| dc.description.abstract | The increasing availability of nanopowders and nanotubes combined with new
processing techniques is enabling the development of new multifunctional materials.
Carbon Nanotubes (CNTs) are one of the recently discovered allotropic forms of
carbon. They have exceptional mechanical, electrical and thermal properties. The
application of CNTs in the reinforcement of ceramic nanocomposites has not yet been
fully investigated and is the subject of this study. Alumina is the main matrix used in
this study. CNTs need to be de-agglomerated and homogeneously distributed in
ceramic nanocomposites. Dimethylformamide (DMF) produces fine and stable CNT
and alumina dispersions. All nanocomposites were sintered by Spark Plasma
Sintering (SPS). Nanocomposites prepared using DMF dispersions showed better
dispersions, higher electrical conductivity and mechanical properties as compared to
those prepared using ethanol dispersions. The addition of CNTs or Carbon Black
(CB) to alumina significantly aids its densification. The CNTs produce significant
grain growth retardation. CNTs were found to be well preserved in alumina after
being SPSed up to 1900 oC. Structural preservation of CNTs in ceramic
nanocomposites depends on the nature of ceramic and SPS processing conditions. The
electrical conductivity of alumina – CNT nanocomposites is four times higher as
compared to alumina – CB nanocomposites due to the fibrous nature and high aspect
ratio of CNTs. Alumina coated CNTs were used for better interfacial adhesion with
the matrix. Oxidative resistance of CNTs was increased by coating them with alumina
and by decreasing the grain boundary area in alumina – CNT nanocomposites. Coated
and uncoated CNTs showed higher mechanical reinforcement in alumina
nanocomposite as compared to CB. The future for ceramic – CNT nanocomposites is
very bright, especially for applications associated with the electrical and thermal
properties. Apart from a good understanding of nanocomposites, the commercial
development of CNT based technologies heavily relies on the availability and price of
CNTs. | en_US |
