OPTIMIZATION OF CARBON NANOTUBES AS ADDITIVE IN LUBRICANT

Carbon nanotube (CNT) has a high potential in automotive lubricating application due
to its ultra small size and stiffness that can contribute towards better anti-wear and
anti-friction properties. Conventional additives such as molybdenum dithio�carbamates and zinc dialkyldithiophosphates can cause heavy emission of the
pollutants such that their usage is limited. This in turn will result in an inefficient
engine that can increase the fuel consumption and produce excessive emission. Thus
there is a demand for an alternative additive in order to alleviate the environmental
problem. With CNTs as the alternative additive, specific characteristics are required
in order to improve the lubricant performance. The objective of the work is to study
the effect of the growth parameters on CNTs properties namely diameter size and
crystallinity in order to produce CNTs with optimum characteristics using floating
catalytic chemical vapour deposition. The growth parameters investigated were the
weight of ferrocene, flow rate of ethylene and argon, and the reaction temperature.
Samples of CNTs produced were characterized using scanning electron microscopy,
transmission electron microscopy, thermo-gravimetric analysis, X-Ray diffraction and
Raman spectroscopy. Temperature of 850°C under 20 seem of ethylene with 0.1 g
ferrocene is the optimum condition for CNT growth with the diameter range of
29-70 nm and crystallinity (Id/Ig) of 0.54. Different weight percentage (0.01wt% to
0.10wt%) of crude, purified multiwall CNTs produced using optimum conditions and
commercialized single-wall CNT sample were incorporated into the lubricant, MACH
5 PETRONAS in order to conduct the four-balls-wear test and ball-on-disc test.
Significant reduction (71%) in the diameter of wear scar can be achieved with the
incorporation of 0.02 wt% of crude MWCNTs into the lubricant. With this crude
MWCNTs sample, a loading of 392 N can reduce the friction coefficient by 54%.
Under the loading of 20N a reduction offriction coefficient from 0.099 to 0.0222 can
be achieved. This study gave a great approach to rationalize CNTs as alternative
additive in lubricant by providing promising results in friction and wear reduction.