Crystallization of TiO2 nanotubes by in situ heating TEM

Alberto Casu*, Andrea Lamberti, Stefano Stassi, Andrea Falqui

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

The thermally-induced crystallization of anodically grown TiO2 amorphous nanotubes has been studied so far under ambient pressure conditions by techniques such as differential scanning calorimetry and in situ X-ray diffraction, then looking at the overall response of several thousands of nanotubes in a carpet arrangement. Here we report a study of this phenomenon based on an in situ transmission electron microscopy approach that uses a twofold strategy. First, a group of some tens of TiO2 amorphous nanotubes was heated looking at their electron diffraction pattern change versus temperature, in order to determine both the initial temperature of crystallization and the corresponding crystalline phases. Second, the experiment was repeated on groups of few nanotubes, imaging their structural evolution in the direct space by spherical aberration-corrected high resolution transmission electron microscopy. These studies showed that, differently from what happens under ambient pressure conditions, under the microscope’s high vacuum (p < 10−5 Pthe crystallization of TiO2 amorphous nanotubes starts from local small seeds of rutile and brookite, which then grow up with the increasing temperature. Besides, the crystallization started at different temperatures, namely 450 and 380 °C, when the in situ heating was performed irradiating the sample with electron beam energy of 120 or 300 keV, respectively. This difference is due to atomic knock-on effects induced by the electron beam with diverse energy.

Original languageEnglish (US)
Article number40
JournalNanomaterials
Volume8
Issue number1
DOIs
StatePublished - Jan 13 2018

Keywords

  • Amorphous-crystalline phase transition
  • Anodic oxidation
  • Electron beam effects
  • High resolution transmission electron microscopy
  • In situ transmission electron microscopy
  • TiO amorphous nanotubes

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Materials Science(all)

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