Elaboration of porous mullite-based materials via SHS reaction

In order to produce cheaper mullite from kaolinitic clays we worked on the opportunity to use self-propagating high-temperature synthesis (SHS) reaction to obtain this phase. Two ways were explored during the combustion of metals mixed with the clay. The first one concerns the nature of the combustion gas (air or pure oxygen) which was tested on mixtures of clay and metal powders. The second one showed the influence of magnesium addition in clay/Al mixture. Results conclude that to obtain porous mullite at low-cost by SHS process the best conditions are the addition of magnesium powder and combustion in oxygen gas. Because a SHS reaction is always quicker, we compared this process with the traditional reactive sintering in order to explain the structure and the microstructure of the SHS products.