Ultrasonic Absorption Measurements Research Articles

Effect of sodium hydroxide pretreatment on the relaxation spectrum of concentrated agar-agar gels

Stress relaxation and ultrasonic absorption measurements were made for agar-agar pretreated by various concentrations of sodium hydroxide, in order to clarify the dominating factors in its rheological properties. Stress relaxation measurements were made up to 30 hours. Relaxation spectra were obtained by the reduced variable method. Gels prepared from agar-agar pretreated by concentrated sodium hydroxide show a larger relaxation modulus than those pretreated by dilute sodium hydroxide and those without alkaline pretreatment. It is suggested that hydrogen bonds are newly created as a result of desulfation in the molecule, and then, the microcrystalline structure is stabilised.

Ultrasonic absorption measurements with a millilitre short-path pulse cell

A simple ultrasonic pulse cell with reduced variable pathlength for millilitre liquid samples (frequency range about 15-155 MHz) is described. The liquid cavity made from stainless steel has PTFE seals and gaskets and is resistant against many liquids. Attenuation and velocity measurements have been performed for H2O, CH3OH, C2H5OH and C2H5OC2H5 at 25 degrees C. The measurements, using a quartz effective diameter of 9 mm and pathlengths from 7-21 mm, show that diffraction correction terms are apparently not necessary.

Ultrasound propagation near the critical mixing point of sodium-ammonia solutions

Ultrasonic absorption and dispersion measurements near the critical mixing point of sodium-ammonia solutions are reported. The results are interpreted in terms of a coupling of the ultrasonic wave and mass diffusional modes. The critical behavior of sound propagation shows features not observed in organic binary mixtures.

Critical Divergence of Ultrasonic Absorption in Binary Fluids

Ultrasonic absorption measurements for a critical binary mixture of 3-methylpentane-nitroethane have been made over a wide reduced frequency range, 10-1<ω*106; ω*=ω/ωc, where ω is the frequency of sound and ωc is the relaxation frequency. Near the critical temperature Tc=26.50°C a critical divergence of sound absorption was observed. The experimental results were analyzed numerically within the framework of the existing mode coupling theory for sound propagation. In order to clarify the discrepancy between the theory and the experiment, a computer calculation was made on a set of critical relaxation curves and temperature dispersion relations. As a result, it is shown that the existing mode coupling theory breaks down over a wide range of frequency and temperature. The universal scaling function for this binary mixture has been derived empirically using the extended dynamical scaling approach.

Ultrasonic propagation properties of collagen

Ultrasonic absorption measurements in the range 0.5-56 MHz, and measurements of velocity at 8.87 MHz, were made in collagen suspensions in which molecular integrity was preserved, in a range of concentrations 0.07-0.7% by weight, at 10 to 20 degrees C. Absorption and velocity values, per unit concentration, exhibited by collagen are much greater in magnitude than those exhibited by globular proteins.

Théorie de l'absorption ultrasonore des solutions micellaires d'amphiphiles. Application à l'effet de la force ionique sur la dynamique d'échange d'amphiphiles entre micelles et solution environnante

An expression for the amplitude of the ultrasonic relaxation arising from the exchange of amphiphiles between micelles and surrounding solution has been derived on the basis of the same assumptions as used by Aniansson and Wall to obtain the expression of the relaxation time for this process. The derived expression somewhat extends the range of investigation of micellar systems which can be performed by means of the ultrasonic relaxation method. It has been used for the quantitative interpretation of ultrasonic absorption measurements concerning the effect of ionic strength on the dynamics of the exchange process in micellar solutions of potassium decanoate.

