Optimizing the interface bonding in Cu matrix composites by using functionalized carbon nanotubes and cold rolling
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Optimizing the interface bonding in Cu matrix composites by using functionalized carbon nanotubes and cold rolling Guijun Liu1, Jingmei Tao1,a), Fengxian Li1, Rui Bao1, Yichun Liu1, Caiju Li1, Jianhong Yi1,b) 1
Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China Address all correspondence to these authors. e-mail: [email protected] b) e-mail: [email protected] a)
Received: 23 January 2019; accepted: 17 June 2019
Nonuniform dispersion and weak interfacial bonding between carbon nanotubes (CNTs) and Cu matrix are two critical issues for achieving high strength and good ductility of CNT/Cu composites. Here, acid-treated CNTs precoated with Ni coatings were used to enhance the dispersion uniformity of CNTs and interfacial bonding between CNTs and Cu matrix in the CNT/Cu composites fabricated through spark plasma sintering and subsequently cold rolling. Scanning electron microscopy analysis revealed the homogeneous dispersion of Nicoated CNTs (Ni-CNTs) in the composite compared with uncoated CNTs. Transmission electron microscope observation indicated that Cu2O nanoparticles were in situ formed at the interface in Ni-CNT/Cu composite, where CNTs were uncovered by Ni coatings. After rolling, the distribution of Ni-CNTs transformed into ribbons aligning along the rolling direction. The ultimate tensile strength (UTS) of 261 MPa was achieved in rolled 1 vol% Ni-CNT/Cu composite, which was 24.3% higher than that before rolling. The UTS of 2 vol% Ni-CNT/Cu composite obviously decreased, which could be attributed to the agglomeration of Ni-CNTs in the Cu matrix due to the increased volume content.
Introduction Since their discovery by Iijima in 1991 [1], carbon nanotubes (CNTs) have attracted comprehensive interest in scientific community [2, 3] and have been regarded as ideal nanoreinforcements of ceramic and polymer composites. In recent years, CNTs have also aroused widespread interest in the field of metal matrix composites (MMCs) due to their outstanding properties [4]. However, due to the large specific surface area, CNTs as reinforcements of MMCs are prone to agglomerate under Van der Waals force [5]. In addition, due to the poor wettability between untreated CNTs and metal matrix, only mechanical interfaces can form between them with no interfacial interaction [6, 7]. Therefore, the attainment of homogeneous dispersion of CNTs in metal matrix and the formation of strong interfacial bonding between CNTs and metal matrix are two critical issues for the development of CNT-reinforced MMCs. By changing the surface conditions of CNTs, the interface microstructure can be optimized, thus improving the dispersion uniformity of CNTs in the metal matrix and the interfacial
ª Materials Research Society 2019
bonding strength between CNTs and the matrix [8, 9, 10, 11]. In general, acid treatment is a common method used to change the surface conditions of CNTs. By acidizing CNTs in a mixed sulfuric/nitric solution, oxygen-containing functional group, including ato
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