基体石墨的孔隙结构及其对单质Ag扩散的影响

Pore Structure of Matrix Graphite and Its Effect on Ag Diffusion

高温气冷堆燃料元件的基体石墨是一种多孔复合材料,是燃料元件的主要组成部分,其结构影响燃料元件的性能和裂变产物在燃料元件中的扩散。本文利用压汞法表征基体石墨的孔隙结构,并讨论了基体石墨制备工艺中最大压制压强与热处理过程对孔隙结构的影响。结果表明,基体石墨大孔孔径分布为600~1900 nm,高温热处理使基体石墨的总孔隙率、中值孔径、大孔孔容均减小;基体石墨热处理样品的大孔孔容随最大压制压强的增加而呈线性减少,热处理过程单质Ag在石墨基体中的扩散速度与大孔孔容变化具有正相关性。

As a high temperature gas cooled reactor fuel element,matrix graphite is a porous composite material that is a major component of the fuel element.The structure of matrix graphite affects the performance of the fuel element and the diffusion of fission products inside.In this paper,the pore structure of matrix graphite was characterized by mercury intrusion method,and the influences of the maximum pressing pressure in the preparation process and further heat treatment process on the pore structure of matrix graphite were discussed.The results show that the pore size of large pores in the matrix graphite is 600~1900 nm.High-temperature heat treatment reduces the total porosity,the median pore diameter and the volume of large pores in the matrix graphite.The volume of large pores in the matrix graphite decreases linearly with the increase of the maximum pressing pressure in preparation process.Meanwhile,the diffusion rate of Ag in the graphite matrix has a positive correlation with the variation of the pore volume during high-temperature heat treatment.