硼硅酸盐玻璃浸出前后结构变化的研究

Changes in Structure of Borosilicate Glass in Leaching Condition

硼硅酸盐玻璃作为最具工业化应用前景的高放射性废物的固化基材,其中的放射性核素主要以浸出方式进入生物圈。本工作采用了MCC-1静态浸泡法对在90℃去离子水中浸泡28 d后的硼硅酸盐玻璃的浸出行为进行了研究。借助电感耦合等离子体发射光谱(ICP-OES)、傅里叶红外光谱(FTIR)、拉曼光谱(Raman)以及掠入射X射线衍射(GIXRD)等方法对玻璃的浸出性能及微观结构进行研究。此外,还使用了扫描电镜观测了浸出样品的截面。FTIR、Raman及GIXRD结果表明,浸出后,样品表层中的Si-O-Si结构明显增多,而硼结构单元则消失,表层的微观结构与熔融石英的结构较为相似。此外,在扫描电镜中观察到浸出7 d后的样品表面出现腐蚀层,同时在玻璃基底和腐蚀层中间出现裂隙,由此导致了浸出表面积的增加,从而最终引起浸出7 d时元素归一化标准浸出率的异常增大。

Borosilicate glass is one of the most possible candidates for the immobilization of high-level radioactive nuclear waste and leaching is the main way that radionuclides inside the vitrification(borosilicate glass form)enter the biosphere.The leaching properties of borosilicate glass by deionized water were investigated using the MCC-1 static leaching method at 90℃for 28 d.With the static leaching method developed by American Nuclear Waste Material Characterization Center,the leaching behavior and the corresponding micro-structures of the borosilicate glass were investigated,adopting a variety of spectral characterization methods including inductively coupled plasma optical emission spectrometry(ICP-OES),Fourier transform infrared spectroscopy(FTIR),Raman spectroscopy(Raman),and the grazing incident X-ray diffraction(GIXRD).All of the data from FTIR,Raman and GIXRD indicate that,with corrosion in water,the proportion of Si-O-Si structures in glass increases while the B-related structures disappear,and the micro-structures in the layer near the surface are similar to fused silica.After being immersed for 7 d,a corrosion layer and cracks between the corrosion layer and glass base are observed in the surface of samples,which is identified by scanning electron microscope.The formation of the cracks led to a increase in surface area of glass samples.That finally led to an abnormal increase in the leaching rates of Na and Si elements.