The energy and electronic parameters of the inversion ground (GS) and transition states (TS) of the isoelectronic imines Н2С=NХНn (ХНn = СН3(I), NH2(II), OH(III), F(IV), SiH3(V), PH2(VI), SH(VII), Cl(VIII)) have been calculated using DFT (B3LYP/6-311+G(d,p)) method. When imines I-IV and V-VIII are considered separately, the energies of the nitrogen lone pairs (LP) decrease and this energies difference between TS and GS, s-character of LP and its population increase with increasing і- and -constants of ХНn substituents. The energies of the donor-acceptor intramolecular interactions, in which the nitrogen lone pairs participate, and the negative charges on the nitrogen atoms are always higher for the GS. These parameters usually decrease with an increase in both X atom electronegativity along of the period and s-character of the nitrogen lone pare. Inverse relation is observed for charges on the nitrogen atoms and total energies of intramolecular interactions. Electronegativity of ХНn substituent has a dominant influence on the change of s-character of the nitrogen lone pare, the charge on the nitrogen atom and the valence angle С=N–X. The population of the nitrogen lone pair, in general, depends on the energies of the donor-acceptor interactions. The mechanisms of influence of the substituent electronegativity on the energies of the intramolecular interactions have been considered. Charges on the imino-carbon atoms are proportional to the energies of the interactions between the X atom orbitals and the imino-group orbitals. Donating ability of ХНn substituents, in general, increases in the following series: С
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67-71
The informativeness of quality indicators of compressor lubricating oils
Authors: A.B. Grigorov, E.V. Bogoyavlenskaya
Number of views: 311
Experimentally determined standard measures of the quality of refrigerator oils (kinematic viscosity, water mass fraction, ignition temperature, corrosion activity) are presented in this work. Optical and electrical quality ratings, which are not regulated by established standards, are given too. Oxidation products was stated to make a significant contribution to the change in operating characteristic of compressor oil, these oxidation products being formed both under the action of high temperatures and pressures during the compressor operation and in case of ingress of refrigerant (ammonia) into it. The oxidation products in the presence of water will contribute to the beginning of corrosion of copper-containing components of compressor via the electrochemical mechanism. The generated electrolytes and corrosion products significantly change the optical and electrical properties of oil. The informativeness coefficients of the quality of oils were calculated. The informativeness coefficients were selected which adequately reflect the changes in the refrigeration oil properties during compressor operation, they are as follows: water mass fraction, optical density and electrode potential. Some methods were developed to determine the changes in oil performance that are not regulated by established standards. Based on the analysis of the obtained results, such indexes as the amount of moisture, optical density and electrode potential have been selected to perform the express analysis of the quality of refrigerator oils in compressor equipment which uses R717 refrigerant (ammonia).
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72-77
The decomposition of the benzene in cavitation fields
Authors: Z.O. Znak, Yu.V. Sukhatskiy, O.I. Zin, S.V. Khomyak, R.V. Mnykh, A.V. Lysenko
Number of views: 267
The authors studied the process of cavitation decomposition of benzene under the action of acoustic vibrations of the ultrasound range. It was established on the basis of the analysis of oscillograms of the acoustic signal that the amplitude of the sound pressure of the cavitation fields generated in simulated wastewater with benzene was 1.6 times higher than in water. It was found that the dependence of the degree of benzene decomposition on the specific power of cavitation treatment has a maximum at a specific power of 68 kW m-3 and 22.7 kW m-3 for stationary mode and for the mode of initiation of the reaction, respectively. The expediency of using the reaction initiation mode is shown to reduce significantly the energy consumption in the process of benzene decomposition in cavitation fields. An abnormally low degree of decomposition of benzene was detected at a temperature of 313 K; this can be explained by the consumption of energy that was supplied to the system on the formation of stable gas nano-bubbles (babstons) and also by the maximal variability of water structures according to the kinetic theory of Frenkel's fluid. By means of the method of graphical differentiation, it is ascertained that the process of decomposition of benzene in cavitation fields proceeds as a pseudo-first order reaction. The values of the rate constants of the benzene decomposition process are determined.
