O. V. Lapshin

Macroscopic theory of mechanochemical synthesis in heterogeneous systems

Physical and mathematical models of mechanochemical synthesis in the macroscopic approximation were suggested. The mathematical model is based on the equations of (a) heat balance in a reactor, (b) dynamics of excess energy in condensed matter (defining the effect of mechanical activation on the rate of chemical reaction), (c) chemical kinetics, and (d) comminution and change in the surface area of reactive interface. The suggested model was analyzed analytically. Syntheses in a preliminarily activated system (two-stage) and directly in a mechanoactivator (single-stage) were comparatively studied. The expressions for the process parameters were derived. The accuracy of predictions was checked by numerical simulation.

Mechanochemical synthesis of nanosize products in heterogeneous systems: Macroscopic kinetics

Suggested is a mathematical model (in a macroscopic approximation) for mechanochemical synthesis of nanopowders. The model involves the equations for heat balance in a reactor, for the dynamics of excess energy in processed powders (defining the effect of mechanoactivation on the reaction rate), for the chemical kinetics, and for powdering and changes in the state of reactive interface. Investigated is the effect of inert diluent on the process under study.

Mathematical simulation of mechanochemical synthesis in a macroscopic approximation

Physical theory of mechanochemical synthesis and its mathematical model in a macroscopic approximation are developed. The model is analyzed using analytic methods. The synthesis in a pre-activated system (two-stage synthesis) and in a reactor with mechanical reaction activation (one-stage synthesis) is studied. Relations determining the characteristics of the process are obtained. The accuracy of the analytical estimates is tested by numerical simulation.

Dynamics of mechanochemical synthesis in heterogeneous systems

The operating conditions for one-stage combustion synthesis and practically important two-stage mechanochemical synthesis, in which a heterogeneous system is pre-activated mostly at the first stage and the synthesis itself is effected at the second stage, are studied. Analytical relations governing the dynamics of two-stage combustion synthesis are developed and their validity and accuracy are tested by numerical solutions. The obtained formulas are used to propose methods in which the effective kinetic constants and all parameters of the mathematical model are determined using experimental data (method of inverse problem).

Estimation of kinetic constants for reactions in thin films

The problem of synthesizing a product in thin films taking into account a finite reaction rate at the phase boundaries is considered. Formulas are derived that determine the dynamics of synthesis in the diffusive regime and in the regime controlled by the boundary kinetics. Based on these formulas, procedures are proposed for estimating the parameters of the boundary kinetics.

Dynamics of the Homogenization of Binary Powder Mixtures

The effect the initial structure of a two-component reaction powder mixture has on the dynamics of its isothermal homogenization is investigated. Relations for determining the duration of homogenization are obtained. A technique for calculating kinetic parameters is proposed.

On possibility of formation of metastable compounds in a wave of gasless combustion

Suggested and investigated was a mathematical model of gasless solid-flame combustion in two-component green compacts admitting formation of a metastable product. Outlined are the conditions at which the reaction yields either a metastable or stable product. Suggested is a procedure for deriving thermodynamic constants from experimental data.

Influence of mechanical activation on gasless combustion of three-component SHS systems with competing (parallel) reactions

AbsrtactSuggested is a mathematical model that describes the process of mechanical activation (MA) in three component SHS systems with competing (parallel) reactions. Preliminary MA of starting blends and their mixtures was found to change combustion modes and result in non-uniqueness of burning velocity and product composition.

Combustion of Granulated Gasless Mixtures in a Flow of Inert Gas

Combustion of granulated gasless mixtures in a flow of inert gas was numerically explored in terms of a two-temperature approximation to mathematical modeling of unsteady combustion. The regimes of combustion wave propagation were analyzed as a function of gas flow characteristics and parameters of interphase heat transfer.

Mathematical formalism to the theory of multiple (reiterated) self-propagating high-temperature synthesis

Suggested was a mathematical model for reiterated temperature-dependent frontal processes of metastable product formation and its decomposition. The rates of product synthesis and decomposition were numerically estimated and a procedure for evaluation of kinetic parameters was suggested.