ISSN:
1573-9171
Schlagwort(e):
technetium
;
aluminum oxide
;
paramagnetic centers
;
ESR
;
adsorption
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
Notizen:
Abstract An investigation was made into the nature of paramagnetic centers in a Tc/Al2O3 system under varying conditions as to heat treatment and technetium content, and in O2 and CO adsorption environments. It was found that in the case of reduction at 573 K Tc2+ ions and, conceivably, other ionic forms developed and stabilized on the carrier surface. After reduction at 973 K two types of electron center appeared, whose concentration increased as reduction was prolonged. Signals were observed in the low fields (3–20 mT) of the ESR spectra having g1 ≈ 13.5 and g2〉30, which could be assigned to free charge carriers in a cluster of metal atoms or ions. Adsorption of O2 at 300 K caused O 2 − ion radicals to form on the surface of the reduced Tc/Al2O3 samples, both electron centers and technetium ions constituting the electron donors. In the case of CO adsorption paramagnetic (CO) 2 − particles appeared on the Tc/Al2O3 samples after prolonged exposure. On reaction with O2 two types of O 2 − ion-radical with differing thermal stability were formed.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00863566
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