Farbe und Konstitution bei anorganischen Feststoffen. VIII [1] A. Spektralphotometrische Ermittlung der Kationenverteilung im nickelhaltigen Magnesiumaluminiumspinell

Abstract

Durch eine spektralphotometrische Untersuchung des Systems NixMg1‐xAl2O4 wird festgestellt, daß sich auch bei kleinen Nickelkonzentrationen (x = 0, 01) Ni2+ nicht nur auf Oktaeder‐, sondern auch auf Tetraederplätzen befindet. Durch einen Vergleich der Spektren von NixZn1‐xO (x = 0, 01; I), NixMg1‐xO (x = 0, 1; II) und NixMg1‐xAl2O4 (x = 0, 01 und 0, 1; III) ergibt sich, daß bei den Übergängen I → III und II → III die Hauptabsorptionsmaxima von [Ni2+]4 und [Ni2+]6 nach UV verschoben werden, bedingt durch eine Zunahme des jeweiligen Feldstärkeparameters Dq. Gleichzeitig nimmt auch der die interelektronische Abstoßung berücksichtigende Racah‐Parameter B für [Ni2+]4, nicht aber für [Ni2+]6 zu.

The Effect of Transition Alumina (γ‐, η‐, χ‐Al2O3) on the Activity and Stability of Chromia/Alumina Catalysts. Part II: Industrial‐Like Catalysts and Real Plant Aging Conditions

“…Figure b shows such a function constructed for our catalysts with these assumptions. The boundary values for the curve are 16 600 and 17 550 cm −1 for 0% (α‐Cr 2 O 3 ) and 100% (α‐(Cr 0.2 Al 0.8 ) 2 O 3 ) insertion, respectively. It is seen that the Cr 2 O 3 ‐into‐Al 2 O 3 insertion degree increases in the order Cr 2 O 3 /η‐Al 2 O 3 < Cr 2 O 3 /γ‐Al 2 O 3 < Cr 2 O 3 /χ‐Al 2 O 3 , revealing that the η‐Al 2 O 3 ‐based catalyst is the least deteriorated, in agreement with the textural and XRD data.…”

“…Industrial dehydrogenation conditions induced great changes in the catalysts’ phase composition: the patterns of parent aluminas and α‐Cr 2 O 3 are greatly reduced while new reflections developed. These reflections are from the crystallites isomorphous to α‐Al 2 O 3 (JCPDS 00‐046‐1212) and belong to α‐(Cr x Al 1− x ) 2 O 3 , where x is around 0.13–0.20, as may be judged from experimental lattice parameters (Table 1SI, Supporting Information) a and c (R c ) and from the literature data on the dependence of lattice parameters on x . In chemical terms based on XRD data, the aging of the dehydrogenation catalyst may be written as in Equation . …”

Temperature resistant red and purple ceramic pigments based on the solid solution series BaZn2−xNixSi2O7 and BaMg2−xNixSi2O7

“…The colour of inorganic pigments is mainly affected by the ligand field, generated by the ions surrounding the chromophore [26]. This field depends on various parameters such as the coordination of the chromophore and the surrounding ions and the distances between these ions [27,28].…”