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Gold-ionic liquid nanofluids with preferably tribological properties and thermal conductivity.

Wang B, Wang X, Lou W, Hao J - Nanoscale Res Lett (2011)

Bottom Line: In comparison with pure [Bmim][PF6] and the nanofluids possessing poor stability, the nanofluids with high stability exhibited much better friction-reduction and anti-wear properties.The results indicate that the TC of the nanofluid (1.02 × 10-3%) is 13.1% higher than that of [Bmim][PF6] at 81°C but no obvious variation at 33°C.Our results should open new avenues to utilize Au NPs and ILs in tribology and the high-temperature heat transfer field.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China. wjlou@licp.cas.cn.

ABSTRACT
Gold/1-butyl-3-methylimidazolium hexafluorophosphate (Au/[Bmim][PF6]) nanofluids containing different stabilizing agents were fabricated by a facile one-step chemical reduction method, of which the nanofluids stabilized by cetyltrimethylammonium bromide (CTABr) exhibited ultrahighly thermodynamic stability. The transmission electron microscopy, UV-visible absorption, Fourier transform infrared, and X-ray photoelectron characterizations were conducted to reveal the stable mechanism. Then, the tribological properties of these ionic liquid (IL)-based gold nanofluids were first investigated in more detail. In comparison with pure [Bmim][PF6] and the nanofluids possessing poor stability, the nanofluids with high stability exhibited much better friction-reduction and anti-wear properties. For instance, the friction coefficient and wear volume lubricated by the nanofluid with rather low volumetric concentration (1.02 × 10-3%) stabilized by CTABr under 800 N are 13.8 and 45.4% lower than that of pure [Bmim][PF6], confirming that soft Au nanoparticles (Au NPs) also can be excellent additives for high performance lubricants especially under high loads. Moreover, the thermal conductivity (TC) of the stable nanofluids with three volumetric fraction (2.55 × 10-4, 5.1 × 10-4, and 1.02 × 10-3%) was also measured by a transient hot wire method as a function of temperature (33 to 81°C). The results indicate that the TC of the nanofluid (1.02 × 10-3%) is 13.1% higher than that of [Bmim][PF6] at 81°C but no obvious variation at 33°C. The conspicuously temperature-dependent and greatly enhanced TC of Au/[Bmim][PF6] nanofluids stabilized by CTABr could be attributed to micro-convection caused by the Brownian motion of Au NPs. Our results should open new avenues to utilize Au NPs and ILs in tribology and the high-temperature heat transfer field.

No MeSH data available.


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The TC of [Bmim][PF6] and [Bmim][PF6] containing CTABr (5 mmol) (a), and the TC enhancement of Au/[Bmim][PF6] nanofluids (b) with various concentrations varying with temperature.
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Figure 11: The TC of [Bmim][PF6] and [Bmim][PF6] containing CTABr (5 mmol) (a), and the TC enhancement of Au/[Bmim][PF6] nanofluids (b) with various concentrations varying with temperature.

Mentions: Figure 11 shows the TC of [Bmim][PF6] and [Bmim][PF6] containing CTABr (5 mM) and the TC enhancements of Au/[Bmim][PF6] nanofluids defined as (knf - k0)/k0 (%) with various concentrations in temperature range of 33 to 81°C, where knf and k0 is TC of the nanofluids and [Bmim][PF6] at various temperatures, respectively. The TC of [Bmim][PF6] and [Bmim][PF6] containing CTABr (5 mM) in Figure 11a is both slightly temperature-dependent and the later is no remarkable differences compared with the former, indicating the low amount of CTABr has no obvious effects on the TC of [Bmim][PF6]. Therefore, the effects on the TC of base liquid induced by CTABr are omitted in the following discussion on the TC enhancements of the nanofluids. The TC enhancements of nanofluids in Figure 11b increases slightly at low temperatures (≤53°C) but sharply at high temperatures (≥60°C), exhibiting non-linear increment as a function of temperature and the remarkable effect of stable Au NPs on the TC of base liquid especially at high temperatures. The TC of the nanofluid (1.02 × 10-3%) at 81°C is 13.1% higher than that of base liquid, indicating the addition of low concentration of stable Au NPs can greatly improve the thermal properties of [Bmim][PF6] under high temperature.


