Enhancing Cuo nanolubricant performance using dispersing agents

doi:10.1016/j.triboint.2020.106338

Tribology International

Volume 150, October 2020, 106338

https://doi.org/10.1016/j.triboint.2020.106338 Get rights and content

Highlights

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Tiny CuO nanoparticles were added to PAO oil using two techniques to disperse it.
•
The friction and wear are proportional to the poor dispersion of nanoparticles in oil.
•
The better tribological performance was found to the Toluene use as dispersant.
•
The stability of nanoparticles in suspensions governs the nanolubrication mechanisms.

Abstract

This paper reports on the use of organic dispersing agents to prevent the agglomeration of tiny CuO nanoparticles in synthetic oil, by developing low concentrations of nanolubricants with good stability. Tiny nanoparticles were added to polyalphaolefin (PAO) oil with the aid of three organic dispersing agents (toluene, hexane and ethylene glycol) at a low concentration of 0.1 wt%. The tribological performance of nanolubricants was evaluated under boundary lubrication conditions. The dispersion results showed more uniform nanoparticle distribution in oil when toluene was used as a dispersing agent. Furthermore, this dispersant provided a substantial decrease in the coefficient of friction and lower wear losses in tribological tests. Good dispersion results in a lower friction coefficient and less wear.

Introduction

The main challenge in using nanoparticles in lubricants is related to their dispersion in liquids, because metal oxide nanoparticles easily agglomerate due to their high surface tension. Their intrinsic instability means nanoparticles may form agglomerates that can be easily redispersed or create a non-dispersible aggregate cluster.

Nanoparticle agglomeration is minimized when the nanolubricant is produced by a one-step physical process such as vacuum evaporation or laser ablation onto an oil substrate [1,2]. However, these techniques are limited by the space in the vacuum chamber and their high cost [3].

Most researchers have produced nanolubricants in two-steps. Nanoparticles are first produced separately, for example using the microwave-assisted hydrothermal method, according to Alves et al. [4], and then dispersed into a fluid in a second processing step. In this case, nanoparticle surfaces must be modified in order to prevent particle aggregation. According to Nagarajan and Hatton [5], surface modifications can be used to passivate a very reactive nanoparticle or stabilize a very aggregative one in the medium where the nanoparticles are dispersed. The most commonly used surface modification includes functionalization by electrostatic or steric stabilization. In the first method, ionic surfactants are adsorbed onto the nanoparticle surface, and in the second, steric repulsion is produced by the formation of a polymer or surfactant coating (monolayer) on the nanoparticle surface [6]. High molecular weight hydrocarbon sources, such as oleic acid, can be used as coating.

Adding dispersants to two-phase systems is an easy and economical method to enhance nanofluid stability [7]. In addition, sub-10 nm nanoparticles exhibit better dispersion stability when the surfactant surface is modified using steric stabilization [[8], [9], [10], [11]]. Size is another crucial factor that influences the antiwear properties of nanolubricants. Tiny nanoparticles are more susceptible to increased antiwear and less friction [12]. Thus, nanoparticle agglomeration can act negatively in lubrication due to the reduced shear effects [[13], [14], [15]], in addition to causing problems such as clogging and contact starvation [16].

Introducing a dispersing agent makes the nanoparticle soluble, keeping the particles in suspension in the system. In some cases, the dispersant may function as a removable or permanent surfactant. Good nanoparticle dispersion was obtained using organic dispersants, whose the most frequently investigated are the toluene, hexane and ethylene glycol [4,[17], [18], [19], [20], [21], [22], [23], [24], [25]].

This study aimed to evaluate the enhancement of nanolubricant performance using both techniques to disperse nanoparticles: a surface modifier to functionalize them and organic dispersants to help keep them in stable suspensions. In the present study, low concentrations of tiny CuO nanoparticles were functionalized with oleic acid and dispersed in PAO with the aid of toluene, hexane and ethylene glycol.

Section snippets

Nanolubricant production

The CuO nanoparticles were prepared using the microwave-assisted hydrothermal method, according to Alves et al. [4]. Next, they were functionalized with oleic acid and characterized as proposed by Alves et al. [20]. The nanolubricants were produced with 0.1% (0.008 g) by weight of nanoparticles in polyalphaolefin oil (PAO), according to the mixing conditions described in Table 1.

First, the nanoparticles were added to each dispersant under stirring for 1 h at 20 °C and the solution added to the

Nanoparticle characterization

The diffraction patterns of the nanoparticles (Fig. 1a) showed a pure phase and diffraction peaks indexed to the monoclinic structure of CuO. The angulation of the characteristic peak agreed with the limits established by some authors [[27], [28], [29]]. The intense narrow peak seen in XRD suggests a highly crystalline phase-pure material [30].

The estimated particle sizes (around 5 nm) were calculated using Scherrer's equation [31]. A TEM image was used to determine nanoparticle shape and size (

CRediT authorship contribution statement

V.S. Mello: Conceptualization, Methodology, Visualization, Project administration, Writing - review & editing. E.A. Faria: Data curation, Methodology, Writing - original draft. S.M. Alves: Supervision, Writing - review & editing. C. Scandian: Funding acquisition, Writing - review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This study was partially funded by the Coordination for the Improvement of Higher Education Personnel (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES) - Funding Code 001. The authors would like to thank the Surface Engineering Laboratory of the University of São Paulo (USP) for supporting this research.

