TITLE:
Study of Chromium-Lead-Phosphate Glasses by XRD, IR, Density and Chemical Durability
AUTHORS:
Radouan Makhlouk, Nadia Beloued, Said Aqdim
KEYWORDS:
Chemical Durability, Phosphate Glasses, Chromium Oxide, IR, XRD, SEM, Nu-clear and Chemical Wastes
JOURNAL NAME:
Advances in Materials Physics and Chemistry,
Vol.8 No.6,
June
29,
2018
ABSTRACT: Glasses
in the ternary system Cr2O3-PbO-P2O5 were prepared by direct melting of the mixture with stoichiometric proportions
of the reagents Cr2O3, PbO and (NH4)2HPO4 at 1080℃. The glasses obtained are transparent in
colour and have a non-hygroscopic appearance. The study of the dissolution rate
was carried out on ternary glasses xCr2O3-(45-x)PbO-55P2O5 with (1 ≤ x ≤ 4; mol%), immersed in distilled water at 90℃ for 24 days, indicating a maximum of chemical durability when the level of chromium oxide passed
through 2 mol%. Both, IR spectra and X-ray diffraction have indicated the
predominance of metaphosphate or cyclic metaphosphate groups with some traces
of isolated orthophosphate groups when the Cr2O3 content
is equal to x = 2. Analysis of the density values also, has showed
a maximum density for x = 2 mol%. The covalent radius values of oxygen have indicated that the minimum value rcal (O2–) is observed for x = 2 mol%
and therefore a relatively high reinforcement of the metal-oxygen-phosphorus
(Cr-O-P) bonds. SEM Micrographs have exhibited two phases, a vitreous phase and
a crystalline phase. The radical change in the structure from ultraphosphate Q3 groups to ring metaphosphate Q2 and orthophosphate groups Q0 seems
to be the cause of the formation of crystallites. Beyond 2 mol% of Cr2O3,
the structure of the glass changed
relatively and the orthophosphate phases increased to the detriment of the
metaphosphate phases. We observed a decrease in chemical durability. However,
it was confirmed that the dissolution rate (DR) of the S2 analysed compound is comparable to the values of borosilicate glasses which are
used as alternative materials for the immobilisation of nuclear waste
substances.