Carbon Nanotubes (CNTs)-Reinforced Magnesium-Based Matrix Composites: A Comprehensive Review

Abstract

In recent years considerable attention has been attracted to magnesium because of its light weight, high specific strength, and ease of recycling. Because of the growing demand for lightweight materials in aerospace, medical and automotive industries, magnesium-based metal matrix nanocomposites (MMNCs) reinforced with ceramic nanometer-sized particles, graphene nanoplatelets (GNPs) or carbon nanotubes (CNTs) were developed. CNTs have excellent material characteristics like low density, high tensile strength, high ratio of surface-to-volume, and high thermal conductivity that makes them attractive to use as reinforcements to fabricate high-performance, and high-strength metal-matrix composites (MMCs). Reinforcing magnesium (Mg) using small amounts of CNTs can improve the mechanical and physical properties in the fabricated lightweight and high-performance nanocomposite. Nevertheless, the incorporation of CNTs into a Mg-based matrix faces some challenges, and a uniform distribution is dependent on the parameters of the fabricating process. The characteristics of a CNTs reinforced composite are related to the uniform distribution, weight percent, and length of the CNTs, as well as the interfacial bonding and alignment between CNTs reinforcement and the Mg-based matrix. In this review article, the recent findings in the fabricating methods, characterization of the composite's properties, and application of Mg-based composites reinforced with CNTs are studied. These include the strategies of fabricating CNT-reinforced Mg-based composites, mechanical responses, and corrosion behaviors. The present review aims to investigate and conclude the most relevant studies conducted in the field of Mg/CNTs composites. Strategies to conquer complicated challenges are suggested and potential fields of Mg/CNTs composites as upcoming structural material regarding functional requirements in aerospace, medical and automotive industries are particularly presented.

Keywords: carbon nanotubes; composite; corrosion behavior; fabrication process; magnesium; mechanical properties.

Figure 1

Schematic representation of properties and applications of carbon nanotubes (CNTs).

Figure 2

Schematic illustration of the morphological structure of CNT.

Figure 3

A brief historical timeline for CNTs showing the major developments that guided applications of CNTs [19].

Figure 4

Different metallurgical methods for fabricating composites: (a) powder metallurgy [15], (b) hot press sintering, (c) hot-extrusion, (d) hot rolling, (e) spark-plasma sintering (SPS), (f) stir casting (SC), (g) disintegrated melt deposition (DMD) [11], and (h) high-pressure die casting [15].

Figure 5

An illustration of fabricating Mg/CNTs using Gemini dispersant.

Figure 6

Schematic illustration of fabricating a micro-nano layered structure of Mg/CNTs composites [73].

Figure 7

Schematic illustration of compressive shear buckling of CNTs in ZK60A/CNTs nanocomposite (τ₁ and τ₂ are planar shear stresses where τ₁ < τ₂) [100].

Figure 8

Plot of the changes of (a) wear mass loss, and (b) coefficient of friction against the concentration of CNTs in AZ31-CNTs composite under dry sliding conditions [35].

Figure 9

Scanning electron microscope (SEM) images of worn surfaces of AZ31-CNTs composites including (a) 1.0 wt.%, (b) 0.5 wt.%, (c) 0.1 wt.%, and (d) 0 wt.% of CNTs, under dry sliding conditions [35].