PREPARATION OF THIN-SECTIONS OF COATED FIBERS FOR CHARACTERIZATION BYTRANSMISSION ELECTRON-MICROSCOPY

A method of preparing transmission electron microscopy (TEM) specimens of coated ceramic fibers has been developed, which produces large ele ctron transparent areas due to the minimal preferential milling of the fiber, coating, or epoxy matrix. Multiple individual fibers or tows a re impregnated with a high-temperature epoxy and contained to assure a high fiber-to-epoxy volume ratio, The samples are then sectioned and mechanically thinned either parallel or normal to the fiber axes using a wedge polisher on diamond lapping films to achieve a thickness of l ess than 5 mu m. The thinned sample is then ion-milled to electron tra nsparency in less than 30 min, giving representative specimens of the coating, fiber, and coating-fiber interface. This technique is also we ll suited to preparing extremely flat specimens for scanning electron microscopy analysis of thin coatings. Examples of TEM sections of coat ed fibers prepared using this technique are presented.