The Ultra-Low Friction of Layer Structures

The article investigates the process of obtaining the properties of thin films of layered materials, applied vacuum ion-plasma deposition methods. A study of the tribological properties was performed electron diffraction and electron microscopy studies of the structure. It was found a positive effect of the deposition of wear-resistant sublayer and alloying of the antifriction layer, which led to a considerable increase endurance and appearance of ultra-low (super-low) friction. The generalized model of crystal growth mechanism and ultra-low friction, which is based on the possibility of mass transfer non-dissipative (energy) in the absence of resistance forces during the move. Also found that the ultra-low (super-low) friction, superconductivity and superfluidity are related phenomena defined by the phase transition of the energy distribution of particles through a critical value (energy potential barrier). Energetically favorable arrangement of the particles in the crystal lattice of the lattice for the realization of the non-dissipative movement with the disappearance of forces of resistance are the Van der Waals areas, which is followed by predicting the implementation of the investigated phenomena.


Introduction
To protect work surfaces and improve the physical and mechanical properties of the surface layers are applied anti-friction wear-resistant coatings deposited by various methods.Modern high-tech industries, which require the use of accurate low-friction running clearance required the creation of new technologies for applying thin coatings to protect sliding surfaces from wear.Features of the crystal structure and anisotropy in different crystallographic directions led to the use for these purposes dichalcogenides of transition metals (Bulaevskii, 1975).
Particularly relevant is the protection of friction pairs, made from materials that are prone to setting, followed by catastrophic wear (especially in a high vacuum).Austenite stainless steel and titanium alloys are among these materials.Vacuum ion-plasma methods of applying such coatings based on ion (cathode) sputtering, have a number of advantages.Coatings deposited by cathodic sputtering, have high adhesion to a substrate, maintaining the stoichiometry of uniformity of distribution and uniformity in thickness.When changing the process conditions applied in the preparation of ion-vacuum plasma coating becomes possible to form different crystal structures and, consequently, the change in their physical, mechanical and tribological characteristics.Thus, the development of technology allows you to manage the process of producing coatings and create the desired properties (Nozhenkov, 2012a(Nozhenkov, , 2012b(Nozhenkov, , 2013a(Nozhenkov, , 2013b(Nozhenkov, , 2013c(Nozhenkov, , 2014)).

Goal of the Work
The work is aimed at establishing the effect of applying process conditions on the crystalline structure of coatings based on the dichalcogenide of transitional metals of groups IV-VI obtained by the vacuum ion-plasma methods and on their t tribotechnical properties.

Objects and Methods of Studies
Polished specimens from compact ceramics Al 2 O 3 , SH-15 steel and 12X18H10T steel served as substrates for application of coatings.The substrates were coated with molybdenum disulfide and diselenide (MoS 2 , MoSe 2 ) and tungsten disulfide and diselenide (WS 2 , WSe 2 ).The method of applying the coatings with ion-plasma sputtering is described in (Nozhenkov, 2012a(Nozhenkov, , 2012b(Nozhenkov, , 2013a(Nozhenkov, , 2014)).The coatings were applied at a substrate       (atoms, molecules, clusters) in the absence of external influences and turning them into the inertial reference system.These particles have the possibility movement on a solid surface uniformly, without dissipation of energy, that is the possibility of zero change of the interaction energy with the surface of a solid body in motion.The most likely implementation of such a phenomenon on singular plane (0001) with the realization of ultra-low (zero) friction without energy dissipation, in the absence of resistance forces the process of moving.
The obtained results of improving the tribotechnical characteristics and the mechanism of growth of crystallites with planes (101 -0) and (112 -0) of the crystallites with hexagonal (110) and cubic structures that were almost perpendicular to the flow of deposited particles can be explained using the model developed in Nozhenkov (2012aNozhenkov ( , 2012bNozhenkov ( , 2013aNozhenkov ( , 2013bNozhenkov ( , 2013cNozhenkov ( , 2014) ) and Ginzburg (2000).These works consider the process of the formation of condensed solid body from the flux of atomized particles, and a model is proposed for crystallite growth due to the possibility of the diffusive migration of deposited atoms on the growing coating surface and the creation of mobile particulate monolayers on dichalcogenide packs of the two-dimensional gas during the friction of the obtained doped coatings.This migration of particulate monolayers is possible when the heat energy of the particles exceeds the surface-potential barriers.The mobile particles reduce the interaction between chalcogen-metal-chalcogen packs, and facilitate the mutual sliding of dichalcogenide packs.This will be shown in the following.

