Ultrasonic velocity measurements

Pandey et al. have used ultrasonic velocity measurement to study compatibility of EPDM and acrylonitrile-butadiene rubber (NBR) blends at various blend ratios and in the presence of compa-tibilizers, namely chloro-sulfonated polyethylene (CSM) and chlorinated polyethylene (CM) [22]. They used an ultrasonic interferometer to measure sound velocity in solutions of the mbbers and then-blends. A plot of ultrasonic velocity versus composition of the blends is given in Eigure 11.1. Whereas the solution of the neat blends exhibits a wavy curve (with rise and fall), the curves for blends with compatibihzers (CSM and CM) are hnear. They resemble the curves for free energy change versus composition, where sinusoidal curves in the middle represent immiscibility and upper and lower curves stand for miscibihty. Similar curves are obtained for solutions containing 2 and 5 wt% of the blends. These results were confirmed by measurements with atomic force microscopy (AEM) and dynamic mechanical analysis as shown in Eigures 11.2 and 11.3. Substantial earher work on binary and ternary blends, particularly using EPDM and nitrile mbber, has been reported. 

McClements, D.J. and Povey, M.J.W. 1987. Solid fat content determination using ultrasonic velocity measurements. Int. J. FoodSci. Technol. 22 491-499. 

The development of damage in the form of matrix cracks within 1-D CMCs subject to tensile loading has been traced by direct optical observations on specimens with carefully polished surfaces, and by acoustic emission detection,7 9 62,79-81 as well as by ultrasonic velocity measurements.82 Interrupted tests, in conjunction with sectioning and SEM observations, have also been used. Analysis of the matrix damage found in 1-D CMCs provides the... 

On the other hand, the fact that ultrasonic velocity is independent of droplet size In the low and high frequency limits allows droplet concentrations to be determined without prior knowledge of the droplet size distribution from ultrasonic velocity measurements. Whether measurements are to be made In the low- or high-frequency regime depends on the size of the droplets and the range of frequencies which can be measured using available ultrasonic equipment (typically 0.1-100 MHz). 

For liquids, the velocity of ultrasound depends on the compressibility and density of the liquid. For suspensions, the velocity depends also on the drag of particles in the liquid under the influence of the ultrasonic wave. At low frequencies, small particles tend to move in phase with the liquid and the ultrasonic velocity may differ widely from that in the pure liquid. As particle size and ultrasonic frequency increases, the particles tend to lag more and more behind the movement of the liquid and the ultrasonic velocity approaches that of the suspension acting as a uniform fluid. There is a transition frequency range between complete entrainment and no entrainment of the particles that can be used to obtain particle size information. The hydrodynamic model of Marker and Temple [267 ] can be used to calculate ultrasonic velocity. This model takes into account the effects of fluid viscosity, of concentration, density and elastic modulus of both particles and fluid and can predict ultrasonic velocities accurately for volume fractions between 5% and 20%. Ultrasonic velocity measurements in the 50 kHz to 50 MHz can be used to determine particle size distributions in the range of about 0.1 to 30 pm. 

McClements, D.J., and M.J.W. Povey, Comparison of Pulsed NMR and Ultrasonic Velocity Measurements for Determining Solid Fat Contents, Ibid. 23 159-170 (1988). 

Figure 10.03 Photograph of the glass samples used in ultrasonic velocity measurements.

Ultrasonic velocity measurements are convenient for measuring hydration numbers from ion compressibilities (Padova 1964). For the di- and trivalent cations of the first transition series, the aqua ions are octahedral [M(H20)6] or [M(H20)6] , although in Cr(II), Mn(II) and Cu(II) definite distortions of the octahedra are present (Cotton and Wilkinson 1980). 

Ultrasonic velocity measurements have been reported on oriented smectic A samples of 4,4 -azoxydibenzoate. The first studies by Lord for two values of (0 and 90 ) established the anisotropy of the velocity of propagation. Subsequently, Miyano and Ketterson investigated the angular dependence of the sound velocity and from a least squares fit with (5.3.45) were able to determine the elastic coefficients A , and C. By analogy with the elasticity theory of solids, we may write... 

Fig. 5.3.10. Temperature dependence of the elastic constants of the smectic A phase of diethyl 4,4 -azoxydibenzoate determined by ultrasonic velocity measurements open circles, 2 MHz filled circles, 5 MHz triangles, 12 MHz crosses, 20 MHz. (After Miyano and Ketterson. )...

