Multi-Walled Carbon Nanotube-Aluminum Matrix Composites Prepared by Combination of Hetero-Agglomeration Method, Spark Plasma Sintering and Hot Extrusion

Abstract

Multi-walled carbon nanotubes (MWCNTs) with outstanding mechanical properties are considered as an ultimate reinforcement for conventional metals such as aluminum (Al), though they require uniform dispersion and intimate contacts with the host metal matrix. However, bundled structure of chemically stable, pristine MWCNTs has been the main challenge to achieving the expected structural reinforcement. In addition, the sole contribution of MWCNTs in strengthening the metal matrix has not been recognized yet, due to the concurrent strengthening mechanisms such as metal's work hardening, grain refinement, etc. Here, we prepared MWCNT-Al matrix composite powders with uniform MWCNT dispersion by using hetero-agglomeration principle, and fabricated fully dense 1.0 vol% MWCNT-Al matrix composite bulk by using spark plasma sintering (SPS) and a subsequent hot extrusion process, with a 40% improved tensile strength and an elongation to failure of 27.3% similar to that of cast pure Al. During the SPS process, the nanoscale surface defects of MWCNTs were infiltrated by momentarily formed liquid Al and an intimate Al 4 C 3 -free interface was formed between MWCNTs and bare Al matrix. After the hot extrusion process, straight MWCNTs aligned in the extrusion axis found intimate contacts with the dynamically recovered, crack-free Al matrix. Our study suggests that the tensile improvement realized in our extruded/SPSed composites is directly originated from an effective load transfer at the MWCNT/Al interface, because no evidence of Al work hardening or the formation of interfacial Al 4 C 3 crystals was detected.

Influence of dispersion/mixture time on mechanical properties of Al–CNTs nanocomposites

“…It is essential to find a compromise between these two factors. The techniques described in the literature, which confer the best results of CNT dispersion, are comprise of mechanical processes [4,5] and the chemical and physical modifications of the CNTs (CNT functionalization) [6].…”

Core/Shell Structure of TiO2‐Coated MWCNTs for Thermal Protection for High‐Temperature Processing of Metal Matrix Composites

“…ose processing routes include powder metallurgy [6][7][8][9][10][11][12][13][14], high-energy ball milling [15,16], friction stir processing [17], spark plasma sintering [18], plasma spraying [19][20][21], and more recently laser sintering [22]. However, the obtained results are still not completely satisfactory, because the extreme processing conditions, either thermal or impact, can damage the CNT structure and cause a detrimental effect on the final mechanical properties of the composite.…”

Metallurgical Challenges in Carbon Nanotube-Reinforced Metal Matrix Nanocomposites

“…A recent study by Rashad et al [146] showed that the formed intermetallics in MWNTs-dispersed Mg-3Al-1Zn alloys are refined with the CNTs inclusion. Figure 23 indicates the schematic demonstration of Mg 17 Al 12 generation at the interface of Mg-3Al-1Zn/MWNTs composite, where the coarse particles of Mg 17 Al 12 can be refined through the incorporation of MWNTs into the matrix. Figure 22.…”

“…To overcome this challenge, a broad spectrum of dispersion methods is developed. Among these techniques, the mechanical methods [15], surface treatment [16], and chemical methods [17] are the most conventional. Each of these techniques has their own advantages and disadvantages, being discussed in the next sections.…”