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Tribological performance of Graphene/Carbon nanotube hybrid reinforced Al2O3 composites.

Yazdani B, Xu F, Ahmad I, Hou X, Xia Y, Zhu Y - Sci Rep (2015)

Bottom Line: Benchmarked against the pure Al2O3, the composite reinforced with a 0.5 wt% GNP exhibited a 23% reduction in the friction coefficient along with a promising 70% wear rate reduction, and a hybrid reinforcement consisting of 0.3 wt.% GNPs + 1 wt.% CNTs resulted in even better performance, with a 86% reduction in the wear rate.The wear mechanisms for the composites were analysed based on the mechanical properties, brittleness index and microstructural characterizations.GNPs played the important role in the formation of a tribofilm on the worn surface by exfoliation; whereas CNTs contributed to the improvement in fracture toughness and prevented the grains from being pulled out during the tribological test.

View Article: PubMed Central - PubMed

Affiliation: College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK.

ABSTRACT
Tribological performance of the hot-pressed pure Al2O3 and its composites containing various hybrid contents of graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) were investigated under different loading conditions using the ball-on-disc method. Benchmarked against the pure Al2O3, the composite reinforced with a 0.5 wt% GNP exhibited a 23% reduction in the friction coefficient along with a promising 70% wear rate reduction, and a hybrid reinforcement consisting of 0.3 wt.% GNPs + 1 wt.% CNTs resulted in even better performance, with a 86% reduction in the wear rate. The extent of damage to the reinforcement phases caused during wear was studied using Raman spectroscopy. The wear mechanisms for the composites were analysed based on the mechanical properties, brittleness index and microstructural characterizations. The excellent coordination between GNPs and CNTs contributed to the excellent wear resistance property in the hybrid GNT-reinforced composites. GNPs played the important role in the formation of a tribofilm on the worn surface by exfoliation; whereas CNTs contributed to the improvement in fracture toughness and prevented the grains from being pulled out during the tribological test.

No MeSH data available.


Related in: MedlinePlus

High resolution SEM images from S0.3-1 showing (a) embedded CNTs, (b) embedded GNPs on the top of a worn surface, (c) CNT bridging cracked grains (arrowed) and GNP lying on the worn surface (circled).
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f11: High resolution SEM images from S0.3-1 showing (a) embedded CNTs, (b) embedded GNPs on the top of a worn surface, (c) CNT bridging cracked grains (arrowed) and GNP lying on the worn surface (circled).

Mentions: The reduced grain pull-outs could be a result of less tangential frictional forces between the ball and the composite surface, due to formation of a protective tribofilm by the GNT exfoliation on the wear surface. Fig. 11a–c provides evidence for the direct role of GNTs in the formation of the protective tribofilm during the wear test. The embedded GNTs from unpolished (ground only) surface will be exposed and spread on the wear track during the reciprocating movements, to form the tribofilm (Fig. 11a,b). The flattened GNTs on the worn surface are clearly visible in Figs 10f and 11c (circled), which could be the feeding stock for the tribofilm. GNPs are likely to contribute more effectively to the tribofilm than that of CNTs, due to their layered and their easy to be exfoliated structures; whilst CNTs’ rolling effect, along such tribofilm, cannot be ignored in the reduction of COF and wear rates24.


Tribological performance of Graphene/Carbon nanotube hybrid reinforced Al2O3 composites.

Yazdani B, Xu F, Ahmad I, Hou X, Xia Y, Zhu Y - Sci Rep (2015)

High resolution SEM images from S0.3-1 showing (a) embedded CNTs, (b) embedded GNPs on the top of a worn surface, (c) CNT bridging cracked grains (arrowed) and GNP lying on the worn surface (circled).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4477330&req=5

f11: High resolution SEM images from S0.3-1 showing (a) embedded CNTs, (b) embedded GNPs on the top of a worn surface, (c) CNT bridging cracked grains (arrowed) and GNP lying on the worn surface (circled).
Mentions: The reduced grain pull-outs could be a result of less tangential frictional forces between the ball and the composite surface, due to formation of a protective tribofilm by the GNT exfoliation on the wear surface. Fig. 11a–c provides evidence for the direct role of GNTs in the formation of the protective tribofilm during the wear test. The embedded GNTs from unpolished (ground only) surface will be exposed and spread on the wear track during the reciprocating movements, to form the tribofilm (Fig. 11a,b). The flattened GNTs on the worn surface are clearly visible in Figs 10f and 11c (circled), which could be the feeding stock for the tribofilm. GNPs are likely to contribute more effectively to the tribofilm than that of CNTs, due to their layered and their easy to be exfoliated structures; whilst CNTs’ rolling effect, along such tribofilm, cannot be ignored in the reduction of COF and wear rates24.

Bottom Line: Benchmarked against the pure Al2O3, the composite reinforced with a 0.5 wt% GNP exhibited a 23% reduction in the friction coefficient along with a promising 70% wear rate reduction, and a hybrid reinforcement consisting of 0.3 wt.% GNPs + 1 wt.% CNTs resulted in even better performance, with a 86% reduction in the wear rate.The wear mechanisms for the composites were analysed based on the mechanical properties, brittleness index and microstructural characterizations.GNPs played the important role in the formation of a tribofilm on the worn surface by exfoliation; whereas CNTs contributed to the improvement in fracture toughness and prevented the grains from being pulled out during the tribological test.

View Article: PubMed Central - PubMed

Affiliation: College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK.

ABSTRACT
Tribological performance of the hot-pressed pure Al2O3 and its composites containing various hybrid contents of graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) were investigated under different loading conditions using the ball-on-disc method. Benchmarked against the pure Al2O3, the composite reinforced with a 0.5 wt% GNP exhibited a 23% reduction in the friction coefficient along with a promising 70% wear rate reduction, and a hybrid reinforcement consisting of 0.3 wt.% GNPs + 1 wt.% CNTs resulted in even better performance, with a 86% reduction in the wear rate. The extent of damage to the reinforcement phases caused during wear was studied using Raman spectroscopy. The wear mechanisms for the composites were analysed based on the mechanical properties, brittleness index and microstructural characterizations. The excellent coordination between GNPs and CNTs contributed to the excellent wear resistance property in the hybrid GNT-reinforced composites. GNPs played the important role in the formation of a tribofilm on the worn surface by exfoliation; whereas CNTs contributed to the improvement in fracture toughness and prevented the grains from being pulled out during the tribological test.

No MeSH data available.


Related in: MedlinePlus