Mechanism of Ultra-Low Friction
Features of the crystal structure and anisotropy caused use for various purposes, the materials with laminated (lamellar) structure, for example, transition metal dichalcogenides.It is a crystalline substance with a lamellar structure in which together with the strong ionic-covalent interactions between the atoms in the individual lamella are weak van der Waals forces between adjacent layers.Transition metal dichalcogenides metal finish building the d-electron is consisted the associated by weak van der Waals packages chalcogen-metal-chalcogen (X-M-X), within which there are strong exchange interactions formed complex ion-covalent bonds with applying metal interactions in the center of the package.For example, molybdenum disulfide (α-MoS 2 ), wherein the bivalent and tetravalent molybdenum sulfur have electronic configuration Mo 4 -4d 5 5s; S 2 -3s 2 3p 4 with ionic radius for Mo +4 -0.068 nm for the S -2 -0.182 nm there exists in the hexagonal crystal system.
In the formation of bonds involved dsp-orbit.In the molybdenum disulfide is d 4 sp-hybridization, i.e. ties involved in the formation of 4d-, 5s-and 5p-electrons of the central atom, and the only one not involved in the communication orbit molybdenum atom is occupied by two electrons.Interactions between packets have the dispersion nature, which are based on instantaneous dipoles formed by the action of the collective phonon vibrations of the atoms inside the package X-M-X.These vibrations cause additive phonon vibrations associated with the polarization of opposite sign in the next package.The additivity of the dispersion interaction causes his long-range nature and potential of this interaction decreases with increasing size of the gap by doping dichalcogenide by law r -2 .
In the study of changes in surface layers dichalcogenides during sliding above it was found that the initial structure with a preferred crystal orientation (texture) with the [101 -0] is converted into the texture with the [0001] direction perpendicular to the substrate.The implementation process of the shift and further slip planes basis (0001) for each other is the most energetically favorable and occurs at the lowest cost to the relative movement of solids.The determining factor in this process is to not break the binding energies of Ur in the contact area, and the shift of the atomic planes with overcoming potential barriers, sliding over each other surfaces U b .
Established (Nozhenkov, 2012a(Nozhenkov, , 2012b(Nozhenkov, , 2014) ) that the occurrence of ultra-low friction due to the presence of migrating phase on friction surfaces in a state of two-dimensional gas.In this phase, the particles (atoms, molecules, clusters) can be adsorbed from the environment or introduced in the solid lattice when shaping it.For very low coefficients of friction in normal conditions the air to shift the phase transition in the temperature range less than 300 K, ie, the binding energy of atoms adsorbed on the (0001) dichalcogenide for free migration on the surface to be less than the kinetic energy of the atom under normal conditions.Moving the masses without the heat loss can be along the lines of equipotential surface field.Moving across the lines of equipotential field is accompanied by energy costs to heat dissipation.The presence of the alloying particles monolayers on friction surfaces increases the distance between the (0001) planes (Figures 17,18) and reduces the energy of the interaction between layers U r .Such particles in the case of the possibilities for diffusion migration to the surface (0001) provide ease of sliding of the opposite surfaces (0001) and thus to move in the particles along the equipotential field lines of the surface (0001) there is possibility of movement without energy dissipation.