Gold-ionic liquid nanofluids with preferably tribological properties and thermal conductivity.

Wang B, Wang X, Lou W, Hao J - Nanoscale Res Lett (2011)

The TC of [Bmim][PF6] and [Bmim][PF6] containing CTABr (5 mmol) (a), and the TC enhancement of Au/[Bmim][PF6] nanofluids (b) with various concentrations varying with temperature.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211321&req=5

Figure 11: The TC of [Bmim][PF6] and [Bmim][PF6] containing CTABr (5 mmol) (a), and the TC enhancement of Au/[Bmim][PF6] nanofluids (b) with various concentrations varying with temperature.
Mentions: Figure 11 shows the TC of [Bmim][PF6] and [Bmim][PF6] containing CTABr (5 mM) and the TC enhancements of Au/[Bmim][PF6] nanofluids defined as (knf - k0)/k0 (%) with various concentrations in temperature range of 33 to 81°C, where knf and k0 is TC of the nanofluids and [Bmim][PF6] at various temperatures, respectively. The TC of [Bmim][PF6] and [Bmim][PF6] containing CTABr (5 mM) in Figure 11a is both slightly temperature-dependent and the later is no remarkable differences compared with the former, indicating the low amount of CTABr has no obvious effects on the TC of [Bmim][PF6]. Therefore, the effects on the TC of base liquid induced by CTABr are omitted in the following discussion on the TC enhancements of the nanofluids. The TC enhancements of nanofluids in Figure 11b increases slightly at low temperatures (≤53°C) but sharply at high temperatures (≥60°C), exhibiting non-linear increment as a function of temperature and the remarkable effect of stable Au NPs on the TC of base liquid especially at high temperatures. The TC of the nanofluid (1.02 × 10-3%) at 81°C is 13.1% higher than that of base liquid, indicating the addition of low concentration of stable Au NPs can greatly improve the thermal properties of [Bmim][PF6] under high temperature.

Bottom Line: In comparison with pure [Bmim][PF6] and the nanofluids possessing poor stability, the nanofluids with high stability exhibited much better friction-reduction and anti-wear properties.The results indicate that the TC of the nanofluid (1.02 × 10-3%) is 13.1% higher than that of [Bmim][PF6] at 81°C but no obvious variation at 33°C.Our results should open new avenues to utilize Au NPs and ILs in tribology and the high-temperature heat transfer field.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China. wjlou@licp.cas.cn.

ABSTRACT
Gold/1-butyl-3-methylimidazolium hexafluorophosphate (Au/[Bmim][PF6]) nanofluids containing different stabilizing agents were fabricated by a facile one-step chemical reduction method, of which the nanofluids stabilized by cetyltrimethylammonium bromide (CTABr) exhibited ultrahighly thermodynamic stability. The transmission electron microscopy, UV-visible absorption, Fourier transform infrared, and X-ray photoelectron characterizations were conducted to reveal the stable mechanism. Then, the tribological properties of these ionic liquid (IL)-based gold nanofluids were first investigated in more detail. In comparison with pure [Bmim][PF6] and the nanofluids possessing poor stability, the nanofluids with high stability exhibited much better friction-reduction and anti-wear properties. For instance, the friction coefficient and wear volume lubricated by the nanofluid with rather low volumetric concentration (1.02 × 10-3%) stabilized by CTABr under 800 N are 13.8 and 45.4% lower than that of pure [Bmim][PF6], confirming that soft Au nanoparticles (Au NPs) also can be excellent additives for high performance lubricants especially under high loads. Moreover, the thermal conductivity (TC) of the stable nanofluids with three volumetric fraction (2.55 × 10-4, 5.1 × 10-4, and 1.02 × 10-3%) was also measured by a transient hot wire method as a function of temperature (33 to 81°C). The results indicate that the TC of the nanofluid (1.02 × 10-3%) is 13.1% higher than that of [Bmim][PF6] at 81°C but no obvious variation at 33°C. The conspicuously temperature-dependent and greatly enhanced TC of Au/[Bmim][PF6] nanofluids stabilized by CTABr could be attributed to micro-convection caused by the Brownian motion of Au NPs. Our results should open new avenues to utilize Au NPs and ILs in tribology and the high-temperature heat transfer field.

No MeSH data available.


Related in: MedlinePlus