M. V. Boiko

Thermodynamic and kinetic analyses of probable chemical reactions in the tribocontact zone and the effect of heavy pressure on evolution of adsorption processes

The paper presents thermodynamic and kinetic analyses of probable chemical reactions and adsorption processes depending on their energy, temperature, and pressure. It is shown that only lubricating adsorption films that appear on the rubbing surfaces due to mechanoactivated reactions can play a significant role in improving the tribological properties of a sliding contact. It is also demonstrated that heavy pressures in the zone of real contact between the asperities of rubbing surfaces enhance equilibrium adsorption of low-molecular-weight additives and of a number of high-molecular-weight additives to fluid lubricants.

Population of transition states of triboactivated chemical processes

The population of transition states of friction-induced chemical processes and similar thermo-induced reactions is analyzed. Friction is shown to be a unique natural phenomenon that involves the occurrence of highly inverse transition states of chemical interaction between contact material particles, as opposed to thermally populated transition states analogous in terms of the energy level of the reactions. It is found that in evaluating the population of transition states of mechano- and thermoactivated reactions, the specific chemical interactions do not matter and only the energies of the transition states of the thermo- and mechanoactivated processes are of importance.

Investigation of tribochemical processes in lubricating compositions that contain coordination compounds of transition metals

Tribochemical processes in the formation of lubricating layers under conditions of boundary friction in oils containing coordination compounds of transition metals are investigated. The formation of nickel nanoparticles involved in the formation of a tribopolymeric nanocomposite from a complex compound has been proved. A mechanism that explains the observed phenomena has been proposed

Mechanoactivation in friction and the laws of sliding and rolling friction

The concepts of the collision theory and the activated complex theory, widely known in chemical kinetics and adapted to the description of contact between asperities on rubbing surfaces, are used to derive the expressions of Amontons’ law for sliding friction and Coulomb’s law for rolling friction. A semiquantitative relation between the sliding and rolling friction coefficients is found. Based on the expressions, the energy of interaction between the asperities and the friction coefficient in systems with selective transfer is estimated.

Kinetics of mechanoactivation of tribochemical processes

Active collision theory and activated complex theory are used to derive the general kinetic equations of the mechanoactivation of tribochemical processes in systems with boundary and mixed sliding friction. The nature of the weak temperature dependence of the velocities of tribochemical reactions compared to the corresponding thermoactivated processes is discussed. Various specific cases of mechanoactivation kinetics are considered and some of them are illustrated using examples of reactions with the selective transfer and wear of rubbing solids.

Effect of pressure on chemical reactions in the zone of direct friction contact of systems with selective transfer

The paper deals with the effect of heavy pressure in the zone of real tribocontact on the rate of the reactions of complexing of copper chelates that provide the formation of a servovite film and implementation of selective transfer. It is shown that heavy pressures accelerate significantly the complexing reactions at the initial stages of servovite film formation during selective transfer. The procedure of search for potential complexing agents for implementing selective transfer can be simplified by using the developed method of mole volumes. This method allows the prediction of the efficiency of a complexing ligand at the initial stage of servovite film formation with account for heavy real pressures.

Molecular polarizability of organic compounds and their complexes: LIX. Molar volumes, intrinsic atomic solvation radii, and spatial structures of certain conformationally flexible compounds in solutions

The molar volumes and structures in individual liquids and solutions of a series of conformationally flexible compounds, such as alkanes and diaryl-substituted systems with sp3-hybridized bridging atoms, were analyzed in terms of intrinsic solvation radii of atoms constituting the molecule. Intrinsic solvation atomic radii were determined for various molecules to show that they are larger than the van der Waals radii of the same atoms. An approach to parametrization of the intrinsic solvation radii of atoms constituting a molecule, using appropriate model compounds, was proposed. From the resulting values of intrinsic atomic solvation radii, the possible conformations of a series of diphenylmethanes, diphenylsilanes, diphenyl sulfides, diphenyl sulfoxides, and diphenyl sulfones in solutions were assessed.

Tribochemical processes in engine oil with copper nanoparticles and azomethine ligand

The tribochemical processes in SAE 10W40 engine mineral oil with complexing compound and dioctylphtalate have been studied. A tribofilm that reduces the coefficient of friction is found to be formed on the friction surfaces; it is probed via optical and scanning electron microscopy, FTIR infrared spectroscopy, and X-Ray fluorescence and is established to be composed of copper covering the steel surface and a tribopolymer film. The effect of tribochemical processes with involving the steel surface, copper nanopowder, ligands, coordination compounds, and complex ether in the formation of a tribofilm has also been elucidated.

Molecular polarizability of the organic substances and their complexes: LX. Molecular volume and spatial structure of the series of heterocycles, their structurally nonrigid derivatives, and chromium tricarbonyl π-complexes in solutions

We have analyzed the molar volumes and structures in solutions of a series of azines, azoles, conformationally nonrigid bis(2-substituted benzimidazol-1-yl)methanes, and chromium tricarbonyl complexes of arenes. For most of the compounds, the rules of molar volume additivity with respect to the bonds and groups increments hold. Molecules of bis(2-substituted benzimidazol-1-yl)methanes exist in the form of conrotatory comformers with aryl fragments being out of the plane of bridging NCN bond angle. Strong linear correlations between the molar volume and molar refraction have been revealed within the studied compounds classes. In the case of chromium tricarbonyl complexes of arenes, the coordination bond polarity has increased with growing π-donor ability of the ligand, the molar volume increment of Cr(CO)3 has increased as well, due to transfer of π-electron density from the ligand. The simplification of dipole moment and Kerr constant determination has been demonstrated.

Molecular polarizability of organic compounds and their complexes: LV. Molar volume and structure of some nitrogen compounds, their structural analogues, and some sterically hindered systems in solution

The molar volumes in solutions of a wide range of aliphatic and alicyclic amines, substituted acetanilides, 9- and 9,10-substituted anthracenes, and 1- and 1,8-substituted naphthalenes were estimated and discussed. Conformations of alkyl substituents in the aliphatic amines are similar to the conformations of the respective alkanes. Conformations (chair) of the molecules of alicyclic amines and cyclohexane are almost identical. In the molecules of acetanilides, the C(O)CH3 group is conjugated with aromatic ring and is oriented toward the latter and toward the nitrogen of the amide group in the same manner as in acetophenone. A systematic decrease in the values of the molar volume increments of the substituents R in going from substituted benzene to substituted naphthalene and anthracene was revealed, which indicates the extension of the π-systems over the C-R bond. The orientation of 1,8-substituents relative to the naphthalene ring was found to be approximately orthogonal. A possibility to simplify the methods for determining the dipole moments and Kerr constants of compounds on the basis of their additive molar volumes was demonstrated.