Nondestructive evaluation of structural ceramics by photoacoustic microscopy. Final report
A photoacoustic microscopy (PAM) digital imaging system was developed and utilized to characterize silicon nitride material at the various stages of the ceramic fabrication process. Correlation studies revealed that photoacoustic microscopy detected failure initiating defects in substantially more specimens than microradiography and ultrasonic techniques. Photoacoustic microscopy detected 10 to 100 micron size surface and subsurface pores and inclusions, respectively, up to 80 microns below the interrogating surface in machined sintered silicon nitride. Microradiography detected 50 micron diameter fracture controlling pores and inclusions. Subsurface holes were detected up to a depth of 570 microns and 1.00 mm in sintered silicon nitride and silicon carbide, respectively. Seeded voids of 20 to 30 micron diameters at the surface and 50 microns below the interrogating surface were detected by photoacoustic microscopy and microradiography with 1 percent x-ray thickness sensitivity. Tight surface cracks of 96 micron length x 48 micron depth were detected by photoacoustic microscopy. PAM volatilized and removed material in the green state which resulted in linear shallow microcracks after sintering. This significantly limits the use of PAM as an in-process NDE technique.
- Research Organization:
- General Motors Corp., Indianapolis, IN (USA)
- OSTI ID:
- 5251107
- Report Number(s):
- N-88-16868; NASA-CR-180858; NAS-1.26:180858; EDR-12815
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CERAMICS
DEFECTS
PHOTOACOUSTIC SPECTROSCOPY
SILICON CARBIDES
SILICON NITRIDES
DIGITAL SYSTEMS
FRACTOGRAPHY
INCLUSIONS
PROGRESS REPORT
SENSITIVITY
VOIDS
CARBIDES
CARBON COMPOUNDS
DOCUMENT TYPES
NITRIDES
NITROGEN COMPOUNDS
PNICTIDES
SILICON COMPOUNDS
SPECTROSCOPY
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies