Solid-state reactions  of SiC–TiO2–MgO system and phase relations in SiC–SiO2–TiC–TiO2–MgO system

W.Z. Sun*,
Z.K. Huang,
Y.J. Lu,
L.M. Liu,
Z. Xiao

School of Materials Science and Engineering, North Minzu University, Ningxia, Yinchuan, 750021, China
Powder Metallurgy - Kiev: Frantsevich Institute for Problems of Materials Science NASU, 2021, #11/12


Preliminary experiments revealed solid-state reactions in the SiC–TiO2–MgO system that resulted in forming TiC compound, providing, thus, a new reaction system for the formation of TiC–SiC ceramic matrix composites. This system's high-temperature physicochemical reaction and the phase equilibrium relations of TiC–SiC with salt compounds in the SiC–TiO2–MgO system will be examined in this paper. The obtained findings may significantly contribute to the composition of TiC–SiC ceramic composites. Solid-state reactions in the SiC–TiO2–MgO system were investigated during experimental procedures employing thermodynamic computing. Chemical kinetics of some reactions were highlighted and discussed, including mutual displacement reaction of SiC + TiO2 = TiC + SiO2 to form TiC, the acid-based reaction of MgO with SiO2 or TiO2 to form Mg-silicates (Mg2SiO4, MgSiO3) or Mg-titanates (Mg2TiO4, MgTiO3, MgTi2O5), the reduction reaction of 2TiO2 + C = Ti2O3 + + CO (g) with the involvement of excessive TiO2. The appearance of Ti2O3 may also be due to significant surface defects of rutile TiO2 (110) derived from its bulk Ti3+ defects. However, Mg-silicates and Mg-titanates were not found in the design of the current SiC–TiO2–MgO system but the oxide design of the MgO–TiO2–SiO2 system. As the SiC–TiO2–MgO ternary system was extended to the SiC–SiO2–TiC–TiO2–MgO quinary system, the phase relations form a combination of the TiC–SiC phase relations with all salts of the TiO2–MgO–SiO2 system. Experiments confirmed the formation of TiC and its coexistence with SiC and all binary compounds of the TiO2–MgO–SiO2 system, specifying an interaction in the SiC–SiO2–MgO–TiO2–TiC system. The phase relations of the quinary system were established, followed by constructing its phase diagram relations at 1400 °C, which would be beneficial for the compositional design of TiC–SiC, TiC–ceramic, and SiC–ceramic composites