Preparation of ultra-and nanoporous glasses and study of their structural and electrokinetic characteristics in 1: 1 electrolyte solutions

Nano-and ultraporous glass membranes with pore radii of 4.5–150 nm are prepared from sodium borosilicate glasses of various compositions. Structural parameters (structure resistance coefficient, volume porosity, and filtration factor) and electrokinetic characteristics (conductivity, counterion transport numbers, and electrokinetic potential ζ _α ^* ) of membranes are determined at various KCl and NaCl solution concentrations (10^?4?10^?1 M) in a neutral pH region. The passage from nano-to ultraporous glasses is accompanied by an increase in |ζ _α ^* | values, which is apparently related to a decrease in the thickness of a gel layer due to the removal of ion-permeable secondary silica from pore channels. The comparison of electrokinetic characteristics of glass membranes (counterion transport numbers, efficiency coefficients, and electrokinetic potentials) measured in NaCl and KCl solutions indicates a higher specificity of K⁺ counterions as compared to Na⁺ ions.     

An urban ecosystem as a superposition of interrelated active media

A space-time model that treats the urban ecosystem as a superposition of active media is expanded to take the heterogeneity of anthropogenic and natural factors into account. The approach is based on representation of urban ecosystems as conjugated active media and is aimed at identifying the threshold values of control parameters. The theoretical basis of the system analysis of the stability of urban ecosystems is provided by synergetic ideas concerning autowave self-organization in active media.     

Structure,phase composition,and spectral luminescence properties of partially stabilized zirconium dioxide crystals doped with Yb<Superscript>3+</Superscript> ions

Investigation of partially stabilized zirconium dioxide crystals via transmission electron microscopy has revealed a developed twin structure therein. The following compositions of the above crystals have been selected for this study: 97.2 mol % ZrO₂–1.0 mol % Y₂O₃–1.8 mol % Yb₂O₃; 97.2 mol % ZrO₂–2.0 mol % Y₂O₃–0.8 mol % Yb₂O₃; 97.2 mol % ZrO₂–2.5 mol % Y₂O₃–0.3 mol % Yb₂O₃; and 96.3 mol % ZrO₂–3.4 mol % Y₂O₃–0.3 mol % Yb₂O₃. X-ray diffraction analysis of these crystals indicate the presence of transformable (t) and nontransformable (t') tetragonal phases. Optical spectroscopy measurements of ZrO₂–Y₂O₃–Yb₂O₃ crystals with tetragonal and cubic structures have highlighted in Yb³⁺-doped zirconium dioxide samples the formation of the optical centers of the Yb³⁺ ions is observed, whose crystal surrounding is similar to those in cubic zirconium dioxide crystals.     

Electrosurface Properties of Hydr(oxides) and Oxide Nanostructures in 1 : 1 Electrolyte Solutions: 1. Adsorption Characteristics of Boehmite, Goethite, and Silicon Dioxide

The adsorption of potential-determining ions on aluminum and iron hydroxides and silicon dioxide was measured in KCl and NaCl background solutions. It was shown that dependences of the adsorption on pH and the concentration of a background 1 : 1 electrolyte (NaCl) have the shape characteristic of oxide surfaces; the of values pH_PZCwere determined. Results of adsorption measurements were used for the determination of constants of surface reactions and adsorption potentials of ions in terms of the 2-pK model.