Discussion of Results
It should be noted that the phenomenon of superconductivity and ultra low friction was observed in the crystal structures of layered dichalcogenide type (MX 2 ) and diboride (MB 2 ) metals (M: metal; X: chalcogen; B: boron) (Bulaevskii, 1975;Ginzburg, 2000;Kirzhnits, 2001).It is a crystalline substance with a lamellar structure in which the on-line with the strong ionic-covalent interactions between the atoms in the individual lamellae of (layers) are weak van der Waals forces between adjacent layers.For example, transition metal dichalcogenides metal finish building the d-electron shells are composed of-span of the associated by weak van der Waals packages chalcogen-metal-chalcogen (X-M-X), within which there are strong exchange interactions formed complex ion-covalent metal overlay communication interactions in the center of the package.For example, molybdenum disulfide (α-MoS 2 ), wherein the bivalent and tetravalent molybdenum sulfur have electronic configuration Мо 4 -4d 5 5s; S 2 -3s 2 3р 4 with ionic radius for Mo +4 0.068 nm, for the S -2 0.182 nm-there exists in the hexagonal crystal system.In the formation of bonds involved dsp-orbit.In the molybdenum disulfide is d4sp-hybridization, ie ties involved in the formation of 4d-, 5s-and 5p-electrons of the central atom, and the only one not involved in the communication orbit molybdenum atom is occupied by two electrons.
Interactions between packets have the dispersion nature, which are based on the dipoles formed by the action of the collective phonon vibrations of the atoms inside the package X-M-X.These vibrations cause additive phonon vibrations associated with the polarization of opposite sign in the next package.The additivity of the dispersion interaction (as opposed to binary interactions of exchange type) causes his long-range nature and potential of this interaction decreases increasing size of the gap by doping dichalcogenide by law r -2 .
High-temperature transport of mass (energy) without dissipation (heat dissipation) is possible along the lines of equipotential surfaces (0001) anisotropic layered compounds in the presence of a layered structure of solid spaces van der Waals forces.Owing to the special condition of the layered solid-the availability of space Van der Waals forces-which are long-range dispersion forces, and there are no free valence electrons capable of forming a strong exchange interactions, there is a possibility of moving particles without dissipation (scattering) of energy.Dissipative processes are the result of the forces of resistance arising in the metabolic processes of interaction.The strength of the resistance movement occurs in the case of change of speed of movement (the emergence of the acceleration) at the intersection (movement across) the force lines of the equipotential field F = ma = m dV/dt (4) Figure 16 shows that for the migration of the particles on the surface (0001) Solid State must inform the latter of the diffusion activation energy to overcome the potential barrier surface, the activation energy does not exceed the energy of the particle and the surface to avoid desorption (reispareniya) particles from the surface.Requires the creation of conditions for the migration of the particles (using the appropriate temperature of the friction pair) and freezing of high energy particles (photons, phonons), resulting in a two-dimensional gas desorption, which provides ultra-low friction.
In the study of the transfer of electric charges and the atoms of helium at low temperatures observed phenomena of superconductivity and superfluidity (Bulaevskii, 1975;Ginzburg, 2000;Kirzhnits, 2001).The basis of these physical phenomena is the formation of Cooper pairs of electrons and superconductivity or of helium-3, with superfluidity, which leads to a lack of heat loss with the flow of the particles and the disappearance of the friction between the moving particles and the lattice of a solid.Electrons and nuclei of helium-3 are fermions with half-integer spin ½.The atoms of the isotope helium-3 (helium 3 He) are fermions, but at sufficiently low temperatures combined into Cooper pairs with integer spin, representing bosons.Fermion through a field directly interacts with another fermion with the emission of a photon and form a boson with integer spin.The emission of a photon in the process of formation of the Cooper pairs-the radiation of excess energy when two electrons, like the rays of the electron and proton in a hydrogen atom to form an integral particles, as discussed in (Nozhenkov, 2012b).Formation boson happens to the radiation of energy education, the decay with the corresponding radiation.To save the opposite curvature of Riemann and Lobachevsky fields in the hydrogen atom emission occurs on the outside of the atomic electron's orbit, and in a Cooper pair from the center, located between the electrons.The radius of curvature of the mass of a photon emitted by a hydrogen atom, is equal to the radius of the main orbit of the hydrogen atom, de Broglie radius of a photon emitted by a hydrogen atom in the ground state, in 1/α times the radius of the mass of the photon.The size of the Cooper pairs is proportional to the fine structure constant α and the diameter of the main orbit of the hydrogen atom.Formed by a Cooper pair is stable, resistant and has the ability to move in the lattice of a solid at zero-point oscillations of the atoms of the latter without energy dissipation.For the destruction of the Cooper pairs (the creation two fermions of one boson) particles are needed with the appropriate energy E f , which is the activation energy of decay and numerically equal to the energy of formation of boson.The destruction of the Cooper pair without decomposition activation energy is impossible.The task of maintaining the Cooper pairs in a stable condition for high-temperature superconductivity is to absorb particles (photons, phonons) c energies equal to the corresponding activation energy of decomposition Cooper pairs.Emerged after the collapse of bosons fermions are scattered by the crystal lattice of the solid (phonons, lattice defects) with the dissipation of energy, which creates obstacles to their free movement and the movement of the particles is carried out with the presence of heat dissipation.
