S.A. Uporov

Synthesis and properties of magnetic superhydrophobic mesoporous Fe2O3–SiO2 composites

Ways to obtain Fe2O3–SiO2 iron-containing silica composites with organized mesoporous structure (MCM-41) and large specific surface area (up to 1476 m2 g–1) were considered. The influence exerted by the method used to synthesize the materials on their structure, texture characteristics, particle size, and magnetic properties were studied. The aggregative stability of samples was examined. It was shown that treatment of the resulting composites with compounds from the chlorosilane group affects their hydrophobic properties.

Preparation and magnetic characteristics of mesoporous nickel oxide–silica composites

Mesoporous NiO–SiO2 (MCM-41) silica-matrix composites with various nickel oxide concentrations (NiO : SiO2 = 0.025 : 1 to 0.2 : 1) have been produced by oxide cocondensation under hydrothermal synthesis conditions in the presence of cetyltrimethylammonium bromide as a template and (2-cyanoethyl) triethoxysilane as an organosubstituted trialkoxysilane additive. X-ray diffraction data have been used to evaluate the maximum nickel(II) oxide concentration (NiO : SiO2 = 0.1 : 1) that allows the ordered mesopore structure of MCM-41 to persist in the silica-matrix composites. We have studied the magnetic properties of this material as functions of temperature and magnetic field. The results demonstrate that the magnetic properties of the nanocomposite with NiO : SiO2 = 0.1 : 1 at low temperatures (T < 20 K) are determined by incomplete spin compensation in the matrix and on the surface of the NiO nanoparticles.

Influence of oxygen non-stoichiometry on physical properties of NdSr2Mn2O7±δ

Abstract NdSr 2 Mn 2 O 7+δ compounds were synthesized by ceramic method under three different cooling conditions. The NdSr 2 Mn 2 O 7+δ samples were characterized by powder X-ray diffraction (XRD). Oxygen non-stoichiometry data for the studied powders were determined by using gravimetric and X-ray photoelectron spectroscopy (XPS) methods. The correlation of cooling method and oxygen as non-stoichiometry was established. The electroconductivity in samples was studied by using four-point probe method, and the strong correlation with non-stoichiometry was found out. Magnetization measurements were carried out. It was found that the magnetic and transport properties of the samples were also influenced by oxygen non-stoichiometry. The evolution of the magnetic properties could be explained by the formation of magnetic clusters in the vicinity of oxygen vacancies (OV) and strong competition between the superexchange and double exchange interactions.

Specific features of phase formation in initial and mechanically-activated perovskite-like Gd1 − xCaxMnO3 ± δ

The regularities of crystal structure formation and features of developed magnetic states of solid solution Gd1 − xCaxMnO3 ± δ (x = 0.0, 0.1, 0.2, 0.3, and 0.4) with temperature and partial pressure of oxygen has been established in coarse-grained and nanostructured states of samples.