N. B. Kondrashova

Preparation of mesoporous silicon dioxide with high specific surface area

The influence of the reactant ratio on the specific surface area, total pore volume, and mean pore diameter of mesoporous silicon dioxide prepared by the sol-gel method was examined. The optimal reactant ratio for preparing the material with a high specific surface area was determimed.

Study of the effect of organo-substituted trialkoxysilanes on the textural and structural properties of mesoporous silica

The effect of additives of organo-substituted trialkoxysilanes: (3-aminopropyl)triethoxysilane (APTES), (2-cyanoethyl)triethoxysilane (CNETES), and tris(trimethylsiloxy)silane (TTMSS) as cosources of silica on its textural and structural properties was studied. The influence of organo-substituted trialkoxysilane additives on the variation of porous structure parameters of mesoporous silica during the hydrothermal treatment was demonstrated. The synthesized mesoporous silica samples were characterized by low-temperature nitrogen adsorption, X-ray powder diffraction, scanning electron microscopy, thermal and elemental analysis, and Raman spectroscopy.

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.

Influence of the temperature-time conditions on the textural and structural properties of mesoporous silicon dioxide synthesized in an ammonia-alcohol medium

The conditions for the formation of mesostructural silica materials (MSMs) in the ammonia-alcohol media were determined. Mesoporous silicon dioxide was synthesized by the template liquid-phase condensation method at high concentrations of the surfactant. The effect exerted by temperature and time of the synthesis, autoclaving, and by organosilane additive [(trimethylsiloxy)silane] used in synthesis on the structural and textural properties of the mesoporous material was determined. The temperature-time conditions for the preparation of mesostructured silicon dioxide were optimized.

Gas-Chromatographic Determination of Acrylic Acid in Aqueous Solutions

A procedure was developed for determining acrylic acid in aqueous solutions at its concentration within 0.5-20 MPC.

Hydrophobized Silicas as Functional Fillers of Fire-Extinguishing Powders

This paper presents a comparative evaluation of the use of hydrophobized silica materials as functional fillers in ammonium phosphate-based fire-extinguishing powders (FEPs). To this end, we have hydrophobized the surface of different silicas: commercially available fumed silica and Aerosil and monodisperse silica prepared by the Stöber method under laboratory conditions. We have optimized the content of hydrophobized silica fillers in FEPs so that the powder materials exhibit superhydrophobic properties and the lowest flow resistance.

Control over Rheological Properties of Powdered Formulations Based on Phosphate-Ammonium Salts and Hydrophobized Silicon Oxide

Surface of silicon oxide (white black BS-120) was hydrophobized with a polymethylhydrosiloxane solution. IR spectroscopy demonstrated that the hydrophobization process involves free silanol groups of the silicon oxide surface. It was found that a stable superhydrophobic state of the surface is observed upon hydrophobization of silicon oxide, with the wetting angle exceeding 150°. Introduction of hydrophobized silicon oxide into a fire-extinguishing powdered formulation based on ammonium phosphates can improve its rheological characteristics. The influence exerted by the fraction composition of dispersed systems based on phosphorus-ammonium salts on their rheological properties was examined.

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.

Sorption properties of polysulfones based on diallylaminophosphonium salts

The sorption properties of polysulfones based on diallylaminotris(diethylamino)phosphonium tetrafluoroborate and chloride were studied. The diallylaminotris(diethylamino)phosphonium tetrafluoroborate polysulfone shows rather high sorption capacity with respect to rhenium(VI) and good kinetic characteristics of sorption. When both Re(VII) and Mo(VI) are present in acidic or weakly acidic solutions, rhenium can be separated from molybdenum by the ion exchanger in question. At pH > 6, these metals are extracted together.

The effect of composition of the reaction medium on the structural-textural characteristics of mesoporous silicon dioxide

The conditions for the preparation of mesoporous silicon dioxide in water-alkali, alcohol-alkali, water-ammonia, alcohol-ammonia, and acid media were determined and its textural characteristics were studied.