钡硼硅酸盐玻璃陶瓷固化体的制备工艺及固化硫的研究

发布时间：2018-06-27 06:00

  本文选题：钙钛锆石 + 玻璃陶瓷　； 参考：《西南科技大学》2015年硕士论文

【摘要】：针对目前高放废液硼硅酸盐玻璃固化体存在锕系核素溶解度较低、热力学稳定性较差等不足,以及在玻璃熔制过程中容易出现分离的含硫黄色第二相(黄相)问题,通过在钡硼硅酸盐玻璃体系(Ba O-B2O3-Na2O-Si O2)中加入不同含量的氧化钙(Ca O)、二氧化钛(Ti O2)和锆英石(Zr Si O4)(记为CTZ),采用熔融-热处理工艺制备了含有钙钛锆石晶相的钡硼硅酸盐玻璃陶瓷固化体。系统研究了CTZ含量(0~55 wt%)对钡硼硅酸盐玻璃陶瓷固化体的晶相组成、显微结构和化学稳定性的影响;研究了钙含量变化(Ca O:Ti O2:Zr O2=x:2:1,x=0.5~10)对钡硼硅酸盐玻璃陶瓷的晶相结构和显微结构等的影响;采用正交试验法优化了钡硼硅酸盐玻璃陶瓷的热处理工艺参数,并比较了一步法(核化和晶化同时进行)和二步法(核化和晶化分开进行)热处理工艺对玻璃陶瓷结构的影响;研究了钡硼硅酸盐玻璃陶瓷对硫元素(以Na2SO4形式引入)的最大包容量。结果表明:含CTZ的钡硼硅酸盐基础玻璃的熔制温度为1150~1250℃样品的玻璃转变温度为615~650℃且随着CTZ含量增加而升高。CTZ含量为35 wt%和45 wt%的样品分别在900℃和850℃附近出现了明显的放热峰。当CTZ含量≥35 wt%时,钙钛锆石晶相开始析出;CTZ含量为45 wt%时,样品中出现了大量均匀分布的柱状钙钛锆石晶相;CTZ含量达55 wt%时,样品致密性较差,除钙钛锆石晶相外还有榍石和二氧化硅晶相析出。产品一致性试验(Product Consistency Test,PCT)结果表明,CTZ含量为45 wt%的固化体的抗浸出性能较好,42 d后Na和B的归一化质量损失约为0.2 g/m2,Si和Ca约为0.02 g/m2。当Ca O:Ti O2:Zr O2=2:2:1和4:2:1时,可以获得仅含钙钛锆石晶相的玻璃陶瓷。正交试验结果表明,核化温度和晶化温度对玻璃陶瓷体内钙钛锆石含量影响较大,而核化时间和晶化时间的影响相对较小。二步法和一步法热处理工艺对玻璃陶瓷结构无显著影响,当晶化温度较高或晶化时间较长时,均会出现榍石晶相。钡硼硅酸盐玻璃陶瓷能够包容3 mo l%的Na2SO4而不出现分层,硫含量在0~3mol%范围内样品晶相组成仅有钙钛锆石,且硫含量变化对钙钛锆石晶体数量和分布影响不大;当Na2SO4含量大于3 mo l%时,玻璃陶瓷结构疏松,存在少量孔洞,样品体内含有钙钛锆石和榍石晶相,表面形成了由硫酸钡和硫酸钠组成的白色分离层。样品PCT实验表明,当Na2SO4含量低于3 mol%时,元素归一化质量损失在7 d之后基本保持稳定:NLB和NLCa为0.01 g/m2,NLBa为0.001 g/m2,NLNa为0.1 g/m2。当Na2SO4含量超过3 mo l%后,7 d之后NLB和NLNa随时间增加而增加,NLBa和NLCa在28 d之后基本保持稳定,分别为10-4 g/m2和10-2 g/m2数量级。
[Abstract]:In view of the shortcomings of low solubility of actinide nuclides and poor thermodynamic stability in the present high level waste liquid borosilicate glass solidification, the second phase (yellow phase) containing sulfur is easy to be separated in the process of glass melting. Barium borosilicate (barium borosilicate) containing calcium oxide (Cao), titanium dioxide (TIO 2) and zircon (Zr Sio 4) (denoted as CTZ) was prepared by melt heat treatment in the barium borosilicate glass system (BaO-B2O3-Na2O-SiO 2). Salt glass ceramic solidified body. The effects of CTZ content (0 ~ 55wt%) on the crystal phase composition, microstructure and chemical stability of barium borosilicate glass ceramics were systematically studied. The effect of calcium content (Cao: TIO 2: Zr O 2: x 2: 1: 1) on the crystal phase structure and microstructure of barium borosilicate glass ceramics was studied, and the heat treatment process parameters of barium borosilicate glass ceramics were optimized by orthogonal test. The effects of one-step heat treatment (nucleation and crystallization at the same time) and two-step heat treatment (nucleation and crystallization) on the structure of glass ceramics were compared. The maximum inclusion capacity of barium borosilicate glass ceramics for sulfur (introduced in the form of Na _ 2SO _ 4) was studied. The results show that the melting temperature of barium borosilicate base glass containing CTZ is 1 150 鈩，

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