to the different volume fractions and variants of precipitates. (c) 2018 Elsevier Ltd. All rights reserved.

Abstract: Epitaxially grown ultra-thin Si layers are often used to passivate Ge surfaces in the high-k gate module of (strained) Ge FinFET devices. We use Si4H10 as Si precursor as it enables epitaxial Si growth at temperatures down to 330 degrees C. C-V characteristics of blanket capacitors made on Ge virtual substrates point to the presence of an optimal Si thickness. In case of compressively strained Ge fin structures, the Si growth results in non-uniform and high strain levels in the strained Ge fin. These strain levels have been calculated for different shapes of the Ge fin and in function of the grown Si thickness. The high strain is the driving force for potential (unwanted) Ge surface reflow during the Si deposition. The Ge surface reflow is strongly affected by the strength of the H-passivation during Si-capping and can be avoided by carefully selected process conditions.

Abstract: Based on extensive Langevin Dynamics simulations we investigate the structural properties of a two-dimensional ensemble of magnetic rods with a peapod-like morphology, i.e, rods consisting of aligned single dipolar beads. Self-assembled configurations are studied for different directions of the dipole with respect to the rod axis. We found that with increasing misalignment of the dipole from the rod axis, the smaller the packing fraction at which the percolation transition is found. For the same density, the system exhibits different aggregation states for different misalignment. We also study the stability of the percolated structures with respect to temperature, which is found to be affected by the microstructure of the assembly of rods.

Abstract: Cold atmospheric plasma (CAP) has shown its potential in biomedical applications, such as wound healing, cancer treatment and bacterial disinfection. Recent experiments have provided evidence that CAP can also enhance the intracellular uptake of glucose molecules which is important in diabetes therapy. In this respect, it is essential to understand the underlying mechanisms of intracellular glucose uptake induced by CAP, which is still unclear. Hence, in this study we try to elucidate the possible mechanism of glucose uptake by cells by performing computer simulations. Specifically, we study the transport of glucose molecules through native and oxidized membranes. Our simulation results show that the free energy barrier for the permeation of glucose molecules across the membrane decreases upon increasing the degree of oxidized lipids in the membrane. This indicates that the glucose permeation rate into cells increases when the CAP oxidation level in the cell membrane is increased.

Abstract: Today, further downscaling of mobile electronic devices poses serious problems, such as energy consumption and local heat dissipation. In this context, spin wave majority gates made of very thin ferromagnetic films may offer a viable alternative. However, similar downscaling of magnetic thin films eventually enforces the latter to operate as quasi-2D magnets, the magnetic properties of which are not yet fully understood, especially those related to anisotropies and external magnetic fields in arbitrary directions. To this end, we have investigated the behaviour of an easy-plane and easy-axis anisotropic ferromagnet-both in two and three dimensions-subjected to a uniform magnetic field, applied along an arbitrary direction. In this paper, a spin-1/2 Heisenberg Hamiltonian with anisotropic exchange interactions is solved using double-time temperature-dependent Green's functions and the Tyablikov decoupling approximation. We determine various magnetic properties such as the Curie temperature and the magnetization as a function of temperature and the applied magnetic field, discussing the impact of the system's dimensionality and the type of anisotropy. The magnetic reorientation transition taking place in anisotropic Heisenberg ferromagnets is studied in detail. Importantly, spontaneous magnetization is found to be absent for easy-plane 2D spin systems with short range interactions.

Abstract: Among transition metal oxides, MnO2 is of considerable importance for various technological end-uses,from heterogeneous catalysis to gas sensing, owing to its
structural flexibility and unique properties at the nanoscale. In this work, we demonstrate the successful fabrication of supported MnO2 nanomaterials by a catalyst-free, plasmaassisted process starting from a fluorinated manganese(II)
molecular source in Ar/O2 plasmas. A thorough multitechnique characterization aimed at the systematic investigation of material structure, chemical composition, and
morphology revealed the formation of F-doped, oxygendeficient, MnO2-based nanomaterials, with a fluorine content tunable as a function of growth temperature (TG). Whereas phase-pure β-MnO2 was obtained for 100 °C ≤ TG ≤ 300 °C, the formation of mixed phase MnO2 + Mn2O3 nanosystems took place at 400 °C. In addition, the system nano-organization could be finely tailored, resulting in a controllable evolution from wheat-ear columnar arrays to high aspect ratio pointed-tip nanorod assemblies. Concomitantly, magnetic force microscopy analyses suggested the formation of spin domains with features dependent on material morphology. Preliminary tests in Vislight activated photocatalytic degradation of rhodamine B aqueous solutions pave the way to possible applications of the target materials in wastewater purification.

