Synthesis, band structure, and optical properties of Ba2ZnV2O8

A novel compound Ba₂ZnV₂O₈ has been synthesized in high temperature solution reaction and its crystal structure has been characterized by means of single crystal X-ray diffraction analysis. It crystallizes in monoclinic system and belongs to space group P2₁/c with a=7.9050(16), b=16.149(3), , β=90.49(3). It builds up from 1-D branchy chains of [ZnV₂O₈⁴⁻]_∞, and the Ba²⁺ cations are located in the space among these chains. The IR spectrum, ultraviolet-visible diffuse reflection integral spectrum and fluorescent spectra of this compound have been investigated. The calculated results of energy band structure by the density functional theory method show that the solid-state compound of Ba₂ZnV₂O₈ is an insulator with direct band gap of 3.48 eV. The calculated total and partial density of states indicate that the top valence bands are contributions from the mixings of O-2p, V-3d, and Zn-3d states and low conduction bands mostly originate from unoccupied antibonding states between the V-3d and O-2p states. The V-O bonds are mostly covalence characters and Zn-O bonds are mostly ionic interactions, and the ionic interaction strength is stronger between the Ba-O than between the Zn-O. The refractive index of n_x, n_y, and n_z is estimated to be 1.7453, 1.7469, and 1.7126, respectively, at wavelength of 1060 nm for Ba₂ZnV₂O₈ crystal.     

Untersuchung der Temperaturabhängigkeit derg ik -Tensoren von Polyäthyleneinkristallen

Zusammenfassung Es wurden die Kristallitgröße und die Änderungen der parakristallinen Gitterstörungen aus den Linienbreiten des Röntgenweitwinkeldiagramms von lösungskristallisiertem linearem Polyäthylen bei den Temperaturen 15°K, 73°K, 173°K und Zimmertemperatur bestimmt. Es wurde eine Zunahme der Gitterstörungen mit fallender Temperatur gefunden.

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Summary The crystallite size and the paracrystalline distortions in polyethylene single crystals were evaluated by the measurement of the linewidth in the X-ray wide angle diagram at four different temperatures (15°K, 73°K, 173°K and 297°K). An increase of the lattice distortions with decreasing temperature was found.

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Mit 3 Abbildungen

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Vorgetragen auf der Arbeitssitzung des Fachausschusses Physik der Hochpolymeren in der Frühjahrstagung 1970 des Regionalverbandes Hessen-Mittelrhein-Saar der Deutschen Physikalischen Gesellschaft in Darmstadt, 10.–13. März 1970.     

Über die Stereochemie der Hydrogenolyse von N-Benzyl-Bindungen I. Die Hydrogenolyse von Derivaten der 2-Amino-2-phenyl-propionsäure.

The stereochemistry of the hydrogenolysis of benzyl-N bonds was studied using S(+)-2-dimethylamino-2-phenyl-propionic acid (I) and its derivatives, and R(?)-2-anilino-2-phenyl-propionic acid (II). The configuration of I was confirmed, that of II established by ORD. measurements, after transformation of the phenyl into cyclohexyl groups. On a palladium catalyst the hydrogenolysis of I, its methyl and ethyl esters and its amide proceeded with 72 to 99% inversion of configuration, that of II with at least 66% inversion. The ester of the quaternary ammonium derivative of I gave as much inversion as retention (= racemisation).     

The effect of metal oxides on the oxidation of polybutadiene

Carboxy-terminated polybutadiene (CTPB) was oxidised as a coating on various metal oxides by heating in air on a thermobalance. The oxidation was found to be free from diffusion control and was catalysed by certain of the oxides. The catalysis was shown to be independent of semiconductor type and to be associated with those oxides for which the width of the forbidden zone between the valence and conduction bands (U) is less than 1.9 eV. In general, low values of U result in high catalytic activity. It is proposed that catalysis occurs by a redox mechanism, viz. RO₂H + p → RO₂^. + H⁺, RO₂H + e → RO^. + OH^?.     

