Microstructural Changes in Copper–Graphite–Alumina Nanocomposites Produced by Mechanical Alloying

Abstract

Microstructural features of nanostructured copper-matrix composites produced via high-energy milling were studied. Copper-graphite-alumina batches were planetary ball milled up to 16 h; copper-graphite batches were also prepared under the same conditions to evaluate the effect of contamination from the milling media. The microstructure of the produced materials was characterized by field emission gun scanning electron microscopy/energy-dispersive spectroscopy and related to Raman, X-ray diffraction, and particle size analysis results. Results showed that alumina was present in all milled powders. However, size reduction was effective at shorter times in the copper-graphite-alumina system. In both cases the produced powders were nanostructured, containing graphite and alumina nanoparticles homogeneously distributed in the copper matrix, especially for longer milling times and in the presence of added alumina. Copper crystallite size was significantly affected above 4 h milling; nanographite size decreased and incipient amorphization occurred. A minimum size of 15 nm was obtained for the copper crystallite copper-alumina-graphite composite powders, corresponding to 16 h of milling. Contamination from the media became more significant above 8 h. Results suggest that efficient dispersion and bonding of graphite and alumina nanoparticles in the copper matrix is achieved, envisioning high conductivity, high strength, and thermal stability.

Nanostructured copper-carbon nanotubes composites for aircraft applications

“…Dry milling on its turn renders d 50 = 28.2 for Cu-dry_16. It should be mentioned that these values are much higher than previously obtained results in the same systems milled using alumina jar and alumina balls (Rodrigues et al , 2014). Also, resulting powders are less equiaxed.…”

“…In the current work, the only source of alumina are the jar walls (as copper balls were used), which are less exposed to high-energy collisions than the balls and are somewhat protected by the copper coating welded in Stage 2. A high availability of alumina was proven to accelerate the production of homogeneous nanostructured powders and to contribute to overall powder size decrease (Rodrigues et al , 2014).…”

“…As a result, powder size and size distribution [Figure 7(b)] results are quite similar with or without isopropyl alcohol addition. The use of graphite as a PCA in a previous work showed that isopropyl alcohol is required to avoid copper agglomeration even in the presence of graphite (Rodrigues et al , 2014). This result suggests that CNTs have a more powerful lubricant action in copper powder systems than graphite.…”

Preparation and Properties of Graphite/Antimony Composites Based on Coal Tar Pitch

“…Since carbon or graphite material is filled with a large number of microspores which decrease the mechanical strength and oxidation resistance of the material, impregnation and reinforcement methods are typically employed to fill pores. Many achievements have been made in impregnating porous carbon/graphite with nonmetals (such as resin) or metals (such as aluminum, copper, Babbitt metal and antimony) effectively compacting pores, improving material performance parameters such as oxidation resistance, strength and hardness, and enhancing applications in extreme operating conditions including high temperatures, heavy loads and high abrasion environments [2][3][4][5][6][7][8][9][10]. As an impregnating material, antimony is superior to others, and has become a recent focus in the field of impregnated carbon/graphite materials [1,[12][13].…”

Solid State Reaction Mechanism and Microstructure Evolution of Ni-Al Powders during High Energy Ball Milling Revisited by TEM

“…The technique of high energy ball milling (HEBM) has been extensively used to synthesize intermetallic powders and then to fabricate bulk materials with fine grain size (Koch & Whittenberger, 1996; Moshksar & Mirzaee, 2004; Joardar & Murty, 2007; Fan et al, 2012; Rodrigues et al, 2015). This technique was first developed by Benjamin et al (1970) at the International Nickel Company in the late 1960s in order to produce oxide-dispersion-strengthened alloys for high temperature structural applications.…”