Chromite spinels

An example [59] for chromite spinels, where the EEL spectra are measured at different incident beam orientations and under strong localization conditions, is shown in Figure 7a. For orientation (a) the octahedral sites were selectively enhanced. For orientation (b) the tetrahedral sites are selected. However, because of the superior energy resolution of EELS ( 1 eV), it is possible also to detect changes in oxidation states by the small chemical shifts observed in the onset of the core-loss... 

Figure 7a. EEL spectrum of a chromite spinel under different incident beam orientations showing enhancement for the octahedral (a) and tetrahedral (b) sites. The position of the detection aperture to achieve enhanced localization for the low energy O-K edges is shown in the insert...

A successful catalyst development in the last few years has made possible the direct hydrogenation of fats to fatty alcohols in a one-stage process. The laborious transesterification of the the fats can be dispensed with. Beside the high-quality coconut and palm oils, lower quality, acid-containing fats and oils can now be hydrogenated by using new acid-stable copper chromite spinel catalysts. 

Regarding ceramic-containment materials," sihca, SiO, and alumina, Al O, are strongly attacked and hence readily dissolve in liquid lithium. By contrast, alkaline-earth oxides such as beryllia (BeO), magnesia (MgO), and calcia (CaO) and rare-earth oxides such as ceria (CeOJ, yttria (YfiJ, chromite spinel (FeCr OJ, and yttrium aluminum garnet (Y AljOj ) seem to be noncorroded below 500 C, while aluminum, titanium, and zirconium nitrides or... 

The stability of the titanate spinels has been discussed in the previous chapters. The chemistry of the chromite spinels has been reviewed by Ulmer (1971). Experimental data with direct bearing on lunar petrology have been presented by Muan et al. (1972)... 

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