Mechanismus der OberflÄchenoxydation von Kupfer

Zusammenfassung Im experimentellen Teil sind die Oxydationskurven von Kupfer bei 300–550 °C und die Ergebnisse des Studiums der Oberflächenstruktur von Kupfer mittels Elektronenstrahlen, das bei verschiedenen Temperaturen bis über 600 °C oxydiert wurde, angegeben. Auf Grund eigener Messungen und der Literaturangaben versuchte der Autor, eine Erklärung zu geben für den Zusammenhang zwischen dem Verlauf der Oxydationskurven und der Oberflächenstruktur von Kupfer, das in reinem Sauerstoff mit ausreichendem Druck oxydiert wurde, wobei die Geschwindigkeit der Oxydation bestimmt wird durch die Diffusion der Kupferionen durch die Oxydschicht.     

Catalytic deallylation of allyl- and diallylmalonates

Substituted allylmalonates undergo the selective C-C bond cleavage in the presence of triethylaluminum and a catalytic amount of nickel and ruthenium phosphine complexes, resulting in the loss of the allyl moiety and formation of monosubstituted malonates. Comparison of reactivity of the nickel and ruthenium complexes showed that the use of the former is general with respect to the structure of the substituted allylmalonates, and the activity of the latter depended on the substitution pattern of the double bond of the allylic moiety. The smooth deallylation may encourage the use of the allyl group as a protective group for the acidic hydrogen in malonates.     

Die Magnetische SuszeptibilitÄt von Kristallinem n-CdGeAs2

The specific magnetic susceptibility of polycrystalline and powdered samples was measured between 77 °K and 570 °K. This dependence was interpreted in intrinsic range suggesting the susceptibility is given as a sum of contributions of the lattice ^G and of free carriers _L. The temperature dependence of the lattice susceptibility _G= _G ⁰ +T was checked: _G ⁰ =–2·35× ×10^–7, =4·5×10^–11. The contribution _L enabled to check the effective mass of holes m_h=0·25m₀ suggesting m_em_h.

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Herrn A. Hrubý gilt mein Dank für die Vorbereitung des polykristallinen Ingots von CdGeAs₂.     

Lattice defects of Bi2Se3 doped with germanium

Homogeneous Bi₂Se₃ crystals with various germanium content were prepared by means of modified Bridgman technique. Reflectivity measurements in the region of plasma resonance frequency of the free carriers revealed a shift of the reflectivity minimum towards shorter wavelengths for samples with higher germanium content. Combining the reflectivity data and the results of the Hall constant measurement we determined the free-carrier concentration for individual Ge-doped Bi₂Se₃ samples. It is shown that the germanium atoms give rise to donor levels. The ionization energy of these levels was estimated at less than 0·026 eV. The donor levels are most probably connected with the existence of singly ionized germanium atoms in interstitial positions.     

Der I. Kongress der tschechoslowakischen Physiker

Ohne Zusammenfassung     

Magnetic susceptibility of CdSb doped with Mn,Fe, Ni and La

This paper is devoted to the study of the temperature dependence of the magnetic susceptibility of CdSb doped with Mn, Fe, Ni and La. Analyzing the measured curves on the assumption that the impurities are substitutional and using the Hall constant measurements, we were able to determine the magnetic moments of Fe and Ni impurities and to obtain some information concerning the bond of these atoms with their nearest neighbours. The impurities Mn and La are dissolved in CdSb only partly as substitutional impurities, the major part most probably forming with antimony a new phase which is strongly paramagnetic and fully overgrows the diamagnetism of the parent semiconductor compound.     

Thermal behavior and decomposition kinetics of ETN and its mixtures with PETN and RDX

Erythritol tetranitrate (butane-1,2,3,4-tetrayl tetranitrate, ETN) has become one of the most synthesized improvised explosives nowadays as it can be found on public internet discussion boards. However, the low melting point, nitrocellulose gelling ability, high energy content, and availability of its precursor make the substance potentially useful in industry as an energetic component or additive in certain gun propellants. Mixtures of ETN with other high explosives are also frequently discussed on web pages dealing with improvised explosives. This article describes thermal behavior and decomposition kinetics of pure ETN and its mixtures with pentaerythritol tetranitrate and cyclonite (1,3,5-trinitro-1,3,5-triazinane, RDX). The thermal behavior and decomposition kinetics of such mixtures are described using non-isothermal DSC and TG techniques. Kissinger method, Soviet manometric method, and modified Kissinger–Akahira–Sunose method were used for data evaluation.