In-situ synthesis of porous magnesia spinel/TiB2 composite by combustion technique

In this work, the very weak exothermic formation reaction of MgAl2O4 spinell is successfully conducted in a self-sustaining manner with the advantages of energy savings, high reaction rate and highly porous product. The energy and Al2O3 required for this reaction are obtained from the combustion reaction of TiO2-B2O3-Al while MgO is added to the reactive mixture. Ignition of the reaction mixture is carried out at room temperature despite the dilution effect of MgO (19 vol%). Reduced aluminium grain size and preheating the reactant before ignition were found to be very effective to complete the formation reaction of MgAl2O4 spinel. Thermodynamic calculations of adiabatic combustion temperatures and spinel molten fractions at different initial temperatures were carried out. Oxidation resistance study of this new composite shows that it can safely work up to 600 degrees C in open atmosphere and that 700 degrees C is considered to be its threshold oxidation temperature. (C)2009 The Ceramic Society of Japan. All rights reserved.