Hydrothermal Synthesis of Nanocrystalline Powders of Various Crystalline Phases of ZrO2 and TiO2статья
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:Abstract
—Nanocrystalline ZrO2
and TiO2
powders were hydrothermally synthesized from 0.01–1.8 M
ZrO(NO3)2
and TiO(NO3)2
precursor solutions under high pressures of 4.0–5.0 GPa at temperatures from 403
to 523 K. The samples synthesized were characterized by X-ray powder diffraction, X-ray line broadening analysis
(XLB), thermogravimetry (TG), and transmission electron microscopy (TEM). The BET specific surfacearea was determined by capillary nitrogen adsorption. From ZrO(NO3)2
solutions, the stable monoclinic m-ZrO2 was synthesized with the grain size d= 6–8 nm. From TiO(NO3)2 aqueous solutions at 523 K (τ= 10 min),
nanocrystalline samples of anatase (the metastable TiO2 phase) with d= 10 nm were first formed; after 6 h of hydrothermal exposure, they converted to the thermodynamically stable rutile (d = 50 nm). High-temperature hydrolysis of zirconyl nitrate solutions at 523 K and 4.0 GPa for 30 min yielded a mixture of the monoclinic and tetragonal phases; from titanyl nitrate solutions, only rutile (the stable phase) was formed. Short-term hydrothermal processing (τ= 10 min) of hydroxide gels yielded metastable phases: in the case of ZrO(OH)2,
tetragonal t-ZrO2(d= 10–12 nm) was formed at 403 K, which was gradually converted by subsequent hydrothermal processing to the stable monoclinic phase; in the case of TiO2·nH2O at 523 K, anatase (d= 27 nm)was produced.