Effect of TiO2 on the crystallization and properties of MgO-Al2O3-SiO2 glass-ceramics prepared by an "one-step" method from laterite ore

In the current paper, we proposed a novel, "one-step" method to simultaneously prepare MgO-Al2O3-SiO2 glass-ceramics and Ni-Fe alloy from laterite ore with the addition of TiO2. The "one-step" method makes full use of the thermal energy of the molten slag so that the energy consumption for the production of the glass-ceramics is much lower than that in a more conventional method. Moreover, the slag utilization rate can reach 100%. In this method, 0-4 g of TiO2 as a nucleating agent was added into laterite ore to control the phase composition and microstructure of glass-ceramics. The effects of the addition of different amounts of TiO2 on the crystallization behaviour, major crystalline phase, microstructure and various properties of glass-ceramics were investigated by XRD, SEM, EDS and a Vickers hardness tester. The results show that with an increase in the amount of TiO2 added (0-3g), the mu-cordierite gradually precipitated and became the main crystalline phase of the glass-ceramics. Meanwhile, the crystallinity, grain size and acid/alkali resistance were all enhanced with increased TiO2 addition. The micro-hardness increased from 6.699 GPa to 9.156 GPa. However, as the amount of TiO2 added increased up to 4 g, a large amount of sapphirine ((Mg4Al4)(Al4Si2)O-20) precipitated in the glass-ceramics. The major crystalline phase of the glass-ceramics begins to change from mu-cordierite to sapphirine, accompanied by a decrease of its density, acid/alkali resistance and micro-hardness. This study is helpful for extending the "one-step" method of simultaneously preparing glass-ceramics and metals to other low-grade ores and not just laterite ore.