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Characterization of green ceramics by microwaves and ultrasound

: Kröning, M.; Schneider, R.; Netzelmann, U.

Bartos, A.L.; Green, R.E.; Ruud, C.:
Nondestructive characterization of materials VII. Pt.1
Zürich: Trans Tech Publications, 1996
ISBN: 0-87849-729-3
International Symposium on Nondestructive Characterization of Materials <7, 1995, Prag>
Conference Paper
Fraunhofer IZFP ()
alumina; aluminium; Anisotropie; anisotropy; density gradient; green ceramic; Grünkeramik; microwave; Mikrowelle; nondestructive testing; synthetic pulse; time of flight measurement; Ultraschall; ultrasound; zerstörungsfreie Prüfung

Time-of-flight measurements using ultrasound at 2 MHz and microwaves at 75-100 GHz were performed on samples of green state alumina. Spatially resolved measurements showed an inverse correlation of time-of-flight measured by ultrasound and microwaves. The findings can be explained by a lower compaction density in the center of the sample cylinders. A model assuming small spherical pores does not explain the experiment completely. An uniaxial anisotropy of longitudinal sound velocity was found