Ultrasonic spectroscopy

Electrical measurements can thus be used in input for on-line intelligent closed-loop process control and automatic quality monitoring, even in multicomponent mixtures. 

The general principles of HR-US measurements are simple. A generated electronic signal is transformed by a piezotransducer into the ultrasonic wave travelling through the sample in a 30 fiL to 4 mL cell. Another piezotransducer transforms the received ultrasonic wave into an electronic signal 

The analytical power of ultrasound spectroscopy was recently illustrated [905]. For ultrasound imaging, cfr. refs. [906,907]. Atomic force acoustic microscopy (AFAM) is a new SPM technique that enables measurement of qualitative and quantitative local elastic properties of different materials and is awaiting application. 

Ultrasonic spectroscopy allows measuring a wide variety of liquid systems, from dilute to concentrated solutions, and can be used to monitor processes such as molecular structural changes, thermal transitions, chemical reactions, aggregation formation, crystallisation, etc. Attenuation measurements are used for particle sizing in emulsions and suspensions and for kinetics of fast chemical reactions. 

US velocity and attenuation measurements can also be used to determine solid-state material properties such as concentration and dispersion of fillers [908,909]. The active level of the acoustic emission signal of PP/talc composites was related to the degree of dispersion of the filler in the matrix [910]. LDPE/28-32 wt.% Mg(OH)2 and HDPE/0-10 wt.% Mg(OH)2 samples were examined over a wide range of temperatures (160-200°C) and pressures (up to 60 bar) to determine the effect of melt T, p and filler concentration on US velocity and attenuation in the melt [911]. Ultrasound velocity is affected by melt T, p and material density (filler content) US attenuation increases with increasing filler content. As US calculated filler concentrations deviated consistently from off-line TGA measured values (Fig. 1.43) it is obvious that further validation is required. In principle, extmsion processing data can be used to predict filler concentration. Accurate determination of filler concentration in real time is potentially useful to reduce excess and unnecessary usage of filler, to reduce scrap product and save production costs. 

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Recently ultrasonic spectroscopy has become a more common NDE technique and specialized instruments are commercially available now for inspection of aerospace structures, ball bearings, and even concrete [2],[3]. 

Aerospace struetwes made of composite. As part of the evaluation of the developed ultrasonic spectroscopy system the NSC software was tested on ultrasonic resonance spectra from composite panel samples. Spectra were collected with four different types of damages, and from flawless samples. The damages included a small cut in one of the carbon fiber... 

Fokker Bond Tester. An ultrasonic inspection technique commonly used for aircraft structures is based on ultrasonic spectroscopy [2]. Commercially available instruments (bond testers) used for this test operate on the principle of mechanical resonance in a multi-layer structure. A piezoelectric probe shown in Figure 3b, excited by a variable frequency sine signal is placed on the surface of the inspected structure. A frequency spectrum in the range of some tens of kHz to several MHz is acquired by the instrument, see Figure 3a. 

We have presented a neural network based spectrum classifier (NSC) aimed at ultrasonic resonance spectroscopy. The ultrasonic spectroscopy and the NSC has been evaluated in many industrial applications, such as concrete inspection, testing of aerospace composite structures, ball bearings, and aircraft multi-layer structures. The latter application has been presented in some detail. 

Andrews, J. Blanchard, T. Stepinski, L. Ericsson, Ultrasonic spectroscopy for NDT, Presented at Int. Symp. Non-Destructive Testing in Civil Engineering (NDT-CE), Berlin, 1995... 

Ultrasonic Spectroscopy. Information on size distribution maybe obtained from the attenuation of sound waves traveling through a particle dispersion. Two distinct approaches are being used to extract particle size data from the attenuation spectmm an empirical approach based on the Bouguer-Lambert-Beerlaw (63) and a more fundamental or first-principle approach (64—66). The first-principle approach implies that no caHbration is required, but certain physical constants of both phases, ie, speed of sound, density, thermal coefficient of expansion, heat capacity, thermal conductivity. 

Fig. 11. Particle size analyzer based on ultrasonic spectroscopy where DSP = digital signal processor, and RS 232 is a standard serial connection that allows...

