Structural Characterization of Micron-scaled Reticulated Copper Foams
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Structural Characterization of Micron-scaled Reticulated Copper Foams Stephanie J Lin1 and Jason H. Nadler2 1 School of Material Science and Engineering, Georgia Tech ,771 Ferst Drive, Atlanta, GA 30332 2 Georgia Tech Research Institute, 925 Dalney St, Atlanta GA 30332 Abstract The development of a multifunctional, micron-scaled, reticulated copper foam that reliably exhibits high intrinsic thermal conductivity, efficient capillary fluid and evaporative transport over a wide area presents a unique challenge. In this work, the relationship of critical foam processing variables such as sintering temperature and template size on the pore size distribution and pore neck/body ratio is investigated using image analysis. The resulting fluid permeability values of these foams are estimated by using the Kozeny Carman equation and the porosity, surface area per unit area and tortuosity obtained through image analysis. Estimating the fluid permeability of these foams is useful for predicting the mass and heat transfer within the porous network, and provides a metric for optimizing the foam’s structural characteristics for a particular application. Introduction Open celled metallic foams are a type of engineered structural porous material characterized by an interconnected pore network confined by an interconnected solid phase. Metallic foams are of particular practical interest because their structures can be designed for applications far beyond those of the constituent material. Some metallic foams are being used in applications such as filters, flow straighteners and heat exchangers; applications where fluid transport properties are dictated by the pore network. Though it has been desirable to estimate the fluid permeability through structural analysis, and much work has addressed the permeability of porous media [1-3] there has been very little focus on determining the permeability of open celled metallic foams. To better understand how processing effects the permeability and the structural characteristics of reticulated copper foam produced using a sacrificial templating method, copper foams were made varying the batch composition and the heat treatment temperature. Features such as interfacial area per unit volume porosity, pore size and tortuosity can be estimated from images of the porous microstructure. Most methods of calculating the fluid permeability of open cell metallic foams involve homogenization techniques or pore level simulation of the fluid flow through individual cells, but both are computationally expensive [2]. The Kozeny Carman equation, Eq. 1, commonly used to empirically calculate the permeability of porous media [4,5] from structural features, was applied in a modified form to calculate the effective permeability of a reticulated copper foam. Modifications to this expression have been made to better fit experimental data from consolidated porous media and materials with high porosity and anisotropy through the use of a specific area term instead of a particle diameter.
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3 s2
(1) where , poro
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