Thermoluminescence studies of Al2O3 crystals doped with Cobalt impurity

Thermoluminescence (TL) studies of cobalt-doped Al₂O₃ crystals irradiated with X-rays have shown that the TL glow curve consists of three peaks at 105, 195 and 260°C. Bleaching, annealing and quanching studies have been performed in order to understand the nature of colour centers responsible for the formation of the three peaks. The values of the fundamental parameters like trap depth and frequency factor are estimated from TL data and the results obtained are discussed.     

High-temperature X-ray irradiation induced thermoluminescence and half-life calculations in NaYF4 polycrystalline samples

Elevated irradiation temperature studies with NaYF₄ samples reveal that the intensity of the two glow peaks observed around 120 and 180°C enhances. The effect of temperature of irradiation (T_irr) on the sensitisation of the both peaks are studied. The half lives of these glow peaks were calculated and concluded that the half lives of these peaks decreases with the increase in irradiation temperatures.     

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)°.