Synthesis and characterization of chromium spinels as potential electrode support materials for intermediate temperature solid oxide fuel cells

Kinetics Oxidation and Characterization of Cyclically Oxidized Layers at High Temperatures for FeMnSiCrNiCe and FeSiCrNi Alloys

“…Secondly, in cerium presence, the oxidation mechanism can change, decreasing cation diffusivity across oxide layer, and promoting oxide layer increase only by anion diffusion 26 , also observed to other rare earths additions 18 . Finally, as Mn oxides and Cr-Mn spinel are p-type semiconductor 9,27 and as the Mn and Cr assume Mn +3 , Mn +2 and Cr +3 valences 28 , the addition of cerium, presenting Ce +4 valence, according to Wagner-Hauffe rules should increase the oxidation rate 29 . On the other hand, some spinels can change to a n-type conductor behavior when doped of other specimens, as the case of Mg 1,5 27,30 .…”

“…Finally, as Mn oxides and Cr-Mn spinel are p-type semiconductor 9,27 and as the Mn and Cr assume Mn +3 , Mn +2 and Cr +3 valences 28 , the addition of cerium, presenting Ce +4 valence, according to Wagner-Hauffe rules should increase the oxidation rate 29 . On the other hand, some spinels can change to a n-type conductor behavior when doped of other specimens, as the case of Mg 1,5 27,30 . Rare earth and NiO additions in Cr 2 O 3 forming steel also changed the conduction of this oxide from p-type to n-type in low oxygen pressures, reducing the mass gain during high temperature oxidation 31 .…”

Mössbauer studies of spinellides of Mg(FeXCr2-X)O4 system obtained by the hydroxide co-precipitation method

“…The wide range of properties determine their use in production of electrodes [1][2][3], as catalysts [4,5], adsorbents [6] of materials with high resistance and low losses in the long-wave part of SHF range [7], etc.…”

“…Special features of complexing processes involving polymeric ligands of the crosslinked structures are related to their cooperative nature [3]. Cooperative nature of complexites manifests itself in various interactions of functional groups in the polymer chain, its configuration and supramolecular changes, determining the conformation of matrix of a polymer and groups.…”

“…Cooperative nature of complexites manifests itself in various interactions of functional groups in the polymer chain, its configuration and supramolecular changes, determining the conformation of matrix of a polymer and groups. In other words, in such systems, the primary balance, a heterogeneous chemical reaction of formation of supramolecular complex compounds between polymer groups and metal ions, is accompanied by the above-mentioned so-called "polymeric effects" [3]. The latter influence physical-chemical characteristics of HMCC and are the reason why their properties differ from analogous properties of low molecular complex compounds (LMCC) [2].…”