Journal of Materials Science

, Volume 48, Issue 7, pp 2893–2907

Reduction of nickel oxide particles by hydrogen studied in an environmental TEM

  • Q. Jeangros
  • T. W. Hansen
  • J. B. Wagner
  • C. D. Damsgaard
  • R. E. Dunin-Borkowski
  • C. Hébert
  • J. Van herle
  • A. Hessler-Wyser
Energy Materials & Thermoelectrics

DOI: 10.1007/s10853-012-7001-2

Cite this article as:
Jeangros, Q., Hansen, T.W., Wagner, J.B. et al. J Mater Sci (2013) 48: 2893. doi:10.1007/s10853-012-7001-2

In situ reduction of nickel oxide (NiO) particles is performed under 1.3 mbar of hydrogen gas (H2) in an environmental transmission electron microscope (ETEM). Images, diffraction patterns and electron energy-loss spectra (EELS) are acquired to monitor the structural and chemical evolution of the system during reduction, whilst increasing the temperature. Ni nucleation on NiO is either observed to be epitaxial or to involve the formation of randomly oriented grains. The growth of Ni crystallites and the movement of interfaces result in the formation of pores within the NiO grains to accommodate the volume shrinkage associated with the reduction. Densification is then observed when the sample is nearly fully reduced. The reaction kinetics is obtained using EELS by monitoring changes in the shapes of the Ni L2,3 white lines. The activation energy for NiO reduction is calculated from the EELS data using both a physical model-fitting technique and a model-independent method. The results of the model-fitting procedure suggest that the reaction is described by Avrami models (whereby the growth and impingement of Ni domains control the reaction), in agreement with the ETEM observations.

Supplementary material

10853_2012_7001_MOESM1_ESM.pdf (1 mb)
Supplementary Figure: Irradiation damage observed in the ETEM. a Creation of a Ni3O4 superstructure upon introduction of H2 gas into the ETEM when performing HRTEM. b Anisotropic erosion of NiO at a dose rate of ~ 8000 e nm−2 s−1 at a temperature of 365 °C. c Carbon encapsulation during NiO reduction at 500 °C. d Formation of Au nanoparticles on the SiO2 film at 600 °C. (PDF 1075 kb)

Copyright information

© Springer Science+Business Media New York 2012

Authors and Affiliations

  • Q. Jeangros
    • 1
  • T. W. Hansen
    • 2
  • J. B. Wagner
    • 2
  • C. D. Damsgaard
    • 2
  • R. E. Dunin-Borkowski
    • 3
  • C. Hébert
    • 1
  • J. Van herle
    • 4
  • A. Hessler-Wyser
    • 1
  1. 1.Interdisciplinary Centre for Electron MicroscopyEcole Polytechnique Fédérale de LausanneLausanneSwitzerland
  2. 2.Center for Electron NanoscopyTechnical University of DenmarkLyngbyDenmark
  3. 3.Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg InstituteJülich Research CentreJülichGermany
  4. 4.Industrial Energy Systems LaboratoryEcole Polytechnique Fédérale de LausanneLausanneSwitzerland

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