**4. Conclusions**

58 Tribology in Engineering

energy to reaction space.

combined with their homolytic dissociation.

mixture as well as activation energy.

thermodynamic methods. From the purely thermodynamic point of view, the central problem of mechanochemistry is the exchange of energy between the (long-range) elastic

There is no clear theory which could be adapted to mechanochemistry, however the most recent approach [16] should be mentioned here. The i model applied for tribochemical applications can also be adapted to mechanochemistry. This model can be helpful in general dependences formulation, related to kinetics of mechanochemical reactions and to mechanical forces used for reactions activation. The theory based on i model assumes that mechanical energy introduced into solid body – reagent or catalyst, is accumulated in it and then emitted as low energy electrons or photons of energy equal or higher than activation energy of the reaction. The general Eqn. (19) can be used to determine quantitatively relationship between mechanical stress (L), the possibility of solid body to accumulate and

Mechanochemistry, especially results of investigations shown above can be explained by hypothesis based on i model. On the other hand the positive effect of mechanical stress on catalyst efficiency confirms this hypothesis. However the reason of this effect can be

Rodriguez et al. [17] found out the influence of ultrasound radiation on catalysts effectiveness. They tested a new advanced method for dechlorination of 1,2,3-, 1,2,4-, and 1,3,5-trichlorobenzenes in organic solvent catalysed by palladium on carbon support and solid hydrazine hydrochloride yields benzene in short reaction times. The catalyst system can be efficiently reused for several cycles. Ultrasound radiation of the heterogeneous catalyst reaction increases remarkably the rate of dechlorination. Moreover, Rodriguez found that there is optimum energy of ultrasound radiation which results maximum catalysts efficiency. This effect is not seen when ultrasound radiation act liquid reactants. Rodriguez results confirm thesis that energy, in this case of ultrasound radiation is useful in reaction rate increasing when solid body – particles of catalyst are present in reaction mixture. This energy is cumulated by catalyst and emitted to the space near catalyst surface, what is the reason of reaction rate increasing. This effect can not be explained by the changes of the structure of catalysts surface, like in other mechanochemical effects (eg. during milling) so the only one probably mechanism is emission of cumulated in solid catalyst

The concept of mechanochemistry to modify molecular reactivity has a rich history for a long time. For instance Kauzmann an Eyring as early as 1940 [18] suggested that the mechanical perturbation of diatomic molecules could alter the reaction coordinates

The chemical kinetic quantitatively describes homogenous reactions, where the rate of reaction depends only on heat introduced to reaction system. Kinetic equations concern reagents concentration, and according to Arrhenius equation: temperature of reaction

energy and the (short-range) energy accumulated in individual bonds.

then emit energy (e0 cos ) and kinetics of mechanochemical reaction.

mechanically (eg. during milling) produced changes of catalysts surface.


iv. The energy emitted from surface as pulses ranges 3–5 eV and can reach the value of activation energy (Ea) and the triboreaction process starts to proceed or reaches the critical rate.

A New Attempt to Better Understand Arrehnius Equation and Its Activation Energy 61

[2] Kajdas C.K, Kulczycki A. A New Idea of the Influence of Solid Materials on Kinetics ofChemical Reactions. Materials Science – Poland 2008, 26, 787 - 796.

[3] Kajdas C.K, Kulczycki A, Kurzydłowski K.J, Molina G.J. Activation Energy of Tribochemical and Heterogeneous Catalytic Reactions. Materials Science-Poland 2010, 28, 523-533. http://materialsscience.pwr.wroc.pl/bi/vol28no2/articles/ms\_15\_2009-

[4] Dante R.C, Kajdas C.K, Kulczycki A. Theoretical Advances in the Kinetics of Tribochemical Reactions. Reaction, Kinetics Mechanisms and Catalysis 2010, 99, 37 – 46. [5] Klier K. The Transition State in Heterogeneous Catalysis, Topics in Catalysis 2002, 18, 3-

[6] Sato N, Seo M. Chemically Stimulated Exo-emission from a Silver Catalyst. Nature

[7] Hrach H. Energy Angular Distribution of Electrons Emitted from MIM Systems. Thin

[8] Jablonski A, Zemek J. Angular Distribution of Photoemission from Amorphous and Polycrystalline Solids. Physical Review B, 1993, 48, 4799-4805.

[9] Kulczycki A. The Correlation Between Results of Different Model Friction Tests in Terms of an Energy Analysis of Friction and Lubrication. Wear 1985, 103, 67-75. [10] Hebda M, Wachal A. Trybologia, Warszawa: Wydawnictwa Naukowo-Techniczne,

[11] Hrach R, May J. Electrons Emitted from MIM Structures. Physica Status Solidi (a), 1977,

[12] Gould R.D, Hogarth C.A. Angular Distribution Measurements of Electrons Emitted from Thin Film Au–SiOx–Au Diode and Triode Structures. Physica Status Solidi (a),

[13] Hrach R. Emission of Electrons from MIM Systems: Disscussion of Processes in the Cathode. Czechoslovak Journal of Physics B, 1973, 23(2), 234-242.

[14] Fitting H.-J, Glaefeke H, Wild W, Lang J. Energy and Angular Distribution of

[15] Baláž P, Choi W.S, Fabian, M, Godocikova E. Mechanochemistry in the Preparation of

[16] Hiratsuka K, Kajdas C. Mechanochemistry as a Key to Understand the Mechanisms of Boundary Lubrication, mechanolysis and Gas Evolution during friction. Proc. IMechE

[17] Rodriguez J.G, Lafuente A. A New Advanced Method for Heterogeneous Catalysed Dechlorination of 1,2,3-, 1,2,4-, and 1,3,5 – Trichlorobenzenes in Hydrocarbon Solvent.

Solid Films 1973, 15, 65-69. http://dx.doi.org/10.1016/0040-6090(73)90204-6

http://materialsscience.pwr.wroc.pl/bi/vol26no3/articles/ms\_2008\_375.pdf

373kajdas.pdf

4, 141 -156.

1980.

1, 637-642.

1967; 216(Oct) 361-362. DOI:10.1038/216361a0

1977, 41, 439-442. DOI: 10.1002/pssa.2210410212

http://link.springer.com/article/10.1007/BF01587248?null

Exoelectrons. Physica Status Solidi (a), 1977, 42, K75–K77.

129.http://actamont.tuke.sk/pdf/2006/n2/5balaz.pdf

Tetrahedron Letters 2002, 43, 9645 – 9647. http://144.206.159.178/ft/1010/73973/1269348.pdf

Advanced Materials. Acta Montanistica Slovaca 2006, 11(2), 122-

Part J: J. Engineering Tribology, 2012 (submitted for publication).

DOI:10.1103/PhysRevB.48.4799


In the summary it can be said that the problem of Arrhenius equation adaptation to heterogeneous catalysis as well as tribocatalysis might be solved using i model. Instead of Arrhenius equation in reaction rate description should be used the quotidian of reaction rate constant according to Arrhenius equation and the stream of energy emitted by the surface of catalyst in angle . The reaction rate constant described by the above ratio leads to another explanation of the mechanism of catalytic effect than, based on Arrhenius equation, decreasing of the value of activation energy. This effect is due to addition portion of energy emitted by catalysts surface to the reaction space. At this point it should be emphasized that equation (19) describes both catalytic and tribocatalytic reactions. This equation quantitatively characterizes all kinds of energy introduced into the reaction system, including mechanical energy and properties of catalyst, explained by energy emitted from its surface to reaction space.
