On the limiting grain sizes in carbon nanotube nanocomposites

Gopalan, H and Chokshi, AH (2019) On the limiting grain sizes in carbon nanotube nanocomposites. In: Materialia, 5 .

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Abstract

Despite their continuing popularity over the past two decades, the influence of carbon nanotubes on grain growth is not understood clearly and often a Zener analysis is applied erroneously. The role of second phase particle drag on grain boundaries and the Zener limiting grain size behavior is well documented for spherical particles. Surprisingly, no such reports of limiting grain size in carbon nanotube composites are available in the literature, which may be related potentially to issues with poor dispersion. Systematic grain growth studies in well dispersed multiwall carbon nanotube reinforced alumina composites show for the first time a limiting grain growth behavior. The drag force exerted by cylindrical nanotubes on grain boundaries was calculated and compared with spherical particles. Due to nanometric dimensions, radial flexibility and the unique tendency of nanotubes to be present only at the grain boundaries, a Zener analysis is inapplicable for analyzing grain growth in these composites. Therefore, a simple geometrical analytical model was developed that rationalizes the experimentally observed limiting grain growth behavior. The influence of grain size distributions on the limiting grain size was determined, showing that the limiting grain size is reduced with an increase in the standard deviation. The geometric grain boundary coverage model proposed here can be used as a guideline for tailoring microstructures based on size, shape and volume fraction of nanometric carbon-based reinforcements, for exploring interesting properties including superplasticity. © 2019 Acta Materialia Inc.

Item Type:	Journal Article
Publication:	Materialia
Publisher:	Elsevier B.V.
Additional Information:	The copyright for this article belongs to Elsevier B.V.
Keywords:	Alumina; Aluminum oxide; Carbon nanotubes; Drag; Grain boundaries; Grain growth; Grain size and shape; Nanotubes; Particle size analysis; Reinforcement; Size distribution, Carbon nanotube nanocomposites; Carbon-nanotube composites; Grain boundary coverage; Grain size distribution; Limiting grain sizes; Multi-wall carbon-nanotube-reinforced alumina composites; Nanometric dimensions; Second phase particles, Multiwalled carbon nanotubes (MWCN)
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	13 Dec 2022 04:48
Last Modified:	13 Dec 2022 04:48
URI:	https://eprints.iisc.ac.in/id/eprint/78315

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