Investigation of the Interaction of Quartz with Hydrogen under Supply of Mechanical Energy (II) Investigation by IR Spectroscopy

Infrared investigations demonstrate a chemical interaction of quartz in hydrogen atmosphere during mechanical activation: By means of the SiH stretching band the number of formed SiH-groups is estimated as a function of the period of activation. of activation. This number is more than one order of magnitude less than the total number of adsorbed molecules.     

X-ray and X-ray photoelectron spectra of vanadium oxides

X-ray (XS) and X-ray photoelectron (XPS) spectra are reported for vanadium oxides. Because of the multivalent character of vanadium in the oxide system high quality measurements can be used for chemical shift investigation. Both inner level and valence band spectroscopy give information on the electronic structure and their systematic change with increasing oxidation state. The experimental results are discussed favourable in terms of molecular orbital theory (MO-theory). The complete set of XS and XPS data reported here for V-oxides allows the identification of unknown vanadium oxidation states too.     

Synthesis and Characterization of the Levyne-like Structure SAPO-35, Prepared with Cyclohexylamine as Templating Agent

The microporous aluminophosphate SAPO-35 with the levyne-like structure was prepared hitherto only with quinuclidine as templating agent. In this paper it is shown that also cyclohexylamine can be used for the synthesis of SAPO-35. The samples were characterized by X-ray diffraction, thermal analysis, adsorption isotherms, and micrographs. These investigations confirm the few data reported on SAPO-35 and give further informations. The number of acid sites (Brönstedt centres) was determined from the differential molar heat of chemisorption of NH₃ to three per unit cell.     

Crystallization Kinetics of Silicalite-1: Use of Tetrapropylammonium Bromide and Chloride as Templates

Silicalite-1, the aluminum-free end number of the ZSM-5 zeolites, was synthesized from a batch composition of 3.25 Na₂O · 40.0 SiO₂ · 552 H₂O · 2.00 TPA by using tetrapropylammonium bromide (TPA-Br) or chloride (TPA-Cl) as templates in the temperature range of 100 to 175 °C in a batch system. Conversion of silica in the starting batch composition into silicalite-1 in the product was followed quantitatively. The activation energies of nucleation and crystallization were determined as 37.2 and 66.5 kJ/mol, respectively. The use of TPA-Cl as the template instead of TPA-Br results in longer induction period for crystallization to start and a larger crystal size in product.     

Crystal and molecular structure of 2.2′-dihydroxyazobenzene

C₁₂H₁₀N₂O₂; monoclinic, space group P1 2₁/c 1 (Z = 2), 826 observed independent reflexions, R = 0.043; lattice dimensions at 25 °C, a = 975.8(3) pm, b = 466.8(1) pm, c = 1186.8(2) pm, β = 108.51(1)°.     

Effect of Electric Field on Dielectric Properties of SnO2 Sb2O3 and their Mixed Thin Films

Thin films of various thicknesses in the MIM structure have been prepared from the the powders of SnO₂, Sb₂O₃ and (SnO₂ + Sb₂O₃) of high purity by the thermal evaporation technique in a vacuum of 10⁻⁵ Torr. Dielectric properties of SnO₂, Sb₂O₃, and their mixed thin films have been studied with ac and dc electric fields and frequency. Capacitance and loss tangent are almost independent on dc voltage upto 1.0 V for SnO₂, 10.0 V for Sb₂O₃ and 2.5 V for mixed films. These capacitors become unstable at 1.0 V for SnO₂ films and 2.5 V for mixed films. For higher film thicknesses the decay in these films starts at higher voltages. Capacitance and loss tangent increases with applied ac voltage in SnO₂, Sb₂O₃, and their mixed films. A comparison of the capacitance values of SnO₂, Sb₂O₃, and their mixed films showed that the capacitance values are less in Sb₂O₃ as compared to SnO₂ films. In mixed films the capacitance is greater than the constituent films. These studies have shown that Sb₂O₃ films are found to be more stable compared to SnO₂ and their mixed films for ac and dc voltages. The results thus obtained on SnO₂, Sb₂O₃, and their films are presented and discussed.     

The Influence of Mechanical Activation of Quartz and Quartz/γ-Al2O3 Mixtures on the Sodium A Zeolite Formation

It could be shown that the preparation of sodium A zeolite is possible by the reaction of quartz and γ-Al₂O₃ with NaOH-solution. The zeolite formation is dependent on the mechanical preliminary treatment of quartz. Only the partially crystalline part of quartz dissolves and reacts with Al₂O₃ to form zeolite. The grinding of quartz/γ-Al₂O₃ mixtures can in certain limits raise the zeolite formation but essentially only influences the kinetics of the zeolite formation.