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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

SEM images of the wear track of sample S0.5-0, under various sliding loads.(a) 5 N, (b) 15 N, (c) 25 N, and (d) 35 N.
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f5: SEM images of the wear track of sample S0.5-0, under various sliding loads.(a) 5 N, (b) 15 N, (c) 25 N, and (d) 35 N.

Mentions: The SEM images of wear tracks of S0.5-0 under four different sliding loads are shown in Fig. 5, which are entirely dissimilar to wear tracks of pure Al2O3, as shown in Fig. 4. Under 25 N sliding load (Fig. 5c), there are no grains being pulled out for S0.5-0, whilst such a sliding load caused severe damage to the worn surface of the pure Al2O3 (Fig. 4c). Based on these detailed pictorial worn surfaces, it seems that the higher fracture toughness of S0.5-0 compared with pure Al2O3, as summarised in Table 1, strengthened the grain boundaries and stopped the grains being pulled out at low sliding stresses and strains. Even under 35 N load for S0.5-0 (Fig. 5d), the grain pull-out damage was minimal compared with the pure Al2O3 under the same sliding load (Fig. 4d). However, the grove traces in Fig. 5c,d indicate a deformation controlled wear behaviour under 25 N and 35 N sliding loads. This wear behaviour change probably weakened the lubricating merit of the GNPs in the composites under coarse wear, hence the reduction in COF for S0.5-0 under higher sliding loads is not so obvious, as shown in Fig. 3a. In this context, the 15 N sliding load was kept constant for comparing the wear performance of various Al2O3-GNT composites.


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)

SEM images of the wear track of sample S0.5-0, under various sliding loads.(a) 5 N, (b) 15 N, (c) 25 N, and (d) 35 N.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f5: SEM images of the wear track of sample S0.5-0, under various sliding loads.(a) 5 N, (b) 15 N, (c) 25 N, and (d) 35 N.
Mentions: The SEM images of wear tracks of S0.5-0 under four different sliding loads are shown in Fig. 5, which are entirely dissimilar to wear tracks of pure Al2O3, as shown in Fig. 4. Under 25 N sliding load (Fig. 5c), there are no grains being pulled out for S0.5-0, whilst such a sliding load caused severe damage to the worn surface of the pure Al2O3 (Fig. 4c). Based on these detailed pictorial worn surfaces, it seems that the higher fracture toughness of S0.5-0 compared with pure Al2O3, as summarised in Table 1, strengthened the grain boundaries and stopped the grains being pulled out at low sliding stresses and strains. Even under 35 N load for S0.5-0 (Fig. 5d), the grain pull-out damage was minimal compared with the pure Al2O3 under the same sliding load (Fig. 4d). However, the grove traces in Fig. 5c,d indicate a deformation controlled wear behaviour under 25 N and 35 N sliding loads. This wear behaviour change probably weakened the lubricating merit of the GNPs in the composites under coarse wear, hence the reduction in COF for S0.5-0 under higher sliding loads is not so obvious, as shown in Fig. 3a. In this context, the 15 N sliding load was kept constant for comparing the wear performance of various Al2O3-GNT composites.

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