METHOD FOR MAKING POROUS ACICULAR MULLITE BODIES

摘要

Acicular mullite bodies are made in two-step firing process in which a green body is converted first to a fluorotopaz and then to acicular mullite. The bodies are contained within an enclosed region of the furnace. A flow of process gas is provided through the enclosed region during the fluorotopaz-forming step. The process gas is introduced into the enclosed region through multiple openings on at least one side of the enclosed region, and withdrawn through multiple openings on another side of the enclosed region. During the acicular mullite-forming step, a flow of purge gas is maintained in the exterior portion of the furnace. This purge gas may be removed by flowing it into the enclosed region of the furnace and out of the furnace from the enclosed region without re-entering the exterior portion for the furnace.