A. A. Malygin

Chapter 1.8 The chemical basis of surface modification technology of silica and alumina by molecular layering method

Publisher Summary The molecular layering method (ML) and its main principles were formulated on the basis of solid substance chemistry using the skeleton hypothesis of Aleskovskii made in the fiftieth. The detailed account of the results of the chemical aspects of the ML method was found much later (1968-1978) in articles, inventions, monographs and textbooks of Aleskovskii, Koltsov, Volkova, Malygin, and others. Just in this period qualitative accumulation of theoretical and experimental data, as well as quantative ones, prepared the transition of researches to another level—evaluation of the most perspective areas of application of the new method of synthesis and creation of scientific principles of ML technology and its subsequent development. The application of chemical principles of ML method to study the reactions between porous silica and alumina and elements of II-VIII groups of the Periodic Table chlorides has allowed, at first, to justify the principles of ML, experimentally and, secondly, to define its realization as the one of perspective areas for creation effective inorganic sorbents and heterogeneous catalysts. This chapter generalizes from the present results on study of chemical conversions on surfaces of inorganic sorbents (silica and alumina) in reactions with phosphorus, vanadium, chromium, titanium, chlorides, and other chemicals.

Interaction of Titanium Tetrachloride with Products of Thermal Decomposition of Basic Magnesium Carbonate

The interaction of titanium tetrachloride vapor with products formed in thermal decomposition of basic magnesium carbonate in the temperature range 200-800°C was studied.

Thermal stability of polymer compositions with modified alumina

Thermal stability and combustibility of polymer compositions: foam plastic (trade mark PEN-I) based on an epoxide novolak block copolymer, and poly(methyl methacrylate, containing modified alumina of various dispersion as a filler, were investigated.

The role of a reference sample in the study of the titanium-containing silicas by ultraviolet-visible diffuse reflectance spectroscopy

On the example of the silica gel with grown titanium oxide structures, in which titanium has two coordination enviromments (anatase, rutile) we showed the effect of the choice of a reference (MgO, SiO2) on the shape of the ultraviolet-visible diffuse reflectance spectra and the result of their mathematical processing (the Kubelka-Munk function, first derivative).

Synthesis of titanium oxide structures on mesoporous silicon dioxide surface by molecular layering

The formation of titanium oxide structures through the repeated successive treatment of SBA-15 mesoporous silicon dioxide with vapors of TiCl4 and H2O at 200°C is investigated. The influence of the number of synthesis cycles on the character of the buildup of the surface titanium oxide structures and changes in the adsorption and structural characteristics of modified silica is shown.

Possibility of quantum chemical evaluation of the probability of various chemical transformations in syntheses of phosphorus-, titanium-, silicon-, and vanadium-containing structures on the silica surface

Application of minimum quantum-chemical models for predicting chemical transformations in syntheses of phosphorus-, titanium-, silicon-, and vanadium-containing structures on the silica gel surface by molecular layering is considered. Possible pathways for transformation of the groups synthesized under the action of water vapor and hydrogen chloride are analyzed in terms of the models constructed.

Mechanism of Thermal Oxidation of Silicon Carbide Modified by Chromium Oxide Structures

Differential thermal analysis (DTA) and X-ray photoelectron spectroscopy (XPS) were used to study the oxidation of dispersed silicon oxide modified with chromium oxide structures by means of molecular layering, under linear heating in air to 1450°C. The mechanism of surface transformations of silicon carbide during its thermal oxidation was considered. It was shown that the oxidation resistance of the samples increased with increasing concentration of chromium in the surface film.

Perspectives of application of the molecular layer deposition technique for controlling operational properties of materials for shipbuilding

The results of investigations of surface modification of glass hollow microspheres are summarized. The regularities of the chemical molecular layering nanotechnology and its application for production of fillers and composite materials of low density with improved operational properties are discussed. Influence of chemical modification on thermal stability and combustibility of various polymer composites is investigated.

Structure of the products of TiCl4 chemisorption on the surface of porous silica in the process of vapor-phase hydrolysis

Changes in coordination environment of titanium atoms in the composition of the titanium oxychloride groups chemisorbed on the surface of porous silica after the vapor-phase hydrolysis are considered. It is shown that after the substitution of chlorine atoms by the OH groups, additional coordination bonds between the titanium-containing group and neighboring hydroxo groups are formed, that leads to an increase to 6 in the coordination number of titanium in the composition of the surface polyhedra.

Thermal transformations of a polymeric composite consisting of poly(methyl methacrylate) and phosphorus-containing nanodispersed aluminum oxide

Thermal-oxidative properties of polymeric composites based on poly(methyl methacrylate), containing surface-modified nanosized aluminum oxide as filler, were examined. The possibility of chemical grafting to the Al2O3 surface of phosphorus-containing groups to decrease the combustibility of filled polymeric composites was examined by IR spectroscopy.