Abstract: In this work we study energy transport in a gliding arc discharge with two diverging flat
electrodes in argon gas at atmospheric pressure. The discharge is ignited at the shortest electrode
gap and it is pushed downstream by a forced gas flow. The current values considered are
relatively low and therefore a non-equilibrium plasma is produced. We consider two cases, i.e.
with high and low discharge current (28 mA and 2.8mA), and a constant gas flow of 10 lmin −1 ,
with a significant turbulent component to the velocity. The study presents an analysis of the
various energy transport mechanisms responsible for the redistribution of Joule heating to the
plasma species and the moving background gas. The objective of this work is to provide a
general understanding of the role of the different energy transport mechanisms in arc formation
and sustainment, which can be used to improve existing or new discharge designs. The work is
based on a three-dimensional numerical model, combining a fluid plasma model, the shear stress
transport Reynolds averaged Navier–Stokes turbulent gas flow model, and a model for gas
thermal balance. The obtained results show that at higher current the discharge is constricted
within a thin plasma column several hundred kelvin above room temperature, while in the low-
current discharge the combination of intense convective cooling and low Joule heating prevents
discharge contraction and the plasma column evolves to a static non-moving diffusive plasma,
continuously cooled by the flowing gas. As a result, the energy transport in the two cases is
determined by different mechanisms. At higher current and a constricted plasma column, the
plasma column is cooled mainly by turbulent transport, while at low current and an unconstricted
plasma, the major cooling mechanism is energy transport due to non-turbulent gas convection. In
general, the study also demonstrates the importance of turbulent energy transport in
redistributing the Joule heating in the arc and its significant role in arc cooling and the formation
of the gas temperature profile. In general, the turbulent energy transport lowers the average gas
temperature in the arc, thus allowing additional control of thermal non-equilibrium in the
discharge.

Abstract: Methane needle-plane discharge has practical application prospect and scientific research significance since methane conversion heavy oil hydrogenation is formed by coupling methane needle-plane discharge with heavy oil hydrogenation, which can achieve high-efficient heavy oil hydrogenation and increase the yields of high value-added light olefins. In this paper, a two-dimensional fluid model is built up for numerically simulating the methane needle-plane discharge plasma at atmospheric pressure. Spatial and axial distributions of electric intensity, electron temperature and particle densities are obtained. Reaction yields are summarized and crucial pathways to produce various kinds of charged and neutral particles are found out. Simulation results indicate that axial evolutions of CH3+ and CH4+ densities, electric intensity and electron temperature are similar and closely related. The CH5+ and C2H5+ densities first increase and then decrease along the axial direction. The CH3 and H densities have nearly identical spatial and axial distributions. Particle density distributions of CH2, C2H4 and C2H5 are obviously different in the area near the cathode but comparatively resemblant in the positive column region. The CH3+ and CH4+ are produced by electron impact ionizations between electrons and CH4. The CH5+ and C2H5+ are respectively generated by molecular impact dissociations between CH3+ and CH4 and between CH4+ and CH4. Electron impact decomposition between electrons and CH4 is a dominated reaction to produce CH3, CH2, CH and H. The reactions between CH2 and CH4 and between electrons and C2H4 are critical pathways to produce C2H4 and C2H2, respectively. In addition, the yields of electron impact decomposition reactions between electrons and CH4 and reactions between CH2 and CH4 account for 52.15% and 47.85% of total yields of H-2 respectively.

Abstract: Because of its unique properties, plasma technology has gained much prominence in the
microelectronics industry. Recently, environmental and energy applications of plasmas have gained a lot of attention. In this area, the focus is on converting CO 2 and reforming hydrocarbons, with the goal of developing an efficient single-step ‘gas-to-liquid’ (GTL) process. Here we show that applying tri-reforming principles to plasma—further called ‘plasma-based multi-reforming’—allows us to better control the plasma chemistry and thus the formed products. To demonstrate this, we used chemical kinetics calculations supported by experiments and reveal that better control of the plasma chemistry can be achieved by adding O 2 or H 2 O to a mixture containing CH 4 and CO 2 (diluted in N 2 ). Moreover, by adding O 2 and H 2 O simultaneously, we can tune the plasma chemistry even further, improving the conversions, thermal efficiency and methanol yield. Unlike thermocatalytic reforming, plasma-based reforming is capable of producing methanol in a single step; and compared with traditional plasma-based dry reforming, plasma-based multi-reforming increases the methanol yield by more than seven times and the thermal efficiency by 49%, as revealed by our model calculations. Thus, we believe that by using plasma-based multi-reforming, ‘gas-to-liquid’ conversion may be made efficient and scalable.

