Refractory Spheres, Heavy Duty Ceramics for Pebble Heaters

Applications of heavy ceramics to the aerospace effort are reviewed and heat exchange spheres selected for discussion. Oxide candidates for such spheres are considered, balancing upper temperature limits against other physical properties and cost. Oxide purity is stressed for obtaining top quality spheres and the most economic overall furnace performance. Isostatic pressing is indicated as a superior sphere forming method. It is suggested that the potentials of composite bed design have not been fully explored.