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78-86
Modern diagnostic methods and technological principles of fabrication of bioresistant ceramic materials
Authors: L.S. Koss, E.Yu. Fedorenko, N.F. Lesnyh, M.I. Ryschenko, Т.D. Ryschenko
Number of views: 270
The expediency of the development of biocide-free and bioresistant facade materials is validated in the work. An express method has been proposed which implies complex climatic and biological tests of the facade products and allows accelerating the biostability testing. On the basis of the analysis of materials surface properties, criteria for estimating of their biostability have been suggested which characterize the change in the degree of the surface roughness and wettability after testing. The probability of the destruction of facade materials by bioagents (algae, fungi, mosses) was shown to increase with an increase in the materials open porosity and their surface roughness. To produce bioresistant facade ceramics, it is necessary to ensure the formation of a low-viscous melt, which is capable of crystallizing water-insoluble phases of mullite and diopside, and provide a rapid firing (at the temperature of up to 1150C). The compositions of the masses have been developed and the process of the formation of biostable ceramics has been studied. The ceramic masses based on alkaline kaolins and containing a complex sintering intensifier (3 wt.% of fluorite and 6 wt.% of dolomite) ensure the fabrication of densely sintered ceramic panels at 1100C, these products have a water absorption of up to 0.07% and a high biostability (the value of the average quantum yield of fluorescence is 0.009).
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87-91
Negative thermal expansion of titanium (III) oxide
Authors: A.V. Nosenko, Y.S. Hordieiev, V.I. Goleus
Number of views: 378
The aim of the present work was to determine the thermal properties of titanium (III) oxide as a possible component of solder powder compositions. Titanium (III) oxide was obtained by solid-phase sintering of titanium (IV) oxide powders and metallic titanium. It has been established that the samples of titanium (III) oxide, which were obtained by roasting in a high vacuum atmosphere at 1450C, have an anomalous negative thermal expansion in the temperature range of 20 to 425C. The material exhibits the highest negative thermal expansion coefficient, equal to minus 34010-7 K-1 in the temperature range of 125 to 225C. According to the results of X-ray diffraction analysis, Ti3O5 is present in the obtained material together with the main Ti2O3 crystalline phase. The data of differential thermal analysis showed that the powder of titanium (III) oxide is sufficiently resistant to oxidation upon heating to 620C, an intense oxidation of Ti2O3 with the formation of TiO2 is observed at higher temperatures. The thermal treatment of the samples in the temperature range of 350–620C results in the change in their color: from dark purple to deep blue. The results obtained in this work showed that titanium (III) oxide can be used as an additive allowing tuning the thermal expansion of composite soldering materials. By changing the amount of Ti2O3, it is possible to create composite materials with positive, negative and near-zero coefficients of thermal expansion.
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92-95
Choice of ceramic masses for the manufacture of electrical ceramics
Authors: O.S. Khomenko
Number of views: 287
This paper gives the results of comparative study of molding and thermal properties of ceramic masses for the production of electrical porcelains manufactured by "Pershotravensky Electrotechnical Porcelain Plant" (mass no. 1) and "Ceramic Masses of Donbas Plant" (mass no. 2). It has been found that the ceramic mass no. 2 is more preferable to press the products of a simple configuration because it has an enhanced binding capacity due to the presence of the hydromica component in the mineralogical composition. The ceramic mass no. 1 is advantageously to use for the manufacture of products of a more complex profile, since it contains quartz sand and have a less shrink. It has also been established that the water absorption of calcined specimens of less than 0.5% is achieved at the temperature of 1280°C for the samples from the mass no. 1 and at the temperature of 1250°C for those from the mass no. 2. This should be taken into account when choosing the temperature regime for the firing of products.
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