ATTENTION !!! SEMINAIRE ANNULE !!! A sapphire single-crystal cell for in situ neutron powder diffraction of solid-gas reactions
Mardi 7 juin 2016 14:00
- Duree : 1 heure
Lieu : ILL 4, Seminar Room (no 163), 71 avenue des Martyrs - Grenoble
Orateur : Holger KOHLMANN (Universität Leipzig - Institut für Anorganische Chemie - Leipzig - Germany)
Reaction pathways in solid state chemistry are often not well investigated and thus rational synthesis planning of new compounds is hardly possible. Identifying and characterizing intermediate phases by in situ studies can be very useful in this regard. In order to investigate time-resolved solid-gas reactions we have constructed a gas pressure cell for elastic neutron diffraction. By proper orientation of a single-crystal sapphire tube as sample holder Bragg peaks from the container material can be completely avoided, thus yielding high quality powder diffraction data with very clean diffraction background and enabling the extraction of high precision crystal structure data. Gas pressures up to 30 MPa (hydrogen and inert gases) may be applied and heating is provided by a two sided laser heating system.
The potential of the gas pressure cell is demonstrated by in situ studies of the reaction of solids with hydrogen, hydrous inert gas or gaseous ammonia, which yield detailed models of the reaction pathways. These were used to successfully predict the existence of further metal hydrides, to explain unusual bonding properties in Zintl phase hydrides, and to optimize the synthesis of metastable metal nitrides and oxides.
Contact : dubouloz@ill.fr
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