Voronezh State University

About: Voronezh State University is a education organization based out in Voronezh, Russia. It is known for research contribution in the topics: Silicon & Boundary value problem. The organization has 5166 authors who have published 6097 publications receiving 31680 citations. The organization is also known as: VSU & Voronezh University.

Studies on functionalized mesoporous materials—Part I: characterization of silylized mesoporous material of type MCM-41

Abstract: The synthesis of organic–inorganic composite materials was performed by the surface modification of mesoporous material type MCM-41 by chlorodimethylphenylsilane and dichloromethylphenylsilane. Applying IR spectroscopy, low temperature nitrogen adsorption/desorption (isotherms BET), thermogravimetric measurements and technique of competitive adsorption of toluene and water it was shown that the degree of silylation, hydrophobicity, surface and volume properties (pore size distribution, pore volume) strongly depends on the nature of silylation agent and the ratio of calculated amount of silanol groups to the modifier. Two types of condensation reaction take place: (1) the reaction of the modifier with surface silanol groups, and (2) an inter-molecular condensation of the modifier, resulting in additional pore blocking. Only 24–36 % of the surface silanol groups react with modifier agent. The materials are stable up to temperatures of about 170 °C that is higher than the corresponding polymeric resins. The TG/DTA data allowed concluding that the degree of grafting depends on the ratio silylation agent to SiOH groups. As shown by Fourier transform diffuse reflectance mode spectroscopy only free silanol groups react with modifier.

Elliptic and circular dichroism effects in two-photon double ionization of atoms.

Abstract: An ab initio parametrization of the two-photon double ionization amplitude from an ${s}^{2}$ subshell of an atom in a $^{1}S$ state is presented and used to predict two light polarization effects on photoelectron angular distributions that do not exist in single-photon double ionization: (i) elliptic dichroism and (ii) circular dichroism at equal energy sharing. Estimates for He show large magnitudes for these effects, which provide a means for polarization control of double ionization by vacuum ultraviolet light.

Crystal structure, optical and magnetic properties of PrFeO3 nanoparticles prepared by modified co-precipitation method

Abstract: In this work, PrFeO3 nanoparticles were synthesized by modified co-precipitation method and annealed at different temperatures up to 850°C. The annealed PrFeO3 nanoparticles have single phase orthorhombic structure and the average particle size of 25-30 nm. Due to the very small particle size the prepared PrFeO3 nanoparticles are capable of being used as photocatalyst materials thanks to their strong adsorption bands at 230-400 nm and 400-800 nm observed from the UV-Vis spectra. Additionally, the PrFeO3 nanoparticles are paramagnetic materials with Hc ~ 10Oe and Mr ~ 0. These findings demonstrate their potential use not only as photocatalysts, but also as magnetic materials.

Unexpectedly large relaxation time determined by in situ high-frequency shear modulus measurements near the glass transition of bulk glassy Pd40Cu30Ni10P20

Abstract: High-precision in situ isothermal measurements of 550 kHz shear modulus G of bulk glassy Pd 40 Cu 30 Ni 10 P 20 slightly below and above the glass transition temperature have been performed. It has been found, contrary to the expectation, that the observed relaxation time exceeds by 20–45 times the Maxwell relaxation time τ m = η / G calculated using independent G and shear viscosity η data. It has been concluded that τ m may not serve as a universal time scale for different relaxation processes in supercooled liquid and glassy states.