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Na-ion batteries have recently attracted great attention regarding their application in large-scale energy storage systems. Among different types of electrode materials for those classes of batteries, so-called Prussian blue analogues (PBAs) are among the very attractive ones due to their comparatively simple and low-cost methods of synthesis coupled with a promising cycle performance. In this study, one of the state-of-the-art PBA battery materials, namely electrodeposited Na2Ni[Fe(CN)6] (NiHCF) thin films, were tested under simulated battery conditions in aqueous and mixed (H2O/organic) electrolytes. Prolonged stability tests in aqueous electrolytes were performed together with in-operando electrochemical AFM monitoring. It is demonstrated that degradation of this material is not associated with noticeable morphological changes (mechanical stress) but is likely caused by changes in the chemical composition of the films. Intercalation and deintercalation reversibility of Na+and thin film stability in aqueous electrolytes appear to be unaffected negatively by changes in the pH to values below 7. However, the films showed unstable behavior in basic media (pH > 10). The increase of the content of acetonitrile, which was used as an additive to simulate the influence of antifreezes in aqueous electrolytes, appears to primarily affect the deintercalation of Na ions in Na2SO4-based aqueous electrolytes.

Rotary friction welding (RFW) was used in the current study to join the dissimilar metals AA7020-T6 aluminium alloy and 316L steel. Neutron diffraction was performed to investigate the texture gradient around the weld line and to map the residual stress over the whole specimen. The texture analysis showed a weak shear component near the bond line of AA7020-T6-T6 side which indicated a plastic deformation of AA7020-T6 during welding. The shear bands were also observed in optical microstructures. Relatively high tensile residual stresses were observed near the bond line on the AA7020-T6 side, which were in-homogeneously distributed from the perimeter to the rod centre, while high compressive residual stresses were found in the sample centre at the bond line in the 316L steel.

All‐diamond ultra‐microelectrode arrays (UMEAs) were fabricated using standard photolithography processes. The array consists of typically 45 ultra‐microelectrodes with a diameter of 10 µm and with a center‐to‐center spacing of 60 µm. The quasi‐reference and counter electrodes are made from conductive diamond and integrated on a 5 × 5 mm2chip. The arrays with different surface terminations were characterized using cyclic voltammetry and the redox couple of ${\rm Fe(CN)}_{{\rm 6}}^{{{{\rm 3}{-} } \mathord{\left/ {\vphantom {{{\rm 3}{-} } {4{-} }}} \right. \kern-\nulldelimiterspace} {4{-} }}} $as probes. A peak‐shaped voltammogram was detected on electrochemically hydrogen‐terminated surface if scanned with a slow scan rate (e.g. 20 mV/s), resulting in a higher ratio of the Faradaic current (signal) to capacitive charging current (background current). A sensitive and reproducible detection of hydrogen peroxide was achieved by using the UMEA. The net‐charge for the oxidation of hydrogen peroxide at 0.4 V (vs. C) is linear with the concentration of hydrogen peroxide in the range of 6.5–650 µM. The detection limit is 2.0 µM, which is 100 times better than that obtained on the macro‐sized boron‐doped diamond electrode.

In this report, the fabrication of all-nanocrystalline diamond (NCD) nanoelectrode arrays (NEAs) by e-beam lithography as well as of all-diamond nanoelectrode ensembles (NEEs) using nanosphere lithography is presented. In this way, nanostructuring techniques are combined with the excellent properties of diamond that are desirable for electrochemical sensor devices. Arrays and ensembles of recessed disk electrodes with radii ranging from 150 to 250 nm and a spacing of 10 μm have been fabricated. Electrochemical impedance spectroscopy as well as cyclic voltammetry was conducted to characterize arrays and ensembles with respect to different diffusion regimes. One outstanding advantage of diamond as an electrode material is the stability of specific surface terminations influencing the electron transfer kinetics. On changing the termination from hydrogen- to oxygen-terminated diamond electrode surface, we observe a dependence of the electron transfer rate constant on the charge of the analyte molecule. Ru(NH3)6+2/+3shows faster electron transfer on oxygen than on hydrogen-terminated surfaces, while the anion IrCl6−2/−3exhibits faster electron transfer on hydrogen-terminated surfaces correlating with the surface dipole layer. This effect cannot be observed on macroscopic planar diamond electrodes and emphasizes the sensitivity of the all-diamond NEAs and NEEs. Thus, the NEAs and NEEs in combination with the efficiency and suitability of the selective electrochemical surface termination offer a new versatile system for electrochemical sensing.

The adsorption and conformational state of the electron transfer protein cytochrome c cyt c on flat, boron doped polycrystalline diamond electrodes was investigated using electrochemical techniques and atomic force microscopy AFM. An electrochemical reduction wave from the adsorbed protein was identified as oxygen reduction, which is catalysed by the deformed heme redox centre of cyt c. We show that this catalytic activity only occurs after partial denaturation of cyt c. Therefore the reduction peak was used for characterization of the conformational state of adsorbed cyt c. AFM characterizations with molecular resolution show different conformational states of cyt c on diamond surfaces ranging from native to denaturated. Both applied techniques indicate that hydrophobic hydrogenated diamond tends to denaturate cyt c upon adsorption, while wet chemically oxidized diamond surfaces can provide extensive but nondenaturating cyt c adsorption. The conformation and orientation of cyt c on wet chemically oxidized diamond is beneficial for the electron transfer between the protein redox centre and the diamond electrode even in the presence of oxygen.

