电沉积修复裂缝中离子迁移的Debye层效应  

Debye layer effect of ion migration in repairing cracks by electrodeposition

作　　者：刘伟 周跃亭[1] 陈庆 朱合华[3] LIU Wei;ZHOU YueTing;CHEN Qing;ZHU HeHua(School of Aerospace Engineering and Applied Mechanics,Tongji University,Shanghai 200092,China;School of Materials Science and Engineering,Tongji University,Shanghai 200092,China;College of Civil Engineering,Tongji University.Shanghai 200092,China)

机构地区：[1]同济大学航空航天与力学学院,上海200092 [2]同济大学材料科学与工程学院,上海200092 [3]同济大学土木工程学院,上海200092

出　　处：《中国科学：技术科学》2021年第7期828-836,共9页Scientia Sinica(Technologica)

基　　金：国家重点研发计划(编号:2018YFC0705400);国家自然科学基金(批准号:11972257,11832014,52078381,51878496,51508404,51478348,51278360,51308407);中央大学基础研究计划资助。

摘　　要：电场作用下电解质离子在裂缝中的迁移规律直接关系到混凝土裂缝电沉积修复的效果.经典的PoissonNernst-Planck(PNP)方程假定电解质离子为理想的质点模型,忽略了离子和裂缝的尺寸效应,难以揭示电解质离子在极端受限条件下纳米裂缝中的迁移规律.本文以双电层厚度为物理基础,建立了电沉积修复中离子迁移的几何模型,采用无量纲Debye数来描述离子浓度和裂缝尺寸等对离子迁移规律的影响;从自由能出发,考虑了离子和裂缝的尺寸效应,推导了修正的PNP方程,并通过有限元仿真获得了修正PNP方程的数值解.结果表明,当Debye数较小时,离子的迁移可以由经典的PNP方程来描述,离子浓度满足电中性关系,电势呈现出线性分布;随着Debye数的进一步增加,经典PNP方程的数值解会出现超高非物理离子浓度O(10^(2)),而基于修正后的PNP方程,可以获得裂缝中更为合理的阳离子饱和浓度值O(10).本研究将为电沉积修复过程的离子迁移分析以及可修复最小裂缝尺寸评定提供理论指导.The migration characteristics of electrolyte ions in cracks under the action of the electric field are directly related to the effect of electrodeposition repair of concrete cracks.The classic Poisson-Nernst-Planck(PNP)equation assumes that electrolyte ions satisfy an ideal particle model that ignores the size effect of ions and cracks.However,it is difficult to reveal the migration of electrolyte ions in micro-nano cracks under extreme confinement.In this paper,the physical model of ion migration is established.The model is based on the thickness of the electric double layer.Moreover,we use the dimensionless Debye number to describe the influence of ion concentration,particle size,and crack size on the ion migration.We start from free energy definition and consider the size effect of ions and cracks.Next,we derive the modified PNP equation and solve it numerically by the finite element method.We demonstrate that when the Debye number is small,the ion migration can be described by the classic PNP equation.In particular,the ion concentration satisfies the neutral relations,and the electric potential is linearly distributed.When the Debye number increases,the numerical solution of the classic PNP equation results in a very high non-physical ion concentration O(10^(2)).To address this issue,we introduce the revised PNP equation.Its solution provides a more reasonable cation saturation concentration of O(10)in the concrete cracks.Our study lays theoretical foundations for the ion migration analysis in the electrodeposition repair process and evaluation of repairable minimum crack size.

关 键 词：电沉积 钢筋混凝土裂缝 Debye层效应 离子尺寸 

分 类 号：TU528[建筑科学—建筑技术科学]