Том 65, № 8 (2016)

The review collates the results of studies on the chemical dispersion and phase transformations of Ti, Zr, and Y alloys with iron and nickel during the reaction with ammonia at a pressure of 0.6—0.8 MPa in the temperature range of 100—500 °C in the presence of NH₄Cl as the activator. Promising working materials for metal hydride hydrogen storage, including alloys (Ti₉₀Mg₁₀, Y₆₇Fe₃₃, and Ti₆₇Fe₃₃) and intermetallics (Ti₂Ni, Zr₂Ni, Zr₃Al₂, ZrV₂), are considered. At 150—250 °C, the mentioned intermetallics absorb considerable amounts of hydrogen with conservation of the initial metallic lattice and formation of the highly dispersed hydrides Ti₂NiH_3.3, Zr₂NiH_4.7, Zr₃Al₂H_1.1, and ZrV₂H_2.2. The phase transformations taking place on heating of the intermetallics from 250 to 500 °C, resulting in mixtures of intermetallic hydridonitrides and metal nitrides, are elucidated. The transformation products of the Ti₉₀Mg₁₀, Y₆₇Fe₃₃, and Ti₆₇Fe₃₃ alloys in ammonia atmosphere in the temperature range of 100—500 °C are established.

In this review we present the applications of phosphonic acids in high-temperature colloidal synthesis of cadmium chalcogenide quantum dots and anisotropic nanocrystals. The influence of these acids on the processes of nucleation and growth, particle shape and size, phase composition and luminescent properties is considered. It is shown that phosphonic acids can significantly increase luminescence quantum yield and time stability.

A highly significant challenge for chemistry is the search of the selective catalytic processes for the direct methane transformation into valuable products. The review discusses activation of inert alkane molecule by coordination to a metal atom via three-center two-electron bond involving donor-acceptor and dative interactions. This coordination weakens the C—H bond and opens up new possibilities for homolytic and heterolytic methane reactions.

Density functional quantum chemical calculations of Roussin’s red esters with phenyl [Fe₂(SPh)₂(NO)₄] and ortho-aminophenyl [Fe₂(SC₆H₄NH₂)₂(NO)₄] ligands, as well as products of partial and complete replacement of functional ligands by glutathione were carried out. Main characteristics of the Fe—S bonds in these compounds were estimated within the framework of the NBO approach and the AIM theory. The possibility for ligand substitution reactions to occur was demonstrated. A possible mechanism of these processes is proposed.

The results of ¹H NMR and quantum chemical studies of hydrolysis of isobutylaluminum aryloxides are presented. According to the data of ¹H NMR spectroscopy, the hydrolysis of monomeric diisobutylaluminum aryloxides (2,6-Bu₂^t—C₆H₃O)AlBu₂ⁱ and (2,6-Bu₂^t,4-Me—C₆H₂O)AlBu₂ⁱ occurs selectively at the Al—OAr bond to form the corresponding sterically bulky phenol and polyisobutylaluminoxane. At the molar ratios Al: H₂O = 2, the formed sterically bulky phenol reacts slowly with diisobutylaluminum monoaryloxide to form isobutylaluminum diaryloxide. Dimeric aryloxide [(2-Bu^t—C₆H₄O)AlBu₂ⁱ]₂ is not hydrolyzed under similar conditions. The quantum chemical calculations confirmed the experimental results: the hydrolysis at the Al—OAr bond has a lower energy barrier than that at the Al—C bond because of the formation of \({H_{{H_2}O}} \ldots {O_{O - Ar}}\) hydrogen bonds.

Intermetallic compounds La_3–xMg_xNi₉ (x = 1.0, 1.1) were synthesized and their hydrogen sorption and electrochemical properties were studied. The maximum hydrogen storage capacities for La₂MgNi₉ and La_1.9Mg_1.1Ni₉ were shown to be 1.6±0.1 and 1.5±0.1 wt.%, respectively, and the unit cell volume increased by 24% and 16%, respectively, upon the hydrogenation of the alloys. The maximum specific capacity of the electrodes with the La_1.9Mg_1.1Ni₉ and La₂MgNi₉ alloys is 390 mA h g^–1 at a discharge current density of 60 mA g^–1, which is 24% higher as compared to the similar data for the LaNi₅ alloy (315 mA h g^–1). The electrodes demonstrate high specific capacity and performance at high current densities, as well as good cyclic stability.

The results of the crush method applied to the experimental determination of the concentration limit of detonation for binary systems based on tetranitromethane and fluoronitromethane are generalized. A universal line (for the class of standard explosives with the atomic composition C_aH_bN_cO_dF_e) dividing the plane of pairs of dimensionless parameters (heat of explosion, coefficient of oxidizer excess) into regions of detonating solutions and those unable of detonation was found.

The influence of the conditions of electrochemical deposition of Cu—Zn—Sn—Se precursor thin films from solutions containing lactic acid on their optical and electrophysical properties was studied. It was found that an additional annealing step of precursor films in a selenium atmosphere at 550 °C is necessary for the preparation of single-phase polycrystalline photoconducting Cu—Zn—Sn—Se films with a band gap energy equal to ~1 eV. The obtained semiconductor CZTSe materials satisfy the composition and property requirements imposed on absorbing layers in solar panels.