Abstract: Multiple electrochemical processes are involved at the catalyst/ electrolyte interface during the oxygen evolution reaction (OER). With the purpose of elucidating the complexity of surface dynamics upon OER, we systematically studied two Ni-based crystalline oxides (LaNiO3−δ and La2Li0.5Ni0.5O4) and compared them with the state-of-the-art Ni−Fe (oxy)- hydroxide amorphous catalyst. Electrochemical measurements such as rotating ring disk electrode (RRDE) and electrochemical quartz microbalance microscopy (EQCM) coupled with a series of physical characterizations including transmission electron microscopy (TEM) and X-ray absorption spectroscopy (XAS) were conducted to unravel the exact pH effect on both the OER activity and the catalyst stability. We demonstrate that for Ni-based crystalline catalysts the rate for surface degradation depends on the pH and is greater than the rate for surface reconstruction. This behavior is unlike that for the amorphous Ni oxyhydroxide catalyst, which is found to be more stable and pH-independent.

Abstract: Microtwin sequences in Ni66Al34 martensite plates of different size were investigated by electron microscopy. Although mostly irregular sequences were observed an average twin width w can be determined which increases with twin length L following the expected relation w ~ sqrt(L). High resolution electron microscopy was used to study the twin branching close to the plate boundaries and an atomic model for the branching of a microtwin and the changes in twin thickness is suggested

Abstract: Nonthermal plasma is a promising alternative for ammonia synthesis at gentle conditions. Metal meshes of Fe, Cu, Pd, Ag, and Au were employed as catalysts in radio frequency plasma for ammonia synthesis. The energy yield for all these transition metal catalysts ranged between 0.12 and 0.19 g-NH3/kWh at 300 W and, thus, needs further improvement. In addition, a semimetal, pure gallium, was used for the first time as catalyst for ammonia synthesis, with energy yield of 0.22 g-NH3/kWh and with a maximum yield of ∼10% at 150 W. The emission spectra, as well as computer simulations, revealed hydrogen recombination as a primary governing parameter, which depends on the concentration or flux of H atoms in the plasma and on the catalyst surface. The simulations helped to elucidate the underlying mechanism, implicating the dominance of surface reactions and surface adsorbed species. The rate limiting step appears to be NH2 formation on the surface of the reactor wall and on the catalyst surface, which is different from classical catalysis.

Abstract: Due to the increasing emission of carbon dioxide (CO2), greenhouse effects are becoming more and more severe, causing global climate change. The conversion and utilization of CO2 is one of the possible solutions to reduce CO2 concentrations. This can be accomplished, among other methods, by direct hydrogenation of CO2, producing value-added products. In this review, the progress of mainly the last five years in direct hydrogenation of CO2 to value-added chemicals (e.g., CO, CH4, CH3OH, DME, olefins, and higher hydrocarbons) by heterogeneous catalysis and plasma catalysis is summarized, and research priorities for CO2 hydrogenation are proposed.

Abstract: The utilization of solar radiation to trigger photoelectrochemical (PEC) water splitting has gained interest for sustainable energy production. In this study, attention is focused on the development of ZnO–TiO2 nanocomposite photoanodes. The target systems are obtained by growing porous arrays of highly crystalline, elongated ZnO nanostructures on indium tin oxide (ITO) by chemical vapor deposition. Subsequently, the obtained nanodeposits are functionalized with TiO2 via radio frequency-sputtering for different process durations, and subjected to final annealing in air. Characterization results demonstrate the successful formation of high purity composite systems in which the surface of ZnO nanostructures is decorated by ultra-small amounts of amorphous titania, whose content can be conveniently tailored as a function of deposition time. Photocurrent density measurements in sunlight triggered water splitting highlight a remarkable performance enhancement with respect to single-phase zinc and titanium oxides, with up to a threefold photocurrent increase compared to bare ZnO. These results, mainly traced back to the formation of ZnO/TiO2 heterojunctions yielding an improved photocarrier separation, show that the target nanocomposites are attractive photoanodes for efficient PEC water splitting.