Doklady Physical Chemistry最新文献

The comparative stability of ionic liquids containing alkyl-substituted imidazolium and phosphonium cations on exposure to gamma radiation (⁶⁰Co source) under the same conditions has been studied for the first time. It has been shown that when exposed to ⁶⁰Co gamma radiation (an absorbed dose of up to 550 kGy) in the presence of air oxygen, phosphonium and imidazolium ionic liquids exhibit high radiolytic stability. Under these conditions, the yield of radiolytic products is no more than 1 wt %. At the same time, in contrast to phosphonium ionic liquids, imidazolium ionic liquids undergo radiolytic staining at absorbed doses in the range studied. Based on IR, UV, and ¹H NMR spectroscopy and known literature data, an assumption has been made about the most probable mechanisms of transformation of imidazolium cations of an ionic liquid under the influence of gamma radiation.

Poly(methacryloylamino galactose) has been synthesized by a modified method, which enables one to increase the yield of the polymer substance. Samples and fractions have been studied by molecular hydrodynamics methods. Molecular masses, scaling relations, and data on equilibrium rigidity of macromolecules have been estimated from the hydrodynamic characteristics.

The study addresses the relationship between the structure of solutions of amphiphilic diblock and random copolymers of 2-(perfluorohexyl)ethyl methacrylate and 2-hydroxyethyl methacrylate in mixed solvents and water contact angles of the surfaces treated with these solutions. For the first time, the solubility and the structuring of homo- and copolymers in mixed solvents were studied and the regions of molecular solubility and microphase and macrophase separation were determined by light scattering techniques. The structure of thin films formed from various solutions was characterized by transmission electron microscopy.

The ionic and phase compositions of Y_2.5Ce_0.5Fe_2.5Ga_2.5O₁₂ ferrogarnet samples obtained by gel combustion with subsequent vacuum annealing were studied for the first time by X-ray photoelectron spectroscopy and X-ray powder diffraction analysis. The X-ray powder diffraction data confirmed the phase homogeneity of Y_2.5Ce_0.5Fe_2.5Ga_2.5O₁₂ and the absence of a cerium dioxide impurity. At the same time, on the surface of Y_2.5Ce_0.5Fe_2.5Ga_2.5O₁₂ particles, along with Ce³⁺, there are Ce⁴⁺ ions.

The rheological behavior of a 1 wt % suspension of highly porous chitosan particles in polydimethylsiloxane in a high electric field has been studied as a function of temperature. The static and dynamic yield stress in an electric field were found to slightly change with a change in shape of the flow curves. The effective response of the electrorheological fluid decreases with increasing temperature. There is a correlation between the electrophysical characteristics of the suspension and its rheological behavior.

The influence of Ti doping on the functional properties of the lithium-rich Li_1.2(Mn_0.67Ni_0.17Co_0.15Ti_0.02)_0.8O₂ cathode material for lithium-ion batteries was studied. The oxide was synthesized by co-precipitation of the appropriate carbonate precursor followed by a solid-state reaction. Doping 2 at % titanium in the transition metal sites increased the material energy and improved its cycling performance. Evidence in favor of positive doping effect on the kinetics of the processes occurring in the cathode material during cycling was obtained.

A phenomenon of change in the frequency of a mechanically activated current was detected for the first time. This phenomenon consists in the fact that electric current pulses produced by a rheological explosion differ in frequency characteristics between a polypropylene‑graphene nanoplates composite and the matrix polymer (polypropylene). It was shown that the Fourier transforms of the current signals from the composite according to the Havriliak–Negami model for the experimental frequency dependence of conductivity agree well with the results of the calculation using the Drude model for multilayer graphene.

The molar heat capacity of europium hafnate at low temperatures (4–345 K) was determined for the first time. The contribution of the Schottky anomaly to the heat capacity was estimated and thermodynamic functions in the range of 0–1300 K were calculated.

The melting point of the high-entropy Cantor alloy CoCrFeMnNi was calculated by the classical molecular dynamics method. Interatomic potential as a set of artificial neural networks was used for simulation of this type for the first time. Neural network coefficients were optimized using machine learning technique with ab initio molecular dynamics data. Ab initio molecular dynamics simulation was carried out for a wide temperature range using the same initial crystalline state. The initial state for ab initio simulations was a special quasi-random structure optimized on pairs of the nearest neighbors. The two-phase method based on the movement of phase boundary in a crystal–melt system was used to calculate the melting point. It should be noted that, although the training set did not contain explicit two-phase configurations, the computed melting point proved to be in a satisfactory agreement with available experimental data. Thus, the melting point of the high-entropy CoCrFeMnNi alloy was calculated without the use of empirical data.

The effect of the internal pressure of the gas in a pore or a cracklike defect on the critical fracture stress has been studied using fracture mechanics approaches. An analytical expression was derived for the dependence of the critical fracture stress on the internal pressure in the crack. The results of this work can be used in powder metallurgy and additive manufacturing of novel materials.