Raman Inspection of CVD Interface Coatings

The Physical Sciences Inc./Penn State team will use Raman spectroscopy as an optical probe for determining the composition and thickness uniformity of fiber interface layers on large areas of silicon carbide fabrics. We will demonstrate that Raman technique can be used to perform quality assurance testing with accept/reject criteria of coated fabrics that will be used in the fabrication of ceramic matrix composites. We will show that Raman data collected from coated silicon carbide fabric can indicate thickness variations of 10% within any layer within the coating stack. We will also demonstrate that that the technique can map composition variations in the individual layers of the stack. A prototype scanning system for mapping thickness and composition variations of coated silicon carbide fabrics will be constructed and tested. The prototype system will be used to demonstrate that 1 m2 of coated silicon carbide fabric can be scanned in less than one hour and map the thickness and composition of individual layers in the coating with a resolution of 100 cm2.