We introduce a mathematical model of the nonequilibrium process of thermal decomposition of hydrocarbon fuel in heated channels of a ramjet combustion chamber cooling system. This mathematical model is based on describing the process using intermediate asymptotics formed when taking into account the equilibrium gas composition, which is determined using open source software for calculating the equilibrium state of the chemical reaction products. A procedure was introduced allowing at different stages of the process of thermal decomposition of fuel to separate kinetically irreversible and reversible chemical reactions and to exclude from consideration chemical reactions which remained incomplete in a limited size engine. We present the features of the process of thermal decomposition of liquid and solid fuels which can be used in high-speed aircraft engines.

The energetic potential of bimolecular crystals (BMCs) containing CL-20 as components of solid composite propellants (SCPs) was investigated. The experimental and calculated values of the standard enthalpies of formation are reported. The maximum heats of explosion, which correlate with the impact sensitivity, were calculated. The specific impulse values and the densities of SCPs based on an active binder, aluminum, and oxidizer (BMC + a small portion of ammonium dinitramide) were evaluated.

The electrochemical oxidation of bis(ethylenedithio)tetrathiafulvalene (ET) in the presence of simple dicyanamide salts of rare-earth metals with the general formula M[N(CN)₂]₃ (M = Gd³⁺, Dy³⁺, and Ho³⁺) as electrolytes was studied for the first time. A novel radicalcаtion salt α-ЕТ₂[С(NCN)₂NH₂] with the unexpected (2,1-dicyano)guanidine anion was synthesized. The crystal structure of the salt and its conducting properties were studied. The structure of the salt is layered with alternating conducting radical-cation and insulating anionic layers. The cationic layers of the α-type are formed by two crystallographically independent radical-cations of ET of various charges. The anionic layers are formed of [С(NCN)₂NH₂]^– anions linked by hydrogen contacts into chains. The crystals of ЕТ₂[С(NCN)₂NH₂] demonstrate a semiconducting character of conductivity in a temperature range of 300—100 K.

The kinetics of the reaction of N,N’-diphenyl-1,4-beznoquinone diimine with thiophenol in a chlorobenzene—propan-1-ol binary solvent at 343 K was studied spectrophotometrically. The nature of the solvent has a pronounced effect on the reaction rate. On going from chlorobenzene to propan-1-ol, the overall reaction rate increases nearly by an order of magnitude. The reaction has a complex mechanism and follows the two directions. The first direction is the chain reaction with the rate increasing upon addition of an initiator. The second direction is non-chain reaction between the reagents; the initiator does not affect the rate of this reaction. A gross rate constant of the non-chain reaction and the rate constants of some elementary steps of the chain reaction were determined. Based on the obtained results, the overall reaction rate, the rates of both chain and non-chain reactions were calculated depending on the content of propan-1-ol in the binary solvent, concentration of the reagents, and the rate of initiating reaction induced by initiator. It is found that an increase in the propan-1-ol content increases the role of the non-chain process.

New 3’-(4-chlorophenyl)-5’,5’-dimethyl-2’-oxospiro[(2H)-chromene-2,4’-1,3-oxazolidine] was synthesized to study the donor influence of the chlorine atom at the N-phenyl substituent on the structure and photochromic properties of 1,3-oxazolidine-containing spiropyrans. Photochemical properties of synthesized 1,3-oxazolidine derivatives were studied at room temperature in toluene. The X-ray diffraction parameters for the new compound were compared with the data obtained earlier for similar spiropyrans.

The kinetics and the products of thermal decomposition of 2,4,6-triazidopyrimidine in the melt were investigated by thermogravimetry, manometry, mass-spectrometry, and IR spectroscopy. The kinetic and activation parameters of the processes were found. Nitrogen was the only gaseous product of the reaction. The structure of the solid reaction product was determined. A mechanism of thermal decomposition of 2,4,6-triazidopyrimidine, including elimination of a nitrogen molecule to give nitrene in the initial step, was proposed. The unusually high pre-exponential factor in the Arrhenius equation (10^16.7±0.7 s^–1) was attributed to a significant contribution of polymerization (polycondensation) to the overall process, resulting in the formation of carbon—nitrogen two-dimensional networks.

The formation of star-like N-isopropylacrylamide (NIPA) polymeric structures in the presence of C₆₀ occurs in two steps. In the polymerization induction period, water-insoluble cores of future star-like polymers (SP) are formed. The cores are composed of one or more C₆₀ molecules linked by a C—C bond, five or six initiator radicals, and several short NIPA polymeric chains. The formation of SP begins after the induction period and continues until the end of polymerization through gradual growth of the polymeric layer at the cores. The solubility of SP in water is determined by a certain initial concentration of NIPA. It is suggested that the mechanism of these processes is determined by a dependence of C₆₀ reactivity on the degree of its “substitution”.

According to DLS the amphiphilic copolymer of N-vinylpyrrolidone with triethylene glycol dimethacrylate of branched topology forms micelle-like particles in isopropyl alcohol with the hydrodynamic radius R_h of ~50 nm. Due to the solubilization of hydrophobic zinc tetra-phenylporphyrinate by polymer particles, the water soluble macromolecular hybrid structures of R_h ~20 nm were obtained. The structures are stable in aqueous buffer solution at pH 6.8—7.0 and demonstrate characteristic fluorescence. According to TEM, the obtained nanoparticles have close to spherical shape. They exhibit low toxicity for cells at the concentration below 700 μg mL^–1. As it is shown by fluorescence microscopy, the polymer particles with encapsulated dye are able to penetrate into the cells.