Measuring the Surface Energy of Metals through Structure-Property Analysis of Electrodeposition Instabilities

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Non-technical SummarySurface energy is one of the most fundamental and important thermophysical properties of metal surfaces as it has a strong influence on the mechanical, electrical, catalytic, and morphological characteristics of the solid. These properties are important to understanding corrosion, catalytic behavior, adsorption on solid substrates, and crystal formation. Measurements of the surface energy have been recognized as an important parameter that has eluded researchers for several decades. This project seeks to develop the structure-property relationships that enable the direct measurement of the surface energy of solid metals near ambient temperature. The approach is based on well-defined patterns that form on the cathode during the electrodeposition of metals in microfluidic channels. Electrodeposition allows highly accurate potential gradients and spacings that can be conducted at room temperature to obtain reliable patterns. These well-defined patterns are associated with the competition between different forces acting on the surface, allowing determination of the surface energy of the metal surface. The method can be translated to any metal surface that is capable of electrodeposition reactions in which the thermophysical parameters are known. The program also includes K-12 outreach with local schools, which include in-class demonstrations, summer research programs, and engineering fairs.Technical SummaryExperimental estimates of the surface energy of metals are very difficult to obtain and have uncertainties of unknown magnitude. The objective of this project is to measure directly the surface energy of solid metals using copper surfaces as a case study. The central hypothesis is that electrodeposition instabilities result in well-defined instability patterns of predictable wavelengths that correlate with the surface energy of the copper surface. The project capitalizes on the ability to measure the formation of a single wave instability pattern during electrodeposition thereby leading to the direct measurement of surface energy. Instability patterns at the surface arise from inherent perturbations of structure, potential or concentration during electrodeposition and are a result of a feedback mechanism that encourages patterns at the cathode. An intelligent choice of electrode dimensions enables a single wave pattern to be formed and detected at the onset of the instability. These onset conditions and the companion patterns are directly related to the surface energy of the solid metal and predicted by the coupled transport and reaction kinetic equations. The expected outcome of this project is a direct method to measure the surface energy of a solid metal surface near ambient temperatures.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.