Mo sulfide thin films were cathodically electrodeposited onto glassy carbon electrodes (GCE) from aqueous electrolytes containing 10 mM (NH 4) 2 MoS 4 and 0.2 M KCl. Film adhesion was adequate only for electrodes pretreated by potential cycling in 1.0 M HNO 3 and 0.1 M NaF to enhance the surface roughness and partially oxidize the GCE. Previous studies report direct cathodic electrodeposition of MoS 2 , but energy dispersive x-ray spectroscopy and x-ray diffraction suggest that the as-deposited film is closer in stoichiometry to MoS 3 , which can be converted to MoS 2 by annealing in Ar at 600°C for one hour. The charge storage capability of electrodeposited Mo sulfide films is studied here for the first time in 1.0 M Na 2 SO 4 over the thickness range 50 nm to 5 µm, and before and after high temperature annealing. The highest
Oxyfuel coal combustion, where coal is burned in oxygen instead of air, offers the potential for simplified CO2 sequestration, since the flue contains little N2 and is mainly CO2. However, the widespread use of flue gas recycling to dilute the pure oxygen feed stream exacerbates corrosion problems in the furnace and boiler tubes by increasing the concentrations of SO2, SO3, HCl, and H2O. In addition, the dew point temperature is raised, making condensation of H2O, H2SO4 and H2SO3more likely during downtime. P91 steel, which contains ~8.4% Cr, 0.9% Mo and 2.2% V, is are widely utilized for high temperature applications in the power industry due to its increased creep strength. However, Cr-containing steels are susceptible to failure in H2O-containing oxidizing environments due to formation and volatilization of compounds such as CrO2(OH)2. We report the formation of Ti and Zr diffusion coatings atop high creep strength steels to improve their corrosion resistance. Ti coatings 10-30 µm thick can be formed on P91 steel by pack cementation at 1000°C in flowing Ar. Similarly, Zr coatings 10-30 µm thick can be formed by pack cementation at 1080°C. The composition as a function of position for both Ti and Zr diffusion coatings is studied as a function of position by scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDX). This demonstrates formation of an inter-diffusion zone, with no sharp interface exists between coating and substrate, which may help limit delamination. Results will also presented for thermogravimetric analysis (TGA) of both Ti and Zr coatings on P91 steel in gas mixtures that contains 5% N2, 70% CO2, 2% CO, 0.3% SO2, 21.7% H2O, 1% O2, and trace levels of HCl.
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