Research on Application of Ultra-Sonic Spectroscopy to Characterize-Surface Modified Layrs

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Glass surfaces modified by diffusion of Ag ion were examined by a scanning acoustic microscope (Hitachi HSAM1000S), with a spherical beam lens and operating frequencies 200 and 400 MHz. The image was taken using the acoustic beam just- and under-focused conditions, and the fringe structure was observed, which has been never seen with an optical microscope.Metals of Ni or Cu joined to Si_3N_4 ceramics with Ag-Cu-Ti and Ni-Cu-TI brazing solders were thermally cycled in vacuum between room temperature and temperatures of 573,723, and 873K,and then the surface distortion and fracture strength of the joints were measured using a scanning acoustic microscopy and a four point bending test. In case of the Si_3N_4/Ni joints the Ni metal shrank at the early stage of the thermal cycling and then it tended to swell with the crack formation near the ceramic-filler interface.By using a slit-type acoustic lens, noisy interference fringe patterns near an interface can be eliminated, and the local measurement of the sonic wave velocity became possible.