Thermal stability of zincite single crystals

The effect of temperature on the stability of synthetic ZnO crystals in neutral (N₂), oxidative (O₂), and reductive (95% Ar-5% H₂) media and in a low vacuum has been studied. In the first and second cases, zincite does not undergo changes up to 1000°C. After an 8-h exposure in oxygen at 1100°C, a decrease in the size of hexagonal growth hillocks on the monohedron face (0001) and smoothing of its relief on the whole have been observed. In the presence of hydrogen, etching traces manifest themselves on the crystal surface even at 760°C; further heating leads to their sublimation. The effect of annealing on the luminescence properties of zincite has been demonstrated.     

A porous open-framework titanium oxophenylphosphate

Highly porous titanium oxophenylphosphate (TPP-1) has been synthesized hydrothermally at 448 K using phenylphosphonic acid (PPA) as the organophosphorus source without the aid of any template or structure-directing agent (SDA). Powder XRD, TEM, SEM-EDS, N₂ sorption, ICP-AES chemical analysis, ¹³C and ³¹P MAS NMR, UV-Vis, XPS spectroscopic tools, TG-DTA and NH₃-TPD were used to characterize this material. XRD, N₂ sorption and TEM image analysis suggested the disordered layered framework structure and the presence of large-size micropores along with mesopores in this material. Spectroscopic data suggested the presence of phenyl group, O, Ti and P in this open-framework material, where Ti centers can adopt both tetrahedral and octahedral geometry. TPP-1 showed fairly good H₂ adsorption capacity under normal pressure to high pressure at 77 K. Physisorption data on hydrogen has suggested the potential application of this porous material in H₂ storage.     

Exact results of statistical analysis of multichannel adaptive systems with continuous gradient algorithms

We obtained some exact expressions for the power of the output signal of adaptive systems with continuous gradient adjustment algorithms. It is shown that fluctuations of weight coefficients result in a decrease in the signal power at the adaptive-system output as compared with the output-signal power in the absence of fluctuations of the weight coefficients. The “overcompensation” phenomenon is explained by the presence of a non-Gaussian statistical relation between the weight- coefficient and input-signal vectors. N. I. Lobachevskii State University, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 9, pp. 914–921, September, 1999.     

Li,Cs||F,NO<Subscript>3</Subscript> ternary reciprocal system

The Li, Cs||F, NO₃ ternary reciprocal system was for the first time described and experimentally studied by differential thermal analysis and differential scanning calorimetry. Phase equilibrium states were determined, and so were the compositions and melting points of two ternary eutectics. Reactions describing the chemical interaction in the system were presented.     

Adsorption interactions of humic acids with biocides

The chemical composition of humic acids from brown coal (Aldrich) was determined by element analysis, ¹³C NMR spectroscopy, and potentiometric titration. The adsorption ability of humic acids with different biocides (cyproconasol, propiconasol, tebuconasol, irgarol 1051, and DCOIT) was studied. The adsorption ability of a mixture of biocides in aqueous solutions was higher than that of the individual components. The limiting concentration of humic acids at which adsorption of biocides was maximum was determined. Adsorption constants were calculated by the Freundlich equation for each biocide in aqueous solution.     

Intercalation of octadecylamine into montmorillonite: molecular simulations and XRD analysis

Intercalation of octadecylamine (ODAMIN) into Na montmorillonite based on the ion-dipole interaction was investigated using molecular mechanics and molecular dynamics simulations combined with X-ray powder diffraction. Molecular modeling revealed the interlayer structure of the ODAMIN-montmorillonite intercalate, the charge distribution on the host layer and guest species, and the energy characteristics, i.e., the total sublimation energy and it's individual contributions (electrostatic and Van der Waals). The present study showed the development of the interlayer structure, basal spacing, and exfoliation energy in dependence on the ODAMIN content.