Compositional and Thermal Characterization of Potential Nano-Carbon Copper Composite
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Covetics are a potentially new type of metal matrix nano-composite (MMnC) material. These materials are formed from face-centered cubic (FCC) metals which are claimed to be super-saturated with up to ~ 10 wt pct of activated nano-carbon powder. Historically, the incorporation of carbon into metals with tightly packed crystal structures, such as FCC structures, has been technologically difficult because of low carbon solubility;[1] for example, in copper, the solubility limit is about .04 at pct C.[2] However, due to novel materials processing, some claim that it is now possible to supersaturate these metals with nanoscale carbon inclusions in a cost-effective manner. The idea behind the theory of covetics is that the nano-carbon reinforcements will enhance the material properties of the base metal matrix such as melting point and strength.[1] Most of the material properties of covetics have not been well characterized, and the role of the nanoscale carbon inclusions in changing or enhancing the properties still needs to be confirmed and phenomenologically explained. It has been hypothesized that the covetic
M. ZAVALA, R.K. EVERETT, and M. ZUPAN are with the University of Maryland, Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250. Contact e-mail: [email protected] E.P. GORZKOWSKI is with the U.S. Naval Research Laboratory (NRL), Washington, DC 20375. Manuscript submitted November 16, 2017. METALLURGICAL AND MATERIALS TRANSACTIONS B
processes of aluminum, silver, copper, and iron, for example, will result in improved physical and mechanical properties. The reported improved properties include, but are not limited to, increased electrical conductivity, increased thermal conductivity, increased yield strength, and increased melting point. For more specifics and details of covetic property assertions, the reader is directed to Zavala.[3] The covetic casting synthesis process is a molten process whereby nano-carbon powders are introduced into molten metal while agitating the charge and applying a constant current through the liquid. This process has been implemented in past studies.[1,4] The patent holders have defined covetics within their patents (with aluminum and copper base metal matrices) as ‘‘a metal-carbon composition including the base metal and carbon, wherein the metal and the carbon form a ‘single phase’ material, characterized in that the carbon does not phase separate from the metal matrix when the ‘single phase’ material is heated to melting temperature.’’[5,6] A few reports have been published on some of the material properties of Al-, Ag-, and Cu-covetics,[1,4,7,8] but systematic studies are lacking. The focus of this study was to provide an analysis of the chemical composition of copper covetic materials varying in nano-carbon concentration, and to characterize the melting point of these materials. The copper covetic materials analyzed in this study were synthesized by the patent holders. The base copper metal, prior to covetic conversion, was of high purity level (99.99 pct),[9] provided b
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