resumo
Phase formation upon hydrothermal crystallization of sodium titanosilicates has been studied in detail. It was shown that an excessive amount of Na and Si with respect to Ti affects the crystallization. It demonstrates that in a clear starting solution, high crystalline microporous titanosilicate (CST, Na2Ti2SiO7.2H(2)O) with sitinakite structure can be formed in 6 h and the crystallization is controlled by nucleation. With less amount of water, CST can be formed in 2 h. At low NaOH content, ETS-4 forms in 2 h at 230 degrees C. By simply increasing NaOH content in starting mixture, the crystallinity of CST improved. With increasing synthesis time CST re-crystallized to AM-4 with unusual hierarchal morphology. The synthesis temperature has a clear influence on the phase formation. At low synthesis temperature, a material with ivanyukite structure (GTS-1) was obtained in 4 h at 150 degrees C. Additionally, we discussed evidence for CST/GTS-1 intergrowths.
palavras-chave
MICROPOROUS TITANOSILICATE; LAYERED TITANOSILICATES; CRYSTAL-STRUCTURE; ANALOG; SIZE; AM-4
categoria
Chemistry; Science & Technology - Other Topics; Materials Science
autores
Lin, Z; Ferdov, S
nossos autores
Zhi Lin
Investigador Principalagradecimentos
Z. L. acknowledges the support of the project CICECO-Aveiro Insti-tute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the Portuguese Foundation for Science and Technology/MCTES. S. F. thanks SEMAT at the University of Minho and FCT (IF/01516/2013) for the support.