This review summarises the research work carried out in the field of carbon nanotube (CNT) metal matrix composites (MMCs). Much research has been undertaken in utilising CNTs as reinforcement for composite material. However, CNT-reinforced MMCs have received the least attention. These composites are being projected for use in structural applications for their high specific strength as well as functional materials for their exciting thermal and electrical characteristics. The present review focuses on the critical issues of CNT-reinforced MMCs that include processing techniques, nanotube dispersion, interface, strengthening mechanisms and mechanical properties. Processing techniques used for synthesis of the composites have been critically reviewed with an objective to achieve homogeneous distribution of carbon nanotubes in the matrix. The mechanical property improvements achieved by addition of CNTs in various metal matrix systems are summarised. The factors determining strengthening achieved by CNT reinforcement are elucidated as are the structural and chemical stability of CNTs in different metal matrixes and the importance of the CNT/metal interface has been reviewed. The importance of CNT dispersion and its quantification is highlighted. Carbon nanotube reinforced MMCs as functional materials are summarised. Future work that needs attention is addressed.

Carbon nanotube reinforced metal matrix composites - a review

One-dimensional carbon nanotubes and two-dimensional graphene nanosheets with unique electrical, mechanical and thermal properties are attractive reinforcements for fabricating light weight, high strength and high performance metal-matrix composites. Rapid advances of nanotechnology in recent years enable the development of advanced metal matrix nanocomposites for structural engineering and functional device applications. This review focuses on the recent development in the synthesis, property characterization and application of aluminum, magnesium, and transition metal-based composites reinforced with carbon nanotubes and graphene nanosheets. These include processing strategies of carbonaceous nanomaterials and their composites, mechanical and tribological responses, corrosion, electrical and thermal properties as well as hydrogen storage and electrocatalytic behaviors. The effects of nanomaterial dispersion in the metal matrix and the formation of interfacial precipitates on these properties are also addressed. Particular attention is paid to the fundamentals and the structure–property relationships of such novel nanocomposites.

Recent progress in the development and properties of novel metal matrix nanocomposites reinforced with carbon nanotubes and graphene nanosheets

Metal matrix composites reinforced by nano-particles are very promising materials, suitable for a large number of applications. These composites consist of a metal matrix filled with nano-particles featuring physical and mechanical properties very different from those of the matrix. The nano-particles can improve the base material in terms of wear resistance, damping properties and mechanical strength. Different kinds of metals, predominantly Al, Mg and Cu, have been employed for the production of composites reinforced by nano-ceramic particles such as carbides, nitrides, oxides as well as carbon nanotubes. The main issue of concern for the synthesis of these materials consists in the low wettability of the reinforcement phase by the molten metal, which does not allow the synthesis by conventional casting methods. Several alternative routes have been presented in literature for the production of nano-composites. This work is aimed at reviewing the most important manufacturing techniques used for the synthesis of bulk metal matrix nanocomposites. Moreover, the strengthening mechanisms responsible for the improvement of mechanical properties of nano-reinforced metal matrix composites have been reviewed and the main potential applications of this new class of materials are envisaged.

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Metal Matrix Composites Reinforced by Nano-Particles—A Review

Rapid innovation in nanotechnology in recent years enabled development of advanced metal matrix nanocomposites for structural engineering and functional devices. Carbonous materials, such as graphite, carbon nanotubes (CNT's), and graphene possess unique electrical, mechanical, and thermal properties. Owe to their lubricious nature, these carbonous materials have attracted researchers to synthesize lightweight self-lubricating metal matrix nanocomposites with superior mechanical and tribological properties for several applications in automotive and aerospace industries. This review focuses on the recent development in mechanical and tribological behavior of self-lubricating metallic nanocomposites reinforced by carbonous nanomaterials such as CNT and graphene. The review includes development of self-lubricating nanocomposites, related issues in their processing, their characterization, and investigation of their tribological behavior. The results reveal that adding CNT and graphene to metals decreases both coefficient of friction and wear rate as well as increases the tensile strength. The mechanisms involved for the improved mechanical and tribological behavior is discussed.

