Ultrasonic Characterization of Nonuniform Porosity Distributions in SiC Ceramic
During fabrication of monolithic ceramic silicon carbide very localized regions of high porosity can be produced. This porosity often consists of a very large density of small pores. Even at ultrasonic wavelengths considerably larger than the pore size, significant effects can be observed in ultrasonic wave propagation through these materials. These effects include attenuation, scattering, and changes in wave velocity. This paper describes the characterization of such a porosity distribution in SiC utilizing these ultrasonic techniques and their correlation with x-ray and optical microscopy measurements. Significant effects were observed due to the nonuniformity of the porosity, which resulted in enhancement of signal amplitudes greatly exceeding attenuation effects due to scattering. This unexpected result proved to be most sensitive to the boundaries of the porosity distribution and provided one of the best techniques for delineating its extent.
KeywordsPorosity Carbide Attenuation Refraction Channeling
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