engleski

Study of Microstructural Changes in TiO2 System Induced by High-Energy Ball Milling Istraživanje strukturnih promjena u TiO2 prahovima nakon uporabe postupka intenzivnog kugličnog mljevenja

Study of microstructural changes in the TiO2 powder induced by high-energy ball milling, performed by hardmetal tools in air and at room temperature, was carried out by applying X-ray diffraction, SEM, Raman and FTIR spectroscopy, and specific surface area (BET) measurements. Observed structural changes followed the phase sequence: anatase Ţ transient (metastable) high-pressure TiO2-II phase Ţ rutile. At the same time specific surface area of powders increased monotonicaly from ~10 m2/g, at beginning, up to ~ 25 m2/g after 3 hours of milling action. In the early stage of milling action the process of particle comminution dominated, and during the later stage the aggregation process was pronounced. The mean crystallite size, evaluated by applying the Scherrer's equation and the estimated half width of the diffraction lines having the highest intensity, and belonging to various phases existing in powder (anatase, TiO2-II, and rutile) varied markedly from beginning of milling action, so that at beginning it was ~30 nm, after 10 minutes of milling it was ~5 nm, and after 3 hours ~10 nm, respectively. These values differed from those regarding the primary particle size, derived from the specific surface area (BET) data, which were (at the same time of milling action) equal to: ~160, ~120 and ~60 nm, respectively. The latter value mentioned indicates that one is capable to prepare successfuly TiO2 "nanocrystalline" powder (with the mean particle size smaller than 100 nm), with different crystallographic forms present in it, if the milling action lasted more than one hour.

Microstructural changes; TiO2 powder; High-energy ball-mill processing; X-ray diffraction; Scanning Electron Microscopy; Raman and FTIR spectroscopies; Specific surface area (BET) measurements

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