Multiwalled carbon nanotubes (MWCNTs) were modified noncovalently with cetyltrimethylammonium bromide. The Nb/Nb5Si3 in situ composite material that was strengthened with MWCNTs was prepared by SPS. The effect of MWCNT content on the microstructure and properties of Nb/Nb5Si3 in situ composites was investigated. The results showed that the composites consisted of Nb, α-Nb5Si3 and β-Nb5Si3 phases. With the addition of over 2 wt% MWCNT, a new Nb4C3 phase was formed in the composites. The properties of the Nb/Nb5Si3 in situ composites were affected by MWCNT addition. The relative density, Vickers hardness and fracture toughness increased with increasing MWCNT addition. When the MWCNT addition was 2 wt%, the relative density and Vickers hardness reached a maximum and increased by ~ 1.4% and ~ 18%, respectively (relative to 0 wt% MWCNT addition). When the MWCNT content exceeded 2 wt%, the relative density and the Vickers hardness decreased. However, the fracture toughness of the Nb/Nb5Si3 composites with 3 wt% MWCNTs reached a maximum (an increase of ~ 68% relative to 0 wt% MWCNT addition). Scanning electron micrographs of the fractography showed brittle cleavage and partial intercrystalline composite fracture. The composite toughening mechanisms arose mainly because of MWCNT removal and bridging.
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In this paper, the research was sponsored by the National Natural Science Foundation of China (Project No. 51271091) and the Nature Science Foundation of Jiangxi Province (Project No. 20161BAB206107) and the technology project of Jiangxi Province Education Department (Project No. GJJ12420).
Bewlay B P, Jackson M R, Subramanian P R, and Zhao J C, Metall Mater Trans A34 (2003) 2043.CrossRefGoogle Scholar