06-09-2012, 02:53 PM
Tribological Properties of Polytetrafluoroethylene, Nano-Titanium Dioxide, and Nano-Silicon Dioxide as Additives in Mixed Oil-Based Titanium Complex Grease
[attachment=33532]
Abstract
Eight titanium complex greases (i.e., benzoic
acid/stearic acid and sebacic acid/stearic acid titanium
complex greases, and greases containing PTFE, or nanotitanium
dioxide, or nano-silicon dioxide) were synthesized
using 3-L reaction vessel. Their physical characteristics
were characterized and their tribological properties were
evaluated by using a four-ball tester. Chemical compositions
of the boundary films generated on worn surfaces
were analyzed with the use of scanning electron microscope
and X-ray photoelectron spectrometer. Results show
titanium complex greases containing PTFE, or nano-titanium
dioxide, or nano-silicon dioxide exhibited excellent
tribological performance. The mechanism for the frictionreduction
and antiwear effect of all titanium complex
greases was also proposed and discussed from a tribochemistry
point of view.
Introduction
In recent years, an explosive growth of research on lithium
greases and other lubricants in tribology has been conducted
[1–8]. Owing to excellent physical–chemical and
extraordinary performance [9–11], titanium complex
greases have received considerable attention in tribological
fields. Kumar et al. [12–14] reported that wear scar
diameters of synthetic oil-based titanium complex are 0.7–
1.0 mm, and those of titanium complex grease containing
different solid lubricants and extreme-pressure additives
are 0.55–0.73 mm. However, there have been few reports
on the effect of different compositions and microparticles/
nanoparticles on the tribological behavior of titanium
complex grease. Moreover, the friction coefficient and
lubricating mechanisms of titanium complex greases have
not been reported in the above-mentioned studies. In this
work, benzoic acid/stearic acid and sebacic acid/stearic
acid titanium complex greases were synthesized using 3-L
reaction vessel. The physical characteristics of titanium
complex grease were characterized and their tribological
behaviors were evaluated using a four-ball test.
Conclusions
a. Titanium complex grease containing PTFE, nano-titanium
dioxide, or nano-silicon dioxide exhibits excellent
friction-reduction and antiwear properties; the
optimum concentration is approximately 2.0, 0.5, and
1.5 wt%, respectively.
b. Different additives at optimal additive concentrations
have no effect on increasing base grease load-carrying
capacity.
c. The main wear mechanism on wear scar is slight
adhesive wear. In the friction process, a synergistic
effect between the adsorbing film formed by titanium
complex grease itself, the greases containing PTFE,
nano-titanium dioxide, or nano-silicon dioxide, and the
titanium chemical sediment contributes to improving
tribological properties.
[attachment=33532]
Abstract
Eight titanium complex greases (i.e., benzoic
acid/stearic acid and sebacic acid/stearic acid titanium
complex greases, and greases containing PTFE, or nanotitanium
dioxide, or nano-silicon dioxide) were synthesized
using 3-L reaction vessel. Their physical characteristics
were characterized and their tribological properties were
evaluated by using a four-ball tester. Chemical compositions
of the boundary films generated on worn surfaces
were analyzed with the use of scanning electron microscope
and X-ray photoelectron spectrometer. Results show
titanium complex greases containing PTFE, or nano-titanium
dioxide, or nano-silicon dioxide exhibited excellent
tribological performance. The mechanism for the frictionreduction
and antiwear effect of all titanium complex
greases was also proposed and discussed from a tribochemistry
point of view.
Introduction
In recent years, an explosive growth of research on lithium
greases and other lubricants in tribology has been conducted
[1–8]. Owing to excellent physical–chemical and
extraordinary performance [9–11], titanium complex
greases have received considerable attention in tribological
fields. Kumar et al. [12–14] reported that wear scar
diameters of synthetic oil-based titanium complex are 0.7–
1.0 mm, and those of titanium complex grease containing
different solid lubricants and extreme-pressure additives
are 0.55–0.73 mm. However, there have been few reports
on the effect of different compositions and microparticles/
nanoparticles on the tribological behavior of titanium
complex grease. Moreover, the friction coefficient and
lubricating mechanisms of titanium complex greases have
not been reported in the above-mentioned studies. In this
work, benzoic acid/stearic acid and sebacic acid/stearic
acid titanium complex greases were synthesized using 3-L
reaction vessel. The physical characteristics of titanium
complex grease were characterized and their tribological
behaviors were evaluated using a four-ball test.
Conclusions
a. Titanium complex grease containing PTFE, nano-titanium
dioxide, or nano-silicon dioxide exhibits excellent
friction-reduction and antiwear properties; the
optimum concentration is approximately 2.0, 0.5, and
1.5 wt%, respectively.
b. Different additives at optimal additive concentrations
have no effect on increasing base grease load-carrying
capacity.
c. The main wear mechanism on wear scar is slight
adhesive wear. In the friction process, a synergistic
effect between the adsorbing film formed by titanium
complex grease itself, the greases containing PTFE,
nano-titanium dioxide, or nano-silicon dioxide, and the
titanium chemical sediment contributes to improving
tribological properties.