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J. Marine. Sci. Appl. (2009) 8: 71-76

DOI: 10.1007/s11804-009-8008-1

Tribological effects of oxide based nanoparticles

in lubricating oils 

GU Cai-xiang*, ZHU Guan-jun, LI Lei, TIAN Xiao-yu and ZHU Guang-yao

Merchant Marine College, Shanghai Maritime University, Shanghai 200135, China

Abstract: In order to enhance the tribological properties of lubricating oil, suitable surfactants such as

Tween-20, Tween-60, Span-20 and Sodium sodecylbenzenesulfonate were selected and lubricating oils

containing CeO2 and TiO2 nanoparticles were prepared. The morphology and size of CeO2 and TiO2 

nanoparticles were examined with a transmission electron microscope (TEM). The tribological properties

of the oils were tested using an MRS-1J four-ball tribotester. The research results show that when the

 proportion by weight of CeO2 nanoparticles to TiO2 nanoparticles is 1:3, and the total weight fraction is

0.6%, the lubricating oil has optimal anti-wear and friction reducing properties. The addition of CeO2 

nanoparticles reduces the required amount of TiO2 nanoparticles.

Keywords: nanoparticles; surfactants; lubricating oil; tribological propertiesCLC number: TE626.3 Document code: A Article ID: 1671-9433(2009)01-0071-06  

1 Introduction1

With the rapid development of marine diesel engine to

new and large models, the consumption of fuel oils has

  been considerably increased whereas the economic

effectiveness decreased, the operation cost of ship

company has been increased correspondingly. So the

inferior fuel oils are used in many marine diesel engines

to enhance the economic effectiveness. However the use

of inferior fuel oils has inevitably put a higher demand for the quality of lubricating oils in the process of the design

and the management of marine engine. The lubricating

oils are the blood of the machine’s operation, and the

service life and economic effectiveness of the machine

are relative to the quality, performance and reasonable

use of the oils[1-2]. Nanoparticles put into lubricating oils

can improve the properties of extreme pressure, anti-wear 

and friction reducing. Efficiency and service life of the

machine were also improved[3]

. In recent years, many

scientific researchers have dedicated themselves to

studying lubricating oil additives as an important project.

These lubricating oil additives have good properties of 

anti-wear, friction reduction and high load-bearing

capability. In addition, they can fill in and repair the worn

surfaces with environment-friendly characteristics[4]. The

lubricating oils containing CaCO3 nanoparticles were

 prepared. They have good properties of extreme pressure,

anti-wear and friction reducing[5]. The lubricating oils

containing the combination of CaCO3 nanoparticles and

Received date: 2008-03-11.

Foundation item: Supported by the Shanghai Municipal Education

Commission(06FZ008); Shanghai Municipal Education Commission Key

Disciplines(J50603).

*Corresponding author Email: cxgu@mmc.shmtu.edu.cn 

rare earth nanoparticles were prepared too; they have

 better properties of anti-wear and friction reducing than

that containing only one kind of nanoparticles[6]. These

lubricating oils containing nanoparticles as mentioned

above have been patented.

In this research, the combination of CeO2 and TiO2 

nanoparticles was put into the lubricating oils for further 

studying the effect of the combination of different

nano-materials as additives in the lubricating oils. It is of theoretical and practical significance to expanding the

application range of nanoparticles and to further 

understanding the mechanism of nanoparticles as

additives in the lubricating oils.

2 Experimental study

2.1 Selection and measurement of nanoparticles

CeO2 is a kind of light rare earth oxide. The CeO2 

nanoparticles have good properties of wear resistance,

chemical erosion resistance and good polishing effect as

abrasive[7]. Some researchers discovered that CeO2 

nanoparticles could restrain the reunification among

  particles and strengthen the stability of nanoparticles in

the organic liquid phase[8].

