Methylenverbindungen von Nichtmetallen. VI. Amide der Methan-bis(phosphonigsäure), -bis(phosphonsäure) und -bis(thiophosphonsäure)

Methylene Compounds of Non-Metals. VI. Amides of Methane-bis(phosphonous Acid), -bis(phosphonic Acid) and -bis(thiophosphonic Acid) Symmetrical- and asymmetrical-substituted amides of methane-bis(phosphonous acid), -bis(phosphonic acid) and -bis(thiophosphonic acid) have been obtained by stepwise aminolysis of the chlorides Cl₂(Z)PCH₂P(Z)Cl₂ ( 1 : Z = electron pair; 7 : Z = S; 13 : Z = O) and the fluoride F₂(S)PCH₂P(S)F₂ 19 with dimethylaminotrimethylsilane. Oxidation reactions of trivalent phosphonous amides with sulfur and dimethylsulfoxide have also been investigated.     

Propagation of Low-Energy Electrons and the Density of Unoccupied States in Ultrathin TCNQ Layers on the Oxidized Silicon Surface

Physics of the Solid State - The formation of unoccupied electronic states and the boundary potential barrier during thermal deposition of tetracyanoquinodimethane (TCNQ) films to 7 nm in thickness...     

Characterization of plasma etching of molybdenum polycid conductor stacks in Cl2/CF4 and Cl2/CF4/O2

The present paper is concerned with an extremly anisotropic two-step patterning process for Mo2Si/poly-Si double layers with an etch-stop on thick P-doped CVD-SiO₂. As etching gas Cl₂/CF₄/O₂ and Cl₂/CF₄ are used. By means of etch rate dependencies, volatilities of possible reaction products and results, obtained from the literature it is attempted to develop a simple qualitative model on the chemism of the process.     

Material laws as a basis for simulation models for the calculation of wheel-soil interaction examination using the finite element method

It is the purpose of this article to present the material laws of the soil in such a way that the complex nature of load cycle and deformation paths are sufficiently taken into account. As an important new aspect, not only the so-called failure strength, but also the deformation-dependent stress behavior prior to failure is considered. Such a formulation of the material behavior is espeically well suited as a basis for modelling of the interaction between the tire or track and the soil. The presentation of the material behavior give here is applied in a numeric simulation model of the tire-soil interaction, in order to determine both drawbar pull and soil deformations. The results correspond well to values obtained from mobility tests.     

Siloxane and silsesquioxane molecules--precursors for silicate materials

Preparation of ceramics by sol-gel method has been known for many years, but recently it has been developed as a method for the synthesis of nanostructural ceramic materials. Hydrolytic polycondensation of simple molecules [e.g. most widely used tetraethoxysilane (TEOS)] leads to xerogel materials that can contain macromolecules of distinct random, ladder and cage or partial cage structure. In order to obtain well-defined silsesquioxanes it is preferred to start the process with more complex molecules, bringing in a specific framework that can govern the structure of the product. In the presented work alkoxy derivatives of cyclosiloxanes and polysiloxanes as well as a hydride derivative of octahedral silsequioxane (T(8)(H)) were applied as precursors in the process of hydrolytic polycondensation. Depending on the reaction conditions, silsesquioxane macromolecules or silica material of ordered structure were obtained. We have prepared mesoporous organiosilica materials without using any template or surfactant whatsoever. The meso-pores are created due to the unique structure of initial oligosiloxane or silsequioxane molecules and the specific interactions in the used catalyst/solvent system. In the case of octasilsesquioxane precursor, the condensation process gives directly mesoporous silica material. Dried polysilsesquioxanes were heated at the temperature of 600°C in argon or air atmosphere (pyrolysis or ceramization). In the atmosphere of argon SiC(x)O(y) glass materials were obtained.     

Vibrational spectra and force constants calculations of the isotopic species of MgCaSiO4

FT-IR and Raman spectra in room and liquid N₂ temperature have been recorded for the isotopic species of the monticellite. The band assignments have been deduced from ²⁴Mg –²⁶Mg, ⁴⁰Ca –⁴⁴Ca and ²⁸Si –³⁰Si isotopic shifts. Based on these data isotopically adjusted GVFF force constants have been calculated with different models (unit cell, isolated SiO₄ anion with C point symmetry). Force constants for izomorphic Mg₂SiO₄ and α-C^sa₂SiO₄ structures have been also obtained.     

Fourier transform infrared investigations of phosphate-silicate coatings on iron

The influence of silica addition and of the annealing on the structure and properties of phosphate coatings are investigated. It has been observed that silica stabilizes phosphates and reduces the transport of iron towards the surface.     

A simple transition-locked and polarization-forced multi-line oscillator for high-power CO2-laser systems

Employing injection-locking techniques an oscillator configuration was found comprising in a simple way all the features required for fusion directed high-power CO₂ laser systems. The oscillator provides emission in single axial modes on rotational transitions which can be freely selected by feeding fluencies of a few mW/cm² at the particular transition into the oscillator cavity. In the same way simultaneous emission on selectable lines can be achieved. By the same principle the oscillator can be forced to emit in any orientation of polarization. The set up is relatively simple, the alignment rather uncritical, and the operation reliable. Gaussian-shaped nanosecond pulses with low forepulse power are produced with the help of a pulse cutter and saturable multiline absorber. The set up is described and its features are demonstrated by measurements. This research was carried out under the auspices of the “Sonderforschungsbereich Nr. 162 Plasmaphysik Bochum/Jülich”.