The velocity of elastic ultrasonic waves in solution is strongly influenced by solute-solvent and solute-solute interactions which are determined by the chemical structure of the solute and solvent molecules. Still, acoustical methods have made only minor contributions to the detailed description of solute-solvent interactions. Ultrasonic velocity measurements are mostly limited to obtaining hydration numbers of molecules in aqueous solution [Br 75]. The successful application of acoustical methods to physico-chemical investigation of solutions became possible after development of adequate theoretical approaches and methods for precise ultrasonic velocity measurements in small volumes of liquids [Sa 77, Bu 79]. 

SYA Syal, V.K., Chaithan, A., and Chaith, S., A study on solutiorrs of poly(vinylpyrrolidone) in binary mixtirres of DMSO + H2O at different temperatirres by ultrasonic velocity measurements, Indian J. Phys, 80, 379, 2006. 

Gross J, Fricke J (1992) Ultrasonic velocity measurements in silica, carbon and organic aerogels J Non-Cryst... 

As far as the volumetric properties are concerned, values at 25°C have been reported for alcohols(31,55-59a), ethers(11b,34, 58,60,61), amines(34,57,62-64), esters(11b,58), ketones(llb,36,58), amides(36,37,63,65), carboxylic acids(62a,b,67), hydroxycarboxylic acids(66c), polycarboxylic acids(66d), polyols(31,42 56,59b), pyri-dines and others unsaturated heterocyclic compounds containing ni-trogen(38), ethylene glycol derivatives(11a,61,68-70), carbohydra-tes(72-74), urea and derivatives(44,74,75) polyamines(76,77a) amino-alcohols and aminoethers(77b), polyethers(6°,61,77c), alkylhalides (61), benzene and derivatives(llc,26c), Moreover the behaviour of the functions = f(T) has been studied for alcohols(10,12,55,56) and polyols(12,55,56,68,78), ethers(12) and polyethers(llb,12,68), ketones and esters(11b), ethylene glycol derivatives(11a,68,71,78). Compressibility data at 25°C have been calculated from ultrasonic velocity measurements for ethers(79), amines(62), alcohols(79-82), polyols(79), ethylene glycol derivatives(68,71), polyethers(68,74, 79) urea and derivatives(74), carbohydrates(72,74). Finally some investigations about the influence of various types of non-electrolytes on the temperature of maximum density(82b,83) and the adiabatic compressibility minimum(84) of water are to be remembered. 

First to evaluate the confidence interval of the ultrasonic velocity measurements, we have performed experiments with pure water. This liquid was chosen because its sound velocity doesn t vary with ultrasonic frequency 23-24. Our results have been compared with previous data found in literature [ 21-22 and show a good agreement up to 0.5 GPa at various temperatures. 

Gross J., Fricke J. Ultrasonic velocity measurements in silica, carbon and organic aerogels. J. Non-Cryst. Sohds 1992 145 217-222 Her R.K. The Chanistry of Silica. New York Wiley, 1979... 

Subsequent ultrasonic relaxation studies - also involved the PVP/SDS system. The reported results are very different from those on the same system given in Reference 225, in the sense that in the binding range the value of 1/Xx is claimed to be nearly independent of the surfactant concentration. This is apparently true for the data in References 226 and 227 (PVP/SDS systems) but certainly not for the results reported in Reference 228 for several other polymer/surfactant systems. There it is clearly seen that 1/Xi is nearly constant over a very short range of concentration but increases linearly with C in the binding range determined from ultrasonic velocity measurements, as predicted by Equation 3.9. Besides in Reference 226 to Reference 228, the range where 1/Xi is nearly... 

Zimmer J.E., Cost J.E., Determination of the elastic constants of a unidirectional fiber composite using ultrasonic velocity measurements. 

In the previous section we demonstrated the use of ultrasonic velocity measurements to characterise creaming, and indirectly to characterise flocculation. However, there is more information to be obtained from an emulsion using ultrasonic spectroscopy. This involves measurement of phase velocity and attenuation of ultrasound as a function of frequency after propagation through the emulsion. There are a number of mechanisms by which ultrasound is attenuated by the emulsion, resulting in characteristic ultrasonic properties. Figure 4.15 shows the prineipal mechanisms of absorption. 

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