Papers by Author: M.A. Karakassides

Abstract: In the light of environmental perspective, clay minerals attract special interest because of their capability to absorb and chemically stabilize heavy metals in their structure [1, 2]. The absolute suppression of heavy element leakage from clay structures to the environment, which is obviously a strict demand, can be achieved with clay vitrification. This work is related to the influence of the addition of (0-50 wt%) of montmorillonite to a borate glass with composition of 0.33Na2O-0.67B2O3 on its structure. This influence has been studied with Raman and FT-IR spectroscopies, Archimedean density measurements, chemical durability in 90°C water and finally by studying of the ultrasonically measured elastic properties, such as Young’s and shear modulus and Poisson’s ratio, of the resultant glasses. The experimental results showed that the glass structure is predominantly comprised from tetrahedral and trigonal borate units and silicon and/or aluminium tetrahedral units. The results of density and chemical durability are fairly well correlated with structure. Higher amounts of montmorillonite lead to glasses of higher mechanical strength and chemical durability.

Abstract: Bioglass films were prepared by reactive magnetron sputtering from a 45S5 target and than annealed in air up to 550 oC in order to relax the mechanical stresses. The mixtures (0, 7 and 15%) of oxygen and argon were used in order to modify the films stoichiometry. Morphological and compositional studies were performed by SEM coupled with an EDAX system. FTIR and micro Raman measurements were performed in order to investigate the molecular vibrations of the BG structure. A modified composition respect to the target one was found for all the films, with lower silicon dioxide concentrations. The films displayed rough surfaces with spherical particles of 10-20 μm diameter embedded in the surfaces. The Raman results evidenced important carbonate lines besides the silica-phosphate bands.