Growth and Electrical Properties of Cs2Nb4O11Crystals

Large, perfect Cs₂Nb₄O₁₁crystals were prepared by off-stoichiometric melt growth, and their electrical properties were studied. The crystals have a noncentrosymmetric orthorhombic structure (sp. gr. Pnn2) at room temperature and undergo a phase transition at 164°C, which is accompanied by a strong anomaly in c-axis dielectric permittivity and seems to be due to ferroelectric ordering. The crystals exhibit high ionic conductivity.     

Phase Transitions and Physical Properties of K3Nb3B2O12 and K3Nb3 – x M x B2O12 (M = Ta, Sb) Crystals

This work continues our studies into the nature and mechanisms of phase transitions in K₃Nb₃B₂O₁₂ (KNB) crystals, which have a framework structure with spacious continuous channels and combine ferroelectric, ferroelastic, and superionic properties. Single crystals of KNB-based solid solutions in which Nb⁵⁺ is partially substituted with Ta⁵⁺ (KNBT) or Sb⁵⁺ (KNBS) are grown from off-stoichiometric melts. The KNBT solid solutions containing more than 15 at. % Ta are found to decompose at room temperature. The introduction of Ta leads to marked broadening of phase transitions but has little effect on the transition temperatures. KNBS solid solutions exist in a limited composition range. Increasing the Sb content shifts the high-temperature phase transitions to much lower temperatures and raises the electric conductivity of the crystals by 1–1.5 orders of magnitude.     

Butadiene polymerization in the presence of VOCl3–dialkylmagnesium catalytic system

The butadiene polymerization in toluene at 25°C on VOCl₃? (n‐C₄H₉)Mg(iso‐C₈H₁₇) catalytic system was investigated. The kinetic parameters of polymerization and molecular characteristics of polybutadiene were determined. It was shown that substitution of traditional organoaluminum cocatalysts in trans‐regulating vanadium systems does not have an effect on its stereospecificity, but significantly influences on the active centers reaction ability. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 596–600, 2003     

Carbonization of heavy residues of different origin

Investigation of the optimization of the feedstock composition on delayed coking units (UZK 21-10/3M) at the Angarsk Petrochemical Company using the introduction of different heavy oil residues and by-products of petroleum chemistry was carried out. The optimal feedstock composition was determined on the model bench-scale delayed coking units. The samples of petroleum cokes obtained from the feedstock of different compositions were analyzed for the sulfur content, and their microstructure was thoroughly studied in detail. The obtained array of experimental data showed that the optimized coking feedstock composition holds promise from the viewpoint of both the improvement of the quality of the petroleum coke and an increase in its production rate.     

Processing sulfate viscose cellulose prepared using oxygen in bleaching

Conclusions -- Two lots of cellulose, from pine wood and from larch, have been developed; these were treated in the first stage of bleaching with oxygen in alkaline medium instead of by chlorination, under experimental conditions.-- From a preliminary evaluation, the process of viscose preparation and preparation of the viscose for spinning under experimental conditions took place without significant deviations from the accepted technological regime. Higher technological indices of the viscose from pine cellulose were noted.-- The process of spinning viscose fibre from experimental lots of viscose from larch wood and from pine took place in a stable fashion; no clogging of the spinnerets was observed.Translated from Khimicheskie Volokna, No. 5, pp. 17–19, September–October, 1990.