Removing Hydroxypropyl Methylcellulose Sizing from Sapphire Fibers by Ultraviolet/Ozone Cleaning

Ceramic-fiber-reinforced metallic and intermetallic matrix composites require well-characterized fiber/matrix interfaces. These interfaces require that the fiber surface be clean prior to the formation of a composite or application of a fiber coating. This work investigates the effectiveness of ultraviolet (UV)/ozone exposure at removing hydroxypropyl methylcellulose sizing from sapphire plates and fibers. The surface cleanliness was characterized using X-ray photoelectron spectroscopy (XPS). It was found that UV/ozone exposure removed the hydroxypropyl methyl-cellulose sizing from the plates and fibers but did not remove inorganic species contained in the coating or on the sapphire surface. These inorganic species were readily removed with a water/methanol rinse, providing a clean sapphire surface for incorporation into a composite.