A nanotextured diamond electrode was utilized to achieve optimized electrochemical redoxinteractions of cytochrome ccyt c with the diamond transducer. The nanotextured surface was realized using a top–down technology where diamond nanoparticles are used as etching masks. Macroscopic characterizations of the OHterminated surface using cyclic voltammetry reveal adsorptioncontrolled cyt celectrode interaction. The adsorption is assigned to the electrostatic attraction force of positively charged cyt cparts with the slightly negatively charged diamond surface in pH 7 buffer. Atomic force microscopy experiments in physiologic buffer solutions on flat diamond surface confirms the adsorption of cyt con OHterminated diamond surfaces without structural changes of cyt c.

Chemical vapour deposition has been utilised for the fabrication of nickel–nitrogen defects in diamond. By introducing nickel, as well as nitrogen into the process gas, this approach offers the advantage, that a direct formation of nickel–nitrogen centres on the growing surface is possible. This could therefore make postannealing steps superfluous. Nanocrystalline diamond films, as well as single crystal layers were grown under addition of nickel and nitrogen using different doping sources, namely: gaseous nickelocene, nickel powder and nickel wire. The amount of nickel present in the gas phase was characterised by optical emission spectroscopy OES. In order to investigate the presence of nickel or nickel–nitrogenrelated defects, photoluminescence PL measurements at different temperatures have been applied. A strong fluorescence in the range between 800 and 900 nm, accompanied by a peak at around 817 nm, as well as a narrow peak at 788 nm has been observed at cryogenic temperatures 10 K. The peak at 788 nm indicates the presence of nickel and nickel–nitrogenrelated complexes in our samples. PL measurements at higher temperatures reveal, an initially rising intensity of a broad emission band at temperatures up to 200 K, while the emission is quenched at 300 K.

Abstract(111)Lead Zirconate Titanate PZT films (fully poled) of the composition PbTi0.75Zr0.25O3have been investigated by Tapping Mode Atomic Force Microscopy (TMAFM). As expected, the PZT crystallites were partitioned into slabs of 90° domains with domain walls oriented along <110>planes. The polarization c-axis of the domains was inclined by ∼35° towards the surface and tilted alternately by +45° or -45° to the surface normal. Mechanical activation of the surface with plasma-sharpened supertips with a force of ∼5 nN allowed to monitor reversible mechanical switching of single domains involving 180° polarization reversal of entire domain slabs. The observed elastic changes in surface topography amounted to ∼1 nm. Similarly, single domains in rhombohedral a-side oriented SrBi2Ta2O9(SBT) crystallites were switched mechanically which was observed by a change in surface corrugation of ∼10 nm.

Submicron scale microcontact printing of silanes onto silicon wafers is studied. Silicon microstructures are used as masters to prepare silicone rubber stamps, which are found to peel off the master easily even at wedge angles of 80° if the master has been silanized before. Stripe structures with periodicities down to 200 nm were generated. At these small scales, capillary condensation in the wedges of the stamp during the stamping process is difficult to avoid. We demonstrate a novel “stamp pad” technique which allows us to overcome this problem.

We study Lagrangian immersions $M^n_1$into Lorentzian complex indefinite space forms $\tilde M^n_1(4 \tilde c), \tilde c \ne 0$and classify all such immersions which are minimal and have constant curvature $c \ne \tilde c$.

In analogy to an inequality of Chen [2], Scharlach and co-workers [7] have found a new, optimal inequality for (equi-) affine spheres. We classify those three-dimensional hyperbolic affine spheres for which the corresponding equality is assumed. This complements the classification of the elliptic case [3].

Consider a smooth manifold with smooth (0, 2)-tensor which changes bilinear type on a hypersurface. We show that there are natural tensors on this hypersurface which control the smooth extension of sectional, Ricci, and scalar curvature. This enables us to adapt the classical characteristic class construction to a large collection of manifolds with such singular pseudo-Riemannian metrics.

We show that {ie319-1} H2dµ = 8 for any complete surface M ? R3 which has positive curvature outside a compact subset of R3. This proves a conjecture of Friedrich.

Local and global properties of the first order spherical functions are generalized to projectively flat manifolds.

We announce and justify two theorems (proofs will appear in Refs. 1 and 2): i) A generalization of the singularity theorem of Hawking and Penrose [3] to space-times with chronology violations. Although it is impossible to remove the chronology condition completely the announced theorem is in a well defined sense optimal: the chronology condition is replaced by a strictly weaker condition that cannot be removed because of counter examples, ii) If the chronology violating setV has compact closure and the strong energy and generic conditions hold, thenV is generated by incomplete null geodesics. It follows that if the region of causality violation does not extend to infinity thenV contains singularities.

Zusammenfassung Es wird eine Übersicht über Tenside auf s-Triazinbasis gegeben.