Mechanical Impact on Chemical Reactions
Investigation of the Mechanisms of Solid Phase Chemical Reactions under Influence of Impulsive Mechanical and High Pressure and Deformation of Shifting
Tech Area / Field
- CHE-IND/Industrial Chemistry and Chemical Process Engineering/Chemistry
- CHE-THE/Physical and Theoretical Chemistry/Chemistry
3 Approved without Funding
Institute of General and Inorganic Chemistry, Armenia, Yerevan
- University of Oxford / Department of Engineering Science, UK, Oxford\nAdvanced Materials Modifications, USA, NJ, New Milford
Project summaryHigh-pressure physics and chemistry are the topics to be covered in the Project by the experienced scientists having former background in the field. Investigations will unfold the peculiarities and create possibilities for channelling of the mechanical energy into the solid phase systems thus setting the opportunities for the designing of principally the new, highly efficient chemical reactors.
This research program aims to investigate the mechanisms of transformation and conservation of mechanical energy, when crystalline solid mixtures are subjected to mechanical perturbation. Particularly, as it was disclosed by our former investigations, it is possible to reduce some metals from their oxides and sulphides in a vibration ball mill or under influence of high pressure and shear deformation with exceedingly high yields and speed (for ex. (PbO-Mg), (CuS-Mg), (MO3-Al) etc.). It has been suggested that the change in the reaction’s kinetics in this case be conditioned by the formation of so-called “activated” complex particles. Being conglomerated during plastic flow and partial chemical interaction, the particles represent a compact mixture of the reagents and the products with an irregular crystalline structure. Due to the current structural changes some part of the mechanical energy accumulated is continuously conserved as the internal energy.
As it has been estimated, in the case of (CuO-Al) system, the value of energy accumulated is of an order of the reaction enthalpy. Formation of the strain regions and mechanical energy accumulation leads to decrease in the activated energy-EA value and provide a reliable contact between components, thus increasing the velocity of the starting mixture interaction.
Thus by mechanical treatment of some type of solid-phase mixtures, we can accumulate mechanical energy, accelerate the reaction’s speed in some order of magnitude and exceedingly increase the reaction’s yield. In the other hand, as was established, the systems (Cu2O-Mg, Cr2O3-Mg etc.) under the same conditions of mechanical impact are not exhibit any significant changes in their chemical interaction behaviour, in spite of the thermodynamic characteristics of all this reactions are approximately the same.
Thus we can conclude, that the mechanical perturbation of a given intensity has different actions on the systems with a similar thermodynamic characteristics and different chemical composition. The value of the accumulated mechanical energy mainly depends on the chemical and structural properties of the starting compounds.
The general interest for us will be represented such systems of solid mixtures, which exhibit a capacity to accumulate mechanical energy. It is clear that the reactions in these systems will accompany, with a fast liberation of both chemical and mechanical energy, and in non-equilibrium conditions. What is important, that this “activated” state have a very long time of relaxation (practically in order to year) and may be considered as a separate object of investigation.
Using peculiarity of such systems any interesting practical results and new technologies for carrying out of different endothermic reactions might be obtained.
There are many possibilities for the practical application of the peculiarity of mentioned activated state:
1. The synthesis of diamond-like materials. By applying the explosive kinetics of some solid-phase reactions, when the bulk of exothermic energy is liberated within 10-3-10-5 sec., the syntheses of hard and diamond like materials can be realise.
2. Metallic, diamond-like and compositional coatings. Direct syntheses of protective and functional coatings, can be plied by the appropriate energy balancing and the selection of the matching materials [9-10], particularly for the interior finishing of metallic tubes and machine parts.
3. Obtaining of Amorphous Metallic Powders. For mechanically activated systems of solids containing an oxide or sulphide of the given metals and the reducing agent (usually - metals), the low temperature synthesis follows. As a result, the reactivated metals are obtained in amorphous state.
Despite a numerous experiments in this area has been carried out by us, however as the mechanisms of reagent’s chemical interaction, as well as the channels of mechanical energy transformation and conservation, under influence of mechanical perturbation is not yet clear for us. Because of absence of necessary experimental equipment and research possibilities the data presented above, are still of a fragmentary character, and some of important practical results and preliminary conclusions will be defined more exactly in the future.
Practically this influence will be realised by impulsive alloying in boll mill containers or by compressing and shifting between Bridjmen’s anvils.
To meet the specified ends it is to be:
· Experimental set-up elaboration for the evaluation of variation in physical and chemical parameters of some class of solid mixtures under the dynamic perturbation of mechanical energy;
· Crystal’s structural change investigations under the different value and duration of mechanical impact and Investigation of the mechanical energy transfer peculiarities in some class of solid-phase systems;
· Investigation of the Mechanisms of solid-phase reagents explosive interaction induced mechanically
· Investigation of the Mechanisms of mechano-chemical solid-phase surface modification and formation of various coatings.
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