Photolysis of alkaline-earth nitrates

Peroxynitrite and nitrite ions are the diamagnetic products of photolysis (with light at a wavelength of 253.7 nm) of alkaline-earth nitrates; the paramagnetic products and hydrogen peroxide were not found. The structural water in alkaline-earth nitrate crystals did not affect the qualitative composition of the photodecomposition products. The quantum yield of nitrite ions was 0.0012, 0.0038, 0.0078, and 0.0091 quanta^?1 and that of peroxynitrite ions was 0.0070, 0.0107, 0.0286, and 0.0407 quanta^?1 for Sr(NO₃)₂, Ba(NO₃)₂, Ca(NO₃)₂ · 4H₂O, and Mg(NO₃)₂ · 6H₂O, respectively.     

Verification of Solvation Theory of Dilute to Concentrated Solutions of Some Strong 1–1 Electrolytes

Density, ultrasonic velocity and isobaric heat capacity data have been used to study solvation parameters of aqueous solutions of NaCl, NaNO₃, and KI. Using correct thermodynamic relations, quantitative solvation parameters have been determined at temperatures from 278.15 to 323.15 K: the hydration numbers h, the molar isentropic compressibilities of the solvation complexes $ \beta_{S,h} V_{h} , $ the volume V _1h , the coefficient of isentropic compressibility β _1h of water in the solvation shells of ions, and others. It has been shown that h is independent of the temperature in the range of the investigated conditions, $ \beta_{S,h} V_{h} $ is dependent both on the temperature and concentration, whereas the electrostriction compression in the vicinity of ions has a greater effect on its structure than that due to the mere change of pressure.     

An Approach to Structural and Functional Modeling of the Surface Morphology of Materials Based on Fluorinated Polymers

Russian Journal of General Chemistry - Dynamic modeling of the polymodal morphological structure of the polymer surface, with modified polyethylene terephthalate as an example, was performed. In...     

Some Features of Nucleophilic Substitution Reactions of N-2-Haloethyl Derivatives of 5,5-Substituted Hydantoins

Russian Journal of General Chemistry - Reaction of 5,5-dimethyl-3-(2-chloroethyl)- and 5,5-diphenyl-3-(2-bromoethyl)- hydantoins with potassium 4-aminobenzoate in dimethylformamide in the presence...     

Numerical simulation of the formation of compact strikers from low-sphericity linings

We consider the physicomathematical formulation of the problem of explosive formation of a penetrator from a low-sphericity copper lining. Calculations are made for the formation of a penetrator for a phlegmatized hexogen charge for two models of the behavior of the lining material (copper), and the results are compared with the experimental data.     

Radio-frequency superradiance induced by the rheological explosion of polymer composites containing paramagnetic cobalt complexes

Superradiance induced by the rheological explosion of composites based on polystyrene, cobalt acetylacetonate, and/or 3,5-di-tert-butylcatechol has been investigated. The superradiance intensity is determined by solid-phase chemical reactions induced by the rheological explosion. EPR, X-ray diffraction, and electron microscopic characterization of stable products resulting from the rheological explosion in the polymer matrix has demonstrated that the superradiance intensity is related to the electronic properties and structure of two-spin intermediates, namely, radical pairs and organoelement biradicals.     

An improved method for selective catalytic reduction of nitrogen oxides in exhaust gases

