Investigation on the Oxidation State and The Behaviour of Molybdenum in Silicate Glass
- PDF / 405,621 Bytes
- 10 Pages / 420.48 x 639 pts Page_size
- 68 Downloads / 198 Views
INVESTIGATION ON THE OXIDATION STATE AND THE BEHAVIOUR OF MOLYBDENUM IN SILICATE GLASS ANETTE HORNEBER+* , BOUBACAR CARA•A ** AND WERNER LUTZE++ Institut fOr Werkstoffwissenschaften III, Universitat Erlangen-N0rnberg, Martensstr. 5, D 8520 Erlangen; ++Hahn-Meitner-Institut fur Kernforschung Berlin GmbH., Glienicker Strale 100, D 1000 Berlin 39
INTRODUCTION Knowledge about the oxidation state of molybdenum in glasses and glass ceramics
which contain nuclear waste is
important because of the danger of forma-
tion of water-soluble Cs-molybdate with Cs-137. haviour of molybdenum in tigated
In a previous paper , the be-
glasses with and without fission products was inves-
with the aid of ESR and optical spectroscopy.
The present paper con-
tinues this investigation and deals with the following aspects: 1) Oxidation state of Mo when organic reducing agents, formaldehyde,
i.e. formic acid,
tannic acid, are added to the batch.
2) Dependence of Mo "solubility" on the melting atmosphere. 3) Behaviour of the different oxidation states of Mo depending on the temperature and the basicity of the glass. 4)
Redox interaction of Mo with Fe, Cr and Ti.
EXPERIMENTAL PROCEDURE Glasses of the composition 74 % Si0 2 , and different amounts of MoO 3 , Fe 2 0 3 , glasses had Cs 2 0 instead of Na9 O,
20 % Na 2 0, 6 % CaO , mass fractions,
Cr 2 0 3 and TiO2 were investigated.
substituted on a molar basis,
Some
so as to deter-
mine the influence of the basicity of the glass on the oxidation state of Mo. Some phosphate glasses were investigated as welli in order to-allow a comparison. Rock crystal was used as raw material for SiO
The other substances were
p.a. quality. The glasses to be melted under reducing conditions were mixed with the adequate amount
of tannic acid. Melting took place in corundum cru-
cibles in an electric furnace at 1673 K for 4 h. each other were melted simultaneously, ditions. For the ESR, Present address:
Glasses to be compared with
so as to achieve identical melting con-
the samples were ground,
screened, and 100 mg of the
*) Verlag Schmid, D 7800 Freiburg i.Br., und Fasern AG., D 7122 Besigheim
and **)
BASF Farben
280 fractions of 0.6 to 1 mm in diameter were used for each measurement. tra were recorded with the X-band Spectrometer 414 (Bruker Physik). urements were made at 298 K.
The specThe meas-
For the -optical spectra, polished plates were
used.
RESULTS AND DISCUSSION State of Mo in
silicate glass
Molybdenum can occur in different oxidation states in being Mo (VI).
In
the assumption was made,
3
(d , s = 3/2 or s'
glass, the most stable
that besides Mo (VI),
Mo (III)
= 1/2)
was present depending on the concentration of MoO 3 and on the melting atmosphere. The possibility of Mo (V) (d 1 , s = 1/2) being present was not excluded. ined
In
the present work these investigations are exam-
again with an increased range of MoO 3 concentration.
Glasses melted under oxidizing conditions remain colourless. At an MoO 3 content of less than 0.4 %, no ESR spectrum was observe
Data Loading...
