Stability, Thermal Conductivity, Viscosity, and Tribological Characterization of Zirconia Nanofluids as a Function of Nanoparticle Concentration

Thrush, Steven J.; Comfort, Allen S.; Dusenbury, James S.; Xiong, Yuzan; Qu, Hongwei; Han, Xue; Schall, J. David; Barber, Gary C.; Wang, Xia

doi:10.1080/10402004.2019.1660017

Cited by 23 publications

(17 citation statements)

References 23 publications

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“…Table 1 describes the set of lubricant samples used to compare the behavior of base oils with and without ZrO 2 nanoparticles, and any interactions between ZrO 2 and coadditives. The ZrO 2 samples in PAO were prepared identically as that described in Khare et al [16] and Thrush et al [15]. The gear oil samples used were an API Group 3-based automotive gear oil meeting SAE 75W-80 viscosity, with the same additive package as a commercial synthetic SAE 75W-90 gear oil used as a reference in the broader research program of which this study was a part.…”

Section: Lubricant Samplesmentioning

confidence: 99%

“…Of the work reviewed by Dai et al [11], the largest category of NP additives are metal oxides. Zirconium dioxide (ZrO 2 ) is a particularly attractive additive candidate because its high refractive index enables optically clear dispersions [14,15], allowing end users to estimate oil quality visually. In tribological measurements, macroscale tests demonstrate the potential for ZrO 2 NP additives [15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

“…Zirconium dioxide (ZrO 2 ) is a particularly attractive additive candidate because its high refractive index enables optically clear dispersions [14,15], allowing end users to estimate oil quality visually. In tribological measurements, macroscale tests demonstrate the potential for ZrO 2 NP additives [15][16][17][18]. Two recent studies [15,16] focused specifically on ZrO 2 NPs comprised 5 nm diameter particles with organic ligands bound to the NP surface.…”

Section: Introductionmentioning

confidence: 99%

“…In tribological measurements, macroscale tests demonstrate the potential for ZrO 2 NP additives [15][16][17][18]. Two recent studies [15,16] focused specifically on ZrO 2 NPs comprised 5 nm diameter particles with organic ligands bound to the NP surface. Available commercially with high chemical and phase purity and monodispersity, dispersions of these nanoparticles in lubricant base stocks exhibited stability over extended time periods (more than 4 years), in contrast with many other nanoparticles used as oil additives where frequent stirring is required to prevent settling.…”

Section: Introductionmentioning

confidence: 99%

“…Available commercially with high chemical and phase purity and monodispersity, dispersions of these nanoparticles in lubricant base stocks exhibited stability over extended time periods (more than 4 years), in contrast with many other nanoparticles used as oil additives where frequent stirring is required to prevent settling. When suspended in base oil at loadings as low as 0.1 wt%, ZrO 2 additives formed dense, solid, surface-bound tribofilms during minitraction machine (MTM) tests [15].…”

Section: Introductionmentioning

confidence: 99%

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Cooperativity Between Zirconium Dioxide Nanoparticles and Extreme Pressure Additives in Forming Protective Tribofilms: Toward Enabling Low Viscosity Lubricants

et al. 2020

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Realizing the efficiency benefits of low viscosity lubricants requires novel strategies to avoid failures resulting from increased boundary contact. Zirconium dioxide (ZrO 2) nanoparticles (NPs) form protective tribofilms through tribosintering at lubricated contacts in pure hydrocarbon base oils, suggesting they hold promise for reducing boundary contact-induced failures. However, their tribological behavior alongside co-additives found in fully formulated oils has not been examined in depth. Here, the macroscopic tribological performance of dispersed ZrO 2 NPs (1 wt% loading; 5 nm diameter nearly spherical ZrO 2 tetragonal phase NPs with organic capping ligands for oil solubility) with and without the presence of co-additives found in fully formulated commercial gear oils was studied using a mini-traction machine (MTM). The results show that ZrO 2 NPs reproducibly develop surface-bound ~ 100 nm thick tribofilms on both contacting surfaces under a wide range of rolling-sliding contact conditions, from 0 to 100% slide-to-roll ratio. Steady-state traction coefficient values of ZrO 2 tribofilms formed alongside co-additives (0.10-0.11) do not substantially differ from ZrO 2 tribofilms formed in neat polyalphaolefin base oils (0.10-0.13). However, there is improvement in the tribological performance of the contact, with at least a twofold reduction of wear of the steel. This behavior is proposed to be a result of cooperating mechanisms, where the extreme pressure additives adsorbed on the steel surfaces protect them against early adhesive wear, during the time that a protective ZrO 2 tribofilm incorporating the co-additives forms on the steel surfaces, preventing further wear.

