Eine spektroskopische Methode zur Untersuchung des Anfangsstadiums der Metallschichtbildung auf Glas

A simple detection of light metallic deposits (e. g. nickel) on oxidic surfaces can be achieved by means of the spectroscopical measurement of the concentration of hydrogen atoms in the positive column of a glow discharge. – The kinetics analysis of the experimental results shows that the velocity of forming as well as the heterogeneous recombination of hydrogen atoms depend on the amount of nickel being deposited on the surface area. The kinetic data allow conclusions to be drawn concerning the process and velocity of metallic deposits on glass surfaces. The initial phase of film forming, hitherto experimentally difficult to follow, can thus be studied. Measurements of the electrical resistance show the island structure of the thin nickel films. Due to the surface diffusion of hydrogen atoms such a discontinuous film exhibits the same catalytic activity for the recombination of hydrogen atoms as a continuous film.     

Theories of Gravitation

This paper presents a systematic study of the theories of gravitation that have been proposed. We restrict ourselves to an investigation of the linear approximation since new connections with experiment can be expected in this order in χ only. It turns out that all theories that differ from general relativity contain a scalar field and describe gravitation by a mixture of scalar and tensor interactions. The scalar has negative energy in theories with light deflection larger than the Einstein value. As a consequence instabilities of cosmic systems and continuous creation result in this case. Furthermore, the emission of gravitational radiation with negative energy could be the energy source of the quasars. The question of the mass renormalization of the scalar is investigated. No unique answer is possible at present. Finally a new class of gravitational theories is given.     

Zur Bildung von Adsorptionsmischkristallen

By investigating the systems KCl-H₂O-impurity and NH₄Cl-H₂O-impurity the knowledge of the formation of Adsorptionsmischkristallen could be extended. Some specific properties of complex mixed systems are stated.     

HVEM In-situ Deformation Investigations on Cyclically Deformed Nickel Single Crystal

In-situ deformation investigations were carried out on thin foils of a nickel single crystal which was cyclically pre-deformed. The motion of dislocations does not start in the whole specimen simultaneously but begins at localized places in the dislocation-poor regions. The plastic deformation may be characterized by a collective movement of dislocations. Measurements of the effective stress show its characteristic dependence on the position in the direction of the Burgers vector. There are clear indications of structural changes in the dense regions of dislocations at strains exceeding the cyclic total strain amplitude.     

Fundamental problems of the interaction of ions with insulators

The special situation of insulators necessitates a discussion whether the classical collision theory which had mainly been developed with view to metallic systems still holds in ionic or covalently bound solids. Special problems which should be treated are: (a) changes in the interaction potentials due to the localization of electrons of the target atoms, (b) the influence of charge states of the projectiles, which due to slower neutralization processes, might be higher on the average in insulators than in metals, (c) the effect of specific structure, multielemental composition on the trajectories (“focussing”), (d) the importance of covalent binding of the molecular units, and (e) the energy loss via chemical interactions by formation of stable bonds at low kinetic energies and transient ones at higher energies (“chemical stopping”). These problems will be treated by a comparison of experimental results with theory and computer simulation of collision cascades.     

Structural characteristics and residual stresses in oxide films produced on Ti by pulsed unipolar plasma electrolytic oxidation

Oxide films, 7–10 µm thick, were produced on commercially pure titanium by plasma electrolytic oxidation in a sodium orthophosphate electrolyte using a pulsed unipolar current with frequency (f) and duty cycle (δ) varying within f = 0.1–10 kHz and δ = 0.8–0.2, respectively. The coatings comprised a mixture of an amorphous phase with nanocrystalline anatase and rutile phases, where the relative rutile content range was 17–25 wt%. Incorporation of phosphorus from the electrolyte into the coating in the form of PO₂ ^–, PO₃ ^2– and PO₄ ^3–, as demonstrated by EDX and FT-IR analyses, contributed to the formation of the amorphous phase. Residual stresses associated with the crystalline coating phase constituents were evaluated using the X-ray diffraction sin² ψ method. It was found that, depending on the treatment parameters, internal direct and shear stresses in anatase ranged from–205 (±17) to–431 (±27) MPa and from–98 (±6) to–145 (±10) MPa, respectively, whereas the rutile structure is comparatively stress-free.     

Trace-Level Determination of Phenol by Liquid Chromatography with On-Line Precolumn Technology and Fluorescence Detection

Abstract

A strongly basic anion-exchange resin is used for the trace enrichment and automated sample handling of phenol, with subsequent determination by reversed-phase liquid chromatography with fluorescence detection. Because of the presence of high concentrations of ionic compounds in the water samples tested, phenol is first trapped on a relatively long precolumn filled with a highly hydrophobic packing material; during this step, (in) organic anions which are not retained, are flushed to waste. In the next step, phenol is desorbed from this column at high pH and sorbed in a small zone (“peak compression”) on a short precolumn containing the anion exchanger.

In the analysis of tap and river water samples, the detection limit was found to be 10ppt (1:10¹¹).