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Development of nondestructive evaluation (NDE) methods for application to fossil energy systems continues in three areas: (a) mapping axial and radial density gradients in hot-gas filters, (b) characterization of the quality of continuous-fiber ceramic matrix composite (CFCC) joints and (c) characterization and detection of defects in thermal-barrier coatings. In our work, X-ray computed tomographic imaging was further developed and used to map variations in the axial and radial density of two full-length (2.3-m) hot-gas filters. The two filters differed in through-wall density because of the thickness of the coating on the continuous fibers. Differences in axial and through-wall density were clearly detected. Through-transmission infrared imaging with a highly sensitivity focal-plane array camera was used to assess joint quality in two sets of SiC/SiC CFCC joints. High-frame-rate data-capture suggests that our infrared imaging method holds potential for the characterization of CFCC joints. Work to develop NDE methods that can be used to evaluate electron-beam physical-vapordeposited coatings with platinum-aluminide (Pt-A1) bonds was undertaken. Coatings of Zirconia with thicknesses of 125 pm (0.005 in.), 190 pm (0.0075 in.), and 254 pm (0.010 in.) with a Pt-A1 bond coat on RenC N5 Ni-based superalloy were studied by infrared imaging. Currently, it appears that thickness variation, as well as thermal properties, can be assessed by infrared technology.

Ceramic matrix composites are being developed for numerous high temperature applications, including rotors ad combustors for advanced turbine engines, heat exchanger and hot-gas filters for coal gasification plants. Among the materials of interest are silicon-carbide-fiber-reinforced-silicon-carbide (SiC@SiC), silicon-carbide-fiber-reinforced-silicon-nitride (SiC@Si3N4), rduminum-oxide-reinforced-ahtmina (A1203(f)/A1203), etC.In the manufacturing of these ceramic composites, the conditions of the fiber/matrix interface are critical to the mechanical and thermal behavior of the component. Defects such as dehtrninations and non-uniform porosity can directly effect the performance. A nondestructive evaluation (NDE) method, developed at Argonne National Laboratory has proved beneficial in analyzing as-processed conditions and defect detection created during manufacturing. This NDE method uses infrmd thermal imaging for fill-field quantitative measurement of the distribution of thermal diffusivity in large components. Intensity transform algorithms have been used for contrast enhancement of the output image. Nonuniformity correction and automatic gain control are used to dynamically optimize video contrast and brightness, providing additional resolution in the acquired images. Digital filtering, interpolation, and least-squares-estimation techniques have been incorporated for noise reduction and &ta acquisition. The Argonne NDE system has been utilized to determine thermal shock damage, density variations, and variations in fiber coating in a full array of test specimens.

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