Defect engineering of samples for Non-Destructive Evaluation (NDE) ultrasound testing

Defect engineered samples were successfully fabricated by introducing hollow polymer spheres into the bulk of pressed A1 ₂O ₃ samples. The polymer spheres burned out at ∼525°C during sintering of the samples at 1600°C for three hours. An ultrasound C-scan system was used to nondestructively image the spherical pores within the matrix by gating several regions of the bulk and detecting large attenuation changes in the sample. The C-scans revealed different spherical pore distributions for three different gated thickness regions within the bulk. Microscopy was used to evaluate the cross-section of one of the defect engineered samples, and spherical pores were located, confirming the presence of the engineered defects and adding legitimacy to the results of the ultrasound C-scan study.