• YASSER B SADDEEK

      Articles written in Bulletin of Materials Science

    • Fabrication and physical characteristics of new glasses from wastes of limestone and phosphorite rocks

      YASSER B SADDEEK K A ALY RABIE S FARAG M A M UOSIF K H S SHAABAN

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      In this work, new glasses were synthesized from wastes of limestone and phosphate rocks besides commercial borax. The glasses were characterized by FTIR, DTA, ultrasonic techniques and UV spectroscopy. It was found that the concentration of both CaO and P$_2$O$_5$ increases and the concentrations of B$_2$O$_3$ and Na$_2$O decrease as the content of phosphate rocks increases. Variation of the contents of the different oxides affects the concentration of the structural units constituting the glass, which was indicated by the behaviour of the fraction N$_4$ of BO$_4$ units in the borate matrix. The density and the refractive index of the glasses decrease as the CaO and P$_2$O$_5$ contents increase, which was attributed to the increase of [BO$_3$] structural units. On the other hand, the physical parameterssuch as the ultrasonic velocity, the elastic moduli, the optical bandgap and the optical polarizability increased, which was attributed to the higher coordination number of CaO$_6$ compared with the coordination of borate structuralunits and to the former effect of P$_2$O$_5$. As a result, a polymerization of the total co-ordination number of the glass, crosslink density and connectivity within the glass network will occur.

    • Ultrasonic and structural features of some borosilicate glasses modified with heavy metals

      YASSER B SADDEEK

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      A quaternary glass system Na$_{1.4}$B$_{2.8}$Si$_x$Pb$_{0.3−x}$O$_{5.2+x}$, with $0 \lt x \lt 0.3$, was prepared and studied by Fourier transform infrared spectroscopy, density and ultrasonic techniques to debate the issue of the role of SiO2 in the structureof lead alkali borate glasses. The results indicate that SiO2 generates an abundance of bridging oxygen atoms, [BO$_4$] and [SiO$_4$] structural units and changes the bonds B–O–B and Pb–O–B to Si–O–Si and B–O–Si. The latter bonds have higher bond strength and higher average force constant than the former bonds. Therefore, the glass structure becomes contractedand compacted, which decreases its molar volume and increases its rigidity. This concept was asserted from the increase in the ultrasonic velocity, Debye temperature and elastic moduli with the increase of SiO2 content. The present compositional dependence of the elastic moduli was interpreted in terms of the electron–phonon anharmonic interactions and the polarizationof Si$^{4+}$ cation. A good correlation was observed between the experimentally determined elastic moduli and those computed according to the Makishima–Mackenzie model.

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