EFFECT OF THE IRON OXIDE CONTENT ON THE STRUCTURE AND ALKALI RESISTANCE OF GLASS FIBRES PREPARED FROM RED MUD

In this work, glass fibres with red mud, as the main raw material, were prepared. The effect of the iron oxide content on the structure and alkali resistance of the glass fibres was studied by XPS, FT-IR, DSC, SEM-EDS, while the tensile strength and mass loss rate in alkali corrosion were also analysed. The results showed iron existed mainly in the form of Fe3+. The network polymerisation degree of the glasses decreased as the SiO₂/Fe₂O₃ mass ratio (Si/Fe) decreased, which caused a significant reduction in the Tg and the thermal stability parameter ΔT (ΔT=Tc-Tg). The fibre tensile strength deteriorated when the Si/Fe ratio decreased, while the alkali resistance of the fibres strengthened. After 72 h of alkali corrosion, the average tensile strength of fibres decreased significantly, which were all below 500 MPa. The SEM combined with EDS analysis revealed the shell formed on the fibre surface was mainly oxides and hydroxides of insoluble metals (Fe, Ca), preventing further corrosion by OH-.