Strengthening mechanisms in carbon nanotube-reinforced aluminum composites

Although carbon nanotubes (CNTs) are used to reinforce aluminum alloys, the underlying strengthening mechanisms have not yet been clarified. Here, we focus on elucidating several of these mechanisms including load transfer, generation of dislocations from thermal mismatch, and the Orowan looping system to explain the enhanced mechanical properties of CNT-reinforced Al. The sample preparation procedure involves mechanically pulverizing Al in paraffin oil mixed with CNTs dispersed in dichloroethane. The mixture was then sintered and melt-blended to produce solid samples. The formation of covalent bonds (Al₄C₃) between Al and CNT walls was confirmed by X-ray diffraction, Raman spectroscopy, and transmission electron microscope measurements. The yield strength and tensile strength were improved by 60% and 23%, respectively, with the addition of 0.2 wt% CNTs. These enhancements corroborate well with the predicted values from the multiple strengthening mechanisms.