Length Scales in Alloy Dissolution

这笔赠款涉及亚利桑那州立大学(西拉德斯基)和弗吉尼亚理工大学。(Corcoran)探索了通过一种称为脱合金化的合金溶解过程来演化纳米多孔金属的基础物理和材料科学。本研究旨在通过研究预先存在的长度尺度对孔隙率演化的作用以及表征这一过程的临界电位等电化学参数，来区分最近的几种脱合金理论。为了了解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显微组织的固定成分合金的脱合金化行为。将考察两种类型的微结构：可调谐调幅微结构(Ag-Ni和Au-Ni合金)和成分调制超晶格(Ag-Ni、Au-Ni和Au-Ag合金)。这些行为将与单相固溶体合金(例如，Ag-Au)进行比较，后者也具有由合金成分决定的预先存在的长度标度(渗流团簇结构)。除了标准的电化学、X射线和电子显微镜表征外，还将使用原位小角中子散射(SANS)来实时确定纳米孔微结构的演变。测量将使用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，例如与薄膜硅基结构兼容。用于生产多孔性金属的脱合金方法是非常多才多艺的，因为孔洞的尺寸尺度可以在3 nm到大于10 mm的范围内精确地调节。电极几乎可以以任何几何形状生产，包括块状和薄膜状。可以生产多种长度刻度和分级结构，以根据应用精确地定制电极性能。因此，这类材料的应用非常广泛，包括过滤、电池和燃料电池的超高表面积电极、催化剂和传感器，特别是在生化应用中。拟议的努力对本科生和研究生的教育产生了广泛的影响，开发了将造福全社会的医疗技术等领域的技术，并发展了基础科学，影响了材料科学的许多领域。

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.