Ultrasonic spectroscopy technology, developed in the early 1990s, is proving useful in the lubricant and food industries for measurement of od-in-water emulsions at process concentrations. This technology is anticipated to find a wide range of industrial appHcations. 

The authors thank A. Migliori for facilitating his ultrasonic spectroscopy apparatus for the elastic constant measurements. This work was supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Science. 

Although NMRI is a very well-suited experimental technique for quantifying emulsion properties such as velocity profiles, droplet concentration distributions and microstructural information, several alternative techniques can provide similar or complementary information to that obtained by NMRI. Two such techniques, ultrasonic spectroscopy and diffusing wave spectroscopy, can be employed in the characterization of concentrated emulsions in situ and without dilution [45],... 

In terms of measuring emulsion microstructure, ultrasonics is complementary to NMRI in that it is sensitive to droplet flocculation [54], which is the aggregation of droplets into clusters, or floes, without the occurrence of droplet fusion, or coalescence, as described earlier. Flocculation is an emulsion destabilization mechanism because it disrupts the uniform dispersion of discrete droplets. Furthermore, flocculation promotes creaming in the emulsion, as large clusters of droplets separate rapidly from the continuous phase, and also promotes coalescence, because droplets inside the clusters are in close contact for long periods of time. Ideally, a full characterization of an emulsion would include NMRI measurements of droplet size distributions, which only depend on the interior dimensions of the droplets and therefore are independent of flocculation, and also ultrasonic spectroscopy, which can characterize flocculation properties. 

R. Chanamai, N. Herrmann, D. J. McClements 2000, (Probing floe structure by ultrasonic spectroscopy, viscom-etry, and creaming measurements), Langmuir 16, 5884. 

Ultrasonic relaxation loss, of vitreous silica, 22 429-430 Ultrasonics, for MOCVD, 22 155 Ultrasonic spectroscopy, in particle size measurement, 13 152-153 Ultrasonic techniques, in nondestructive evaluation, 17 421—425 Ultrasonic testing (UT) piping system, 19 486 of plastics, 19 588 Ultrasonic waves, 17 421 Ultrasonic welding, of ethylene— tetrafluoroethylene copolymers,... 

Capillary hydrodynamic chromatography Fraunhofer diffraction Light-scattering photometry Phase Doppler anemometry Ultrasonic spectroscopy... 

Sensitivity Enhancement by the use of Acoustic Resonators in cw Ultrasonic Spectroscopy. 

Matsuoka, H. and he, N. Small-Angle and Ultra-Small Angle Scattering Study of the Ordered Structure in Polyelectrolyte Solutions and Colloidal Dispersions. Vol. 114, pp. 187-232. Matsushige, K, Hiramatsu, N. and Okabe, H. Ultrasonic Spectroscopy for Polymeric Materials. Vol. 125, pp. 147-186. 

Negishi, K. and Ri, H. U. (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. 70-4. Ministry of Education, Science, and Culture, Japan. [100,102]... 

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]... 

Tsukahara, Y., Ohira, K Saito, M and Briggs, G. A. D. (1989b). Evaluation of polymer coatings by ultrasonic spectroscopy. In Acoustical imaging, Vol. 17 (ed. H. Shimizu, N. Chubachi, and J. Kushibiki), pp. 257-64. Plenum Press, New York. [214] Tsukahara, Y., Ohira, K., and Nakaso, N. (1990). An ultrasonic micro-spectrometer for the evaluation of elastic properties with microscopic resolution. IEEE 1990 Ultrasonics Symposium, pp. 925-30 [149]... 

Ultrasonic spectroscopy has been utilized for real-time measurements of polymerization reactions and polymer melt extrusion.15,16 In these applications the time required for the ultrasonic waves to propagate through the sample to a transducer was measured. The velocity of the sound wave in the medium is related to the modulus and density of the sample matrix. 

The ring-opening metathesis polymerization of dicyclopentadiene was monitored by ultrasonic spectroscopy.16 The thermoset poly(dicyclopentadiene) is formed by ringopening and cross-linking in a reaction injection molding system. A reaction cell with a plastic window was constructed for use with pulse echo ultrasonic spectroscopy. Realtime measurements of density, longitudinal velocity, acoustic modulus and attenuation were monitored. Reaction kinetics were successfully determined and monitored using this technique. 

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