1,720,971 research outputs found
A new test to characterise low voltage cables subjected to thermal and mechanical stressesAnnual Report Conference on Electrical Insulation and Dielectric Phenomena
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Effect of preparation method on activity and stability of LaMnO3 and LaCoO3 catalysts for the flameless combustion of methane
Full text linkA set of LaMnO3 and LaCoO3 catalysts was prepared through different synthesis procedures. The selected techniques included the sol-gel method, flame hydrolysis from aqueous solution, complexation through EDTA and solid-state reaction. The last was accomplished through reactive grinding by ball-milling either in a vibration mill or in a planetary mill. EDTA complexation was applied for LaCoO3 only and did not improve significantly catalyst activity or stability, with respect to other techniques. Ball-milling never allowed obtaining a pure perovskitic phase, at least under the most energetic grinding conditions permitted by our apparatus. The highest activity for the catalytic flameless combustion of methane was obtained with the sol-gel prepared samples, though thermal resistance revealed insufficient for high temperature applications. A bit lower activity, but coupled with good thermal stability was obtained with the samples prepared through flame hydrolysis
NLO Polymers and Optical Waveguides based Thereon
No full textNLO Polymers and Optical Waveguides based Thereo
Catalytic combustion of methane on LaBO3 (B=Mn, Co): Effect of catalyst preparation route
No full textThe catalytic combustion of methane has ben studied over LaBO3 typer perovskites. This work, in collaboration with Pirelli Labs, aimed at the comparison of different preparation methods for such samples to impart activity and thermal stability. The innovative use of mechanochemical synthesis through ball milling was compared with flame hydrolysis and sol gel
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
La1-x A ' xCo1-yFe (y) O-3 +/-delta (A ' = Ce,Sr) catalysts for the flameless combustion of methane
No full textA set of La1-x A' (x) Co1-y Fe (y) O-3 +/-delta samples (A'= Ce,Sr; x= 0.1, 0.4, y= 0, 0.5, 0.8, 1) was prepared by means of the sol-gel citrate method and characterised through X-ray diffraction (XRD), N-2 adsorption/desorption and temperature programmed desorption-reduction (TPD-TPR). Their activity for the catalytic flameless combustion of methane was tested and the results interpreted focusing on the effect of doping at A and/or B position. It was found that Ce doping of lanthanum ferrite catalysts could suppress suprafacial activity and slightly enhance intrafacial activity, due to the change of oxygen mobility. However, catalytic activity seems independent of the type of electronic conductivity (p- or n-type), the activity of an analogously Sr-doped sample being similar to that of the Ce-doped one. Mixed B-metal composition can help in modulating both oxygen mobility and catalyst stability under reducing reaction conditions. High Fe content allows to optimise this last parameter. However, depression of oxygen mobility and hence of activity has to be prevented by proper doping at A-position
Percolative Small-polarons conduction regime in Ce1-xGdxO2-x/2, probed by the EPR spectral intensity of Gd3
No full textEPR analysis is carried out with Ce1 xGdxO(4 x)/2 (x=0.1; 0.2) nanopowders aimingat obtaininginformation about their
oxidation and reduction properties. The EPR spectrum of these systems is composed of a single feature. The first derivative peak-topeak
spectral intensity decreases at higher temperatures, but this trend deviates from that of Curie’s law with the x=0.1 sample, at
difference with the x=0.2 sample. This unexpected result is related to oxygen deficiency, due to gas–solid equilibrium, present in the
former sample only. As a consequence, some Ce3+ ions would form providingit with conduction electrons propagating as small
polarons in a percolative way. This would result in a thinner skin depth at higher temperatures, able to explain the deviation of the
spectral intensity from its expected value. Indeed, this deviation from Curie’s law is reduced or disappears at all after thermal
treatment of the x=0.1 sample with O2
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