Bypass cement dust from the Rabigh plant in Saudi Arabia was examined for use in the preparation of technical coloured glass and glass ceramic materials. The bypass cement dust made up about 57 wt-% of the batch constituents, depending on composition. The bypass composition was sometimes modified by additions of other ingredients such as silica sand, granite and magnesite. Batches were melted and then cast into glass, which was subjected to heat treatment to induce crystallisation. Techniques including differential thermal analysis, polarising light microscopy, X-ray diffraction and indentation microhardness testing were then applied. The obtained coloured glass and glass ceramic materials possess very high hardness, indicating high abrasion resistance, and making them suitable for many applications under aggressive mechanical conditions.
Transparent glasses were prepared from processed nepheline syenite-magnesite mixtures. Incorporation of TiO 2 in the base glasses changes the glass colour from white to amber or dark brown. Translucent porcelainous glass ceramics with white, creamy and a variety of bluish colorations were obtained in glasses containing non-magnetic nepheline syenite. However, dark marblelike glass ceramics were developed in glasses containing middling and tailing nepheline syenite. Aluminium diopside [Ca(Mg,Al)(Si,Al) 2 O 6 ], nepheline, forsterite, magnesium titanate MgTi 2 O 5 and hematite were developed by heat treatment of these glasses. SEM micrographs tend to show fine and uniform bulk with increasing Fe 2 O 3 contents in the parent glass ceramic samples, however addition of TiO 2 enhances nucleation and the microstructure becomes of evenly good uniform fine structure in the sample with lowest iron content.
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