Russian Journal of Physical Chemistry A最新文献

In this work, spinel magnesium manganese oxides MgMn₂O₄ were successfully synthesized via a sol-gel method followed by calcination. In order to alleviate the particles aggregation of MgMn₂O₄, carbon spheres (CS) as the sacrificial template were introduced during the sol-gel synthesis process. The addition of CS templates at weight ratios of 5 and 20% relative to Mg²⁺ respectively yields products characterized by well-dispersed nanoparticles and hollow porous nanocages. Galvanostatic charge-discharge tests demonstrated that the MgMn₂O₄ with a 5% CS template could deliver the maximum discharge capacity of 155.5 mA h/g, while still maintaining a reversible capacity of 115 mA h/g after 100 cycles at a current density of 100 mA/g. The MgMn₂O₄ derived from a 20% CS template displays a hollow porous nanocages, with a capacity slightly lower than that of the 5% CS template. However, it exhibits excellent cycling stability, especially at a high current density of 300 mA/g, where after 250 cycles, the capacity retention rate remain as high as 93%.

In this paper, Fe₂TiAl–Fe₂Ti alloy was prepared by arc melting method, and its corrosion and tribocorrosion behaviors were investigated in detail. The results showed that Fe₂TiAl–Fe₂Ti alloy exhibited better corrosion and tribocorrosion resistance compared to 0Cr18Ni9 stainless steel in 0.5 mol/L H₂SO₄ solution due to the formation of TiO₂–Al₂O₃–Fe₂O₃ protective layer on the surface. Compared to static corrosion, the alloy exhibits a lower corrosion potential, higher corrosion current, and noticeable fluctuations in the polarization curves under sliding conditions. With the onset of sliding, the OCP value of the alloy decreases and the current density increases, with an inversely varying relationship between the friction coefficient and the OCP, indicating a significant wear-accelerated corrosion effect. At higher potentials, the wear volume of Fe₂TiAl–Fe₂Ti alloy and 0Cr18Ni9 stainless steel increases, indicating that corrosion accelerates wear.

Novel graphdiyne (GDY) materials with tunable electronic and nonlinear optical (NLO) properties are always desirable for material development. Herein, we conducted a comprehensive prediction of silagraphdiyne (SiGDY) with the adsorption of alkali metals (M) and superalkalis molecules (M₂F) onto its surface, and their geometric structures, electronic properties, charge transfer and nonlinear optical responses were systematically studied. Our calculations demonstrate that the M/M₂F molecules can be adsorbed stably on large delocalized SiGDY surfaces reflected by high binding energies. Notably, the SiGDY can accept almost an electron transferred from M/M₂F, forming strong intramolecular charge-transfer (CT) process, while the reduced vertical ionization potentials (VIP) create the necessary conditions for enhancing the NLO response. Furthermore, it is found that both the substitution of silicon atoms within GDY and the adsorption of M/M₂F onto SiGDY significantly modulate electronic properties, and narrow the HOMO–LUMO gaps of complexes. More interestingly, the adsorption of M/M₂F on SiGDY enhances remarkably the first hyperpolarizability (β_tot) of complexes, especially for M@SiGDY, of which Li@SiGDY possesses the exceptionally large β_tot value (~7.65 × 10⁵ a.u.), further explained by two-level model. The present findings show that the functionalized SiGDY materials can be considered as promising candidate of novel carbon-based NLO nanodevices for future applications.

The electrical conductivity of ionic liquids (ILs) is an important figure of merit for any electrochemical application. In this regard, we measured electrical conductivities of N,N-dimethylethanolammonium based PILs at different temperatures from T = 293.15–323.15 K, and the results are discussed in terms of the effect of temperature, hydrophobicity, and H-bonding abilities of ions on conductivity. The investigation into alterations in the electrical conductivity of ionic liquids (ILs) in both polar protic and aprotic solvents holds significant importance for advancing the industrial applications of IL solutions. To broaden the potential applications of ILs, we conducted measurements of the specific conductivity (κ) in binary mixtures involving N,N-dimethylethanolammonium carboxylates [DMEA] [Carboxylates], a protic ionic liquids (PILs), with water, ethanol, and acetonitrile at 298.15 K. The aggregation behavior of the PILs in various solvents was studied by determining the critical aggregation concentration (CAC), and standard Gibbs energy of aggregation ((Delta G_{{text{a}}}^{^circ })). The findings from studies on the electrical conductivity of mixtures involving [DMEA] [Carboxylates] with molecular solvents are analyzed with a focus on ion-solvent interactions. The discussions encompass the impact of hydrophobicity, as well as the influence of H-bonding abilities exhibited by both the ionic liquid (PIL) and the solvent on the aggregation behavior observed in the mixtures.