Shao Xin[9] et al discovered that TiO2 nanoparticles filled

to poly (phthalazine ether sulfone ketone) (PPESK)

composite materials could remarkably improve the

tribological properties.

The structure, shape and diameter of nanoparticles play

an important role in the lubricating oils as additives. In

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GU Cai-xiang, et al. Tribological effects of oxide based nano-particles in lubricating oils72

this paper, the morphology and size of CeO2 nanoparticles

and TiO2 nanoparticles were examined by Hitachi H-600

Transmission Electron Microscope (TEM). The detailed

measurement methods were given in the references[10]. 

2.2 Preparation of lubricating oils containing

nanoparticlesIn order to make CeO2 nanoparticles and TiO2 

nanoparticles evenly disperse in the lubricating oils,

Tween-20, Tween-60, Span-20 and Sodium

sodecylbenzenesulfonate were selected. The nanoparticles

were treated by these surfactants.

The steps of preparing the lubricating oils containing

combination nanoparticles are as follows:

1) Evenly mix Tween-20, Tween-60, Span-20 according

to the weight proportion of 2:2:1.

2) Adequately blend the mixture above-mentioned with

Sodium sodecylbenzenesulfonate according to the weight

  proportion of 5:1, then add the combination of CeO2 

nanoparticles and TiO2 nanoparticles in the mixture (The

weight proportions of CeO2 nanoparticles and TiO2 

nanoparticles are 0:1, 1:1, 1:2, 1:3, 1:4, 3:1, 2:1, 1:0,

respectively).  Blend the mixture in electrothermal

constant temperature water bath spot for 10 minutes at

70~80℃.

3) Put the nanoparticles treated by surfactants into 500SN

 base oil (the weight fractions of nanoparticles in the oilare 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, respectively), then put

the mixture into the KQ218 ultrasonic vibration

instrument to vibrate for 20 minutes so as to disperse the

nanoparticles adequately.

4) Put the mixture into the H97-A constant temperature

magnetic force mixer, and stir it for about 2 hours at 85℃ 

while revolutionary speed is 1 300 r/min.

Repeat the step 3) and step 4) for many times, the

dispersion and stirring time are determined according to

the content of nanoparticles.

In this paper, 40 kinds of lubricating oils were prepared,

according to different weight fractions and different

weight proportions of CeO2 nanoparticles and TiO2 

nanoparticles.

2.3 Tribological properties of lubricating oils

containing nanoparticles 

The maximum non-seized load  P  B was examined by

MRS-1J four-ball tribotester produced by Jinan Shijin

Group Co., Ltd. according to GB/T12583-1998, and wear 

spot diameters D of steel balls and friction coefficients  μ 

of lubricating oils were measured and calculated after 

running for an hour under the load of 392 N. The

diameter of the steel ball (GCr15) is 12.7 mm (0.5 in.),

and the grade is 25 EP (super light). The steel balls were

 provided by Shanghai Danan Chemical Grease Co., Ltd.

Wear spot diameters  D were measured by 15 Jmicroscope produced by Shanghai No.5 Optical

Instrument Factory. Wear scar morphology photographs

were shot by XTZ-D/E continuously multiple microscope

taking CCD visible probe.

3 Results and discussion

3.1 Morphology observation and diameter

measurement of nanoparticles

Morphology and diameter of nanoparticles were observed

and detected by TEM. Fig.1 shows that the shape of CeO2 

nanoparticles is spherical and the average diameter 

measured is about 10.4 nm, while the shape of the TiO2 

nanoparticles is grain and the average diameter measured

is about 15.2 nm. The shapes of these two kinds of 

nanoparticles are all uniform and equiaxed.

3.2 Tribological properties of lubricating oils

containing nanoparticles 

Tribological properties of oils are shown in Table 1,

Table 2 and Table 3. Wear scar morphology of 500SN

 base oil and lubricating oils containing nanoparticles are

shown in Fig.2.

