• Zhiwei Luo

      Articles written in Bulletin of Materials Science

    • Effects of MO (M = Mg, Ca, Ba) on crystallization and flexural strength of semi-transparent lithium disilicate glass–ceramics

      Zhiwei Luo Junlin Zhou Jing Li Changjian Zhang Anxian Lu

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      In this study, semitransparent lithium disilicate glass–ceramics in the Li2O–K2O–Al2O3–Y2O3–La2O3–SiO2 system was investigated by incorporation of P2O5 as nucleation agent and alkaline earth oxides as additive. The influence of alkaline earth oxides on the structure of glasses network, crystalline phases, microstructure and mechanical properties were investigated by means of Raman spectra, differential scanning calorimetry (DSC), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The mechanical strength was measured corresponding to norm ISO 6872. The Raman spectra predominantly showed that small additions of alkaline earth oxides not only form asymmetrical vibrations of the M–Si–O bonds, but also enhance the intensities of symmetrical vibrations of the P–O bonds, making the glass network more stable. And the small additions of CaO or BaO has more influence on the crystallization behaviour, crystalline phase, microstructure and mechanical properties of the glass–ceramics than the addition of MgO. The additions of alkaline earth oxides enhanced the first exothermic peak temperature but decreased the flexural strength of lithium disilicate glass–ceramics.

    • In situ synthesis and properties of self-reinforced Si$_3$N$_4$–SiO$_2$–Al$_2$O$_3$–Y$_2$O$_3$ (La$_2$O$_3$) glass–ceramic composites

      ZHIWEI LUO ANXIAN LU LEI HAN JUN SONG

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      In-situ-grown $\beta$-Si$_3$N$_4$-reinforced SiO$_2$–Al$_2$O$_3$–Y$_2$O$_3$ (La$_2$O$_3$) self-reinforced glass–ceramic composites were obtained without any $\beta$-Si$_3$N$_4$ seed crystal. These composites with different compositions were prepared in a nitrogenatmosphere for comparison of phase transformation and mechanical properties. The results showed that SiO$_2$–Al$_2$O$_3$–Y$_2$O$_3$ (La$_2$O$_3$) glass can effectively promote $\alpha$- to $\beta$-Si$_3$N$_4$ phase transformation. The crystallized Y$_2$Si$_2$O$_7$–La$_{4.67}$Si$_3$O$_{13}$ phaseswith a high melting point significantly benefited the high-temperature mechanical properties of the composites. TheSi$_3$N$_4$–SiO$_2$–Al$_2$O$_3$–Y$_2$O$_3 $(La$_2$O$_3$) glass–ceramic composites exhibit excellent mechanical properties compared with unreinforcedglass–ceramic matrix, which is undoubtedly attributed to the elongated $\beta$-Si$_3$N$_4$ grains. These glass–ceramic Si$_3$N$_4$ composites with excellent comprehensive properties might be a promising material for high-temperature applications.

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