Temperature Dependence of Excited-State Proton Transfer and Geminate Recombination Processes in Water and in Glycerol-Doped Ice

The reversible proton dissociation and geminate recombination of photoacids was studied as a function of temperature in neat water, binary water mixture containing 0.6 mol% glycerol, and doped ice containing 0.6 mol% glycerol. The deuterium isotope effect on both condensed phases was also studied. 8-hydroxypyrene-1,3,6 trisulfonate trisodium salt was used as the electronically-excited-state proton emitter. The experimental data are analyzed by the Debye–Smoluchowski equation solved numerically with boundary conditions to account for the reversibility of the reaction. We propose a qualitative model to describe the unusual temperature dependence of the proton transfer rate in the liquid phase. We also propose a model for proton transfer in solid ice based on L-defects transport as proton acceptors. While in the liquid phase at t > 10°C the proton dissociation rate constant is almost temperature independent, in glycerol-doped ice we find a large temperature dependence.     

Sol-gel synthesis of compact nanohybrid structures based on silica gels

Our recent achievements in the synthesis of monolithic SiO₂ xerogels (nonfractured upon drying), as well as hybrid composite nanomaterials and silica glasses based on these xerogels, are considered briefly. A number of new promising methods are developed for preparing organic-inorganic nanohybrids, inorganic nanohybrids, and xerogels doped with transition metal and lanthanide complexes that are chemically bound to the silica matrix and exhibit interesting and technically valuable photophysical, photochemical, and electrochemical properties.     

Magnesiothermal synthesis of W-WB powders in ionic melts

Conditions for synthesis of W-W₂B and W-WB powders by simultaneous reduction of the metal oxide- and boron-containing compounds with magnesium in molten salts of the NaF-NaCl system (1: 1) have been considered. It is shown that synthesis involves successive redox reactions yielding tungsten powders with variable concentrations of boride phases. The powder fineness characteristics have been determined in experiments. The volume particle size distribution of the powders has been calculated. It is found that the specific surface area decreases from 1.18 × 10⁶ to 0.63 × 10⁶ as the concentration of the boride phase in the powders rises to ～40%.     

Production of High Quality Castings by the Centrifugal Electroslag Method

Abstract

The Ukrainian-based E. O. Paton Electric Welding Institute has developed new technology for the production of high-quality castings using the centrifugal electroslag casting process (CESC). The technology consists of preparing molten metal in an electroslag crucible furnace from where it is poured, together with the slag, into a rotating casting mould. The authors show that the initial metallic materials may consist of rolled off-cuts, worn-out parts and tools, lumpy waste, and cast stock from continuous casting plants. The use of electro-slag melting technology ensures that there is no loss of alloying elements from the basic charge materials and that there is an absence of harmful contaminants. It is said that the energy characteristics of the electroslag crucible furnace are not inferior to those of induction or arc furnaces. The process technology facilitates the production of high-quality close-to-form castings. The paper presents results of integrated studies of CESC casting quality and describes the method employed in the effective refining of the metal structure. The results of the authors' studies, together with industrial testing and evaluation, show that CESC castings can compete with forgings and stampings in the manufacture of special-purpose components.     

Hole Restoration in situ Using a Mobile Machine Tool,without Disassembly

Russian Engineering Research - The geometrical precision of functionally important surfaces of large crusher components may be restored by means of a mobile multifunctional machine tool, without...     

Statistical Analysis of the Tensile Strength of Oriented Polyamide-6 Fibers

Technical Physics Letters - Statistical analysis of distribution of the tensile strength of commercial oriented polyamide-6 (PA-6) fibers has been performed in the framework of the Gaussian and...     

Method of Evaluating Residual Stresses in the Product Material

Strength of Materials - The method of evaluating the level of residual surface stresses in the products without the loss of their integrity at elastoplastic strains and under static and cyclic...