Formation and Morphological Evolution of Nanoporous Metals

一种生产纳米多孔金属的新方法是利用合金腐蚀进行选择性溶解。这一过程包括电化学分离二元合金中的一种元素，以产生剩余元素的高度纳米多孔金属。虽然这一过程在腐蚀界是众所周知的，但使用选择性溶解过程生产高表面积电极的潜在好处尚未被探索。这项资助提供了在良好控制的环境条件下，金属合金在选择性溶解过程中产生的纳米孔隙度的详细表征。设计这些条件是为了改变粗化和平滑过程的相对速率。小角中子散射（SANS）表征了孔隙度的全三维形貌。SANS实验是在国家标准与技术研究所的冷中子研究设施进行的。扫描隧道显微镜（STM）表征表面形态变化发生在脱合金过程中。STM还可以量化在各种合金化环境中较贵重元素的表面扩散率。研究计划包括：(1)量化选择性溶解过程中形成的全三维孔径分布随电化学环境、外加电压和合金成分的原位时间演化；(2)将多孔金属的粗化动力学量化为温度、电化学环境和合金元素熔点的函数；(3)利用STM测量在选择性去除表面原子过程中形成的岛大小随电化学环境的变化。本研究首次详细地描述了电化学环境对合金化过程中孔隙形成的影响。研究数据为使用选择性溶解来创建用于安培传感器的高表面积电极（对生物医学传感有特殊兴趣）提供了基础。纳米多孔金属在电化学能量存储和转换的高表面积电极，疾病诊断和治疗的生物医学传感器应用以及在高腐蚀性环境中的独特过滤应用等各个领域具有巨大的潜力。＊＊＊

9975190CorcoranA novel method for the production of nanoporous metals is using alloy corrosion for selective dissolution. This process involves electrochemically parting one element from a binary alloy to produce a highly nanoporous metal of the remaining element. Although this process is well known within the corrosion community, the potential benefit of using the selective dissolution process to produce high surface-area electrodes has not been explored. This grant provides a detailed characterization of the nanoporosity created in metal alloys during selective dissolution under well-controlled environmental conditions. The conditions are designed to change the relative rates of the roughening and smoothing processes. Small angle neutron scattering (SANS) characterizes the full three-dimensional morphology of the porosity. The SANS experiments are carried out at the Cold Neutron Research Facility of the National Institute of Standards and Technology. Scanning tunneling microscopy (STM) characterizes the surface morphological changes that occur during dealloying. The STM can also quantify the surface diffusivity of the more noble element in the various dealloying environments. The research plan includes: (1) quantifying the in-situ time evolution of the full three-dimensional pore size distribution that is formed during selective dissolution as a function of electrochemical environment, applied voltage and alloy composition; (2) quantifying the coarsening kinetics of porous metals as a function of temperature, electrochemical environment, and melting point of the alloying elements; and (3) using STM to measure the evolution of island sizes developed during selective removal of surface atoms as a function of the electrochemical environment.%%%This research gives the first detailed morphological characterization of the effect of electrochemical environment on formation of porosity during dealloying. The research data provide a foundation for using selective dissolution to create high surface-area electrodes for amperometric sensors (with a specific interest in biomedical sensing). Nanoporous metals have tremendous potential in such diverse areas as high surface-area electrodes for electrochemical energy storage and conversion, biomedical sensor applications for disease diagnosis and treatment, and unique filtration applications in highly corrosive environments. ***