Chemical modification of iron oxide surface with organosilicon and organophosphorous compounds

The feasibility of modifying iron oxides (α-Fe₂O₃, γ-Fe₂O₃, and an oxide covering the surface of carbonyl iron) with various organosilicon and organophosphorous compounds has been studied. It has been shown that the surfaces of these oxides can be successfully modified with ethoxysilanes and diethyl ester of butylphosphonic acid. Resultant grafted layers have being found to be rather hydrolytically and thermally stable. The effect of the modification on the corrosion and erosion stability of carbonyl iron has been investigated. It has been demonstrated that the modifying layers can efficiently protect carbonyl iron particles from corrosion.     

Preparation of well-dispersed magnetorheological fluids and effect of dispersion on their magnetorheological properties

In this work, we describe methods for the preparation of suspensions of micron-sized iron particles grafted with different surfactants. The aim is to obtain well-dispersed magnetorheological (MR) fluids. The effectiveness of the surfactants as dispersants was analyzed quantitatively by means of rheological measurements. With this objective, the viscosity of the suspensions was measured, and the results were compared with the prediction of the Batchelor’s formula (Batchelor, J Fluid Mech 83:97–117, 1977). The effect of dispersion on the MR properties of the suspensions was also studied. It was found that the quality of the dispersion of a suspension does not have an important effect on the magnitude of the field-induced yield stress but does on the change of viscosity induced by the field. It was also found that the transition from the solid-like state to the liquid-like one happens very smoothly for well-dispersed suspensions, contrarily to the abrupt transition for poorly dispersed suspensions.     

Solid-state NMR spectroscopic study of the structure of grafted layers of phosphonic acid ester-modified hydroxyapatite

Interaction of hydroxyapatite (HAP) surface with phosphonic acid esters is studied under different conditions. The urgency of the study is due to the fact that HAP is one of the main components of bone tissue and is widely applied in the production of materials designed for filling bone defects. Modification of the surface properties of HAP may result in the development of materials with increased biocompatibility. It is revealed that, in the absence of solvents or in the medium of an aprotic solvent, phosphonic acid esters interact with HAP surface to yield pyrophosphate groups. The interaction with the surface does not take place in the presence of protic solvents.     

Chemical modification of alumina and silica with alkylphosphonic acids and their esters

Alumina and silica were modified with alkylphosphonic acids and diethyl butylphosphonate. The boundaries of hydrolytic stability of the obtained surface-modified materials were determined.     

A convenient method for the synthesis of chlorocymantrene and bromocymantrene

Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2046–2047, November, 1994.     

ESR probe study of acid sites on the silica surface modified by organotin compounds

Bronsted acid sites formed due to the interaction of coordinately unsaturated tin atoms with water on the silica surface modified by organotin compounds were found and studied using an ESR spin probe technique. The half-life period of a probe at room temperature can serve as an additional characteristic of the acidity of the surface.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 144–146, January, 2005.