Abstract
An alumina-based nanocomposite is fabricated through the addition of secondary nanophase material to an alumina matrix to alter and tailor the properties of alumina. The addition to alumina of semi-conductive materials, such as silicon carbide (SiC), and high conductive materials, such as carbon nanotubes with a characteristic size in the nanometer range, can alter the mechanical strength, hardness, toughness, and electrical and thermal properties of alumina. This paper discusses recent advances in the synthesis of alumina–SiC and alumina-carbon nanotube (CNT) nanopowders and their consolidation using conventional and non-conventional techniques. Mechanical (hardness, fracture toughness and flexural strength) and functional (thermal and electrical) properties are discussed. The influence of the microstructure on the properties of alumina–SiC and alumina–CNT nanocomposites is discussed. Furthermore, potential applications and current related research trends are described.
Highlights
Alumina is an extensively used technical ceramic due its hardness, high temperature strength and high thermal and electrical insulating properties
The fracture toughness was found to improve by 40%. Niihara concluded that this increase in strength was a result of an overall refinement of the microstructure and a reduction in processing flaws resulting from the addition of fine silicon carbide (SiC) particles to the alumina matrix [2,7,123]
Several researchers have consolidated alumina–SiC nanocomposites with different volumes of SiC nanoparticles, but none have reproduced the results reported by Niihara
Summary
Alumina is an extensively used technical ceramic due its hardness, high temperature strength and high thermal and electrical insulating properties. To tailor the mechanical and functional (thermal and electrical) properties of alumina–CNT nanocomposites, critical steps must be followed These include homogenous distribution of CNTs in the alumina matrix to avoid agglomeration resulting from van der Waals forces [33,34], a better consolidation process (e.g., spark plasma sintering (SPS)) to avoid CNT damage during processing and optimal bonding between the CNTs and alumina through the provision of interfacial compatibility, and good adhesion. The transport (thermal and electrical) properties of alumina-based nanocomposites are dependent on the content of the conductive reinforcement phase and the extent of its dispersion. The interfacial resistance of nanocomposites is very high due to the high surface area of nanoparticles Several models, such as Hasselman and Johnson’s model, Maxell’s model and Hamilton and Crosser’s model [28], have been developed to estimate the thermal conductivity of ceramic composites. Two nanocomposites (alumina–SiC and alumina–CNT nanocomposites) are discussed in terms of their preparation, mechanical properties, microstructures, thermal properties and electrical properties, and applications of the nanocomposite system are elucidated
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