The intercalation enhances the superconducting of dichalcogenides (Bulaevskii, 1975) and in certain circumstances, allows you to get ultra-low friction phenomenon (Nozhenkov, 2012a(Nozhenkov, , 2012b(Nozhenkov, , 2013a(Nozhenkov, , 2013b(Nozhenkov, , 2013c(Nozhenkov, , 2014)).The arrangement of atoms of doping element in the van der Waals interlayer spaces accompanied by the formation of two-dimensional electron gas.The electrons of a Cooper pairs move in two parallel spaces van der Waals forces between the layered material packages.When creating the appropriate conditions in a layered crystal structure with high anisotropy properties formed Cooper pair can exist long enough under normal conditions.In the papers (Nozhenkov, 2012b(Nozhenkov, , 2014) ) that this stability of the particles and the lack of heat dissipation (in the form of photon emission) is ensured by the proportionality of the geometric structure of the particles of the fine structure constant α.
Accordingly can imagine superconducting and superfluid state of matter with the help of Equations ( 2), in which the properties of a substance depend on the proportion of the two phases.Superfluidity and superconductivity, which can be regarded as the superfluidity of the electron gas are related phenomena, as well as ultra low friction, determined by the mobility of two-dimensional gas of particles.
Consequently, in the case of superconductivity and superfluidity applied for the emergence of ultra-low friction ratio ( 17) can be represented as the ratio of normal and superconducting (or superfluid) phase with the corresponding phase transition as a transition curve of particle energy (Equations 2, 3) through the critical value (potential barrier critical temperature) Properties of the substance depend on the proportion of the two phases, and the change of state is seen in the case of superfluidity as a phase transition of type II normal liquid 4He and 3He in superfluid He II (Bose condensation).Then Equation ( 4) can be regarded as the ratio of the two phases in the two-fluid hydrodynamics Landau where ε is the coefficient of particle energy; B HeII is the number of particles of the Bose-condensate, C He is the number of particles of normal liquid 4 He and 3 He; A is the value depending on the structure and properties of the deposited material; К sf is the relative magnitude of the forces of resistance movement of the fluid particles.In the case of superconducting phase transition occurs in the normal electrons in a Bose condensate of Cooper pairs of the superconducting phase (Figure 18): where В SC isthe number of particles of the superconducting phase Bose, C nisthe number of particles of normal conduction electron phase; K SC is the electrical resistance of the test substance, respectively, growing with increasing temperature T.
Consequently, in the case of superconductivity and superfluidity Equations (2, 3) can be represented as the ratio of the normal and superconducting (or superfluid) phase with the corresponding phase transition of the energy distribution of particles over a critical value (a potential energy barrier), as in the case of ultra-low friction, which is related phenomenon (Figure 17).
Therefore, the phenomenon of non-dissipative movement of mass (energy) along the lines of equi-potential fields, which manifests itself in the form of ultra-low friction, superconductivity and superfluidity of matter can be under normal conditions between the surface of solid along the force lines of equi-potential field, determined by the shape and value of the Fermi surface in k-space.In this energetically favorable arrangement of the particles in the crystal lattice for the realization of the non-dissipative movement with the disappearance of forces of resistance are van der Waals areas, which are followed to predict the possibility of the appearance of the investigated phenomena. Figu Figur temperatu Figure 12 Figure 1 appear equipote Figure