OBTAINING AND PHYSICO-CHEMICAL PROPERTIES OF MATERIALS BASED ON EXPANDED VERMICULITES OF VARIOUS COMPOSITIONS
Abstract
Optimal conditions for chemical and thermal treatments of natural vermiculites from various deposits were determined. The aim of obtaining expanded vermiculites with a minimum bulk density was pursued. Optimum temperature for producing thermal expanded vermiculites was 700 °C. According to scanning electron microscopy chemical expanded vermiculite has more developed surface in comparison with thermal expanded vermiculite. Chemical composition of natural vermiculites of various deposits and expanded vermiculites based on them was defined by X-ray fluorescence. It was shown that the vermiculite of the Tatar deposit contains a large amount of iron distributed over the surface. As a result, the vermiculite from Tatarstan can not be modified by hydrogen peroxide because of the active decomposition reaction of hydrogen peroxide on the surface of vermiculite. It was established that the chemical compositions of natural vermiculites as well as expanded vermiculites based on them do not differ. According to Mössbauer spectroscopy the ratio Fe(II)/Fe(III) in natural vermiculate was 1:4 and in thermal expanded vermiculite was 1:8. It should be noted that chemical expanded vermiculate contains only Fe(III). According to X-ray phase analysis the phase composition of natural vermiculite changes at 350 °C. It was defined that natural vermiculite and thermal expanded vermiculite after adsorption of moisture from the air have the same position of the X-ray maximum. When natural vermiculite was heated two areas of water loss were observed by the thermogravimetric analysis. The anisotropy of tensile strength for samples of the same density taken along and across the rolling axis of vermiculite foil obtained by pressing expanded vermiculite without a binder was described. The thermal conductivity coefficient of vermiculite foil was determined. This makes it possible to use the material as heat shield and fire protector.
Forcitation:
Kalashnik A.V., Ionov S.G. Obtaining and physico-chemical properties of materials based on expanded vermiculites of various compositions. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 6. P. 76-82
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