References (48)

H. Wender et al.
Sputtering deposition of nanoparticles onto liquid substrates: recent advances and future trends
Coord Chem Rev
(2013)
S.M. Alves et al.
Nanolubricants developed from tiny CuO nanoparticles
Tribol Int
(2016)
C.P. Koshy et al.
Evaluation of the tribological and thermo-physical properties of coconut oil added with MoS2 nanoparticles at elevated temperatures
Wear
(2015)
L. Sun et al.
Synthesis and characterization of DDP coated Ag nanoparticles
Mater Sci Eng, A
(2004)
S.M. Alves et al.
Nanolubricants developed from tiny CuO nanoparticles
Tribol Int
(2016)
G. Yang et al.
Trans Nonferrous Metals Soc China
(2012)
P. Rabaso et al.
Boundary lubrication: influence of the size and structure of inorganic fullerene-like MoS2 nanoparticles on friction and wear reduction
Wear
(2014)
J.C. Sánchez-López et al.
Surface-modified Pd and Au nanoparticles for anti-wear applications
Tribol Int
(2011)
S.G. Rejith et al.
Optical, thermal and magnetic studies on zinc-doped copper oxide nanoparticles
Mater Lett
(2013)
H. Wang et al.
Preparation of CuO nanoparticles by microwave irradiation
J Cryst Growth
(2002)

X. Liu et al.

Temperature-controlled self-assembled synthesis of CuO, Cu2O and Cu nanoparticles through a single-precursor route

Mater Sci Eng

(2007)

R. Xu

Progress in nanoparticles characterization: sizing and zeta potential measurement

Particuology

(2008)

D.H. Napper

Steric stabilization

J Colloid Interface Sci

(1977)

E.B. Zhulina et al.

Theory of steric stabilization of colloid dispersions by grafted polymers

J Colloid Interface Sci

(1990)

H.L. Yu et al.

Characterization and nanomechanical properties of tribofilms using Cu nanoparticles as additives

Surf Coating Technol

(2008)

L.M. Liz-Marzan

Nanometals: formation and color

Mater Today

(2004)

G.B. Yang et al.

Preparation and tribological properties of surface modified CuO nanoparticles

Trans Nonferrous Metals Soc China

(2012)

Y.Y. Wu et al.

Experimental analysis of tribological properties of lubricating oils with nanoparticles additives

Wear

(2007)

A.R. Sadrolhosseini et al.

Synthesis of gold nanoparticles dispersed in palm oil using laser ablation technique

J Nanomater

(2017)

J.A. Eastman et al.

Thermal transport in nanofluids

Annu Rev Mater Res

(2004)

Nagarajan et al.

Nanoparticles: Synthesis, stabilization, passivation, and functionalization ACS symposium series

(2008)

M. Gulzar et al.

Tribological performance of nanoparticles as lubricating oil additives

(2016)

Wei Yu et al.

A review on nanofluids: preparation, stability mechanisms and applications

J Nanomater

(2012)

Z. Jiang et al.

Tribological properties of oleylamine-modified ultrathin WS2 nanosheets as the additive in polyalpha olefin over a wide temperature range

Tribol Lett

(2016)

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Citation Excerpt :
It is possible to use different kinds of nanoparticles, either organic or inorganic nanoparticles [2]. Organic nanoparticles mainly include polymers, exosomes, liposomes, protein-based nanoparticles, coal fly as, etc., while inorganic nanoparticles consist of silica nanoparticles, metal nanoparticles, carbon nanotubes, quantum dots and so forth [3–7]. Organic-inorganic, or hybrid, nanoparticles have caught the interest of researchers due to their potential applications because they can combine useful chemical, optical, and mechanical properties while retaining the various benefits of nanolubricants.
The primary objective of the present analysis is to investigate the thermophysical properties of hybrid nanocellulose and copper (II) oxide nanoparticles added to engine oil as a lubricant for piston ring-cylinder liner application. Kinematic viscosity, viscosity index (VI) and dynamic viscosity have been performed for measurement of properties at varying temperatures (ranging from 30 °C to 90 °C) and different concentrations (ranging from 0.1 % to 0.9 % volume concentration). Thermal characteristics have been measured using similar temperatures and concentrations to determine thermal conductivity and specific heat capacity. In the results, as the concentration of the CNC-CuO nanoparticle increases, the VI also increases. This proves the combination of CNC-CuO particles with engine oil improves the lubricity of the base oil concerning its viscosity by 44.3 %-47.12 %. The lowest and highest improvements in the dynamic viscosity were 1.34 % and 74.81 %. The highest increment of thermal conductivity ratio for the selected nanolubricant was 1.80566 % in the solid concentration of 0.1 % at 90 °C. The specific heat capacity of nanolubricant tends to reduce slightly with an increase in temperature. Overall, the addition of CNC-CuO nanoparticle in the engine improved thermophysical properties behaviour's performance at 0.5 % concentration. The results can benefit the heat transfer application, especially tribological.

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Enhancing Cuo nanolubricant performance using dispersing agents

Highlights

Abstract

Introduction

Section snippets

Nanolubricant production

Nanoparticle characterization

CRediT authorship contribution statement

Declaration of competing interest

Acknowledgments

Coord Chem Rev

Tribol Int

Wear

Mater Sci Eng, A

Tribol Int

Trans Nonferrous Metals Soc China

Wear

Tribol Int

Mater Lett

J Cryst Growth

Mater Sci Eng

Particuology

J Colloid Interface Sci

J Colloid Interface Sci

Surf Coating Technol

Mater Today

Trans Nonferrous Metals Soc China

Wear

Synthesis of gold nanoparticles dispersed in palm oil using laser ablation technique

J Nanomater

Thermal transport in nanofluids

Annu Rev Mater Res

Nanoparticles: Synthesis, stabilization, passivation, and functionalization ACS symposium series

Tribological performance of nanoparticles as lubricating oil additives

A review on nanofluids: preparation, stability mechanisms and applications

J Nanomater

Tribological properties of oleylamine-modified ultrathin WS2 nanosheets as the additive in polyalpha olefin over a wide temperature range

Tribol Lett