The isobaric heat capacity of pyrochlore gadolinium titanate Gd₂Ti₂O₇ is measured in the 2–1825 K range of temperatures. Thermodynamic functions (entropy, enthalpy change, reduced Gibbs energy) are calculated using consistent smoothed values of heat capacity. The Gibbs energy of the formation of Gd₂Ti₂O₇ from oxides in the high temperature range is estimated.

The phase formation of neodymium tungstate Nd₂WO₆ from mechanically activated oxides was studied in a wide temperature range: 25–1600°C. Conditions for the formation of various polymorphic modifications were determined: low-temperature orthorhombic β-Nd₂WO₆ and δ-Nd₂WO₆ (P2₁2₁2₁ (no. 19)); high-temperature monoclinic Nd₂WO₆ (C12/c1 (no. 15)). Optical absorption spectra were studied for polymorphic ceramics with a nominal composition of Nd₂WO₆. Differences in the spectra of δ-Nd₂WO₆ and monoclinic Nd₂WO₆ were detected. Both modifications (δ-Nd₂WO₆ and monoclinic Nd₂WO₆) showed proton conductivity with activation energies of 1.05 and 1.06 eV, respectively. For the Ca-containing solid solution with a monoclinic structure (Nd(_{{1 - x}})Ca_x)₂WO(_{{6-delta }}) (x = 0.01), whose overall conductivity increases compared to that of pure monoclinic Nd₂WO₆, hole conductivity predominates in air.

In this work, the shear viscosity (η) of the liquid alkali metals including Rb, Cs, and Na is determined based on the Stokes–Einstein’s equation by an improved mean spherical approximation theory using an effective square-well potential relation for intermolecular interaction in a wide range of densities and temperatures. In this way, the PVT data and the linear isothermal regularity equation of state are used to determine the radial distribution function at a contact point at any thermodynamic state. The results obtained showed that the calculated values for viscosity increased strongly with increasing density and increased slightly with temperature. A reasonable agreement has been found between the calculated values of η and their available experimental data. Furthermore, a correlation relation between the effective molecular diameter and the temperature was found and the order of magnitude and sign of the coefficients were determined.

The paper presents the results of anticorrosion gravimetric studies of the quaternary nitrogen-containing derivatives of 2-allyl-4-isodecylphenol, namely, the quaternary ammonium salts 2-allyl-4-isodecyl-6-diethylaminomethylphenol (I) and 2-allyl-4-isodecyl-6-piperidinomethylphenol (II) on steel St.3 plates in a system consisting of a 3% aqueous NaCl solution and hydrocarbons (kerosene) at a ratio of 9 : 1 (vol/vol). The influence of the temperature and concentration of the compounds on the corrosion rate, metal surface coverage, and protective effect was studied (test time 5 h). Compounds I and II were found to have high inhibitory properties. The thermodynamic parameters of adsorption (ΔG, ΔH, ΔS) were determined, based on which the chemisorption blocking mechanism of steel St.3 surface protection was proposed. The chemisorption process is described by the Langmuir isotherm.

The authors propose an algorithm for determining the reliability of physicochemical properties using zinc nitrate hexahydrate as a case study. This compound is a promising phase change energy-saving material at low temperatures. The approach underscores the need to verify the informational reliability of a vast amount of experimental data. Dubious experimental values are averaged or excluded in determining the reliability of such properties as enthalpy, temperature of melting, density in the solid and liquid phases, heat capacity in the solid and liquid phases, and viscosity. Reliable literature properties are identified, and experimental measurements are made of the characteristics of zinc nitrate hexahydrate of various classifications to find correlations between reliable literature and experimental data.

Adsorbents based on Silipore 200 silica noncovalently modified with complex compounds of nickel(II) with acetylacetone, benzoylacetone, and ethyl acetoacetate were obtained. The interaction of the vapors of aromatic compounds with the silica surface was studied by gas chromatography: the Henry constants were calculated, the thermodynamic characteristics of adsorption of the class of compounds under study were determined based on chromatographic data, and the contributions of modifying additives to the retention of adsorbates were calculated. The effects of the ligand functional groups in the chelate complex on the differential molar heat of adsorption and the change in the adsorption entropy were studied. The possibility of using the sorbents for gas chromatographic separation of complex mixtures of organic compounds was shown.