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BioMed Research International
Volume 2014 (2014), Article ID 768254, 10 pages
http://dx.doi.org/10.1155/2014/768254
Research Article

Characterization of Multiwalled Carbon Nanotube-Reinforced Hydroxyapatite Composites Consolidated by Spark Plasma Sintering

1School of Materials Science and Engineering, Yeungnam University, Gyeongbuk 712-749, Republic of Korea
2Department of Advanced Materials Engineering, Dong-A University, Busan 604-714, Republic of Korea
3Department of Polymer Science and Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea
4Advanced Ceramics Group, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan

Received 16 December 2013; Accepted 18 January 2014; Published 4 March 2014

Academic Editor: Oh Hyeong Kwon

Copyright © 2014 Duk-Yeon Kim et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Pure HA and 1, 3, 5, and 10 vol% multiwalled carbon nanotube- (MWNT-) reinforced hydroxyapatite (HA) were consolidated using a spark plasma sintering (SPS) technique. The relative density of pure HA increased with increasing sintering temperature, but that of the MWNT/HA composite reached almost full density at 900°C, and then decreased with further increases in sintering temperature. The relative density of the MWNT/HA composites increased with increasing MWNT content due to the excellent thermal conductivity of MWNTs. The grain size of MWNT/HA composites decreased with increasing MWNT content and increased with increasing sintering temperature. Pull-out toughening of the MWNTs of the MWNT/HA composites was observed in the fractured surface, which can be used to predict the improvement of the mechanical properties. On the other hand, the existence of undispersed or agglomerate MWNTs in the MWNT/HA composites accompanied large pores. The formation of large pores increased with increasing sintering temperature and MWNT content. The addition of MWNT in HA increased the hardness and fracture toughness by approximately 3~4 times, despite the presence of large pores produced by un-dispersed MWNTs. This provides strong evidence as to why the MWNTs are good candidates as reinforcements for strengthening the ceramic matrix. The MWNT/HA composites did not decompose during SPS sintering. The MWNT-reinforced HA composites were non-toxic and showed a good cell affinity and morphology in vitro for 1 day.