Tables 1~3 show that the properties of extreme pressure,

wear spot diameters, and friction coefficients of 

lubricating oils containing nanoparticles have been

considerably improved, compared with 500SN base oils

( P  B is 362 N, wear spot diameter  D is 0.72 mm, friction

coefficient  μ is 0.124 0). In the case of adding single type

of TiO2 nanoparticles into 500SN base oils, the best

tribological properties can be obtained when the weight

fraction of TiO2 nanoparticles is 0.8%. However, in the

case of adding TiO2 nanoparticles and CeO2 nanoparticles

into 500SN base oils, only when the weight proportionand the weight fraction of nanoparticles are appropriate

can the combination lubricating oils achieve best

  properties of anti-wear and friction reducing. When

ω(CeO2):ω(TiO2)=1:3, ω(CeO2+TiO2)=0.6%;  P  B can

reach 510 N, D reaches a minimum 0.448 mm and  μ also

reaches a minimum 0.0774. Compared with 500SN base

oil,  P  B is increased by 40.8%. Wear spot diameter  D is

decreased by 37.7%, and friction factor is decreased by

37.6%. It indicates that the addition of CeO2 

nanoparticles can reduce the required amount of TiO2 

nanoparticles.

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 Journal of Marine Science and Applicaton (2009) 8: 71-76 73

 

(a) CeO2 nanoparticles 100000× (b) TiO2 nanoparticles 100000×

Fig.1 TEM morphology of nanoparticle

Table 1 The maximum non-seized load of lubricating oils containing combination nanoparticles  

ω(CeO2 ):ω(TiO2 ) ω(CeO2+ TiO2 ) 

/%  0:1 1:1 1:2 1:3 1:4 3:1 2:1 1:0

0.2 431  431  431  431  431  431  461  461 

0.4 461  461  461  461  461  461  490  461 

0.6 461  461  490  510 490  461  490  461 

0.8 490  490  490  461  461  490  461  461 

1.0 490  490  461  461  461  461  490  461 

Table 2 The wear spot diameters of lubricating oils containing combination nanoparticles

ω(CeO2 ):ω(TiO2 ) ω(CeO2+ TiO2 ) 

/%  0:1 1:1 1:2 1:3 1:4 3:1 2:1 1:0

0.2 0.684  0.661  0.621  0.572  0.703  0.653  0.626  0.682

0.4 0.571  0.647  0.562  0.497  0.598  0.610  0.571  0.663

0.6 0.515  0.624  0.512  0.448  0.498  0.586  0.537  0.639

0.8 0.498  0.598  0.481  0.490  0.554  0.553  0.552  0.678

1.0 0.558  0.614  0.542  0.522  0.631  0.579  0.587  0.690

 

Table 3 The friction coefficients of lubricating oils containing combination nanoparticles

ω(CeO2 ):ω(TiO2 ) ω(CeO2+ TiO2 ) 

/%  0:1 1:1 1:2 1:3 1:4 3:1 2:1 1:0

0.2 0.113 2  0.101 8  0.109 2  0.089 9  0.108 1  0.104 1  0.112 6  0.113 2

0.4 0.101 3  0.099 6  0.099 0  0.083 0  0.104 7  0.092 2  0.101 3  0.103 3

0.6 0.085 9  0.096 1  0.087 6  0.077 4  0.093 3  0.080 8  0.091 8  0.092 2

0.8 0.079 7  0.091 6  0.079 1  0.083 0  0.098 4  0.076 2  0.101 8  0.099 0

1.0 0.099 0  0.100 1  0.101 3  0.093 3  0.101 8  0.089 9  0.101 8 0.104 1

 

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GU Cai-xiang, et al. Tribological effects of oxide based nano-particles in lubricating oils74

 (a) 500SN base oils (b) ω(CeO2+ TiO2 )=0.2%,ω(CeO2 ):ω(TiO2 )=1:4 

(c) ω(CeO2+ TiO2 )=0.6%,ω(CeO2 ):ω(TiO2 )=1:3 (d) ω(CeO2+ TiO2 )= 1.0%,ω(CeO2 ):ω(TiO2 )=1:3 Fig.2 Wear scar morphology of oils (100×) 

