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Characterization of metal-carbon nanotube composites17eueuMicroscopyandAnalysis | July/August 2017matrix. Fig.9 (b) shows the Vickers microhardness of various Cu-MWCNT composites. The hardness values of Cu-MWCNT composites increase gradually with the increase in the amount of carbon nanotubes in the Cu-MWCNT composites. Carbon nanotubes can withstand higher loads than the Cu matrix and hence there is a substantial increase in the hardness values. This is possibly due to the interfacial bonding between the MWCNTs and the Cu matrix, which is aided by the functionalization of MWCNTs. The highest hardness value was 1.44 GPa achieved for Cu-5 vol. % MWCNTs composites. The hardness enhancement is an indication of good physical bonding at Cu-MWCNTs interface.MWCNT reinforced Cu-based metal matrix composites were fabricated by powder metallurgy method. The dispersion of CNTs in the Cu matrix plays important role in enhancing the wear resistance of the Cu-MWCNTs composites. The wear characteristics for Cu-MWCNTs composites shown in Figure 10 (a) indicate that the wear resistance of the Cu-MWCNTs composites increases with increasing volume fraction of the MWCNTs in the composite.The MWCNTs act as a lubricating carbon film. The low coefficient of friction of the MWCNTs leads to higher wear resistance of the Cu-MWCNTs composite. With the addition of MWCNTs there is reduction in direct contact between the Cu matrix and the indenter. Figs.10 (b-d) show the FESEM images of the wear tracks of Cu-1, 2 and 5 vol. % MWCNTs composites. It can be seen that the width of the wear track reduces with the increase in volume fraction of MWCNTs in the Cu-MWCNTs composite.SUMMARY AND CONCLUSIONSThe relative density of the Cu-MWCNTs composites increase with the increase in the volume fraction of carbon nanotubes in the Cu matrix. However, the Cu-MWCNTs composites do not show significant increase in densification after addition of 2 vol. % of MWCNTs in the Cu matrix.The hardness of Cu-MWCNTs composites increases gradually with the increase in the amount of carbon nanotubes in the Cu-MWCNTs composites. Cu-5 vol. % MWCNTs composite showed highest hardness of 1.44 GPa. Addition of MWCNTs to the Cu matrix improved the wear resistance of the Cu-MWCNTs composites. An increase in wear resistance of the Cu-MWCNTs composites was seen with the addition of upto 5 vol. % of MWCNTs.REFERENCES1 Hull, D. and T.W. Clyne, An Introduction to Composite Materials. 1996: Cambridge University Press.2. Chawla, K.K., Metal Matrix Composites, in Materials Science and Technology. 2006, Wiley-VCH Verlag GmbH & Co. KGaA.3. Chawla, K.K., Composite Materials: Science and Engineering. 1998: Springer.4. Harris, B. and I.o. Materials, Engineering Composite Materials. 1999: IOM.5. Matthews, F.L. and R.D. Rawlings, Composite Materials: Engineering and Science. 1999: CRC Press.6. Miracle, D.B., Metal matrix composites – From science to technological significance. Composites Science and Technology, 2005. 65(15–16): p. 2526-2540.7. Seong-Min, C. and A. Hideo, Nanocomposites—a new material design concept. Science and Technology of Advanced Materials, 2005. 6(1): p. 2.8. Schubert, T., et al., Interfacial design of Cu-based composites prepared by powder metallurgy for heat sink applications. Materials Science and Engineering: A, 2008. 475(1–2): p. 39-44.9. Iijima, S., Carbon nanotubes: past, present, and future. Physica B: Condensed Matter, 2002. 323(1–4): p. 1-5.10. Iijima, S., P.M. Ajayan, and T. Ichihashi, Growth model for carbon nanotubes. Physical Review Letters, 1992. 69(21): p. 3100-3103.11. Iijima, S., et al., Structural flexibility of carbon nanotubes. The Journal of Chemical Physics, 1996. 104(5): p. 2089-2092.12. Iijima, S. and T. Ichihashi, Single-shell carbon nanotubes of 1-nm diameter. Nature, 1993. 363(6430): p. 603-605.13. Fu, H., et al., Synthesis and mechanical properties of Cu-based bulk metallic glass composites containing in-situ TiC particles. Scripta Materialia, 2005. 52(7): p. 669-673.14. Kim, K.T., S.I. Cha, and S.H. Hong, Hardness and wear resistance of carbon nanotube reinforced Cu matrix nanocomposites. Materials Science and Engineering: A, 2007. 449–451: p. 46-50.15. Futaba, D.N., et al., Shape-engineerable and highly densely packed single-walled carbon nanotubes and their application as super-capacitor electrodes. Nat Mater, 2006. 5(12): p. 987-994.16. Li, H., et al., Strong and ductile nanostructured Cu-carbon nanotube composite. Applied Physics FIGure 9 (a) Relative Density plot of various sintered Cu-MWCNTs composite; (b) Vickers hardness plot of various Cu-MWCNTs composite.bA