Thermal density fluctuations in amorphous polymers as revealed by small angle X-ray diffraction

Summary Thermal density fluctuations in amorphous polymethyl methacrylate, polycarbonate and polyethylene terephthalate were studied by means of small angle X-ray scattering. The measurements were performed in a temperature range from 20 °C up to about 50 °C above the glass transition temperatureT _g of the individual sample.AboveT _g the experimental values of the fluctuations are proportional to the isothermal compressibility and the temperature of the sample as predicted by the fluctuation theory for a system in thermodynamic equilibrium.At temperatures belowT _g this relation is no longer correct. The experimentally determined fluctuations are now proportional to the compressibility of the sample in the equilibrium state atT _g and to the actual temperature of the glassy sample. By considering a statistical ensemble with exchange of energy, particles and order between the systems of the ensemble an equation can be derived for the fluctuations of the number of particles per given volume which predicts the observed behaviour. The order parameter takes into account the fact that the properties of the glassy state depend on the way by which the state was produced.

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Zusammenfassung Es wurden thermische Dichtefluktuationen in amorphem Polymethylmethacrylat, Polycarbonat und Polyäthylenterephthalat mit Hilfe der Röntgenkleinwinkelstreuung untersucht. Die Messungen erstrecken sich über einen Temperaturbereich von 20 °C bis zu etwa 50 °C oberhalb der GlastemperaturT _g der jeweiligen Probe.In Übereinstimmung mit den Ergebnissen der Fluktuationstheorie sind die Fluktuationen oberhalb vonT _g proportional zur isothermen Kompressibilität und zur Temperatur der Probe.Unterhalb der Glastemperatur ist diese Beziehung nicht mehr erfüllt. Hier ist die Fluktuation proportional zur Kompressibilität der Probe im Gleichgewichtszustand beiT _g und zur Temperatur. Auf der Basis einer statistischen Gesamtheit mit der Austauschmöglichkeit von Energie, Partikel und Ordnung zwischen den Systemen der Gesamtheit kann eine Beziehung für die Dichtefluktuation abgeleitet werden, die mit den experimentellen Ergebnissen übereinstimmt. Der zusätzliche Ordnungsparameter berücksichtigt die Tatsache, daß die Eigenschaften im Glaszustand wegabhängig sind.

     

Mikrobestimmung von Kohlenstoff und Wasserstoff, sowie von 14C, Tritium und Deuterium im Stickstoffstrom

Zusammenfassung Eine mikroanalytische Kohlenstoff-Wasserstoffbestimmung wird beschrieben, bei der die organische Substanz im Stickstoffstrom verbrannt und deren Crackprodukte mit Sauerstoff oxydiert werden. Halogene und Schwefel werden vom Verbrennungskatalysator (nach Körbl) absorbiert, während eventuell entstandene Stickoxide an einer Kupferschicht zur Reduktion gelangen. Die entstandenen Verbrennungsprodukte CO₂ und H₂O können gravimetrisch erfaßt oder bei radioaktiven Proben durch entsprechende Absorptionsmöglichkeiten in einem Flüssigkeits-Szintillationszähler zur Zählung gebracht werden.Stark quenchende einfache, sowie doppelt markierte Proben, die man auch durch Modifikationen des Zählgeräts nicht mehr genau auszählen kann, können mit gleich hoher Zählausbeute wie nichtquenchende erfaßt werden (75% für ¹⁴C und 30% für ³H), da keine störenden Fremdgase die Zählung beeinflussen.Deuterium wird durch Ausmessen der OD-Bande bei 2500 cm^–1 mit einem Infrarot-Spektrometer quantitativ bestimmt.

