Effect of TiO2 addition on the crystallization and tribological properties of MgO–CaO–SiO2–P2O5–F glasses

The kinetic parameters including the activation energy for crystallization (E), the Avrami parameter (n) and frequency factor (υ) of a glass in the MgO–CaO–SiO₂–P₂O₅–F system were studied using non-isothermal differential thermal analysis (DTA) with regard to small amount of TiO₂ additions. It has been shown that the role of TiO₂ changes from a glass network former to a glass network modifier with increasing TiO₂ content in this system. The kinetic parameters of the crystallizing phases, apatite and wollastonite, indicated changes accompanied with TiO₂ additions, implying that the TiO₂ is an effective nucleating agent for promoting the crystallization of apatite and wollastonite. The most effective addition is of about 4 wt% TiO₂ in this system. The wear rate and friction coefficient decreased from 1.8 ± 0.1 to 0.9 ± 0.2 and 0.87 to 0.77, respectively, when 4 wt% TiO₂ was incorporated to the base glass.