The interaction between mechanics and electrochemistry in extremely thin electrodes

    [abstract] During corrosion, mechanics and electrochemistry interact always to each other. Although there are thermodynamic studies about the stress-caused change in equilibrium potentials, few multiscale computations have been reported in the literature. In this presentation, we report multiscale computations of the interaction between mechanics and electrochemistry, where first-principals calculations and continuum calculations by solving a modified Poisson-Boltzmann equation are carried out on electrode and electrolyte, respectively, and the electric potential produced by electrons and induced charges links the first-principles and continuum calculations. Monolayer graphene and multilayer graphene films are taken as an example to illustrate the hybrid approach. The calculation results illustrate the quantum capacitance in monolayer graphene, the charge-induced deformation in multilayer graphene, and the Li absorption behavior on monolayer graphene with vacancy. Based on Fermi level change and Dirac point shift, the capacitor of the electrochemical cell is consisted of two capacitors in series, the quantum capacitor and the capacitor of the electric double layer. Thus, the total capacitance can be easily calculated once the capacitances of the two capacitors are available. Simple and analytic formulas are proposed for the three capacitances to predict, in sufficient accuracy, the behavior of capacitance versus potential. The surface eigenstress model is further developed to analytically predict the charge-induced deformation in multilayer graphene films. The charge-induced deformation is asymmetric with respect to negative and positive charges, and the thickness-dependent minimal inplane C–C bond length occurs at the same positive charge of about 3.81x1014 |e|/cm2 for the 1 to 6 layers graphene films. The calculations reveal that Li absorption can be significantly affected by the type of electrolyte and the amount of charges. In CCl4 solvent, Li can absorb on a monovacancy of graphene when the charge of electrode is lower than 1.00x1014 |e|/cm2. But in water, only negative charged electrode can lead to Li absorption on the monovacancy.

    时间：2016年8月10日 09:00-09:30

    报告人：张统一

    个人简介

张统一院士

    中国科学院院士，研究领域包括材料的机械性能、微观力学/纳米力学、微结构与材料性能的关系、铁电和压电材料、薄膜、纳米线及纳米管、微桥/纳米桥实验、扩散与相变。从事材料力学性质的研究。预测并证实了钢铁扭转和剪切载荷下的氢脆现象。澄清了电绝缘裂纹面上电边界条件，发展了压电线性和非线性断裂力学；实验证明导电裂纹的电断裂韧性为材料常数，构筑了电致断裂的理论框架。发展了微观/纳观力学：建立了微/纳桥测试理论和方法及薄膜/基体系统中产生位错、微/纳孪晶和裂纹的临界厚度理论；给出了应力腐蚀中裂纹、腐蚀膜和位错交互作用的理论解。曾获国家自然科学二等奖二次、香港裘槎高级研究学者奖、美国ASM International Fellow奖和中国科学技术协会青年科技奖。

    张教授以第一作者及联合作者身份共发表140多篇SCI学术论文。在断裂力学，微观、纳观力学和材料的氢致开裂等领域取得了多项创新性成果，拥有两项美国专利和一项国家专利，获两次国家自然科学二等奖（1987和2007年度），2001年获得美国ASM International Fellow，2003年获香港裘槎高级研究学者奖。收到过5张SCI贺卡和1张Elsevier贺卡，祝贺其论文引用次数名列本领域前1%。组织并主持三次国际学术会议，包括首次在中国召开的第八届国际断裂基础大会。特邀为Mechanics of Material，International Journal of Fracture，Engineering Fracture Mechanics，Composites Science & Technology等学报编辑了八期特刊。

    其中在香港科技大学完成的4篇代表性学术论文，截至2008年12月30日，SCI引用次数分别达到245，180，147和134次。参与撰写三本著作。获得2项美国专利。并受邀在国际、国内学术会议上做大会特邀报告32次。2002年被中国教育部《面向21世纪教育振兴行动计划》“聘请世界著名学者项目”聘请，2001年获美国ASM International Fellow Award，1988年获中国科学技术协会青年科技奖，1987年获中国国家自然科学二等奖（十获奖人中排第三）。