Abstract
In this work, the physical phenomenon of the formation of an oil film containing fullerenes was further developed, on the friction surface of tribosystems, which, in contrast to the known ones, takes into account the structural viscosity and structure of the formed film under the action of the electrostatic field of the friction surface. An increase in load significantly increases the structural viscosity of the gel structure, 13 - 20 times. The concentration of fullerenes in the base lubricant does not significantly affect the dynamic viscosity of aggregates in the composition of the liquid and the structure of the gel. An increase in the tribological properties of the base lubricant medium reduces the value of the structural viscosity of the gel on the friction surface by a factor of 3. At the same time, the concentration of fullerenes in the range of 0.5 - 1.5% does not have a large effect on these indicators. This phenomenon can be explained by the presence or absence of an additive package in the base lubricating medium. For those oils where the additive package is absent or present in a small amount J/m3, the introduction of a fullerene composition promotes the formation of clusters and micelles, which increase the structural viscosity and, consequently, form a film on the friction surface in the form of a gel structure. Conversely, if fullerenes are introduced into a base oil that contains a large and balanced additive package, where tribological properties are high J/m3, interaction at the molecular level does not occur. Fullerenes to a lesser extent will form stable aggregates in the form of micelles. The effect of reducing the coefficient of friction, equal to 96 %, is typical for low and medium loads of operation of tribosystems and base lubricants with average values of tribological properties. With increasing loads or tribological properties of base oils, the effect of the use of fullerenes decreases.
Highlights
The use of fullerenes as anti-wear, extreme pressure and antifriction additives to technical liquid lubricants gives an ambiguous answer about their effectiveness
Where μ s and μ g – structural dynamic viscosity of sol and gel, which are formed under the action of the electrostatic force field of friction surfaces, dimension Pa·s; kl, kf – dimensionless coefficients that take into account the mass concentration of fullerenes per unit of lubricant outside the field of action of electrostatic forces and on the friction surface, in the field of action of electrostatic forces; μl – dynamic viscosity of the base lubricant, dimension Pa·s; μ K, μM – dynamic viscosity of aggregates of structures consisting of Kelvin bodies and Maxwell bodies, dimension Pa·s [7]
This phenomenon can be explained by the presence or absence of an additive package in the base lubricating medium. For those oils where the additive package is absent or present in an insignificant amount Еspec (1,8...3,6) 1014 J/m3, the introduction of a fullerene composition promotes the formation of clusters and micelles, which increase the structural viscosity, and form a film on the friction surface in the form of a gel structure
Summary
The use of fullerenes as anti-wear, extreme pressure and antifriction additives to technical liquid lubricants gives an ambiguous answer about their effectiveness. There is a direction where fullerenes, in the form of nanopowders, are directly introduced into the lubricant and the direction, where pre-dispersion of fullerenes is used in solvents, for example, vegetable high oleic oils, and the introduction of such compositions into technical oils. According to the authors of the work [1], this use of fullerenes gives a better positive effect than the addition of fullerenes in the form of nanopowders to lubricants. The general structural feature of liquid lubricants in the presence of fullerenes in them is that clusters and micelles are formed in the volume of the liquid. Fullerene molecules interacting with each other and oleic acid molecules of vegetable oil form aggregates, and the viscous liquid medium becomes structured
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