Measurement of Ultrasonic Absorption in Critical Binary Mixture by Light Diffraction Method

Measurement of Ultrasonic Absorption in Critical Binary Mixture by Light Diffraction Method

Intensity analysis of f-f transitions and correlation with conductivity and ultrasonic absorption for holmium solvates

Absorption spectra of holmium nitrate in MFA and DMF have been measured in the range 8000–42000 cm −1. The τ λ parameters were evaluated from the experimental oscillator strengths using the Judd equation. For Ho(NO 3) 3 in DMF a considerable increase in τ 2 was observed, suggesting the existence of inner-sphere species in this system. This suggestion was verified by ultrasonic absorption and conductivity measurements.

Ultrasonic studies of n-hexane-perfluoro n-hexane mixtures

Ultrasonic absorption and velocity measurements over the frequency range 1 to 10 MHz at 303 K on mixtures of n-hexane and perfluoro-n-hexane confirm the existence of a rotational isomeric relaxation in the perfluoro-compound, and give evidence of a structural relaxation in the liquid mixtures. This last process occurs at frequencies much higher than those associated with conformational change and its amplitude can be predicted from the excess thermodynamic quantities of mixing.

Ultrasonic studies of glass-filled polymer solids

Ultrasonic absorption and velocity measurements are reported for a range of polymers filled with glass beads. The data were obtained over a frequency range 15-35 MHz and a temperature range 298-348K with a variety of bead sizes and concentrations. In all cases the ultrasonic absorption and tan delta were observed to be larger in the filled than in the corresponding unfilled polymer. Comparison of the observed excess attenuation with that predicted by simple and multiple scattering theories indicates that the major influence on the acoustic propagation is from scattering effects. An additional contribution to the attenuation observed in one of the systems is attributed to a modification of the polymer relaxation spectrum by the inclusion of the glass beads.

Study op V-V transfer in polyatomic molecules by laser-induced fluorescence and ultrasonic absorption measurements

Slow vibrational energy transfer between the two lowest modes of such polyatomic molecules is studied, where the second lowest mode lies above the overtone of the lowest mode. The results of ultrasonic absorption and laser-induced fluorescence experiments in methylene halides are discussed. These results and additional data taken from the literature are correlated. The conditions for inefficient energy exchange between the two lowest modes of molecules are explored. The most important channel at 300 K is probably not energy transfer to the overtone as found by SSH-type calculations, but direct energy exchange between the two fundamentals despite the larger energy gap.

Erbium nitrate complexation in aqueous DMSO

Ultrasonic absorption measurements have been utilized to investigate the complexation reaction between Er(III) and NO 3 − in aqueous DMSO. As water is added to 0.200 M Er(NO 3) 3 in DMSO, an additional reaction step is coupled to inner-sphere complexation, corresponding to a change in coordination number for the solvated Er(III) complex. At a water mole fraction of 0.163, the complex formation rate constant equals 5.6 × 10 7 sec −1.

Characterization of biological fluids by ultrasound and computed tomography.

Blood and blood products, and solutions of albumin and chondroitin sulfate of varying concentrations were imaged by ultrasound and computed tomography in a phantom having ultrasonic and CT characteristics of liver tissue. Measurements of CT number, ultrasonic absorption, and viscosity were obtained for selected fluids. All fluids, including concentrated solutions of albumin and chondroitin sulfate having high viscosity, were detectable as echofree regions on ultrasound scans. Acoustical enhancement distal to fluids was noted to decrease in prominence with increasing sound absorption in the fluid. On CT scans, fluids with CT numbers close to those of their surroundings were poorly detected.

Recent Developments in Ultrasonic Velocity and Absorption Measurement

Recent Developments in Ultrasonic Velocity and Absorption Measurement

Sound propagation in colloidal suspensions in electrolytes

The propagation of ultrasonic waves through colloidal suspensions in electrolytes is of interest from the standpoint of understanding sound propagation in the sea and in biological systems, and as a means for study of colloidal systems. Ultrasonic velocity and absorption measurements have been carried out in suspensions of particles of various configurations, including polystyrene latex (monodispersed spheres of, e.g., 5500 A), kaoline (sodium form, platelets), montmorillonile (sodium form, platelets), and microcrystalline cellulose (rods) over a range of suspensions concentrations at several frequencies. The velocity changes associated with the colloid occur principally because of the difference in static adiabatic compressibility of the colloid phase and bulk electrolyte. With very small particle size—high surface area system, the change in compressibility of the solvent molecules adsorbed on the colloid surfaces may also be significant. The principal factors contributing to the additional absorption ar...

