Length Scales in Alloy Dissolution

这项拨款涉及亚利桑那州立大学（Sieradzki）和弗吉尼亚理工大学。（Corcoran）通过称为去合金化的合金溶解过程探索纳米多孔金属演变的基础物理学和材料科学。该研究的目的是区分最近几个理论的脱合金通过检查预先存在的长度尺度上的孔隙度演变和电化学参数，如临界电位，表征这一过程的作用。为了评估预先存在的长度尺度在图案形成过程中的作用，将研究具有人工定制和可调微结构的固定成分合金的去合金化行为。两种类型的微结构将被检查：可调的调幅微结构（银-镍和Au Ni合金）和成分调制超晶格（银-镍，金-镍和金-银合金）。这些行为将与单相固溶体合金（例如，Ag-Au），其也具有由合金组成确定的预先存在的长度尺度（渗滤簇结构）。除了标准的电化学，X射线和电子显微镜表征，原位小角中子散射（SANS）将用于确定，在真实的时间，纳米多孔微观结构的演变。测量将使用美国国家标准与技术研究所的8米和30米长的SANS仪器进行。这项工作的长期目标是利用对潜在机制的理解来生产各种形式的纳米多孔金属，例如与薄膜硅基架构兼容。 用于生产多孔金属的去合金化方法是非常通用的，因为孔隙度的尺寸尺度可以在3 nm至大于10 mm的范围内精确调节。电极可以以几乎任何几何形状（包括块体和薄膜形式）生产。可以生产多种长度尺度和分级结构，以根据应用精确定制电极性能。因此，这种材料的应用是广泛的，并且包括诸如过滤、用于电池和燃料电池的超高表面积电极、催化剂和传感器等领域，特别是在生物化学应用中。拟议的努力对本科生和研究生的教育，用于医疗技术等领域的技术开发，将造福于整个社会，以及基础科学的发展，影响材料科学许多领域的科学界产生广泛的影响。

This grant involving Arizona State University (Sieradzki) and Virginia Tech. (Corcoran) explores the fundamental physics and materials science of nanoporous metal evolution via an alloy dissolution process known as dealloying. The research aims to differentiate among several recent theories of dealloying by examining the role of pre-existing length scale on porosity evolution and the electrochemical parameters such as the critical potential, characterizing this process. In order to access the role of pre-existing length scale in the pattern formation process, the de-alloying behavior of fixed composition alloys with artificially tailored and tunable microstructures will be studied. Two types of microstructures will be examined: tunable spinodal microstructures (Ag-Ni and Au Ni alloys) and compositionally modulated superlattices (Ag-Ni, Au-Ni and Au-Ag alloys). These behaviors will be compared to that of single-phase solid solution alloys (e.g., Ag-Au) that also have a pre-existing length scale (percolation cluster structure) determined by alloy composition. In addition to standard electrochemical, x-ray, and electron microscopy characterization, in situ small angle neutron scattering (SANS) will be used to determine, in real time, the evolution of the nanoporous microstructures. Measurements will be performed using both the 8 and 30 meter long SANS instrument at the National Institute of Standards and Technology. The long-term goal of this effort is to use the understanding of the underlying mechanisms to produce nanoporous metals in a variety of forms compatible for example with thin film silicon-based architectures. The dealloying method for producing porous metals is extremely versatile in that the size scale of the porosity can be precisely tuned in the range of 3 nm to greater than 10 mm. The electrodes can be produced in virtually any geometry including bulk and thin film form. Multiple length scales and graded structures can be produced to precisely tailor electrode performance depending upon the application. As such, the applications of such materials are broad and encompass such areas as filtration, ultra-high surface area electrodes for batteries and fuel cells, catalysts, and sensors, particularly in biochemical applications. The proposed effort has broad impact to the education of undergraduate and graduate students, development of technology for use in such areas as medical technologies that will benefit society at large, and development of basic science to impact the scientific community across many fields of materials science.