Abstract
Damage to carbon nanotubes (CNTs) during the fabrication process of CNT reinforced composites has great influence on their mechanical properties. In this study, the 2014 Al with powder sizes of 20, 9 and 5 μm was selected to study the effect of initial particle size on the damage to carbon nanotubes (CNTs) during ball milling. The result shows that for CNTs in the ball milled CNT/Al (with powder size of 20 and 9 μm) mixtures, the intensity ratio of the D band and the G band (ID/IG) first increased and then reached a plateau, mainly because most of the CNTs are embedded, to a certain extent, in the aluminum powder after milling, which could protect the CNTs from damage during further milling. While for CNTs in the ball milled CNT/Al (with powder size of 5 μm) mixture, the ID/IG ratio continues to climb from 1.31 to 2.33 with time, indicating continuous damage to the CNTs occurs during the milling. Differential scanning calorimetry (DSC) analysis demonstrates that the chemical instability increased with an increase in the damage level of CNTs, resulting in the formation of aluminum carbide (Al4C3) at a lower temperature before the melting of aluminum, which is detrimental to their mechanical properties.
Highlights
Since discovered by Iijima [1], carbon nanotubes (CNTs) are considered to be ideal reinforcements of composites due to their exceptional strength, high Young’s modulus and low density [2,3].Among many candidate matrix materials for lightweight high-strength composites, aluminum alloys have been considered to be preferential due to their relatively low density and reasonable mechanical properties
The clusters of CNTs were bounded by white dotted elliptical rings, and the tips of the CNTs embedded in the matrix were marked by black arrows
Note that the ductile aluminum powder becomes flattened by the ball-powder-ball collisions, and some bright particles with a size of about several microns are observed on the surface of the flattened aluminum powder, after the ball milling times of 3 h and 6 h
Summary
Since discovered by Iijima [1], carbon nanotubes (CNTs) are considered to be ideal reinforcements of composites due to their exceptional strength, high Young’s modulus and low density [2,3]. Among many candidate matrix materials for lightweight high-strength composites, aluminum alloys have been considered to be preferential due to their relatively low density and reasonable mechanical properties. Called mechanical alloying, has been proven effective to uniformly disperse CNTs within the aluminum matrix [14]. Three size levels of initial aluminum alloy powder were ball milled with 2.0 wt %. CNTs reinforced 2014 Al alloy composites were fabricated by a hot pressing process to characterize their mechanical properties
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