title: In situ observation of the stability of anatase nanoparticles and their transformation to rutile in an acidic solution.
abstract: Thermodynamic stability of anatase nanoparticles and their transformation behaviors to rutile phase in an acidic solution was investigated in situ at two different peptization temperatures using a freeze-drying method. When peptized at 30 degrees C, the initial product was anatase with a significantly distorted atomic structure, a significant amount of hydroxyl group and Ti3+ ions, and, thus, a thermodynamically unstable state. The instability of 30 degrees C-peptized anatase was responsible for a suitable transformation to rutile later via dissolution of the anatase to form a titanium hydroxylate, followed by reprecipitation into rutile. On the other hand, 80 degrees C-peptized anatase had a relatively more ordered atomic structure, a much reduced amount of hydroxyl group, negligible Ti3+ ions, and, thus, a thermodynamically more stable state. Plausible reasons why the 80 degrees C-peptized anatase does not transform to rutile were deduced.
authors.affiliation: School of Materials Science & Engineering, Seoul National University, Seoul 151-742, Korea.
authors.forename: Hyun Suk
authors.initials: HS
authors.lastname: Jung
authors.forename: Hyunho
authors.initials: H
authors.lastname: Shin
authors.forename: Jeong-Ryeol
authors.initials: JR
authors.lastname: Kim
authors.forename: Jin Young
authors.initials: JY
authors.lastname: Kim
authors.forename: Kug Sun
authors.initials: KS
authors.lastname: Hong
authors.forename: Jung-Kun
authors.initials: JK
authors.lastname: Lee