Mechanical and tribological properties of self-lubricating metal matrix nanocomposites reinforced by carbon nanotubes (CNTs) and graphene – A review

Microstructurally inhomogeneous composites: Is a homogeneous reinforcement distribution optimal?

Carbon nanotubes reinforced aluminum matrix composites were fabricated by isostatic pressing followed hot extrusion techniques. Differential scanning calorimetric, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy has been carried out to examine the reaction condition of nanotubes and aluminum, and to analyze the composites structure. The effects of nanotubes content on mechanical properties of composites were investigated. Experimental results showed that nanotubes are homogeneously distributed in the composites. Some nanotubes act as bridges across cracks, others are pulled-out on fracture surfaces of composites. However, nanotubes react with aluminum and form Al4C3 phases when the temperature is above 656.3 °C. The nanotubes content affects significantly mechanical properties of composites. Meanwhile, the 1.0 wt.% nanotube/2024Al composite is found to exhibit the highest tensile strength and Young's modulus. The maximal increments of tensile strength and Young's modulus of the composite, compared with the 2024Al matrix, are 35.7% and 41.3%, respectively.

Processing and properties of carbon nanotubes reinforced aluminum composites

In situ TiBw/Ti-6Al-4V composites with novel reinforcement architecture fabricated by reaction hot pressing

Hot working of Ti–6Al–3Mo–2Zr–0.3Si alloy with lamellar α + β starting structure using processing map

By incorporating the Taylor-based nonlocal theory of plasticity, the finite element method (FEM) is applied to investigate the effect of particle size on the deformation behavior of the metal matrix composites. The contributions of various strengthening mechanisms to overall composite strengthening, and the impact of particle size on each mechanism were explicitly evaluated. Both numerical and experimental results indicate that, at a constant particle volume fraction, there is a close relationship between the particle size and the deformation behavior of the composites. The yield strength and plastic work hardening rate of the composites increase with decreasing particle size. The predicted stress–strain behaviors of the composites are qualitative agreement with the experimental results. It is also found that the particle size has a significantly effect on the dislocation strengthening mechanism, but little on the load transfer strengthening mechanism.

Experimental and numerical studies of the effect of particle size on the deformation behavior of the metal matrix composites

The hot compression behavior of Ti–6.5Al–3.5Mo–1.5Zr–0.3Si alloy with an equiaxed microstructure was examined in the temperature range of 900–1060 °C and strain rate range of 0.001–10 s −1 . The dynamic recrystallization (DRX), flow instability and texture of compressed Ti alloy are characterized by the processing maps and EBSD. The stress–strain curves of Ti alloys show that the continuous flow softening occurs, while the broad oscillations induced by adiabatic shear bands exist above strain rates of 1.0 s −1 . The processing maps exhibit two DRX domains: α phase DRX domain in the range of 900–980 °C and 0.001–0.1 s −1 , and the β phase DRX domain in the range of 1000–1060 °C and 0.01–1.0 s −1 . It is also found that the instable deformation region increases with strain increasing. In addition, EBSD results exhibit that DRX can cause the low angle boundaries (LABs) to decrease and the high angle boundaries (HABs) to increase in the α + β region.

A.B. Li

Papers

Processing and properties of carbon nanotubes reinforced aluminum composites

In situ TiBw/Ti-6Al-4V composites with novel reinforcement architecture fabricated by reaction hot pressing

Hot working of Ti–6Al–3Mo–2Zr–0.3Si alloy with lamellar α + β starting structure using processing map

Experimental and numerical studies of the effect of particle size on the deformation behavior of the metal matrix composites

Characteristics of hot compression behavior of Ti–6.5Al–3.5Mo–1.5Zr–0.3Si alloy with an equiaxed microstructure