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

Large-Scale Fabrication of Boron Nitride Nanosheets and Their Utilization in Polymeric Composites with Improved Thermal and Mechanical Properties

Functionalization is an important way to breed new properties and applications for a material. This review presents an overview of the progresses in functionalized hexagonal boron nitride (h-BN) nanomaterials. It begins with an introduction of h-BN structural features, physical and chemical properties, followed by an emphasis on the developments of BN functionalization strategies and its emerging properties/applications, and ends with the research perspectives. Different functionalization methods, including physical and chemical routes, are comprehensively described toward fabrication of various BN derivatives, hetero- and porous structures, etc. Novel properties of functionalized BN materials, such as high water solubility, excellent biocompatibility, tunable surface affinities, good processibility, adjustable band gaps, etc., have guaranteed wide applications in biomedical, electronic, composite, environmental and "green" energy-related fields.

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Functionalized hexagonal boron nitride nanomaterials: emerging properties and applications.

3.1.1. Covalent Interactions 1355 3.1.2. Noncovalent Interactions 1356 3.1.3. π-π Stacking 1356 3.1.4. Electrostatic Interactions 1357 3.2. In Situ Synthesis Directly on the CNT Surface 1358 3.2.1. Electrochemical Techniques 1358 3.2.2. Sol-Gel Process 1361 3.2.3. Hydrothermal and Aerosol Techniques 1363 3.2.4. Gas-Phase Deposition 1364 3.3. Comparison of Synthesis Techniques 1368 4. Properties and Potential Applications of CNT-Inorganic Hybrids 1368

Carbon Nanotube−Inorganic Hybrids

This article presents an overview of the up-to-date developments in boron nitride nanotubes (BNNTs), including theory, fabrication, structure, physical properties, chemical functionalization and applications. Soon after the discovery of carbon nanotubes, BNNTs were theoretically predicted, followed by their successful fabrication by arc-discharge in 1995. Subsequently, various methods were developed for the BNNT synthesis, although till now, the growth of highly pure single-walled BNNTs at large quantities remains a challenge. The physical property investigations reveal that BNNTs’ exhibit a stable wide band gap, superb mechanical strength, high thermal conductivity, ultra-violet light emission, etc. All these properties build up the solid basis for their future technological applications. Chemical modification is also a decent approach to adjust the BNNTs properties. In recent years the yield of multi-walled BNNTs has reached the grams level, that can allow their detailed chemical functionalization studies. So far, many kinds of functionalizations through different weak interactions and covalent bonding were developed. These treatments improved BNNT dispersions in solvents and extended their fields of applications. Moreover, some application-related studies on multi-walled BNNTs, such as composites fabrication, hydrogen storage, biocompatibility, and mechanical, and electrical breakdown tests have also been started in recent years.

Boron nitride nanotubes

One-dimensional multiwalled carbon nanotube (MWCNT)/SiC porous nanocomposites were prepared via an in situ reaction between Si and MWCNTs induced by the reaction between Na and I2. The as-prepared nanocomposites exhibit outstanding microwave absorbing performances with an absorber thickness of about 2 mm. The absorbing bandwidth for the nanocomposites increases by raising the reaction temperature from 200 to 400 °C. The dielectric polarizations, which originate from the synergistic effect of the defects, porous structures and nanoparticles in the nanocomposites, are responsible for the excellent microwave absorbing performances.

In situ synthesis of one-dimensional MWCNT/SiC porous nanocomposites with excellent microwave absorption properties

Morphology-controllable preparation of NiFe2O4 as high performance electrode material for supercapacitor

Microstructure and fracture toughness of graphene nanosheets/alumina composites

Boron nitride nanotubes (BNNTs)/alumina composites were fabricated by hot pressing. The mechanical properties of the composites are greatly dependent upon the content of BNNTs. In comparison with monolithic alumina, the incorporation of BNNTs results in the improvement of bending strength and fracture toughness owing to the effective inhibition of grain growth. A routine toughening mechanism, especially the bridging of BNNTs at grain boundaries and the sufficient physical bonding between BNNTs and alumina matrix, is dominantly responsible for the increase in mechanical properties.

Microstructure and mechanical properties of alumina ceramics reinforced by boron nitride nanotubes

Boron nitride nanotubes (BNNTs)/alumina composites were fabricated by hot pressing. The effect of BNNTs on the mechanical properties, including ambient and high-temperature flexure strength and fracture toughness was investigated. As a result of sufficient physical and chemical bonding between BNNTs and alumina, the pullout and fracture of BNNTs concurrent with the suppression of BNNTs on abnormal growth of grains contributes to the excellent ambient and high-temperature mechanical properties.

Jianqiang Bi

Papers

In situ synthesis of one-dimensional MWCNT/SiC porous nanocomposites with excellent microwave absorption properties

Morphology-controllable preparation of NiFe2O4 as high performance electrode material for supercapacitor

Microstructure and fracture toughness of graphene nanosheets/alumina composites

Microstructure and mechanical properties of alumina ceramics reinforced by boron nitride nanotubes

Fabrication of Alumina Ceramic Reinforced with Boron Nitride Nanotubes with Improved Mechanical Properties