Gas-phase crystallization of titanium dioxide nanoparticles

Petri Ahonen, Anna Moisala, Unto Tapper, Jorma Jokiniemi, Esko Kauppinen (Corresponding Author)

Research output: Contribution to journalArticleScientificpeer-review

18 Citations (Scopus)

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 languageEnglish
Pages (from-to)43-52
JournalJournal of Nanoparticle Research
Volume4
Issue number1-2
DOIs
Publication statusPublished - 2002
MoE publication typeA1 Journal article-refereed

Fingerprint

Titanium Dioxide
Crystallization
titanium oxides
Titanium dioxide
Nanoparticles
Gases
crystallization
vapor phases
nanoparticles
Crystals
Aerosols
Particle size
Interfacial energy
Crystal
Electron microscopy
Particles (particulate matter)
anatase
Aerosol
Particle Size
Titanium

Keywords

  • aerosol decomposition
  • titanium dioxide
  • nanoparticles
  • anatase
  • crystallization
  • crystal morphology

Cite this

Ahonen, Petri ; Moisala, Anna ; Tapper, Unto ; Jokiniemi, Jorma ; Kauppinen, Esko. / Gas-phase crystallization of titanium dioxide nanoparticles. In: Journal of Nanoparticle Research. 2002 ; Vol. 4, No. 1-2. pp. 43-52.
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Gas-phase crystallization of titanium dioxide nanoparticles. / Ahonen, Petri; Moisala, Anna; Tapper, Unto; Jokiniemi, Jorma; Kauppinen, Esko (Corresponding Author).

In: Journal of Nanoparticle Research, Vol. 4, No. 1-2, 2002, p. 43-52.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Gas-phase crystallization of titanium dioxide nanoparticles

AU - Ahonen, Petri

AU - Moisala, Anna

AU - Tapper, Unto

AU - Jokiniemi, Jorma

AU - Kauppinen, Esko

PY - 2002

Y1 - 2002

N2 - 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.

AB - 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.

KW - aerosol decomposition

KW - titanium dioxide

KW - nanoparticles

KW - anatase

KW - crystallization

KW - crystal morphology

U2 - 10.1023/A:1020180920799

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M3 - Article

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JF - Journal of Nanoparticle Research

SN - 1388-0764

IS - 1-2

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