Micro/Nanostructure and Tribological Characteristics of Pressureless Sintered Carbon Nanotubes Reinforced Aluminium Matrix Composites

Abstract

This study reports the manufacture, microstructure, and tribological behaviour of carbon nanotube reinforced aluminium composites against pure aluminium. The specimens were fabricated using powder metallurgy method. The nanotubes in weight percentages of 0.5, 1.0, 1.5, and 2.0 were homogeneously dispersed and mechanically alloyed using a high energy ball milling. The milled powders were cold compacted and then isothermally sintered in air. The density of all samples was measured using Archimedes method and all had a relative density between 92.22% and 97.74%. Vickers hardness increased with increasing CNT fraction up to 1.5 wt% and then reduced. The microstructures and surfaces were investigated using high resolution scanning electron microscope (SEM). The tribological tests showed that the CNT reinforced composites displayed lower wear rate and friction coefficient compared to the pure aluminium under mild wear conditions. However, for severe wear conditions, the CNT reinforced composites exhibited higher friction coefficient and wear rate compared to the pure aluminium. It was also found that the friction and wear behaviour of CNT reinforced composites is significantly dependent on the applied load and there is a critical load beyond which CNTs could have adverse impact on the wear resistance of aluminium.

Mirostructure and microhardness of aluminum-copper composite reinforced with multi-walled carbon nanotubes prepared by vacuum sintering and hot isostatic pressing techniques

“…With 1 wt.% CNT content, the relative density of H1 (93.5 %) is lower in comparison with that of composite without Cu (94.6%), but microhardness of specimen H1 is nearly 2.3 times higher. The decrease in microhardness when CNT content higher 1.5 % could be due to the porosity formed by CNT clusters as evidenced by many authors [7,18,[26][27][28]. In conclusion, the high microhardness of CNT/Al-Cu composite is due to the synergistic effect of CNTs reinforcement and precipitation hardening of Al-Cu matrix and also affected by the defect and uniform dispersion of CNTs during the preparation process.…”

Tribological Properties of Al-Based Composites Reinforced with Fullerene Soot

“…Other technological additions are stearic acid (1 wt.%) and a mixture of CaCl 2 , NaCl, and KCl in the ratio 2:1: (3 wt.%). Metal-matrix composites containing carbon nanostructures, due to their high hardness and self-lubrication effect, can be considered as a promising solution to provide better wear resistance [4][5][6][7][8][9][10]. It was noted in [4] that in composites, carbon nanotubes prevented the direct contact of two sliding surfaces due to the formation of lubricating film and showed better wear resistance compared to other dispersed particles.…”

“…The addition of 4% carbon nanotubes leads to a decrease in the friction coefficient by 55%. In [5], it was found that CNT-reinforced composites showed a lower wear rate and friction coefficient compared to pure aluminum under soft wear conditions. However, under hard wear conditions these composites showed a higher coefficient of friction and wear rate compared to pure aluminum.…”

“…However, under hard wear conditions these composites showed a higher coefficient of friction and wear rate compared to pure aluminum. It was also found that the friction and wear of CNT-reinforced composites are highly dependent on the applied load, and there is a critical load above which CNTs can have an adverse effect on the wear resistance of aluminum [5].…”

Nanocontact Characteristics of Composite Galvanic Chrome Coatings Detected by Sclerometry and Atomic Force Microscopy

“…Composites with nanotubes as a reinforcing phase are usually manufactured by methods of thermal spraying, sintering, powder metallurgy, spark plasma extrusion, and spark plasma sintering. Due to mechanical alloying in the manufacture of the composite, it was possible to achieve a uniform distribution of CNT in the metal matrix [10,11]. It is known that the degree of uniformity of the CNT distribution in a metal matrix is one of the key factors that affect the resulting physicalmechanical properties of the composite [10].…”