Active Thermochemical Barrier Coatings Using Metal Oxides: First Experimental Results

A new concept of active thermal coating based on the use of reversible thermochemical reactions is presented in this paper. The new active thermal barrier coating uses redox reactions to buffer the temperature changes that a metallic component may suffer at high temperatures. The heat is stored when the temperature is equal/above the reduction temperature of the active coating (endothermic reaction) and the heat is released when the temperature is equal/below the oxidation temperature (exothermic reaction). The paper describes the development and testing of a reactive thermal barrier coating based on the redox reaction of Co₃O₄ and its cyclability. Co₃O₄ was chosen as a reference material due to the high enthalpy of reaction (844 kJ/kg) and redox reversibility. The activity of coatings with 1, 2, and 3 Co₃O₄ layers was demonstrated by simultaneous thermal analysis, showing good stability for 5 five cycles.