Experimental Study on the Phase Relations of the SiO2-MgO-TiO2 System in Air at 1500°C

Abstract

We investigated the phase relations of the SiO2-MgO-TiO2 system in air at 1500°C using the high-temperature isothermal equilibration/quenching technique, followed by x-ray diffraction measurements and direct phase analysis using scanning electron microscopy coupled with x-ray energy dispersive spectrometry. One single liquid phase domain, five two-phase domains (liquid-TiO2, liquid-cristobalite, liquid-MgO·SiO2, liquid-2MgO·SiO2, and liquid-MgO·2TiO2), and five three-phase regions (liquid-TiO2-MgO·2TiO2, liquid-MgO·SiO2-cristobalite, liquid-TiO2-cristobalite, liquid-MgO·SiO2-2MgO·SiO2 and liquid-2MgO·SiO2-MgO·2TiO2) were observed. We constructed a 1500°C isothermal phase diagram based on the experimentally measured liquid compositions. We compared simulations using MTDATA and FactSage thermodynamic software and their databases with the experimental results obtained in this study. These results can be used to provide guidelines for updating the MTDATA and FactSage titania-bearing thermodynamic databases by reassessing the thermodynamic properties of the phase with new experimental data.

The MgO–TiO2–SiO2 system: Experiments and thermodynamic assessment

“…Nevertheless, although the results obtained at 1773 K in this work are limited and not enough to construct the complete equilibrium isothermal section, they are only qualitatively compared with those presented by Chen et al 17 The authors 17 investigated samples of the MgO-TiO 2 -SiO 2 system equilibrated at 1773 K and then quenched (their data are shown in red in Figure 1C). Considering all the above features of the nonequilibrium solidification of the samples in this work, the comparison of the data with the data of Chen et al 17 shows reasonable agreement.…”

“…Numbers in circles denote the three‐phase fields. In Figure 1C (left), small open squares denote the EPMA data obtained in this work (see Table 3), while all in red—small open triangles (EDX data), big solid tie triangles (three‐phase fields), and dotted tie lines (two‐phase field tie lines)—are the data of Chen et al 17 …”

“…An isothermal section at 1773 K with an emphasis on the liquid domain was recently reported. 17 At 1883 K, the phase relations in the MgO-SiO 2 -TiO X were investigated under reducing conditions (p(O 2 ) from 1.94•10 −9 to 2.75•10 −13 atm) 18 and at high pressure of 10−24 GPa. 19 Moreover, a wide area of the liquid immiscibility was investigated at 1883 K. 20 .…”

Phase relations of the MgO–SiO2–CrOx system at 1600°C in air and reducing atmospheres

“…The experiments followed the procedure described in our previous studies 46–48 . The high‐temperature isothermal equilibration experiments were conducted in a vertical Nabertherm furnace (Lilienthal, Germany, RHTV 120‐150/1) equipped with MoSi 2 heating elements and a recrystallized alumina work tube.…”

Phase equilibria of MgO–Al2O3–TiO2 system at 1600°C in air: Emphasis on pseudobrookite and spinel solid solution phases

“…The phase relations of the CaO–SiO 2 –MgO–Al 2 O 3 –TiO 2 system 32,33 and its subsystems have been intensively investigated under different conditions by theoretical calculation and experimental determination. The titania‐containing systems, including Al 2 O 3 –TiO 2 , 34 MgO–TiO 2 , 35 SiO 2 –MgO–TiO 2 , 36 CaO–MgO–TiO 2 , 37 CaO–Al 2 O 3 –TiO 2 , 38 CaO–SiO 2 –TiO 2 , 39 SiO 2 –Al 2 O 3 –TiO 2 , 40 CaO–SiO 2 –10–15 wt.% Al 2 O 3 –TiO 2 , 41,42 CaO–SiO 2 –5–10 wt.% MgO–10–20 wt.% Al 2 O 3 –TiO 2 , 29,31,43 have been well studied in the titania‐bearing slag composition range. However, most of the studies were focusing on the primary phase fields of perovskite or rutile.…”