Characterization of Nanocarbon Copper Composites Manufactured in Metallurgical Synthesis Process

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COMMON metallic materials have a well-known set of basic properties. The mechanical properties of different base materials such as Cu, Al, Mg, Sn, Zn can be increased in various ways, e.g., by alloying materials with different elementary substances, by plastic working, heat treatment and thermo-mechanical treatment of obtained alloys. Those methods are well understood and commonly used all over the world. After the discovery of new carbon forms (graphene and carbon nanotubes), many researchers pursued the idea of combining them with metals. This idea assumes that the addition of nanocarbon will increase the useful properties of existing materials (metals).[1–6] In the last few years, a new method has emerged to incorporate nanocarbon into metals such as Cu, Al, Ag, Au, Sn, Zn, and Pb. It is being reported that those composites have higher electrical and mechanical properties, corrosion resistance, thermal conductivity, and other properties.[7,8,13–18] The inventor of the metallurgical production method of nanocomposite materials called ‘‘Covetic’’ is Third Millennium Materials, LLC (Dayton, Ohio). Historically, the incorporation of carbon into metals that are not strong carbide formers (like Al, Cu, Ag, Au, Sn, Zn, and Pb) has been technologically difficult because of low carbon wettability. Covetic processing, by contrast, provides a straightforward method to incorporate nanocarbon into these metals. This process has only recently been publicized,

TADEUSZ KNYCH, Full Professor, and PAWEŁ KWAS´NIEWSKI, GRZEGORZ KIESIEWICZ, ANDRZEJ MAMALA, ARTUR KAWECKI, and BEATA SMYRAK, Assistant Professors, are with the AGH University of Science and Technology, Krako´w, Poland. Contact e-mail: [email protected] Manuscript submitted August 12, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS B

development by the inventors is still in its early stages, and our experimental work is the first known independent replication of the method. There are other methods to synthesize metal–carbon composites, e.g., powder metallurgy, thermal spray, electrochemical deposition and friction stir additive processing.[1–8,10,19] The subject of metal–carbon composites has been described in some publications. In Reference 11, the authors claimed that it is possible to obtain an increase of electrical conductivity (about 10 pct) of copper–carbon composites vs pure copper. In Reference 9, the author shows an increase of about 15 pct in electrical conductivity of a copper–carbon composite, compared to pure copper. This material was obtained through a chemical deposition process of copper and graphene. In Reference 4, the authors reported increases in hardness of 10 to 70 pct for various combinations of Cu powder, which were deposited with graphite, graphene, and carbon nanofibers. In this paper, we describe our research to independently reproduce the covetic process, and to verify the successful conversion of the carbon to strongly bound, stable nanocarbon in the melt. It is known that carbon solubility in copper is very low under equilibrium conditions