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Molten Salt Synthesis and Characterization of Potassium Polytitanate Ceramic Precursors with Varied TiO 2 /K 2 O Molar Ratios
Author(s) -
SanchezMonjaras Tomas,
Gorokhovsky Alexander,
EscalanteGarcia Jose I
Publication year - 2008
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2008.02574.x
Subject(s) - potassium , crystallization , molten salt , molar ratio , materials science , dehydration , salt (chemistry) , water of crystallization , thermogravimetry , chemical composition , nuclear chemistry , mineralogy , chemistry , inorganic chemistry , organic chemistry , catalysis , metallurgy , biochemistry
Semi‐crystalline potassium titanates, useful as precursors to produce composite materials and coatings, were synthesized by thermal treatment of powdered TiO 2 in molten mixtures of KNO 3 and KOH at 450°–550°C. The products obtained had similar structures of laminar crystals, aggregated in particles of about 3 μm of n =TiO 2 /K 2 O molar ratio in the range 2.8–6.0. The value of n could be regulated by the temperature of synthesis, the weight ratio of [KOH]/[KNO 3 ] in the molten salt mixture, and the number of water washing operations. The reduction of the TiO 2 /K 2 O molar ratio increased the contents of H 2 O in the composition of potassium polytitanate, from 5.3 to 11.4 and from 0.2 to 8.6 (wt%) in the adsorbed and structural forms. The thermal treatment of the potassium polytitanate precursors obtained resulted in dehydration and chemical interaction with unreacted TiO 2 at 500°–750°C, amorphization at 750°–850°C, crystallization of K 2 Ti 4 O 9 (in some cases K 3 Ti 8 O 17 ) at 850°–1090°C, and crystallization of K 2 Ti 6 O 13 at temperatures >1090°C. The mechanisms of the structural transformation and phase evolution were considered as a function of the TiO 2 /K 2 O molar ratio in the potassium polytitanate.