Transmission electron microscopy study of copper–carbon nanocomposite

Abstract

A Cu210C nanocomposite has been synthesised by high energy milling of elemental powders, followed by annealing at 873 K. Phase identification and microstructure characterisation have been carried out with transmission electron microscopy. Copper grain size ranged from 10 to 120 nm for the as milled material and from 10 to 150 nm after annealing. No graphite reflections could be detected by electron diffraction in either the as milled or annealed samples. Nevertheless, both conditions contain clusters of carbon of ,10 nm, which could be of benefit for sliding wear applications. The lattice parameter measured after milling is compatible with a carbon solubility in the copper matrix ,0 . 1 at.-%. The synthesised material showed excellent structural stability at 873 K, which is proposed to be dependent on solute drag effects resulting from boundary segregation. In fact, no grain boundary pinning by nanoparticles has been detected while a decrease in lattice parameter occurred during annealing.

Microstructural Evolution of Cu-10at%C Nanocomposite Powder During High Energy Mechanical Milling

“…The pioneering studies of Saji et al 11 and Yamane et al 12 on mechanical milling of copper-graphite mixtures with different weight ratio of graphite indicated the solubility of carbon in copper can be as high as 28.5at%, while the study carried out by Marque et al 13 on mechanical milled Cu-10at%C composite showed that the carbon content was overestimated by the former researchers and the existence of carbon nanoparticles was shown. Transmission electron microscopy examination confirmed that the microstructure of the mechanically milled Cu-10at%C nanocomposite consisted of nanostructured copper matrix dispersed with carbon nanoparticles 14 . While these studies mainly focus on the carbon solubility in copper achieved by HEMM, the microstructural evolution of copper-graphite nanocomposite powders need to be clarified with more details.…”

“…As shown in Figure 5a, after 6 h of milling, the grain sizes of the Cu matrix were in the range of 20~40 nm, in agreement with the average crystallite size of 30 nm determined based on the XRD pattern of the powder, thus the grain size of copper determined from Williamson-Hall method was considered to be accurate. The light contrast regions marked with arrows were determined to be amorphous carbon 14 . As shown in Figure 5b, the microstructure of the 24 h milled powder particles was quite similar to that of the 6 h milled powder particles.…”

“…In this study, our focus is on the microstructural evolution of Cu-10at%C nanocomposite during HEMM, where the equilibrium solid solubility of carbon in copper is virtually zero 10 . HEMM of Cu-graphite composite powders have been studied by several groups [11][12][13][14][15] . The pioneering studies of Saji et al 11 and Yamane et al 12 on mechanical milling of copper-graphite mixtures with different weight ratio of graphite indicated the solubility of carbon in copper can be as high as 28.5at%, while the study carried out by Marque et al 13 on mechanical milled Cu-10at%C composite showed that the carbon content was overestimated by the former researchers and the existence of carbon nanoparticles was shown.…”