Fig.2 shows that wear spot morphology of 500SN base

oils is extremely not round, and severe adhesive wear and

tearing trace can be seen obviously. The wear scars are

deeper and wider as shown in Fig.2(a). When the CeO 2 

and TiO2 nanoparticles were put into the lubricating oils,

wear scars have been greatly improved. They are

shallower and narrower and have no tearing trace. The

wear spot is round and the wear scar is flat as shown in

Fig.2(b). These indicate that the nanoparticles have good

  properties of anti-wear and friction reducing. When

ω (CeO

 

Tribological properties experiments and wear scar 

morphology observation show that properties of anti-wear 

and friction reducing of CeO

2):ω (TiO2)＝ 1:3, ω (CeO2+TiO2)=0.6%, the

wear spot is more round and more flat than any other 

wear spots. The wear scar is shallow and thin and the

wear spot diameter is the minimum as shown in Fig.2(c).

But when the weight fraction of CeO2 nanoparticles and

TiO2 nanoparticles is 1.0%, wear scar becomes deeper 

and wider; moreover, the wear spot becomes big and not

round as shown in Fig.2(d). It shows that overmany

nanoparticles result in reunification among nanoparticles

and reducing the effects of anti-wear and friction

reduction.

2 nanoparticles and TiO2 

nanoparticles are subjected to two factors, weight fraction

and weight proportion. On the one hand, the weight

fraction should be appropriate to make sure there are

enough nanoparticles spreading on the friction surfaces;

on the other hand, the proportion of CeO2 nanoparticles

and TiO2 nanoparticles should be equally appropriate.

Whenω(CeO2 ):ω(TiO2 )＝1:3, ω(CeO2+ TiO2 )=0.6%,

the optimal tribological properties can be obtained. In

addition, the experimental results show that the weight

  proportion of surfactants is that

Tween-20:Tween-60:Span-20:Sodium

sodecylbenzenesulfonate=2:2:1:1, the combination

surfactants have better dispersing and stable effects on

CeO2 nanoparticles and TiO2 nanoparticles. The reason

may be that surfactants and nanoparticles form

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 Journal of Marine Science and Applicaton (2009) 8: 71-76 75

microcapsule. In addition, the experimental results also

show that the addition of CeO2 nanoparticles can reduce

the required amount of TiO2 nanoparticles.

To sum up, the study on tribological properties of the

combination of CeO2 nanoparticles and TiO2 

nanoparticles used as additives in the lubricating oilsindicates that they can improve base oil’s properties of 

extreme pressure, anti-wear and friction reducing. The

application of the combination of CeO2 nanoparticles and

TiO2 nanoparticles in the lubricating oils plays an

important role in improving and reforming the traditional

lubricating techniques of marine diesel engines.

The lubricating oils containing CeO2 nanoparticles and

TiO2 nanoparticles have the characteristics of being

simple to prepare, technologically feasible and

remarkably effective, which have significant influences

on promoting the lubricating performance and prolonging

the service life of marine diesel engines.

4 Conclusions

1) The weight proportion of surfactants is that

Tween-20:Tween-60:Span-20:Sodium

sodecylbenzenesulfonate=2:2:1:1, the combination

surfactants have better dispersing and stable effects on

CeO2 nanoparticles and TiO2 nanoparticles.

2) Whenω

(CeO2 ):ω

(TiO2 )=1:3,ω

(CeO2+TiO2)=0.6%,lubricating oils containing combination nanoparticles

have the optimum effects of anti-wear and reducing

friction.

3) The adding of CeO2 nanoparticles can reduce the

required amount of TiO2 nanoparticles.

References 

[1] STEPHEN M H. Nano-lubrication: concept and design[J].

