Voprosy khimii i khimicheskoi tekhnologii (Issues of Chemistry and Chemical Technology)

9-13

Authors: A.Yu. Karnina, A.O. Gyrenko, O.P. Mysov

The kinetics of ammonium tetravanadate(IV) thermolysis is investigated in the paper, this compound being the precursor for obtaining nanodispersed vanadium dioxide. On the basis of derivatographic analysis results, the values of reaction order, activation energy and pre-exponential factor are determined which are equal to n = 1, E = 60.0±4.7 kJ/mole, and k0 = 748.3±3.8 s-1, respectively. To determine the reaction order, a method is used which has been suggested by Kissinger. The method is based on determining the maximum temperature of the investigated phenomenon and on the asymmetry of a differential-temperature curve that is assessed by planimetry. The stepwise character of the reaction is studied; the reaction starts at a temperature of 230±5 °С, then reaches a pick at 270±10 °С and is completed at 375±5 °С. The rate of samples heating during the analysis determines the final results; the optimal heating rate is about of 2.5 to 5 °С per minute. A model kinetic equation of ammonium tetravanadate(IV) thermolysis has been derived. The adequacy of this kinetic equation is confirmed by the fact that the two values of temperature coefficient coincide (γan = γexp), the former (γan) is calculated using Van't Hoff rule via the derived model kinetic equation, the later (γexp) is calculated based on the combined analysis of DTG curves within the temperature range of 250 to 320 °С.

20-24

Authors: N.Ya. Kuzmenko, S.N. Kuzmenko, O.V. Skrynnik

New organotitanium compounds of boron which contain butoxy and acrylate groups have been synthesized. The obtained compounds are reddish-brown liquids or solid substances at room-temperature; they are very soluble in aliphatic, aromatic and chlorinated hydrocarbons, lower aliphatic alcohols and ketones. The structure of the oligomeric [(alkoxy)(acrylate)titanate] boranes was confirmed by elemental and functional groups analysis, molecular mass spectrometry, IR and 1H NMR spectroscopies. The synthesis of such compounds by the acidolysis of tris[tri(butoxy)titanate] borane is accompanied by azeotropic distillation of a part of acrylic acid and n-butyl alcohol and by the side reaction of the formation of butyl acrylate and water. The interaction of water with butoxy groups of the end products results in occurring condensation processes; as a consequence, their molecule mass increases. The consumption of acrylic acid in the processes of butyl acrylate formation and its azeotropic distillation with n-butanol leads to the change of the stoichiometric ratio of the starting compounds; in addition, the degree of the substitution of butoxy groups with acrylate groups in the end products decreases compared with a computed value. The synthesized products simultaneously contain two complexing atoms (i.e. boron and titanium), reactive butoxy groups and unsaturated bonds of acrylate groups. This suggests that these compounds will be useful as active components (coupling agents) of polymer compounds to improve their properties.

29-34

Authors: T.L. Rakitskaya, A.S. Truba, А.A. Ennan

The phase composition of the samples of the solid component of welding aerosol (SCWA), which was obtained during welding of steel by means of UONI 13/55 electrode manufactured in Ukrainian, was studied by X-ray phase analysis and IR spectroscopy; the samples being both freshly prepared (FP) and modified by water treatment at 60 °C (M). It has been found that the both samples were polyphase and characterized by a high degree of crystallinity. Ten individual phases have been identified in the FP-SCWA composition as follows: magnetite (Fe3O4), manganochromite ((Mn, Fe)(Cr, V)2O4), goethite (Fe2O3), -Fe2O3H2O, manganese oxide (Mn3O4), calcium fluoride, potassium and sodium carbonates, potassium chromate (K2CrO4), magnesium silicate (MgSiO3), etc. The most intensive reflections are observed for mixed phases. Water treatment of the SCWA results in a disappearance of the reflections of water-soluble phases while the reflections of some individual phases become more intense. Taking into account characteristics of the reflection of (311) magnetite phase for FP-SCWA (2θ = 35.465, d = 2.529 Å) and M-SCWA (2θ = 35.418, d = 2.532 Å), the values of unit cell parameter for the cubic unite cells of spinel were estimated as follows: 8.3877 Å and 8.3976 Å for FP-SCWA and for M-SCWA, respectively. Using the well-known Scherrer equation, the sizes of magnetite nanoparticles were estimated, they were equal to 68.0 nm and 31.5 nm for FP-SCWA and M-SCWA, respectively. IR spectra for both samples are very complicated because of their phase inhomogeneity and structural features of certain phases. However, they contain the bands attributed to stretching and deformation vibrations of M–O and M–OH bonds which are typical of metal oxides and spinels. The results obtained by X-ray phase analysis and IR spectroscopy revealed some changes in the structure of certain phases as a result of hydrothermal treatment of the SCWA. Both FP-SCWA and M-SCWA demonstrate protective properties in respect to ozone at its concentration of 1.0 mg/m3; however, the values of the protection action time being different. The protection action time was 600 min for FP-SCWA, whereas it was 10 times lower for M-SCWA. The catalytic activity of the SCWAs depends on many factors, among them the phase composition, the ratio between phases which are catalytically active in the reaction of ozone decomposition, the unit cell parameter and the size of magnetite nanoparticles.

