Morphological and Structural Changes in Titanium Dioxide during the Fragmentation Process
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SCALE AND NANOSTRUCTURED MATERIALS AND COATINGS
Morphological and Structural Changes in Titanium Dioxide during the Fragmentation Process Yu. V. Kuz’micha, L. G. Gerasimovaa, *, M. V. Maslovaa, and E. S. Shchukinaa aTananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials, Division of Federal Research Center Kola Scientific Center of the Russian Academy of Sciences, Apatity, 184209 Russia *e-mail: [email protected]
Received June 24, 2019; revised October 22, 2019; accepted October 29, 2019
Abstract—The structural and morphological changes of titanium dioxide particles in the process of ultrafine fragmentation have been studied by means of the X-ray diffraction analysis and BET method based on N2 adsorption-desorption. The sizes of crystallites and microdeformations that indicated a breakage of their structural order with the formation of new phase fragments similar to brookite have been calculated from broadening of diffraction reflections using the method of approximation applying the pseudo-Voigt function. In the study of the morphology of titanium phase particles, it was determined that nitrogen adsorption was described by the isotherm of the IVa type in the p/p0 range of 0.1–0.95 and by the isotherm of the II type at p/p0 higher than 0.95 after mechanical activation in the presence of surface-active substance (SAS). The hysteresis loop of the samples' isotherms is related to the H3 type, which is characteristic of particles with a lamellar morphology. The porous particle system was represented by mesopores of a diameter varying within the range of 20–50 nm. The total volume of micropores was not higher than 10% of their total volume. A monophase product with a rutile structure and the crystallites' size increase was formed from the activated sample at annealing. The specific surface area of titanium dioxide after annealing varied in the range of 6.5– 7.5 m2/g, which is about three times higher than the same value for conventional rutile grades. Keywords: titanium dioxide, structure, fragmentation, mechanoactivation, microdeformation, crystallites, surface morphology DOI: 10.1134/S2070205120040176
1. INTRODUCTION The properties of solid substances are significantly determined by their structure and its stability and the morphology of the particle surface. In particularly, four-charge titanium dioxide exists in the form of three structural species—stable rutile and metastable anatase and brookite [1–3]. The basis of the structures of these modifications is represented by TiO6 octahedra, which are arranged such that each oxygen ion belongs to three octahedra. However, there are two common edges per one octahedron in rutile, four in anatase, and eight in brookite. This fact affects the strength of the oxygen–titanium bond in the crystal lattice. Rutile has a stronger bond than do anatase and brookite. Therefore, rutile is resistant to the effects of weather and high temperature, which enables one to use it as base filler in the production of special paintwork material
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