Dissociation constants: NH4OH as a standard

It is proposed that NH4OH be used as a standard for determining dissociation constants on a standard basis. Ultrasonic absorption and electrical conductance measurements as a function of pressure provide the basis for quantitative evaluation of all parameters except activity coefficients. It is shown how the weak ionization of NH4OH can be used to minimize uncertainty due to activity coefficients. Density data at atmospheric pressure confirm the\(\Delta \bar V^\circ\) values used to provide quantitative explanations of the acoustic and conductance data. Application of the differential sound absorption technique should extend the method dissociation constants of other classes of salts, in particular the 1–2, 2–2, and 3–2 sulfates.

Cylindrical Resonator Technique for Ultrasonic Absorption Measurement and Its Application to Cellulose Acetate–Cyclohexanone System

Cylindrical Resonator Technique for Ultrasonic Absorption Measurement and Its Application to Cellulose Acetate–Cyclohexanone System

TOWARDS PRACTICAL NON‐DESTRUCTIVE FATIGUE DAMAGE INDICATORS

Abstract— The applicability of measurements of residual stress, X‐ray diffraction line broadening, ultrasonic absorption, and phase changes, for the purpose of fatigue damage detection was explored on SAE 1008 plain carbon steel and type 304 and type 316 stainless steels. The most promising indicators of progressive damage appear to be residual stress and phase change measurements. While diffraction line broadening is not very useful as an indicator of progressive damage, it can serve as an indicator of the stress or strain range to which a critical part has been subjected, and may therefore prove useful for monitoring and diagnostic purposes. From the limited data on ultrasonic absorption measurements little can be said about their applicability to fatigue damage assessment.

Enhancement of the Proton Exchange Rate in Aqueous Solution by Small Amounts of Hydrophobic Substances, as Determined from Ultrasonic Relaxation

AbstractThe kinetics of the proton transfer reaction between dihydrogen phosphate and imidazole in water with some added methanol, ethanol, and dioxan, respectively, was investigated by means of ultrasonic absorption and velocity dispersion measurements in the frequency range from 0.5 to 36 MHz. The system exhibits a single chemical relaxation time. It reflects a diffusion controlled direct transfer mechanism. The two rate constants have been evaluated as a function of the volume percentage of the added solvent. Both show a sharp maximum at about 0.5%. This effect turned out to be the more pronounced the more hydrophobe the foreign molecules are. Comparatively few molecules of such material therefore seem to appreciably increase the hydrogen bonded water structure in the hydration shells through which proton transfer is mediated.

Absorption of ultrasound near the critical point of sodium-ammonia solutions

Comprehensive measurements of ultrasonic absorption in sodium-ammonia solutions near the critical mixing point and passing through the metal-nonmetal transition are presented and analyzed in detail. A few ultrasonic-velocity measurements in the same system are also reported. The observed critical divergence of the absorption (all the data being in the hydrodynamic regime) is shown to obey the Fixman-Kawasaki multiple-relaxation calculation by the adjustment of three fit parameters. The measured absorption and the characteristic frequency and amplitude parameters all appear to undergo a scaling crossover at a reduced temperature of about ${10}^{\ensuremath{-}2}$. The presence of large-amplitude fluctuations in the solutions near the critical point is inferred as well as the presence of a distribution of relaxations related to the diffusive decay of these fluctuations. The results are also discussed in terms of the microscopic inhomogeneities or clusters proposed by Cohen and Jortner for metal-ammonia solutions.