Unformatted text preview: e thermal
conductivity of the gases is listed in Table 7. Tab. 7: Thermal conductivity of relevant gases .
Gas Thermal conductivity (λ) at 120°C [(Cal· s-1· cm-1· °C-1)x10-6] Ar 45.46 H2 471.11 H2O 46.70 He 376.07 O2 68.19 2.5. In-situ reduction combined with high temperature XRD In-situ reduction experiments employing high temperature XRD were performed at
temperature steps chosen on the results of the TPR experiments. Additionally XRD 2. Experimental 59 ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffifffffffffffffffffffffffffffffffffffff
spectra were also recorded at room temperature before and after the completed
reduction to compare the spectra before and after the reduction process without
distortions of the 2Θ values of the reflections and the height of the amplitudes due to
the temperature differences at the recording. The set up consisted of a high temperature camera (Anton Paar, Austria) in
combination with a Philips diffractometer PW3710 X’PERT, using CuKα radiation
(λ=0.15418 nm). A range from 10° to 70° was investigated at a scanning speed of
0.020°/s for Ni30C900 and 0.010°/s for Ni72C900. The samples were placed on an
electrically heated Pt ribbon and kept throughout the experiments in a flow of the
reduction mixture (5 vol% H2/Ar, Linde). Both samples were heated up at a linear
heating rate of 5°C/min and cooled down at 10°C/min. The samples were scanned at
room temperature, at 300, 600 and 900°C and again after cooling down to room
temperature. During the scans the temperature was kept constant. 2.6. Temperature programmed desorption of CO2 For the temperature-programmed desorption of CO2 (TPD-CO2) the same set up was
employed as for the TPR experiments described above apart from two modifications.
CO2 (technical grade, Polgaz) was used as reactive gas and He as inert gas for
desorption. He (99.9999%, Praxair) was used because of the large difference of the
thermal conductivity of He and CO2, 376.07x10-6 and 43.81x10-6 (Cal· s-...
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