Production and Properties of Nanostructured Metal Oxide Particles

Abstract

Two fundamentally different procedures of metal oxide production, which provide nanometer‐sized oxide particles, are described here. Earthalkaline oxides, e.g., are produced by chemical gas phase deposition with MeO molecules (Me = Ca, Mg) and clusters being directly deposited after gas phase reaction between Me atomes and O2 molecules. The procedure also allows the dotation of MgO with a second component such as CaO and vice versa. In order to obtain information on surface properties like reactivity and surface composition, OH groups as probe species are produced on the surface of the resulting particles. The respective chemisorption as well as thermal desorption of OH groups are monitored by FT‐IR spectroscopy. X‐ray powder diffraction provides information on the bulk composition and bulk structure. Cu2O, on the other hand, is produced by deposition of Cu metal from the vapour and subsequent oxidation of the resulting solid particles, which are then characterized by X‐ray powder diffraction and UV/VIS spectroscopy.

Evidence for emission and transfer of energy from excited edge sites of MgO smokes by photoluminescence experiments

“…Moisture is suspected to deeply etch MgO surfaces in either forms, crystals [18] or smokes [5], and to profoundly perturb their reactivity through change in both surface structure [22] and donor properties of OH groups [1]. Indeed, after exposure of MgO smoke to water vapour and subsequent outgassing, increases in the I 4.6 /I 5.45 ratio [6] and in the intensity of the 2.7 eV contribution [12] were reported.…”

“…at the excitation energy related to 3C sites (see Refs. [5,8,9,11,12] and the discussion in Section. 4.2).…”

“…The common representation of high-area MgO surfaces [1,5,10] is based on the fact that the (1 0 0) face shows by far the lowest surface energy. This view certainly applies to the clean MgO smokes used herein.…”

“…Burning magnesium in air or oxygen produces smokes that mostly consist in small cubic particles showing nearly perfect (1 0 0) faces [4]. Although more complex chemical environment are found at the surface of high specific area samples produced by either chemical vapour deposition [5] or thermal decomposition of hydroxides or carbonates [4], MgO surfaces of any origin are generally assumed to only involve standard sites corresponding to bulk-terminated surfaces. Terraces, steps and kinks are classified in function of their coordination number (five-, four-and three-coordinated sites, i.e.…”

Ozonide ions on the surface of MgO nanocrystals

“…All experiments were performed with MgO powder obtained from the gas phase reaction of Mg (Johnson Matthey, 99.98%) and O 2 (Messer Griessheim, 99.998%) in a CVD system [43][44][45]. The sample was contained in an EPR tube attached to a high vacuum pumping stage providing a base pressure of <10 )6 mbar.…”