Compositional effects on mechanical properties, viscosity, and crystallization of (Li₂O, B₂O₃, MgO)-Al₂O₃-SiO₂ glasses

Compositional effects on mechanical properties, viscosity, crystallization and crystallization kinetics of MgO-Al₂O₃-SiO₂ based high-strength (HS) glass and glass fibers were examined in detail by varying (Li₂O + B₂O₃)/MgO ratio (LB/M). A set of complementary techniques was applied to the crystallization studies, including differential scanning calorimetry (DSC), powder x-ray diffraction (XRD), scanning electron microscopy equipped with energy dispersive spectrometer (SEM/EDS). Phase identification and crystal morphology survey were made. Crystallization kinetics of the HS glass fibers under various thermal conditions was studied in detail to elucidate plausible crystallization mechanisms in relationships to LB/M. Our study showed that the combined, high concentration of Li₂O and B₂O₃, at the expense of MgO, i.e., higher LB/M, suppressed crystal growth in glass. From the DSC studies, exothermic peaks came from formation of β-quartz (s.s.) below 900°Cand subsequent transformation into cordierite greater than 1000 °C according to XRD analysis of the heat-treated samples. For crystallization under the non-isothermal conditions, Kissinger and Matusita & Sakka methods were applied to elucidate glass crystallization mechanism(s). In addition, the HS glass fibers were shown to have 29% higher tensile strength and 15% higher modulus than E-Glass fibers commercially used for a wide range of composite applications. - Highlights: • The crystallized tendency of S-glass can be decided by Kissinger methods. • Li₂O and B₂O₃, as new additives, improving S-Glass processing characteristics. • Crystallization process of HS-glass was from β-quartz (s.s.) to cordierite. • The new HS-glass fibers have 15% higher mechanical properties than E-glass fibers.