The selective catalytic reduction (SCR) of nitrogen dioxide in an air flow modeling the exhaust gas from an internal combustion engine is studied. Granulated V₂O₅ (13.5%)–MnO₂ (0.7–1.0%)/Al₂O₃ powder (AVK-10M catalyst) and ammonia injected into a SCR catalytic cell are used as a heterogeneous catalyst of NO₂ reduction and a reducing agent, respectively. If the efficiency of NO₂ removal is high enough and satisfies the requirements of the State Sanitary Standards for the maximum permissible concentrations of substances emitted into the atmosphere (\(MP{C_{N{O_2}}}\) = 0.085 mg/m³), the reducing agent (ammonia) is not completely consumed during SCR, so a considerable amount of NH₃ can be released into the atmosphere. Therefore, a strict control of both NO₂ and unreacted ammonia emissions is needed. The dependences of the concentrations of [NH₃] and [NO₂] on the [NH₃]/[NO₂] ratio for the model air flow passed through the AVK-10M granular heterogeneous catalyst are measured. It is found that the maximum degree of removal of NO₂ from the air takes place at [NH₃]/[NO₂] = 1.3. In the conventional process, the concentration of [NO₂] drop from 530.00 to 0.07 mg/m³, i.e., below the \(MP{C_{N{O_2}}}\). At the same time, the ammonia concentration increases to [NH₃] = 3.4 mg/m³, which becomes 85 times the \(MP{C_{N{O_2}}}\), 0.04 mg/m³. To remove unreacted ammonia from air flows, we developed [P–(SO₃ ^-)₂ · Me²⁺] sulfocationites, where Me are the Cu and/or Ca ions, P is a styrene–divinylbenzene copolymer. It is shown that the concentration of ammonia passed through the adsorption cell filled with a freshly sulfocationite drops below \(MP{C_{N{H_3}}}\) = 0.04 mg/m³. The dependences of the dynamic exchange capacity (DEC) before ammonia breakthrough for the [P–(SO₃ ^-)₂ · Cu²⁺] delta-sulfocationite on the air flow rate, [NH₃] concentration, and humidity are measured. The maximum value of the DEC, δ = 59.5 mg/cm³, is observed at an air flow velocity of 2.171 m/s, [NH₃] = 0.0035 mg/L, and 75% humidity. To illustrate practical applications of the proposed improved SCR method, it is shown that a 3-L replaceable [P–(SO₃ ^-)₂ · Cu²⁺] sorbent cartridge in a SCR exhaust gas purifier for a car internal combustion engine does not need replacement more frequently than every 50000 km.     

Study of magnetic properties of Pd<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Fe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>0.95</Subscript>Mn<Subscript>0.05</Subscript> alloy using polarized muons and neutrons

The Pd_1?x Fe _x )_0.95Mn_0.05 alloy with random competing interaction was studied by measuring the muon spin relaxation in an external transverse magnetic field and in a zero magnetic field. Using the measured temperature dependence of the dynamic relaxation rate λ and the characteristics of the distribution of local static fields, the phase states of the sample under study are refined. In particular, it is shown that the ferromagnetic and spin-glass states coexist simultaneously in the sample below 25 K. Combined studies of the sample using the μSR and neutron depolarization methods made it possible to determine the size of magnetic inhomogeneities to be 2–6 μm in the temperature range 5–40 K.     

Influence of the growth mechanism and thermoelastic stresses on the lattice dynamics of heteroepitaxial films of barium strontium titanate

Heteroepitaxial thin films of Ba_0.7Sr_0.3TiO₃ (BST-0.3) solid solutions were grown on single-crystal (001) MgO substrates by high-frequency cathode sputtering of a stoichiometric ceramic target. The parameters of the tetragonal unit cell of a film were determined by x-ray diffraction methods, and the temperature dependence of the parameter c was studied depending on the synthesis conditions in the temperature range 293–520 K. An E(TO) soft mode was observed in the Raman spectra, the frequency of which correlates with two-dimensional stresses arising in films. It is shown that the two-dimensional stresses in a film are controlled not only by the film-substrate lattice constant mismatch and the difference of their thermal expansion coefficients but also are significantly dependent on the heteroepitaxial growth mechanism. It is shown that the phase transition to the tetragonal paraelectric phase during film heating occurs irrespective of the growth mechanism.     

Magnetic and thermal properties of single-crystal NdFe<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript>

The neodymium ferroborate NdFe₃(BO₃)₄ undergoes an antiferromagnetic transition at T _N = 30 K, which manifests itself as a λ-type anomaly in the temperature dependence of the specific heat C and as inflection points in the temperature dependences of the magnetic susceptibility χ measured at various directions of an applied magnetic field with respect to the crystallographic axes of the sample. Magnetic ordering occurs only in the subsystem of Fe³⁺ ions, whereas the subsystem of Nd³⁺ ions remains polarized by the magnetic field of the iron subsystem. A change in the population of the levels of the ground Kramers doublet of neodymium ions manifests itself as Schottky-type anomalies in the C(T) and χ(T) dependences at low temperatures. At low temperatures, the magnetic properties of single-crystal NdFe₃(BO₃)₄ are substantially anisotropic, which is determined by the anisotropic contribution of the rare-earth subsystem to the magnetization. The experimental data obtained are used to propose a model for the magnetic structure of NdFe₃(BO₃)₄.