Condensation of all-cis-tetraphenylcyclotetrasiloxanetetraol in ammonia: new method for preparation of ladder-like polyphenylsilsesquioxanes

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Properties of epitaxial layers of p-type germanium-doped gallium arsenide

The electrophysical properties and cathode-luminescence(CL) spectra of p-type layers of GaAsGe with p=1.8·10¹⁷–3.6·10¹⁹ cm^–3 obtained by the method of liquid-phase expitaxy for a Ge content in the solution of 0.4–12 at. % were investigated. Regularities are set up for the change in the Hall constant, the Hall hole mobility, and the CL spectra as a function of the impurity concentration and temperature, which are explained from the viewpoint of an impurity zone mode. On the basis of the data obtained it is assumed that the material properties studied are determined by the impurity centers Ge_As and (Ge_Ga-V_Ga).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 65–69, January, 1989.     

Synthesis of amorphous block copoly(arylene ether ketones) and their characterization

Exchange reactions that may proceed in the course of polycondensation during formation of a polymer from 4,4′-difluorobenzophenone and 4,4′-(isopropylidene)diphenol have been studied. It has been shown that the molecular mass of the polymer decreases under the action of 4,4′-(isopropylidene)diphenol diphenolate. The nucleophilic substitution of the activated aryl halide in DMAA in the presence of potassium carbonate yields high-molecular-mass block copoly(arylene ether ketones) based on 4,4′-difluorobenzophenone and a number of bisphenols. It was demonstrated the synthetic procedure and the chemical structure of block copoly(arylene ether ketones) strongly affect the onset temperature of softening and the mechanical characteristics of the films based on these polymers.     

Kinetics of Reduction of Glycinate and Alaninate Complexes of Palladium(II) on a Dropping Mercury Electrode at Different Temperatures

Kinetics of electroreduction of glycinate and alaninate complexes of Pd(II) is studied polarographically in a test mode at 15–50°C in solutions of pH 3, 5, 10, and 12 containing free ligands and NaF, Na₂SO₄, or NaClO₄ supporting electrolytes. Diffusion coefficients for Pd(II) complexes are calculated from values of limiting currents. Specifically adsorbed Pd(II) complexes with a composition identical to that in the bulk solution take part in the slow electrochemical stage. The mechanism of reduction of the complexes is temperature-independent and identical to that established earlier at 25°C. The study confirms the earlier assumption as to the mechanism of hindering action of the perchlorate and alaninate ions specifically adsorbed on the positively-charged surface of a mercury electrode on the reduction of these complexes.     

Electroreduction of Pd(II) Complexes with α-Alanine on a Palladium Electrode

The kinetics of electroreduction of Pd(II) complexes with -alanine, Pd(ala)₂, is studied on a rotating Pd disk electrode in solutions of pH 8–13 containing large excess of -alanine and various supporting electrolytes (NaF, Na₂SO₄, NaClO₄). On a Pd electrode, complexes Pd(ala)₂ undergo reduction at potentials much more negative than on an Hg electrode. This is attributed to the chemisorption of water on the Pd electrode, which hampers adsorption of Pd(ala)₂ that take part in the slow electrochemical stage. As with the Hg electrode, perchlorate ions hinder the Pd(ala)₂ reduction on a Pd electrode. Studying adsorption of Pd(ala)₂ on a Pd electrode is hampered by parallel processes of hydrogen adsorption and absorption.     

Thermal properties of high-T c superconductors

The termal stabilities of several families of high-T _c superconductors (HTSC), as well as the dependence of phase transitions on temperature and stoichiometry, have been studied by X-ray diffraction, DTA, TG and DSC. Experimental results are discussed in the context of decomposition models.     

Behavior of copper in gallium arsenide with a high tellurium concentration

The electrophysical properties and cathode luminescence spectra of gallium arsenide with a high tellurium concentration (n = 2·10¹⁸ cm^–3) alloyed with copper are investigated under different diffusion conditions. Centers are determined from measurements of the Hall effect with an ionization energy of 0.190 ± 0.006 eV whose concentration does not depend on the arsenic vapor pressure (0.1 and 1 atm) and the cooling rate of the samples from the diffusion temperature. A band with h_m = 1.30–1.32 eV whose intensity depends on the cooling conditions of the samples was observed in the cathode luminescence spectra of these samples. The nature of the observed defects is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 93–99, July, 1979.In conclusion of this article the authors express their gratitude to L. K. Tarasova for preparation of the samples.     

Annulation of pyrrole ring in 4-acylpyridine-3,5-dicarbonitriles in the presence of ammonia

Chemistry of Heterocyclic Compounds - 4-Acyl-2-amino-6-chloropyridine-3,5-dicarbonitriles underwent heterocyclization in the presence of ammonia in aqueous dioxane medium, involving the...     

Reformatsky Reaction of 1-Aryl-3-(2-hydroxyphenyl)prop-2-en-1-ones with Methyl 1-Bromocyclohexanecarboxylate

Russian Journal of Organic Chemistry - 1-Aryl-3-(2-hydroxy-5-R-phenyl)prop-2-en-1-ones reacted with the Reformatsky reagent derived from methyl 1-bromocyclohexanecarboxylate to give...     

Ionic and Phase Compositions of Y2.5Ce0.5Fe2.5Ga2.5O12 Ferrogarnet Powder Produced by Gel Combustion

Doklady Physical Chemistry - The ionic and phase compositions of Y2.5Ce0.5Fe2.5Ga2.5O12 ferrogarnet samples obtained by gel combustion with subsequent vacuum annealing were studied for the first...