溶胶-凝胶法锆英石的合成因素影响分析

Analysis of Factors Affecting the Synthesis of Zircon by Sol-gel Method

高放射性废物的安全处置是核能开发的世界性难题,技术难度大,研究周期长,涉及地质、化学、材料等多门学科。而对于高放射性废物地质处置的第一道人工屏障,高放射性废物固化体的稳定性对于整个处置库具有重要的影响。笔者采用溶胶-凝胶法合成锆英石,研究了反应条件对溶胶-凝胶法合成锆英石的影响,利用物化分析、XRD、电子探针对样品进行检测。结果表明:锆英石前躯体制备的实验优化条件为加水量30mL、pH值为2~3;烧结收缩率均大于20%,显气孔率均大于4%,表观密度均小于5.0 g/cm^3。产物的化学组成以ZrO_2和SiO_2等为主;凝胶后处理过程中经过氨水洗涤的样品其晶体组成主要以锆英石(ZrSiO_4)和斜锆石(ZrO_2)为主,其中含有部分方石英(SiO_2),而未经氨水洗涤的样品,其晶体为单一的单斜锆石(ZrO_2)。

The safe disposition of high level radioactive waste is a global problem for the nuclear development, since the technical is very difficult, the research cycle is longer, and it refers to different subjects including geology, chemistry, materials, and others.As the first artificial barrier of deep geological disposal of HLW, the stability of immobilization has im- portant influence on disposal repository. This paper synthesizes zircon by sol--gel. We dicuss sol--gel reaction conditions how to influence the preparation of precursor. Testing the physical and chemical properties of zircon samples and use XRD, EPMA to analysise the different phase composition and mineral composition of several groups of zircon samples. The exper imental conditions for zircon precursor is： amount of water 30 mL, pH 2-3. The phase of sample washed by ammonia is form of baddeleyite（ZrO2 } and zircon（ZrSiO4 }, the other phase（SiO2 ）. Another without washing only includes baddeleyite （ZrO2 ）. The main compositions of two samples are mainly composed with ZrO2 and SiO2, and ZrO2 is the main content.