Aluminium oxide-hydroxides obtained by hydrothermal synthesis: influence of thermal treatment on phase composition and textural characteristics

Aluminium oxide-hydroxides obtained by means of the hydrothermal synthesis of aluminium nanopowder are of great interest in terms of the potential supports for heterogeneous catalysts due its high specific surface area (200...300 m2/g) and pore size of 4...17 nm. In this work the influence of thermal treatment (150...1300 °C) on structural and phase composition, specific surface area and porosity of aluminium oxide-hydroxides has been investigated. Nanostructured γ-Al2O3 (T=400 °C) was found to have the specific surface area of 328 m2/g and average pore size of ~9 nm. The thermal treatment of aluminium oxide- hydroxides at the temperature of higher and lower than 400 °C has caused the reduction of specific surface area and overall pore volume

Physicochemical aspects of recycling tree leaf litter in the south of Western Siberia by the Eisenia fetida (Savigny) vermiculture

The utility of the compost worm Eisenia fetida (Savigny) for recycling mixed leaf litter of the tree species characteristic of the forests in the south of Western Siberia and used in the landscaping in the city of Tomsk has been demonstrated. The tree species that are the major contributors to the leaf litter in the examined area include the genera Populus, Salix, and Betula. Two-fraction substrates for leaf litter vermicomposting and conventional composting (decomposition with and without earthworms) were prepared of the harvested and dried leaf litter. The feeding fraction consisted of leaf litter moistened with distilled water and the absorbing fraction, of alluvial river sand. The physicochemical properties of the studied leaf litter were weakly acidic pH of aqueous extracts, a very low content of nitrate nitrogen, and a relatively low K + concentration. The prevalent cation in the assayed leaf litter was Ca 2+ . The leaf litter was partially decomposed on the surface of sand substrates during 35-day incubation under humid conditions; accumulation of inorganic ions in the sand was one of the signs indicating this decomposition. Ca 2+ was also prevalent among these ions

Characterization of electroexplosive zinc nanopowders in aqueous suspensions

Zn and ZnO nanosized powders are increasingly in demand of materials engineering, power systems and biotechnology. Meanwhile, elaboration, production and application of nanopowders have created the conditions for nanoparticles release into the environment. The lack of physicochemical information about nanoparticles behaviour in liquid environment does not allow to give deep interpretation of toxic effects of nanoparticles and elaborate new techniques for testing of nanomaterials. This study is primarily focused on the characterization of nanopowder composition, shape and dispersity of electroexplosive zinc nanopowder in aqueous suspensions based on simple physiological solutions of phosphate buffering saline, glucose solution, and distilled water. With the help of SEM images, X-ray analysis, and visualization it was revealed that on the surface of sphere-like Zn nanoparticles formed insoluble oxide-hydroxide compounds with strongly developed structure. The method of laser diffraction was used to give a description of the aggregation status of nanoparticles and its evolution on the time-scale.</jats:p

Acrylate hydrogel modification using a cross-linking agent for increasing multilayer glazing flame resistance

The design of layers for multilayer flame-resistant glass is a vital task in terms of upgrading fire resistance of window glass units. This paper describes chemical modification of flame-proof acrylate hydrogel layers and shows experimentally how a cross-linking agent — hexamethoxymethylmelamine ether – influences the kinetics of hydrogel polymerization and the enhancement of carbonated structures yield. It has been determined that adding HMMM to the hydrogel composition raises the coke residue yield from 10 % to 35 % and increases the 19 mm thick glass flame resistance class from EI30 to EI50.</jats:p

Aluminium oxide-hydroxides obtained by hydrothermal synthesis: influence of thermal treatment on phase composition and textural characteristics

Aluminium oxide-hydroxides obtained by means of the hydrothermal synthesis of aluminium nanopowder are of great interest in terms of the potential supports for heterogeneous catalysts due its high specific surface area (200...300 m2/g) and pore size of 4...17 nm. In this work the influence of thermal treatment (150...1300 °C) on structural and phase composition, specific surface area and porosity of aluminium oxide-hydroxides has been investigated. Nanostructured γ-Al2O3 (T=400 °C) was found to have the specific surface area of 328 m2/g and average pore size of ~9 nm. The thermal treatment of aluminium oxide- hydroxides at the temperature of higher and lower than 400 °C has caused the reduction of specific surface area and overall pore volume

Self-propagating high temperature synthesis of TiB2-MgAl2O4 composites

Metal borides are widely used as heat-insulating materials, however, the range of their application in high-temperature conditions with oxidative medium is significantly restricted. To improve the thermal stability of structural materials based on titanium boride, and to prevent the growth of TiB2 crystals, additives based on alumina-magnesia spinel with chemical resistant and refractory properties have been used. The aim of this work is to study the structure of TiB2 with alumina-magnesia spinel additives obtained by self-propagating high-temperature synthesis (SHS). TiB2 structure with uniform fine-grained distribution was obtained in an MgAl2O4 matrix. The material composition was confirmed by X-ray diffraction analysis (DRON-3M, filtered Co kα-emission), FTIR spectroscopy (Thermo Electron Nicolet 5700, within the range of 1300–400 cm⁻¹), and scanning electron microscopy (Philips SEM 515). The obtained material represents a composite, where the particles of TiB2 with a size of 5 µm are uniformly distributed in the alloy of alumina-magnesia spinel