Technical Papers and Presentations

In modern technology of advanced materials, models play more and more essential role. They are crucial for understanding complex processes occurring during the synthesis. Recently, promising thermoelectric materials used for waste energy recovery have been identified among semiconducting silicides, selenides or antimonides, which might be produced by Self-propagating High-temperature Synthesis (SHS). SHS has several advantages. It is very quick, like flame propagation after ignition of combustible materials. Once initiated, the reaction goes by itself without any external source of heat, which is possible owing to its strongly exothermic nature. It produces no wastes and overall can be classified as eco-friendly. In spite of many advantages of SHS, there are still open questions and problems to be solved, in particular: troublesome upscaling, difficulties in securing adiabatic conditions, sufficient propagation rate and complete conversion of reactants in the entire volume of powder mixture. COMSOL Multiphysics is used for modelling SHS process of magnesium silicides in 3D geometry. Model takes into account mass, energy and momentum equations, different reaction mechanisms as well as change of the sample morphology during SHS process. Suitable boundary conditions correspond to complex, real chamber/sample geometry in argon, helium atmosphere or in vacuum. Gas velocity, temperature, reaction rate and conversion degree fields were calculated. Model was validated on the basis of thermocouple temperature readings during SHS process. Sensitivity analysis of the model was performed. The optimization module was used to find the solution of inverse problem allowing for determination of missing model parameters. Validated model was subsequently used for rescaling and optimization of SHS process.