Process for making ceramic refractory oxide fiber-reinforced ceramic tube

A process for the preparation of a fiber-reinforced ceramic tube with fluid permeable walls comprising the steps of

• A. plying separate yarns of
• 1. a refractory oxide fiber having a softening point above about 750.degree. C. or a fiber of a precursor of the refractory oxide and
• 2. a ceramic binder fiber having a softening point above about 750.degree. C. but at least 50.degree. C. lower than the yarn sag temperature of refractory oxide fiber
• B. winding the plied yarn on a tubular core in multiple layers of spaced helical coils in a criss-cross fashion to form a tube of yarn having a multitude of channels of quadrilateral-shaped cross-sections extending through the walls of the tube of yarn,
• C. firing the tube of yarn for a time and temperature sufficient to
• 1. convert any precursor fibers present to refractory oxide fibers and
• 2. soften the ceramic binder fiber to such an extent that it at least partially flows around the refractory oxide fibers to bind adjacent fibers upon cooling, and
• D. placing a coating composition on the bonded structure and firing to form a refractory oxide matrix at least partially surrounding said fibers but not closing said channels and to provide said tube with a compressive strength of at least 30 psi.