Phase transformation of anatase in high-energy ball milling

• Main Authors: Ci-Ren Luo, 羅啟仁
• Other Authors: Shyh-Lung Huang
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/19114306996793136881

碩士 === 國立東華大學 === 材料科學與工程學系 === 97 === The transformation pathway of anatase TiO2 in high-energy planetary ball-milling was studied. Anatase powders were first milled using stainless ball/jar with the additive of ethanol alcohol for 10 mins to 12 hrs, followed by structure characterization by X-ray diffractometer (XRD) and analytical electron microscope (AEM). XRD revealed complicated phase assemblages in all milled powders, including residue anatase, the transitional TiO2-II phase and the final product of rutile. In the powders milled for up to ~7 hrs, the TiO2-II phase contents could reach ~50-60%. In addition to the above three polymorphs, AEM further identified a fourth monoclinic TiO2 (B) phase in the as-milled TiO2 powders . This TiO2 (B) phase occurs either as isolated nanosized particles or as thin lamellae of ~2-35 nm in thickness in the mixed-phase anatase-TiO2 (B) or TiO2 (B)-TiO2-II particles. Electron diffraction patterns showed that the mixed-phase powders follow specific crystallographic orientation relationships: <010>A ∥<010> B、{103}A ∥{-201} B for anatase-TiO2 (B); <-22-1>Ⅱ∥<010> B 、{10-2}Ⅱ∥{-20-2}B for TiO2 (B)-TiO2-II; <010>II ∥<111>R for TiO2-II – rutile, all of which being formed by sequential shear deformation of TiO2 polymorphs in high-energy milling. These observations, together with the well-known shear transformation of TiO2-II to rutile, unequivocally establish the anatase to rutile transformation pathway during high-energy milling process as: anatase => TiO2 (B) => TiO2-II => rutile, and open the doorway for the future mass production of nano-sized mixed-phase TiO2 powders with various phase assemblages and unique photocatalyst properties.