钙含量对钙钛锆石-钡硼硅酸盐玻璃陶瓷结构的影响

Effect of CaO Content on Structure of Zirconolite-barium Borosilicate Glass-ceramics

  • 摘要: 采用熔融-热处理工艺制备SiO2-Na2O-B2O3-BaO-CaO-TiO2-ZrO2体系玻璃陶瓷,利用差热分析法(DTA)、傅氏转换红外线光谱分析仪(FTIR)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)等技术手段研究了晶核剂(CaO、TiO2和ZrO2)总含量为45%时,不同钙含量(CaO∶TiO2∶ZrO2=x∶2∶1(摩尔比),x=0.5~6)对玻璃陶瓷晶相和显微结构的影响,并采用粉末静态浸泡法(PCT)测试了C2(即x=2)玻璃陶瓷样品的抗浸出性能。结果表明:玻璃网络结构主要由SiO4、BO3和BO4构成,随着Ca含量的增加,更多的B以BO4加入玻璃网络中,玻璃转变温度Tg逐渐升高,放热峰温度逐渐降低,但峰强逐渐增高;x<2时,样品中除CaZrTi2O7晶相外还有其他晶相(如TiO2和ZrO2)出现;当x=2和4时,样品中只有单一的CaZrTi2O7晶相;x=6时,有星状的CaZrTi2O7和柱状的CaTiO3晶相生成。PCT实验结果表明:B、Na、Ca元素的归一化浸出率随浸泡时间的增加而降低,并在28 d后保持不变,分别为8.4、7.8、2.2 mg/(m2•d),与硼硅酸盐玻璃固化体浸出率处于同一数量级。

     

    Abstract: Glass-ceramics belonging to SiO2-Na2O-B2O3-BaO-CaO-ZrO2-TiO2 system were prepared by a melting-heat treatment method. The differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to research the effects of the CaO content (CaO, TiO2 and ZrO2 mole ratio is x∶2∶1, x=0.5-6) on crystalline phases and microstructure of samples when the concentration of nucleating agents (CaO, TiO2 and ZrO2) is 45%. The leaching resistance of zirconolite-barium borosilicate glass-ceramics of C2 (x=2) was characterized by product consistency test (PCT). The results show that the glass network structure is mainly formed of SiO4, BO3 and BO4, the increase of calcium concentration leads to more B ions exist in the form of BO4 tetrahedral units in the glass network. The glass transition temperature Tg gradually increases and the exothermic peak temperature gradually decreases while the strength of exothermic peak increases with the CaO content. The other crystalline phase (ie. TiO2 and ZrO2) forms in addition to CaZrTi2O7 phase with x<2 while only CaZrTi2O7 phase forms with x=2 and 4. The stellate CaZrTi2O7 and columnar CaTiO3 phases are observed for the sample with x=6. The PCT experiment of glass-ceramics shows that the normalized leaching rates of B, Na and Ca gradually decrease with increasing leaching time and remain almost unchanged after 28 d, about 8.4, 7.8, 2.2 mg/(m2•d), respectively, which are the same order of magnitude of borosilicate glass waste.

     

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