Third Day Poster Session, 17 June 2010 - NanoTR-VI

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P
P HR3RBOR3
Poster Session, Thursday, June 17
Theme F686 - N1123
Performance of Zinc Borate Nanoparticles as an Anti-Wear Additive in Mineral Oil
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USevdiye Atakul SavrkUP P*, Mehmet GönenP P, Devrim BalköseP P, Semra ÜlküP
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Pzmir Institute of Technology, Department of Chemical Engineering, Gülbahçe Köyü, Urla, zmir, Turkey
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PPresent address: Süleyman Demirel University, Department of Chemical Engineering, Isparta, Turkey
Abstract- Inorganic borates as a lubricating oil additive received extensive attention in recent years due to the remarkable tribological
properties such as wear resistance, friction-reducing ability and oxidation inhibition. This study reports the synthesis of nano-sized zinc borate,
its characterization as well as its performance in mineral oil as a lubricating additive. Zinc borate nanoparticles with different morphologies
were prepared by two different raw materials groups. Spherical crystals were successfully synthesized by precipitation reaction in aqueous
solutions of NaR2RBR4ROR7R·10HR2RO and ZnNR2ROR6R·6HR2RO, whereas supercritical ethanol drying method is applied to prepare broccoli type species
after the precipitation step in aqueous solutions of HR3RBOR3R and ZnO. The lubricants were prepared by dispersing the zinc borate particles with
sorbitan monostearate (Span 60) which was used as a surface modifier. The tribological properties of the mineral oil were determined by fourball
wear test machine and the results indicated that wear scar diameter is reduced by 54.78% for the lubricant including zinc borate dried by
supercritical ethanol drying compared to that of the mineral oil.
The increasing interest of petrochemical industries on
improving the performance of their products (lubricants,
greases, gasoline, among others) has been simultaneously
generating great incentives to develop additives that are able
to supply the commercial demand of the competitive industrial
markets. For tribology applications, particles as additives in
base oil have been investigated widespreadly. These studies
refer to synthesis and preparation of especially nanoscale
particles, and their tribological properties and mechanisms
[1,2]. The lubrication performance of a lubricant relies partly
upon the thickness of the tribofilm under the severe conditions
controlled by several parameters such as load, temperature,
sliding speed and the mechanical properties of the film. A
variety of mechanisms have been proposed to explain the
lubrication enhancement of the nanoparticles suspended in
lubricating oil. Ball bearing effect and protective film
mechanisms have direct effect of the nanoparticles on
lubrication enhancement, whereas mending and polishing
effects have secondary effect on surface improvement [3].
This study aims to investigate the tribological properties of
mineral oil including zinc borate nanoparticles and to expose
the effect of morphology of the particles on anti-wear
property.
In this project, first group of zinc borate species were
obtained by the homogenous precipitation method described
by Ting et al. using ZnNR2ROR6R·6HR2RO, NaR2RBR4ROR7R·10HR2RO and
ammonia [4]. Second group of zinc borate nanoparticles were
3
prepared by 4.7mol/dmP
Rwith the stoichiometric
amount of ZnO. Supercritical ethanol drying of submicron
zinc borate was performed at 250 °C, 6.5 MPa for obtaining
nano zinc borate particles. All zinc borate samples were
characterized by SEM, TGA, DSC, FTIR, and XRD. The
lubricants were prepared by adding sorbitan monostearate
(Sigma Aldrich) and zinc borate particles into the mineral oil
at 70 °C. They were mixed by both a homogenizer (OMNI
GLH) and a magnetic stirrer (Yellowline MSH Basic) for 2
minutes and 2 hours, respectively. Tribological
characterization of the lubricants was carried out by a fourball
wear test machine (made by Falex Corp.) The test balls
were chrome alloy steel, No. E-52100 with a diameter of 12.7
mm. The wear and friction test was performed at 392 N and
the test duration was 1h. After the test, the morphology of
worn surfaces of the balls run in the lubricant was obtained by
SEM. Moreover, elemental composition of the ball worn
surfaces was determined by EDX analysis.
SEM images of zinc borate nanoparticles produced by
different raw materials groups are shown in Figure 1. The
zinc borate obtained by ZnNR2ROR6R·6HR2RO and
NaR2RBR4ROR7R·10HR2RO includes spherical crystals (Figure 1a). On
the other hand, zinc borate crystals dried by supercritical
ethanol have broccoli type morphologies. Table 1 reports the
tribological properties of the lubricants. It was revealed that
sorbitan monostearate had a dramatic role in the reduction of
wear scar diameter from 1.402 to 0.656 mm. When the
nanoparticles dried by supercritical ethanol were used as
lubricating oil additives, wear scar diameter is reduced to
0.634 mm.
(a)
(b)
Figure 1. SEM images of super critical ethanol dried nanoparticles
obtained from zinc borates a) ZnNR2ROR6R·6HR2RO and NaR2RBR4ROR7R·10HR2RO
and b)HR3RBOR3R and ZnO
Table 1. Tribological properties of lubricants
Wear Scar Friction
Sample Additive
Diameter (mm) Coefficient
L1 - 1.402 1.645
L2 Span 60 0.656 1.635
L3
ZB dried by
SCE +Span 60
0.634 1.601
SEM analysis shows that the worn surface of the ball
lubricated with L3 lubricant including zinc borate and
surfactant exhibits much smoother surfaces without severe
scuffing. Additionally, EDX analysis reveals that boron and
zinc elements are also adsorbed by the worn surface of the
ball.
TÜBTAK (project number: 105M358), OPET Petrolcülük
A. and Izmir Institute of Technology Centre for Material
Research are greatly appreciated.
HT*Corresponding author: sevdiyeatakul@iyte.edu.trT
[1] Zhang M., Wang X., Fu X., Xia Y., 2009. Performance and
anti-wear mechanism of CaCOR3 Rnanoparticles as a green additive in
poly-alpha-olefin, Tribology International, 42:1029-1039.
[2] Choundary R.B., Pande P.P., 2006. Lubrication potential of
boron compounds: an overview. Lubrication Science, 14: 211-222.
[3] Lee K., Hwang Y., Cheong S., Choi Y., Kwon L., Lee J., Kim
S.H., 2009. Understanding the role of nanoparticles in Nano-oil
lubrication, Tribology Letters, 35: 127-131.
[4] Ting C., Cheng D.J., Shuo W.L., Gang F., 2009. Preparation
and characterization of nano-zinc borate by a new method, Journal
of Material Processing Technology, 209:4076-4079.
6th Nanoscience and Nanotechnology Conference, zmir, 2010 733