MgO/Al_2O_3比对MgO-Al_2O_3-SiO_2系统玻璃分相与析晶的影响

Effect of MgO/Al_2O_3 Ratio on Phase-separation and Crystallization of MgO-Al_2O_3-SiO_2 Glass

采用高温熔融法制备了具有不同MgO/Al_2O_3比的堇青石微晶玻璃。采用差热分析仪(DTA)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)等测试技术研究了MgO/Al_2O_3比对该系统玻璃分相和析晶的影响。结果表明:当SiO_2含量不变时,随着MgO/Al_2O_3比的减小,分相形貌由连通的蠕虫状逐渐变为孤立的球形结构,且分相粒子尺寸逐渐减小,从200～300nm减小至30～50nm。当MgO/Al_2O_3比从3降到1,析晶峰温度由997℃升至1 105℃,析晶的难度逐渐提高。当MgO/Al_2O_3比为3时,MgO-Al_2O_3-SiO_2系统玻璃经950℃热处理后即产生大量分相,经1 050℃热处理后在分相液滴中析出大量堇青石晶体,且堇青石优先在富Mg相中析出。提高MgO/Al_2O_3比有利于MgO-Al_2O_3-SiO_2系统玻璃在分相中析晶,反之,则会降低系统的分相和析晶能力。

Cordierite-based glass-ceramics with diverse MgO/Al2O3ratios were prepared by high temperature melting met-hod.The impact of MgO/Al2O3ratio on the phase separation and crystallization behavior of the MgO-Al2O3-SiO2glass were investigated by means of differential thermal analyzer(DTA),X-ray diffraction(XRD)and scanning electron microscope(SEM).The results indicated that with the constant content of SiO2,the decrease of MgO/Al2O3ratios leaded to the morphology change of phase separation droplets from worm-like shape to isolated sphere,and the gradual size reduce of phase separation droplets from 200-300nm to 30-50nm.The increase of crystallization peak temperature(Tp)from997℃to1105℃could be observed as the MgO/Al2O3 ratio decreased from3to1,which made the crystallization become more difficult.When the MgO/Al2O3ratio is3,the MgO-Al2O3-SiO2 glass would produce a large amount of phase separation droplets after heat treatment at 950℃.After heat treatment at 1050℃,substantial cordierite crystals were precipitated in phase separation droplets,which were preferentially precipitated in Mg-rich phase.Increasing MgO/Al2O3 ratio was highly beneficial to the phase separation and crystallization in MgO-Al2O3-SiO2 glass.Conversely,reducing the MgO/Al2O3 ratio would weaken the the ability of phase separation and crystallization of the glass.