Abstract
We have investigated the development of crystal
morphology and phase in ultrafine titanium dioxide
particles. The particles were produced by a
droplet-to-particle method starting from propanolic
titanium tetraisopropoxide solution, and calcined in a
vertical aerosol reactor in air. Mobility size classified
40 nm diameter particles were conveyed to the aerosol
reactor to investigate particle size changes at 20-1200°C
with 5-1 s residence time. In addition, polydisperse
particles were used to study morphology and phase
formation by electron microscopy. According to
differential mobility analysis, the particle diameter was
reduced to 21-23 nm at 600°C and above. Precursor
decomposition occurred between 20°C and 500°C. The
increased mobility particle size at 700°C and above was
observed to coincide with irregular particles at 700°C
and 800°C and faceted particles between 900°C and 1200°C,
according to transmission electron microscopy. The
faceted anatase particles were observed to approach a
minimized surface energy by forming {101} and {001}
crystallographic surfaces. Anatase phase was observed at
500-1200°C and above 600°C the particles were single
crystals. Indications of minor rutile formation were
observed at 1200°C. The relatively stable anatase phase
vs. temperature is attributed to the defect free
structure of the observed particles and a lack of
crystal-crystal attachment points.
| Original language | English |
|---|---|
| Pages (from-to) | 43-52 |
| Journal | Journal of Nanoparticle Research |
| Volume | 4 |
| Issue number | 1-2 |
| DOIs | |
| Publication status | Published - 2002 |
| MoE publication type | A1 Journal article-refereed |
Keywords
- aerosol decomposition
- titanium dioxide
- nanoparticles
- anatase
- crystallization
- crystal morphology