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Microanalytical determination of carbon and hydrogen, ¹⁴C, tritium and deuterium in a stream of nitrogen

A microanalytical method for the determination of carbon and hydrogen is described. The procedure involves the combustion of the organic substance in a stream of nitrogen and the oxidation of the decomposition products with oxygen. Halogens and sulphur are absorbed by the combustion catalyst (according to Körbl), whereas nitrogen oxides are reduced on a copper surface. The combustion products, CO₂ and H₂O are determined gravimetrically; in the case of radioactive samples they are appropriately absorbed and counted in a liquid scintillation counter. Strongly quenching singly and doubly labelled samples, which cannot be accurately counted even by modification of the counting device, give equally high radioactive yields (75% for ¹⁴C, 30% for ³H), since counting is not influenced by other gaseous impurities. Deuterium is quantitatively determined by measuring the intensity of the OD-signal at 2500 cm^–1 with an infrared spectrometer.

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Herrn Prof. Dr. H. Schmid bin ich für das wohlwollende Verständnis meinen Arbeiten gegenüber zu bestem Dank verpflichtet. Sämtliche Glas- und Quarzgeräte wurden in der Glasbläserei unserer Institute von Herrn B. Thueler angefertigt, wofür ich auch ihm an dieser Stelle danken möchte.     

Autoxydationsprodukte des Guaiazulens

Zusammenfassung Guaiazulen wird bei Luftzutritt durch Autoxydation verändert. Die dabei auftretenden Produkte wurden chromatographisch aufgetrennt und die drei als Hauptmenge auftretenden Verbindungen charakterisiert: 3.3-Diguaiazulenyl, 1.4-Dimethyl-3-(3-guaiazulenyl)-6-isopropyl-5H-inden-5-on, 1.4-Dimethyl-3-(3-guaiazulenyl)-5-oxo-6-isopropyl-5H-inden-7-aldehyd.

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Autoxidation products of guaiazulene

Guaiazulene exposed to air undergoes autoxidation. The products were separated by chromatography, and the three major products characterized: 3.3-diguaiazulenyl, 1.4-dimethyl-3-(3-guaiazulenyl)-6-isopropyl-5H-inden-5-one, and 1.4-Dimethyl-3-(3-guaiazulenyl)-5-oxo-6-isopropyl-5H-inden-7-aldehyd.

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Herrn Prof. Dr.H. Nowotny gewidmet.     

Neutronenaktivierungsanalytische Bestimmung von Osmium in Geologischen Proben

A neutron activation analysis procedure was developed for the determination of osmium in geological materials. The method consists in the measurement of the 129.4 keV γ-rays of¹⁹¹Os after radiochemical separation of osmium. The sample decomposition, the chemical separation process and the optimal measuring conditions are described and discussed.      

Distribution of polymer deposition in plasma polymerization. III. Effect of discharge power

Distribution of polymer deposition in an inductively coupled rf discharge system is studied as a function of level of discharge power with acetylene and styrene as monomers. When a fixed flow rate is used, the discharge power has a relatively small effect on the pattern of distribution of polymer deposition as long as values of W/FM, where W is discharge wattage, F is flow rate, and M is molecular weight of monomer, are maintained above a critical level to maintain full glow in the reaction tube. It has been shown that plasma polymerization of two monomers which have different molecular weights can be compared in a fair manner by selecting conditions to yield similar value of W/FM.     

Untersuchungen an Alkylmetallalkoxiden der Elemente Aluminium,Gallium und Indium. III. Eigenschaften und Schwingungsspektren von Dialkylgallium- und Indiumalkoxiden

Studies on Alkyl Metal Alkoxides of Aluminium, Gallium, and Indium. III. Properties and Vibrational Spectra of Dialkylgallium- and Indium Alkoxides The preparation and the properties of dialkyl metal alkoxides R₂MOR′ (with R = CH₃, CD₃, C₂H₅; R′ = CH₃, CD₃ and M = Ga, In) are described. The vibrational data (IR and Raman) of the trimeric methyl derivatives point to puckered six-membered M₃O₃-ring systems.