Microscopy and Microanalysis



Materials Applications

Interaction of Oxide Surfaces with Water: Environmental Transmission Electron Microscopy of MgO Hydroxylation


Marija  Gajdardziska-Josifovska  a1 c1 and Renu  Sharma  a2
a1 Department of Physics and Laboratory for Surface Studies, University of Wisconsin–Milwaukee, Milwaukee, WI 53201, USA
a2 Center for Solid State Science, Arizona State University, Tempe, AZ 85287, USA

Article author query
gajdardziska-josifovska m   [PubMed][Google Scholar] 
sharma r   [PubMed][Google Scholar] 

Abstract

Environmental transmission electron microscopy (ETEM) is opening an important window for in situ studies of interaction of water with oxides. Studies of MgO smoke nanocrystals under partial pressures of water ranging from 10 mTorr to 10 Torr found their {100} neutral surfaces to be extremely resistant to dissociative adsorption of water and hydroxylation, in agreement with recent theoretical predictions. ETEM observations of electron irradiation driven MgO smoke nanocrystal hydroxylation displayed the anticipated volume expansion, but revealed complex shape changes with elongations toward oxide corners. The reaction rate was found to increase with electron flux at constant water pressure. In situ selected area diffraction studies of MgO single crystals showed that the hydroxide grows with its basal (0001) plane parallel to the polar MgO (111) planes. This is the same crystallographic relationship as in dehydroxylation experiments, but with four variants. Electron energy loss spectroscopy found oxygen K-edge changes consistent with bulk hydroxylation.

(Received September 15 2004)
(Accepted February 4 2005)


Key Words: ETEM; MgO; Mg(OH)2; hydroxylation; in situ.

Correspondence:
c1 Corresponding author. E-mail: mgj@csd.uwm.edu