Zeolitic behaviour of water in a new WO

In pyrochlore WO3 water has a zeolitic behaviour which has been studied by TGA and DSC. The evaluated enthalpy change for dehydration is in the range 4-5 kcal.mole–1. This value is discussed in relation with the pyrochlore WO3 structure and related to the 3D system of intersecting empty tunnels

Characterization of transparent conducting pulsed laser deposited films in the Indium Zinc Oxide system

Thin films of indium zinc oxide so called IZO were prepared with pulsed laser deposition. It was found that the crystalline structure, the composition and the morphology of the films as well as the optical and electrical properties were quite sensitive to the deposition conditions namely to the temperature and oxygen pressure. The crystallinity of the ZnkIn2O3+k (k from 1 to 5) thin films increases as the substrate temperature increases. An average transmittance of 85% in the visible region was obtained for any k values. Optical measurements show a continuous decrease of the band gap as the zinc amount increases. The highest conductivity reported is for the ZnIn2O4, thin films deposited at 300°C (σ = 1.2 103 S/cm). Increasing the amount of Zn (i.e. k value) was found to result in a conductivity decrease. Finally, a good correlation between the electric mobility and the optical mobility is obtained

A combined multi-technique in situ approach used to probe the stability of iron molybdate catalysts during redox cycling

A setup combining a number of techniques (WAXS, XANES and UV–Vis) has been used to probe the stability of an iron molybdate catalyst during redox cycling. The catalyst was first reduced under anaerobic methanol/helium conditions, producing formaldehyde and then regenerated using air. Although in this test-case the catalyst and conditions differ from that of a commercial catalyst bed we demonstrate how such a setup can reveal new information on catalyst materials. In particular we observe the formation of two phases during reduction; one which we propose to be an oxygen deficient ‘pseudo-molybdate phase’, the other a molybdenum carbide-like phase, both produced as oxygen is removed from the catalyst. Standard in situ techniques could detect such transient phases, however, the information from multiple techniques, allows us to more accurately identify the nature of these materials and to carry out appropriate complementary ex situ measurements to aid in the analysis. This and similar setups therefore offer a way to more quickly and accurately observe reaction pathways within a catalyst, which may for example, result in the deactivation of the material by different routes to those observed previously. Additionally, the specific combination of these techniques with on-line mass spectrometry, allows us to monitor the activity of the catalyst surface and here observe that different catalytic mechanisms may occur during different stages of the redox process. Therefore this setup should allow for the observation of many novel variations in a catalyst’s reactivity, leading to the improvement of current and development of new materials