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MATERIALS SCIENCE
ArticleName Low-temperature phase formation in a Ti – B – C – O system
DOI 10.17580/tsm.2017.08.12
ArticleAuthor Gorlanov E. S., Bazhin V. Yu., Fedorov S. N.
ArticleAuthorData

LLC “EXPERT-AL”, Saint Petersburg, Russia:

E. S. Gorlanov, Deputy Chief Executive Officer

 

Saint-Petersburg Mining University, Saint Petersburg, Russia:
V. Yu. Bazhin, Dean of a Faculty of Mineral Raw Material Processing, e-mail: bazhin-alfoil@mail.ru
S. N. Fedorov, Post-Graduate Student of a Chair of Metallurgy

Abstract

The paper presents and substantiates the technology of carbothermic reduction of titanium and boron oxides in the composition of reaction mixture in TiО2 – B2О3 – C at the temperatures up to 1070 оC. The initial components of the reaction mixture were titanium and boron oxides in a hydrated form of metatitanate (H2TiO3 = TiO2·H2O) and boric (Н3ВО3 = 1/2В2О3·3/2H2O) acids which made it possible to use “wet” methods of mixing of reactants to increase the reaction surface, first and foremost the Sol-gel technology. The possibility of a low-temperature synthesis of titanium diboride was substantiated by the theory of increased reactivity of compounds in the transformation period of the crystal lattice during phase transitions. A technology was developed and implemented for transfering of anatase-rutile transformation (ART) of titanium oxide from the temperature interval 600–800 оC to the range of 1030–1050 оC of a phase formation development in a Ti – B – O – C system. A research was conducted on preparation (doping) of TiO2 by the Sol-gel technology for modification of an amorphous titanium oxide through fluorine according to the ТiO2·хН2О→TiO(OH)2–xFx↓→TiO2–xFx→α-TiO2–xFx scheme. The temperature intervals of anatase-rutile transformation of titanium oxide in different gas environments were determined. It is shown that conducting the process in vacuum and argon stimulates the transition of ART, including doped titanium oxide. On the other hand, a stable state of the doped anatase α-TiO2–xFx and the state of ART that enables an active interaction can be preserved in an oxygen-containing atmosphere with a temperature up to 1100 оC. The temperature and the atmospheric mode of carbothermic reduction of TiO2 were specified. A sequential phase formation of TiО2→ TinO2n–1→ TiBО3→TiCxO1–x→ TiB2 was realized in a Ti – B – O – C system at 1030–1050 оC, which was recorded by X-ray diffraction (XRD) of the samples after synthesis. The conditions were established for implementation of low-temperature synthesis. They are in compliance with recipes and special modes of the reaction mixture preparation, conditions of heating and cooling of samples in a controlled atmosphere. A mechanism of formation of oxy-carbo-boride phases in each stage of the recovery of the activated titanium oxide is presented for purposes of discussion.

keywords Sol-gel technology, anatase-rutile transformation, phase formation, low-temperature synthesis, oxycarbide titanium, titanium diboride, dynamic vacuum, neutral atmosphere
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