Tribology International, 2004, 37(7): 537-545.

[2] SHAKVOROSTOV D, POHLMANN K, SHERGE M. Anenergetic approach to friction, wear and temperature[J].

Wear, 2004, 257(1/2): 124-130.

[3] QIN Min, CHEN Guoxu, GAO Yongjian. Research process

of nano-lubricating additives[J]. Synthetic Lubricants,

2001(4): 9-14(in Chinese).

[4] BAKUMIN V N, SUSLOV A Y, KUZMINA G N, et al.

Synthesis and application of inorganic nanoparticles as

lubricant components review[J]. Journal of Nanoparticle

Research, 2004, 6: 273-284. [5] GU Caixiang, GU Zhuoming, WANG Renbing, et al. Study

on anti-wearing and friction reducing properties of 

lubricating oils containing CaCO3 nanoparticles[C]//

Modern Ship-Repairing Technology. Dalian: Dalian

Maritime University Press, 2003, 147-150(in Chinese).

[6] GU Caixiang, GU Zhuoming, CHEN Zhigang, et al. Study

on application of environmentally friendly nanoparticles as 

additives in lubricating oils[J]. Journal of Yunnan University

(Natural Sciences), 2005, 27(3A): 20-24(in Chinese).

[7] YANG Ru, LIU Jianhong, LI Ming. Synthesis of 

mesoporous ceria using a non-surfactant template

approach[J]. Journal of the Chinese Rare Earth Society,

2004, 22(6):739-744(in Chinese).

[8] DOU Lixin, GONG liehang, SHEN Jian, et al.   Restriction

mechanism of nano rare earth compounds to aggregation of 

ultrafine particles[J]. Journal of the Chinese Rare Earth

Society, 2003, 21(Suppl.):67-73(in Chinese).

[9] SHAO Xin, TIAN Jun, LIU Weimin, et al. Friction and wear 

  properties of nanometer TiO particle-filled poly

(2

  phthalazine ether sulfone ketone) composite[J]. Polymer 

Materials Science and Engineering, 2003, 19(3):208-210(in

Chinese). 

[10] ZHANG Lide. Preparation and application technology of 

super powder[M]. Beijing: China Machine Press, 2001:

238-239(in Chinese).

GU Cai-Xiang was born in 1964. She is a PhD

candidate, and an associate professor. Her current

research direction: material science and tribology.

ZHU Guan-Jun was born in 1962, and he is a

master. His current research direction: material

science and tribology. 

TIAN Xiao-Yu was born in 1986, and he is a

graduate student. His current research direction:

material science and tribology. 

ZHU Guang-Yao  was born in 1981, and he is

a graduate student. His current research direction:

material science and tribology. 

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GU Cai-xiang, et al. Tribological effects of oxide based nano-particles in lubricating oils76

 

氧化物纳米粒子在润滑油中的摩擦学作用

顾彩香，朱冠军，李  磊，田晓禹，朱光耀 

（上海海事大学 商船学院，上海 200135） 

摘 要：为了提高润滑油的摩擦学性能，选择了吐温-20、吐温-60、司本-20、十二烷基苯磺酸钠作为表面活性剂，制备

了含纳米CeO2和TiO2粒子添加剂的润滑油. 采用透射电子显微镜（TEM）观察、测定了纳米CeO2和TiO2粒子形貌和平均

粒径. 采用MRS-1J四球摩擦磨损试验机测试了含纳米CeO2和TiO2添加剂的润滑油的摩擦学性能. 结果表明，纳米CeO2和

TiO2的复合粒子的最佳添加量为：ω(CeO2):ω(TiO2)=1:3, ω(CeO2+TiO2)=0.6%，该润滑油具有最佳的抗磨、减摩性能. 纳

米CeO2粒子添加可以适当减少纳米TiO2粒子的用量.

关键词：纳米粒子；活性剂；润滑油；摩擦学性能