V. Yu. Gavrilov

Interaction of geomechanical and physicochemical processes in Kuzbass coal

The paper presents laboratory and in situ research data on interaction of geomechanical and physicochemical processes in Kuzbass coal of various ranks, considering temperature effect. Under analysis is the relation of stress-strain state, temperature and infrared radiation of coal. The authors study the role of temperature and microstructure of coal in energy and mass exchange processes (variation of mass, volatile yield, specific surface, internal energy of methane adsorption capacity decrease and moisture content). Interrelation of outburst hazard and fire hazard in coal is discussed from the viewpoint of uniform stagewise thermomechanics and thermochemistry of coal behavior in the course of coal formation and extraction. The article introduces a generalized factor for quantitative description of petrographic properties of coal. Using this factor, the authors classify and describe petrographic groups of Kuzbass coal.

Effect of silicon dioxide on the formation of the phase composition and pore structure of titanium dioxide with the anatase structure

The formation of the structure of titanium dioxide modified with silicon dioxide, which was introduced as tetraethyl orthosilicate, was studied. It was found that the formation of the nanocrystalline structure of TiO2 occurred upon the modification of titanium dioxide with silicon dioxide. This nanocrystalline structure of TiO2 was formed by highly dispersed anatase particles of size 6–10 nm stabilized by silicon oxide layers, which were formed upon the decomposition of tetraethyl orthosilicate. An increase in the modifier concentration resulted in a deceleration of the growth of anatase particles and an increase in the temperature of the phase transition of anatase to rutile. It was found that the anatase phase in the samples containing 5–15 wt % SiO2 was stable up to 1000°C. The stabilization of highly dispersed anatase particles facilitated the retention of the developed fine-pore structure of xerogels with a pore diameter of 4 nm up to 900°C.

Formation of the Structure of Cerium Oxide-Modified Titanium Dioxide

The formation of the structure of titanium dioxide containing 3–15 wt % CeO2 in a wide temperature range (300–850°C) has been investigated by X-ray powder diffraction, electron microscopy, and adsorption methods. Modification of titanium dioxide with cerium oxide causes the formation of nanostructured Ce-Ti-O compounds consisting of incoherently intergrown fine anatase crystallites. The crystallites are separated by interblock boundaries in which cerium ions are stabilized. The nanostructure formed in the Ce-TiO2 oxide system stabilizes the anatase phase, prevents the sintering of anatase particles at high temperatures, and allows modified anatase to retain a larger specific surface area and a higher porosity upon heat treatment than pure titanium dioxide does.

Effect of silica on the stability of the nanostructure and texture of fine-particle alumina

The effect of the modification of aluminum oxide with silicon oxide on the stability of fine-particle Γ- and δ-Al2O3 phases upon heat treatment in the wide temperature range of 550–1500°C was studied. It was found that the Γ- and δ-Al2O3 phases modified with silica are thermally stable up to higher temperatures than pure aluminum oxide. This is due to changes in the real structure of the modified samples, specifically, an increase in the concentration of extensive defects stabilized by hydroxyl groups bound to not only aluminum atoms but also silicon atoms. It is likely that Si-OH groups, which are thermally more stable than Al-OH groups, stabilize the microstructure of Γ- and δ-Al2O3 to higher temperatures, as compared with aluminum oxide containing no additives. Simultaneously, an increase in the thermal stability of the modified samples is accompanied by the retention of a high specific surface area and a developed pore structure at higher treatment temperatures.

The state of Cu2+ ions in concentrated aqueous ammonia solutions of copper nitrate

Stabilization of Cu2+ ions in concentrated aqueous ammonia solutions of copper nitrate in a wide range of ammonium ion concentrations has been studied by EPR and electronic absorption spectroscopy. Three types of Cu2+ associates with different types of orbital ordering have been identified. The ammonium ion concentration in a solution has a decisive effect on the type of orbital ordering of Cu2+ ions in associates. In all cases, Cu2+ ordering in associates is caused by the existence of bridging OH groups in the axial and equatorial positions of [Cu(NH3)n(H2O)6 − n]2+ complexes (n < 6). At a high concentration of ammonium ions, weakly bound associates of tetramminecopper with the

Distribution of the cobalt-containing component in the pore space of HZSM-5 upon a postsynthetic modification of the zeolite with hydroxo compounds of Co2+

d_{x^2 - y^2 }

Adsorption of molecular hydrogen on aluminophosphate zeolites at 77 K

ground state are formed. In solutions with low ammonium concentrations, bulky associates with the