Electrical conductivity of γ-Al2O3 at atmospheric pressure under dehydrating/hydrating conditions

Self Cite

Section: Resultsmentioning

confidence: 90%

Influence of the reactant gas on the electrical properties of alumina-supported tin dioxide catalysts

Scurtu¹,

Hornoiu²,

Căldăraru³

et al. 2011

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“…The conductivity measurements were carried out as a function of temperature/ atmosphere in operando conditions by using the differential steps technique (DST) and a reaction cell specially designed to allow the measurements in powder [21][22][23]. This cell consists of two coaxial tantalum cylinders as electrodes supported on a frit, embedded in a Pyrex glass tube and connected by tungsten wires, to a precision RLC bridge [24].…”

Section: The Methodsmentioning

confidence: 99%

“…2b demonstrates that the sample SnO 2 /B shows a drop of conductivity in the low temperature range. This can be attributed to the presence of the hydroxyl species in the interface domain [21][22][23] between the two oxides (since no such effect was evidenced for the support).…”

Section: The Methodsmentioning

confidence: 99%

Electrical and catalytic properties of SnO2/TiO2 measured in operando conditions

Munteanu

Căldăraru

Brătan

et al. 2011

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The electrical conductivity and the catalytic activity of SnO 2 loaded TiO 2 (anatase) particles were investigated in operando conditions. SnO 2 depositions over commercial TiO 2 samples (Sigma Aldrich and Rhone Poulenc) were obtained by the impregnation method. The samples were characterized by XRD, SEM/EDX and BET-N 2 adsorption techniques. The AC electrical conductivity of the samples were measured between 25 and 400°C under various atmospheres. The effect of the reactant mixture on the electrical conductivity and the catalytic performances of the samples were tested in propene oxidation. The results showed that the conductivity of SnO 2 /TiO 2 samples depends strongly on the surface area of TiO 2 support. The reducing effect of propene is more evident for higher surface area catalysts, these one showing also higher activity. On the other hand, the SnO 2 deposition results in an increase of catalytic performances.

“…The variation of AC electrical conductance G (nS) with temperature/atmosphere was measured in situ at 1592 Hz on catalyst powders (1.5 cm 3 , fraction between 0.25 and 0.5 mm), during linear heating (5°C/min) by using a special reaction cell [23] and the differential steps technique (DST) [23][24][25][26]. The DST consists of successive heating-cooling cycles performed on the same batch of sample in different atmospheres.…”

Section: Methodsmentioning

confidence: 99%

Surface evolution of the Sn–Ce–O powders in various atmospheres

Scurtu

Mihaiu

Căldăraru

et al. 2011

Self Cite

Tin and cerium based oxide ceramics, due to their peculiar properties, are good candidates for using as sensors, solid electrolytes in fuel cells, and catalysts. In the present work, Sn-Ce-O powders with the composition of interest for catalysis applications were obtained by solid state reactions and by thermal decomposition of the different tin and cerium precursors. The structural characterization of the resulted samples was performed by X-ray diffraction. Morphological characteristics were evaluated from X-ray microstructural parameters and BET surface areas measurements. Surface evolution of the studied powders was investigated by electrical measurements in various atmospheres in the 25-400°C temperature range. The samples studied behave as a n-type semiconductor. The catalytic activity for CO oxidation was measured in gas flow between 25 and 400°C. The conversion degree depends on the preparation method of the samples. Magnetic susceptibility measurements at room temperature of the samples before and after catalytic test indicated a paramagnetic behavior. Higher values of magnetic susceptibility of the samples after catalytic test compared to initial ones could indicate the influence of CeO 2 on the catalytic activity.