Theoretical Foundations of Chemical Engineering最新文献

A method of surface modification of the MA8 bioresorbable magnesium alloy (Mg–Mn–Ce) is developed. This method is based on the formation of hybrid coatings containing an organic biocompatible corrosion inhibitor and a bioresorbable polymer material. The anticorrosion properties of the formed coatings are studied in a physiological solution (0.9 wt % NaCl) and Hanks’ solution. Such layers reduce the alloy degradation rate due to the active protection function.

A method for the chemical polishing of metals using a nanostructured system of inverse sodium dodecyl sulfate–butanol-1–kerosene–aqueous acid solution microemulsions is proposed. The boundaries of the areas where microemulsions can exist in this system are shown. The acid concentrations enabling the polishing of copper and aluminum are selected. The conditions providing a decrease of up to 20% in the average roughness of these metals are determined.

Phase equilibria in Ca(NO₃)₂–C₂H₅OH–H₂O system sections and anti-icing properties of calcium nitrate–ethanol compositions with a component ratio from 1 : 3 to 3 : 1 are studied. The temperatures and composition of eutectics with ice and the melting ability of nitrate–ethanol compositions at temperatures of –5 and –10°C are determined. The compositions characterized by good anti-icing properties are revealed.

Statistical regularities of porosity formation during climatic tests of plane-parallel composite materials are revealed. To predict changes in the physical and mechanical properties of composite materials, it is proposed to use the Balshin–Huttig relationship of dimensionless properties and porosity. Taking into account experimental data on the porosity of plane-parallel basalt-plastic and fiberglass composite materials, calculations are made to reduce their physical and mechanical properties.

Abstract—New methods for the synthesis of NASICON of the composition Na_{1 + x}Zr₂P_{3 – x}Si_xO₁₂ (0 ≤ x ≤ 3) were presented. In the work, the method of pyrolysis of organic solutions was used, which takes a minimum time to synthesize the material. Various options for the composition and heat treatment of precursors were considered. The effect of rosin on the pyrolysis process and the phase composition of the final products was discussed. The optimal conditions for the synthesis of the low-dimensional monoclinic polymorph Na₃Zr₂Si₂PO₁₂ with homogeneous composition were determined.

Using the dependences C(REE) = f(τ), fundamental differences in extraction of rare earth elements (REEs) from phosphate raw materials of sedimentary and igneous origin were identified, which consist in the extremal and monotonic plateauing behavior of the kinetic curves, respectively. The discovered features of nitric acid extraction of rare earth elements will make it possible to evaluate the prospects for integrated processing of raw materials and optimal conditions for their recovery from multicomponent systems.

The efficiency of using heat pumps in extractive rectification schemes with partially coupled heat and material flows is studied on the example of separating an allylic alcohol–allyl acetate mixture of various initial compositions with n-butylpropionate as a separating agent. A comparison of schemes with heat pumps and schemes with a traditional two-column scheme of extractive rectification is carried out according to the criteria of reduced energy costs and total annual costs. It is established that with increasing concentration of allylic alcohol in the feed, the energy and economic efficiency of the scheme with a heat pump on the main column of the complex with partially coupled heat and material flows increases. The energy efficiency of the side-section heat-pump circuit decreases with increasing allylic alcohol content in the feed, and the economic efficiency of this circuit increases slightly. The energy efficiency of the scheme in which heat pumps are simultaneously used on the main column and on the side section depends little on the composition of the feed, while the economic efficiency of this scheme increases with increasing concentration of allylic alcohol. For all considered power compositions, the maximum savings in energy costs (by 45.9–49.1%) compared to the traditional two-column scheme is provided by the schemes in which heat pumps are simultaneously used on the main column and on the side section, and the maximum reduction in total annual costs (by 11.7–27.9% with a service life of 20 years) is achieved with the scheme with a heat pump on the main column of the complex with partially coupled heat and material flows.

Abstract—The flotation of impregnated copper-nickel ores is studied using humate agents as depressors, which are obtained from oxidized brown coal by extraction with alkaline reagents. The effect of the humate agents on the flotation of some iron-bearing minerals (pyrite, pyrrhotine, chalcopyrite) among the sulfide ores, as well as the sorption of humates with minerals, are studied. The humate agents are found to have a depressing effect on both nonmetallic minerals and sulfides.

Abstract—Phase equilibria in Ca(NO₃)₂–C₃H₆(OH)₂–H₂O system sections and anti-icing properties of calcium nitrate–propylene glycol compositions with a component ratio from 1 : 3 to 3 : 1 are studied, and the temperatures and composition of eutectics with ice and the melting capacity of nitrate–propylene glycol compositions at temperatures of –5 and –10°C are determined. The compositions characterized by good anti-icing properties are identified.