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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.


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The comparison of Raman scans of pure GNP and Al2O3-GNT composites obtained from surfaces with and without wear.
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f12: The comparison of Raman scans of pure GNP and Al2O3-GNT composites obtained from surfaces with and without wear.

Mentions: Further, the existence of CNTs indirectly contributed more in bridging the grains against crack propagations (due their higher aspect ratio) in case of micro-chipping and grain pull-outs, by improving the mechanical properties of the composites (Figs 10f and 11c). In fact, samples without CNTs but with higher GNP contents (S2-0 and S5-0) drastically degraded the wear resistant property (Fig. 6), because of the poor mechanical properties (Table1) which ended up with severe grain pull-outs (Fig. 9c,d). Therefore, both the lubricating film and the improved mechanical properties together improved the wear resistant properties of the composites. Furthermore, although sufficient amounts of flattened CNTs on the wear track could indeed lubricate the surface, as reported in our previous work on Al2O3-5 wt%CNT composites24, the fact that very low GNP contents (S0.5-0 and S0.3-1) in the composites could lead to the formation of tribofilms suggests the dominant role of GNPs in the improved tribological performance in this context. The existence of the fragmented GNPs during tribology testing is confirmed by our Raman studies, as shown in Fig. 12.


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)

The comparison of Raman scans of pure GNP and Al2O3-GNT composites obtained from surfaces with and without wear.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f12: The comparison of Raman scans of pure GNP and Al2O3-GNT composites obtained from surfaces with and without wear.
Mentions: Further, the existence of CNTs indirectly contributed more in bridging the grains against crack propagations (due their higher aspect ratio) in case of micro-chipping and grain pull-outs, by improving the mechanical properties of the composites (Figs 10f and 11c). In fact, samples without CNTs but with higher GNP contents (S2-0 and S5-0) drastically degraded the wear resistant property (Fig. 6), because of the poor mechanical properties (Table1) which ended up with severe grain pull-outs (Fig. 9c,d). Therefore, both the lubricating film and the improved mechanical properties together improved the wear resistant properties of the composites. Furthermore, although sufficient amounts of flattened CNTs on the wear track could indeed lubricate the surface, as reported in our previous work on Al2O3-5 wt%CNT composites24, the fact that very low GNP contents (S0.5-0 and S0.3-1) in the composites could lead to the formation of tribofilms suggests the dominant role of GNPs in the improved tribological performance in this context. The existence of the fragmented GNPs during tribology testing is confirmed by our Raman studies, as shown in Fig. 12.

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