Vol 69, No 11 (2024)

Single-phase samples of compounds crystalized in the La2O3-CoO-Sb2O5 system have beensynthesized by several methods. Catalytic properties of these samples were studied in the COoxidation reaction. It was found that the LaCo1/3Sb5/3O6 catalyst with a rosiaite structuresynthesized by coprecipitation with hydrothermal treatment of sediment and subsequent annealinghas the largest activity at low temperatures and stability during cyclic tests. This catalyst providesthe 90% CO conversion at 265∘C. The surface of LaCo1/3Sb5/3O6 was studied using XPS, TPD O2 and IR spectroscopy. It is shown that the CO catalytic oxidation proceeds according to the Langmuir-Hinshelwood mechanism and is accompanied by Co3+↔Co2+ and Sb3+↔Sb5+ redoxprocesses with the participation of surfactants and oxygen vacancies. At the same time, antimonyions in this process act as an electron donors, the increasing concentration of which promotes theadsorption and formation of active oxygen species on the surface. The absence of contaminationof the surface during the catalytic process has been established, which eliminates the need for itsregeneration.

Nanocrystalline bismuth ferrite was synthesized using spray pyrolysis and citrate combustion methods. BiFeO3 samples were characterized by X-ray diffraction, infrared spectroscopy, scanning and transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The citrate and spray pyrolysis samples of bismuth ferrite were tested as catalysts for the Fenton-like reaction of the oxidative destruction of methyl orange. The influence of the synthesis method on the composition, morphology of bismuth ferrite particles, as well as catalytic activity has been established. The kinetics of the oxidative destruction of the dye in the presence of bismuth ferrite samples is satisfactorily described by a pseudo-first order model; the reaction rate constant in the case of BiFeO3 synthesized by spray pyrolysis is 0.0072 min-1, for citrate BiFeO3 it is slightly less -0.0049 min-1. The degree of destruction of methyl orange in 120 minutes without a catalyst is 7%, in the presence of spray pyrolysis bismuth ferrite - 62%, in the presence of citrate bismuth ferrite - 51%.

A series of chromophoric complexes NiII(3,6-Cat)(Phen) (1), NiII(3,6-Cat)(DPQ) (2) and NiII(3,6-Cat)(DPPZ) (3) (where 3,6-Cat is 3,6-di-tert-butyl-catecholate dianion) has been synthesized using 1,10-phenanthroline (Phen), dipyrido[3,2-d:2’,3’-f]quinoxaline (DPQ), and dipyrido[3,2-a:2’,3’-c]phenazine (DPPZ). Chromophores 1-3 have a slightly distorted planarstructure of the coordination environment and undergo photoinduced ligand-to-ligandintramolecular charge transfer (HOMOdonor →LUMOacсeptor), thus demonstrating stronglight absorption in visible and near-IR regions. Complexes 1-3are characterized by high thermostability and complete transition to the vapor phase under reduced pressure conditions. Compound 1has high volatility, which makes it a suitable candidate for further testing in thefabrication of optoelectronic devices by “evaporation-deposition” technology.

The synthesis of neodymium carboxylates (neodecanoate and 3,5,5-trimethylhexanoate) and theiruse for the development of Nd-loading liquid organic scintillators is considered. Neodymiumcarboxylates were obtained by one-step (3,5,5-trimethylhexanoate) and two-step synthesis(neodecanoate). The composition of the obtained compounds was confirmed by IR spectroscopy,elemental analysis and MALDI-TOF MS. To introduce neodymium carboxylates into a liquidorganic scintillator, it is proposed to use an additional solvent, tributylphosphate. It has been shownthat the light output of the scintillator when used is higher than without it, and is more than 60% up to a neodymium concentration of 12 g/l.

Erbium titanate was synthesized by co-precipitation of erbium and titanium hydroxides followed by high-temperature annealing. The temperature intervals of the sequence of formation of pyrochlore-type crystal structure were determined. Measurements of the isobaric heat capacity of erbium titanate in the range of 2-1870 K were carried out by relaxation, adiabatic and differential scanning calorimetry methods. On the basis of smoothed values of heat capacity, entropy and enthalpy increment in the region 0-1900 K were calculated, the contribution of Schottky anomaly at temperatures up to 300 K was evaluated, and the Gibbs energy of erbium titanate formation at 298.15 K was calculated.

The interphase distribution of lanthanoids(III) ions between aqueous solutions of HNO3 and solutions of tetrabutyldiglisolamide Bu2C(O)CH2OCH2C(O)NBu2(1), compounds R2P(O)CH2OCH2C(O)NBu2R = Bu (2), R = Ph (3) and phosphoryl-containing podands R2P(O)CH2OCH2P(O)R12R = R1= Bu (4); R = Bu, R1= Ph (5); R = R1= Ph (6)in 1,2-dichloroethane and ionic liquid - 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide has been studied. It has been established that the extraction of metal ions increases significantly in the presence of ionic liquids in the organic phase. The stoichiometry of the extracted complexes was determined, and the influence of the concentration of HNO3 in the aqueous phase and the structure of the extractant on the efficiency of extraction of metal ions into the organic phase was considered.

MAX phases of various compositions have recently found increasing application due to their multilayer structure and properties that are characteristic of ceramic materials and metals. Therefore, the development of easily scalable methods for obtaining these compounds characterized by increased phase purity is of great importance. Within the framework of the work the influence on the composition and properties of such MAX phase, as Ti2AlC, conditions of its preparation with the use of protective melt of salts (on the example of KBr), in particular, ratios ofinitial reagents (n(Ti) : n(Al) : n(C)), temperature and duration of heat treatment has been studied. It was found that at the temperature 1100∘C the highest yield of Ti2AlC (94.4%) can be obtained in the case of using the molar ratio n(Ti) : n(Al) : n(C) = 2 : 1.1 : 0.9. It is shown that the use of synthesis temperatures from 900 to 1100∘C changes the content of the target MAX phase insignificantly(from 94 to 96%), the maximum content of Ti2AlC was found in the case of obtaining a sampleat the temperature 1000∘C. The influence of synthesis temperature (900, 1100 and 1200∘C) on microstructure, thermal behavior in air current and the value of electron work function was alsostudied.

Lithium titanates Li4+xTi5–xMxO12 (M = Sc, Ga, Al, Cr; x= 0, 0.05, 0.1, 0.15) and their composites with carbon nanotubes were synthesized by the sol-gel method and characterized using X-ray diffraction, scanning electron microscopy, impedance and 7Li MAS NMR spectroscopy; their electrochemical testing was carried out. Doping with trivalent cations leads to a decrease in the mobility of lithium ions in Li4+xTi5–xMxO12, which indicates the dominance of lithium transport through vacancies in these materials. The best electrochemical characteristics are demonstrated by the Li4+xTi5–xMxO12 composites with carbon nanotubes.