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Section: Lubricant Samplesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Cooperativity Between Zirconium Dioxide Nanoparticles and Extreme Pressure Additives in Forming Protective Tribofilms: Toward Enabling Low Viscosity Lubricants

et al. 2020

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An experimental study and mechanism analysis on improving dispersion stability performance of Al2O3 nanoparticles in base synthetic oil under various mixing conditions

Hou

Liu

Li³

et al. 2021

J Nanopart Res

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Inhibition of Micro-pitting by Tribofilm-Forming ZrO2 Nanocrystal Lubricant Additives: A Micro-pitting Rig and Transmission Electron Microscope Study

et al. 2022

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The drive to reduce fuel consumption in transportation has encouraged the emergence of low viscosity lubricants to reduce viscous losses in the engine, drivetrain, and other components. However, viscosity reduction increases the risk of surface damage, thus motivating the development of new anti-wear (AW) additives. Capped ZrO2 nanocrystals (NCs) in base oils have been shown to form AW tribo lms within microscale sliding contacts. However, the potential of ZrO2 NCs to protect surfaces subjected to rollingsliding contact from macroscale damage, such as micro-pitting, remains unexplored. Here, we explore the ability of ZrO 2 NCs to form protective tribo lms under harsh conditions using a micro-pitting rig (MPR), consisting of a three ring-on-roller con guration. The experiments were conducted in polyalphaolephin (PAO) base oil, with and without 5 nm diameter ZrO2 NCs, at two levels of slide-to-roll ratio (SRR) (30% and 0%) and at variable test durations up to long durations (119 hours). MPR results showed the use of ZrO 2 NCs gives rise to the formation of a tribo lm covering the roller surfaces and decreases the initiation and propagation of micro-pits compared to tests in pure PAO base stock. Transmission electron microscopy (TEM) performed on focused ion beam (FIB) milled cross-sectional samples of the roller surfaces revealed the growth of dense and 50-100 nm thick ZrO 2 -based tribo lms independent of (SRR), indicating the potential for robust micro-pitting fatigue protection. Nevertheless, small cracks localized within the near surface region of the roller tested at the most severe conditions (30% SRR and 119 hours) were observed. The initiation of these cracks was directly related to the presence of manganese sulphide (MnS) inclusions in the steel, revealed using TEM combined with energy dispersive spectroscopy (EDS).The results highlight the bene ts of the protective tribo lms formed by ZrO 2 NCs and suggest approaches for further optimizing their use.

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Stability, Thermal Conductivity, Viscosity, and Tribological Characterization of Zirconia Nanofluids as a Function of Nanoparticle Concentration

Cited by 23 publications

References 23 publications

Cooperativity Between Zirconium Dioxide Nanoparticles and Extreme Pressure Additives in Forming Protective Tribofilms: Toward Enabling Low Viscosity Lubricants

Cooperativity Between Zirconium Dioxide Nanoparticles and Extreme Pressure Additives in Forming Protective Tribofilms: Toward Enabling Low Viscosity Lubricants

An experimental study and mechanism analysis on improving dispersion stability performance of Al2O3 nanoparticles in base synthetic oil under various mixing conditions

Inhibition of Micro-pitting by Tribofilm-Forming ZrO2 Nanocrystal Lubricant Additives: A Micro-pitting Rig and Transmission Electron Microscope Study

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