Morphology development and crystal growth in nanocrystalline aggregates under hydrothermal conditions: Insights from titania

R. Lee Penn, Jillian F. Banfield

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891 Scopus citations

Abstract

High-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) peak broadening (Scherer) analysis were used to study coarsening and morphology development of nanocrystals. Experimental work used synthetic, equidimensional anatase (TiO2) particles about 5 nm in diameter. Under hydrothermal conditions (100-250°C, 15-40 bars), rapid growth occurs along [001], driven in part by the relatively high surface energy of (001) and in part by a kinetic effect involving a cyclic generation of highly reactive adsorption sites. Rapid growth along [001] depresses the <101> growth rate until (001) surfaces shrink to a critical cluster size. A second major coarsening mechanism significantly reduces the surface energy, especially under acidic conditions. This mechanism involves topotactic attachment of primary particles at high energy surfaces (most commonly {112}), less commonly (001) and can result in elongate single crystals. Oriented attachment may be an important coarsening mechanism under a wide range of conditions encountered in the laboratory and in natural environments.

Original languageEnglish (US)
Pages (from-to)1549-1557
Number of pages9
JournalGeochimica et Cosmochimica Acta
Volume63
Issue number10
DOIs
StatePublished - May 1999

Bibliographical note

Funding Information:
Financial support from The National Science Foundation (Grant No. EAR-9508171), the National Physical Science Consortium (fellowship to R. Lee Penn), and a Mineralogical Society of America Grant for Student Research in Mineralogy and Petrology to R.L.P. Drs. Steven Higgins and Hengzhong Zhang are thanked for their helpful comments.

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