Ultrasonic scanning microscopy

Ultrasonic scanning microscopy is one of the newer and less famiUar methods of examination. It represents a meaningful contribution to the field of ceramography and could create new possibilities for this science. It is used predominantly in the nondestructive characterization and imaging of microcracks, crack paths and pores. 

The ultrasonic scanning microscope operates according to the pulse-echo method to produce an image of the surface and immediate subsurface volume of a flat ground or polished specimen. 

A sapphire cylinder combines the functions of a transducer and an acoustic lens. It features a thin ZnO coating on its top end and a cup-shaped indentation (formed by poUshing) on its front side. It produces, transmits, and receives brief sound pulses (Fig. 47). 

The resolution of the ultrasonic microscope is determined by the aperture and sound wavelength. The sound wavelength, in turn, is determined by the ultrasonic frequency. Using water as the coupling medium, the maximiun resolution is 0.4 pm at 2 GHz, 15 pm at 100 MHz, and 500 pm at 10 MHz. The penetration depth depends on the frequency, the type of material, and the surface quality of the specimen. The scattering of the sound on the specimen surface is influenced by its roughness. The penetration depth can reach several millimeters at low sound frequencies. 

One example of the application of this method of examination is the analysis of defects and weak points in surface layers. In one case involving a Zr02 electrolyte layer on the anode substrate of a fuel cell, an undesirably high permeability to gas was found. This could be attributable to pores, bubbles, or cracks in the surface layer. The image shown in Fig. 49 was created at a frequency of 100 MHz. It clearly shows defects in the surface volume of the electrolyte layer. These defects can be rendered 

---

When the first edition was published in 1992, the resolution of the acoustic microscope techniques used at the time was controlled by the wavelength. In practice the frequency-dependent attenuation of the acoustic wave in the coupling fluid sets a lower limit to the wavelength, and therefore to the resolution, of about 1 pm for routine applications. Since then scanning probe techniques with nanometre scale resolution have been developed along the lines of the atomic force microscope. This has resulted in the development of the ultrasonic force microscopy techniques, in which the sample is excited by... 

There was, however, one topic which was not included in the first edition, which has undergone substantial development in the intervening years. It could have been foreseen in 1986 a paper was presented at the IEEE Ultrasonics Symposium entitled Ultrasonic pin scanning microscope a new approach to ultrasonic microscopy (Zieniuk and Latuszek 1986,1987). With the advent of atomic force microscopy, it proved possible to combine the nanometre-scale spatial resolution of scanning probe microscopy with the sensitivity to mechanical properties of acoustic microscopy. The technique became known as ultrasonic force microscopy, and has been joined by cognate techniques such as atomic force acoustic microscopy, scanning local-acceleration microscopy, and heterodyne force microscopy. 

U. Rabe, M. Kopycinska, S. Hirsekorn, J. Munoz Saldana, G.A. Schneider, and W. Arnold, High resolution characterisation of piezoelectric ceramics by ultrasonic scanning force microscopy tech niques, J. Phys. D Appl Phys 35,2621 2536 (2002). 

Thermal scanning microscopy Temperature-time profile Time/temperature resolved pyrolysis mass spectrometry Thermal ultraviolet Thermal volatilisation analysis Thermal wave infrared imaging Transmission X-ray microscopy Total-reflection X-ray fluorescence (c/r. TRXRF) Ultrasonic force microscopy Ultraviolet photoelectron spectroscopy Ultrasound... 

Suhtnicion nickel powders luive been synthesized successfully from aqueous NiCh at various tempmatuTKi and times with ethanol-water solvent by using the conventional and ultrasonic chemical reduction method. The reductive condition was prepared by flie dissolution of hydrazine hydrate into basic solution. The samples synthesized in various conditions weae claractsiz by the m ins of an X-ray diffractometry (XRD), a scanning electron microscopy (SEM), a thermo-gravimetry (TG) and an X-ray photoelectron spectroscopy (XPS). It was found that the samples obtained by the ultrasonic method were more smoothly spherical in shape, smaller in size and narrower in particle size distribution, compared to the conventional one. 

Burton, N. J Thaker, D. M., and Tsukamoto, S. (1985). Recent developments in the practical and industrial applications of scanning acoustic microscopy. Ultrasonics Int. 85, 334-8. [199]... 

Cargill, G. S. (1980). Ultrasonic imaging in scanning electron microscopy. Nature 286, 691-3. [17]... 

Sherar, M. D., Noss, M. B., and Foster, F. S. (1987). Ultrasound backscatter microscopy images the internal structure of living tumour spheroids. Nature 330,493-5. [174] Shimada, H. (1987). Propagation of multi-mode ultrasonic pulses in non-destructive material evaluation. In Ultrasonic spectroscopy and its application to Materials science (ed. Y. Wada), pp. 50-6. Ministry of Education, Science and Culture, Japan. [148] Shotton, D. M. (1989). Confocal scanning optical microscopy and its applications for biological specimens. J. Cell. Sci. 94,175-206. [177,200]... 

Tsai, C. S. and Lee, C. C. (1987). Nondestructive imaging and characterization of electronic materials and devices using scanning acoustic microscopy. In Pattern recognition and acoustical imaging (ed. L. A. Ferrari). SPIE 768,260-6. [ 110,202] Tsukahara, Y. and Ohira, K. (1989). Attenuation measurements in polymer films and coatings by ultrasonic spectroscopy. Ultrasonics Int. 89, 924-9. [204]... 

Zieniuk, J. K. and Latuszek, A. (1986). Ultrasonic pin scanning microscope a new approach to ultrasonic microscopy. IEEE 1986 Ultrasonics Symposium, pp. 1037-9. IEEE, New York, [xi, 290, 291]... 

Despite the distinct advantages of pneumatic nebulizers, ultrasonic nebulizers may alternatively be used, in some instances, with success. In a recent application, a variation of ultrasonic nebulizer called spray nozzle-rotating disk FTIR interface was successfully applied to confirm the presence of methyltestosterone, testosterone, fluoxymesterone, epitestosterone, and estradiol and testosterone cyp-ionate in urine, after solid-phase extraction and reversed-phase LC separation (151). Using a commercial infrared microscopy spectrometer, usable spectra from 5 ng steroid deposits could be readily obtained. To achieve success with this interface, phosphate buffers in the mobile phase were not used because these nonvolatile salts accumulate on the collection disk and their spectra tend to swamp out small mass deposits. Another limitation of the method was that only nonvolatile analytes could be analyzed because volatile compounds simply evaporated off the collection-disk surface prior to scanning. 

Applications The physical principle of measurement is similar to the scanning acoustic microscopy discussed in the Section 14.23, but applications and the method of data processing are essentially different. Sonic methods were used in the following applications to filled materials the effect of particle size and surface treatment on acoustic emission of filled epoxy, longitudinal velocity measurement of tungsten filled epoxy, and in-line ultrasonic measurement of fillers during extrusion. Numerous parameters related to fillers can be characterized by this non-destructive method. 

---