Modeling the Formation of Self-Ordered Nanoporous Anodic Oxides

该奖项的研究目标是开发合理设计高有序多孔阳极氧化物（PAO）薄膜的新方法。这些薄膜是通过在电化学电池中对金属（如铝和钛）施加电压而形成的。薄膜包含自有序的六边形纳米级孔隙阵列，覆盖宏观区域。虽然许多注意力都集中在使用PAO作为功能器件的模板上，但这些结构是在缺乏对控制膜生长过程的强大理解的情况下根据经验开发的。本研究的目的是建立一个完整的孔隙形成和自排序预测模型。这项工作将以电场和机械应力共同作用下氧化材料传输的概念为指导。实验应力测量将确定控制PAO薄膜界面运动的粘性、静电和氧化诱导应力的工作平衡。利用这些知识，传递过程和驱动力的描述将被表述为预测模拟PAO生长，揭示电化学极化、镀液化学和自排序动力学之间的关系。如果成功，PAO形成的化学-力学模型将为基于模型的自组织多孔阳极膜设计提供基础基础。因此，该模型可以合理地操纵工艺条件，以实现高速率无缺陷薄膜的制造，从而增强基于pao的太阳能转换、催化和生物医学应用功能器件的商业潜力。学生的训练将受益于这个项目的独特方面：化学和力学的紧密结合；严格结合多种实验和建模方法；并与英国的一个材料表征小组进行现场合作。爱荷华州立大学的学生培训将利用研究生和本科课程的强大存在，在系和大学层面上促进代表性不足的群体。

The research objective of this award is to develop new methods for the rational design of highly ordered porous anodic oxide (PAO) films. These films are formed electrochemically by applying voltages to metals such as aluminum and titanium, in electrochemical cells. The films contain self-ordered hexagonal arrays of nanoscale pores, covering macroscopic areas. While much attention has focused on the use of PAO as templates for functional devices, these structures have been developed empirically, in the absence of robust understanding of processes controlling film growth. The goal of this research is to develop a fully predictive model of pore formation and self-ordering. The work will be guided by the concept that oxide material is transported by the combined influence of the electric field and mechanical stress. Experimental stress measurements will determine the operative balances of viscous, electrostatic and oxidation-induced stress governing interface motion in PAO films. Using this knowledge, descriptions of transport processes and driving forces will be formulated as a predictive simulation PAO growth, revealing the relations between electrochemical polarization, bath chemistry, and the dynamics of the self-ordering.If successful, the chemical-mechanical model of PAO formation will provide a fundamental basis for model-based design of self-organized porous anodic films. Thus, the model may permit rational manipulation of process conditions for high-rate fabrication of defect-free films, thus enhancing the commercial potential of PAO-based functional devices for solar energy conversion, catalysis, and biomedical applications. Student training will benefit from the unique aspects of this project: close integration of chemistry and mechanics; rigorous combination of a variety of experimental and modeling approaches; and on-site collaboration with a materials characterization group in England. Student training at Iowa State will take advantage of the strong presence of graduate and undergraduate programs promoting underrepresented groups, both at the Department and University levels.