40-45

Authors: R.D. Apostolova, I.V. Kirsanova, E.M. Shembel'

Thin-layer molybdenum sulphides synthesized by electrolysis method can be used in lithium-ion micro batteries for miniature electronic devices such as smart cards, microsensors, etc. Molybdenum sulphides are deposited on the cathode from thin-layer aluminium which is known to the best anticorrosion constructional material in lithium-ion batteries. Mo-sulphide deposits with satisfactory adhesion to the substrate cannot be produced on smooth aluminium surface that leads to the deterioration of the discharge characteristics of Mo-sulphide lithium-ion batteries at long cycling. The modification of aluminium surface by zincate treatment was used in this work, it contribute to the strengthening of adhesion ability of the Al-substrate and the improvement of the electrochemical properties of Mo-sulphide lithium-ion batteries. It was established a positive effect of zincate treatment on the structure and discharge characteristics of synthesized materials with using X-ray phase analysis and discharge-charge cycling in galvanostatic mode. Mo2S3 sulphide was produced as monophase material on the modified surface of Al-substrate. According to the images of deposits surface obtained by means of atomic-force microscopy the deposit consists of agglomerates of nanometer size (200 to 250 nm). The reversible capacity of Mo2S3 in lithium-ion batteries achieves a value of 225 to 240 mA h g-1. The proposed method of preliminary zincate treatment of the aluminium substrate surface to electrochemically obtain thin-layer molybdenum sulphides for their further using in lithium-ion battery promotes allows increasing the relation of the active component mass to the metal substrate mass.

61-65

Authors: O.А. Kalinichenko, O. Banakx, T. Journot, P.A. Gay, L.A. Snizhko

The formation mechanism and some properties of coatings obtained from tricalcium phosphate solutions on titanium by anodic spark deposition were studied. The process was carried out in galvanostatic mode on unipolar pulses with frequency of 50 Hz at the current density of 400 Am-2 and voltage of 700 V. The propensity of coatings to dissolution in biologically active environments (SBF-test) was assessed by measurement of thickness, X-ray and elemental analysis data obtained before and after testing. It has been established that the basic components of coatings are titanium, titanium dioxide in anatase form, as well as calcium phosphate compounds, such as Ca3(PO4)2, CaTi4(PO4)6, and Ca(PO3)2. Ca/P atomic ratio of 0.35 to 0.45 weekly depended on the concentration of electrolyte and time of electrolysis in the range of 3 to 15 min. After a two weeks' endurance in SBF, Ca/P ratio declined on average by 20%, which testifies to the bioresorptive properties of obtained coatings. At the same time, the thickness of the film and content of titanium have increased, which may indicate the accumulation of titanium dissolution products in sublayer of the coatings.

72-77

Authors: A.Yu. Poloz, Yu.R. Ebich, N.R. Prokopchuk, R.M. Dolinskaya, V.V. Mozgalev

The influence of oligomeric rubbers with reactive groups, such as carboxylic, hydroxyl, epoxy, and acylhydrazone ones, which can interact with epoxy groups of the ED-20 resin matrix, on the properties of the epoxy compositions cured by polyethylenepolyamine was evaluated. The investigated oligomeric rubbers participate in forming the cross-linked structure of epoxy compositions. When oligomeric rubbers have been added in the epoxy matrix, an increase in the energy of deformation was observed which is caused by the presence of flexible fragments of three-dimensional network due to the incorporation of rubbers molecules. The contribution of energies of elastic and viscous deformations to the total energy of deformation was determined at abrasive damage of epoxy compositions at different angles of attack of the abrasive.