Results 1 - 10 of 272
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[en] Processing parameters are refined and a route is found for fabricating wires, coils, and other lengthy electrotechnical elements form high-temperature superconducting ceramic YBa2Cu3O7-δ. The superconducting transition temperature of around 90 K and a critical current density in the terrestrial magnetic field of 35-75 A · cm-2 at 77 K characterize the performance of the wire
[en] Thermal solid-phase conversions of the yttrium-barium-copper salt of tricarboxycellulose (TCC) with a 1-2-3 cation stoichiometry, respectively, have been considered. Yttrium barium cuprate is the end product of the thermal treatment of the triple salt. According to the data of X-ray analysis the onset of 1-2-3 phase formation is noticeable at 750-800 degrees C. The temperature 875 degrees C (with a duration of heating of 12 h) is sufficient for practically complete conversion of the Y-Ba-Cu salt of TCC into YBa2Cu3O7-δ
[en] The results of the study of the interaction of an aqueous solution of strontium nitrate with potas-sium-titanate nanoparticles of different morphology obtained by the hydrothermal method are reported. Comparative analysis showed the advantage of nanotubes as sorbents over nanolayers and nanowires. As can be seen from the experiment conducted with nanotubes containing aluminum, an amount of strontium sorbed from the solution rises with increasing temperature: at 50°C the absorption by the tubular matrix was ≈ 0.76 × 10−3 mol g−1, and at 80°C that was ≈ 2.02 × 10−3 mol g−1. Nanotube samples doped with magnesium had the best sorption characteristics: After 5 h of keeping in a solution at 80°С, the content of strontium in them was ≈3.65 × 10−3 mol g−1. The results show the promise of using potassium titanate nanoparticles to extract strontium from aqueous solutions.
[en] The nitration of hyperbranched polyglycidols was studied. It was confirmed that there is no destruction of the polymeric chain when the nitration reaction is performed. The influence exerted by the molecular mass of polyglycidols on the degree of substitution of hydroxy groups in polyglycidol by nitrate groups was determined. The dependences of the degree of substitution of hydroxy groups on the reaction conditions and duration were found. It was shown that the fundamental aspects found in the study can be used to synthesize polyglycidyl nitrates with controllable degree of substitution from polyglycidols with various molecular masses.
[en] Opportunities given by applying the PC-SAFT (Perturbed Chain-Statistical Association Fluid Theory) for estimating and calculating the speed of sound in natural gas were considered. Examples are presented of prognosticating the density and the speed of sound for five multicomponent gas mixtures containing alkanes, isoalkanes, nitrogen, and carbon dioxide in a wide range of temperatures and pressures (250–450 K and 0.5–60 MPa). The results of calculations are compared with published experimental data. It is shown that the model reproduces with high precision the experimental values of the density and the speed of sound.
[en] Comparative study of fatty acids isolated from vegetable (sunflower and cotton-seed) oils and tall oil fatty acids was carried out as regards the possibility of their application as raw material for production of anti-wear additives to low-sulfur diesel fuels. It was shown that the additives are close to each other in the fatty-acid composition and physicochemical and service properties, which makes it possible to extend the raw-material resources for additives of this type and to diminish the import purchases.
[en] In this study, the effects of the free quenching temperature on mechanical, thermomechanical and thermophysical properties of pigmented polystyrene (PS/TiO2) with 3% of TiO2 were investigated. Thermal conductivity and thermal diffusivity of the titanium dioxide pigmented polystyrene were measured using a periodic method. The results show a slow improvement of the notched Izod impact strength obtained after a second quenching at 15 and 35°C; whereas thermal conductivity and diffusivity reached a minimum value at the quenching temperature of 35°C. However, the effect on the thermophysical properties is only noted for the second quenching temperature 35°C. The study allowed examining the effect of quenching temperature, filler concentration and material thickness on the transient thermal behavior of the titanium dioxide pigmented polystyrene.