Process parameters combustion wave properties

Because it is difficult to account for changes in the properties of the reaction medium (e.g., permeability, thermal conductivity, specific heat) due to structural transformations in the combustion wave, the models typically assume that these parameters are constant (Aldushin etai, 1976b Aldushin, 1988). In addition, the gas flow is generally described by Darcy s law. Convective heat transfer due to gas flow is accounted for by an effective thermal conductivity coefficient for the medium, that is, quasihomogeneous approximation. Finally, the reaction conditions typically associated with the SHS process (7 2(XX) K and p<10 MPa) allow the use of ideal gas law as the equation of state. 

In contrast to the combustion of gases, the combustion process of condensed substances and, in particular, of polymer substances, has a multi-phase character. Each stage of the initial transformation of a substance correlates with a corresponding value (combustion wave) with specific physical and chemical properties (state of aggregation, temperature range, concentration of the reacting substances, kinetic parameters of the reaction etc.). 

The SHS method is expected to be developed as a process for producing new materials from composite powders and solid solutions that are difficult to prepare by conventional synthesis methods. By varying the combustion synthesis parameters, the properties of the product can be tailored to meet specific application needs. The combustion-consolidation method makes it possible to change the metal composition in the ceramic matrix because the initial arrangement of compositional constituents of the green body remains in the product due to the rapid wave propagation of the combustion reaction. 

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