Change In Sound Velocity Research Articles

Simple Ultrasonic Measurement of Concentration in Solutions with Temperature Compensation by a Phase Difference Method

In this paper, we propose a new simple ultrasonic technique for measuring the concentration of solutions by a phase difference method with temperature compensation. This technique relies on sound velocity changes due to variations in solution concentration. An empirical equation of the sound velocity for both the sugar and NaCl solutions, which covered a concentration range of 0.0–20.0% and a temperature range of 15–45°C, was obtained by analyzing the measurements of various sound velocities through the least squares method. It became evident that a similar temperature-compensation factor can be used for both the solutions in terms of dependence on temperature in their equations. An empirical equation was applied to design a temperature compensation circuit. The measuring system with temperature compensation was shown to yield a 0.01% accuracy of concentration determination, independent of the temperature variation of ±0.9°C around 25.2°C for the sugar solution and of ±1.0°C around 25.4°C for the NaCl solution.

Sound attenuation of polymerizing actin reflects supramolecular structures: viscoelastic properties of actin gels modified by cytochalasin D, profilin and alpha-actinin.

Polymerization and depolymerization of cytoskeletal elements maintaining cytoplasmic stiffness are key factors in the control of cell crawling. Rheometry is a significant tool in determining the mechanical properties of the single elements in vitro. Viscoelasticity of gels formed by these polymers strongly depends on both the length and the associations of the filaments (e.g. entanglements, annealings and side-by-side associations). Ultrasound attenuation is related to viscosity, sound velocity and supramolecular structures in the sample. In combination with a small glass fibre (2 mm x 50 microm), serving as a viscosity sensor, an acoustic microscope was used to measure the elasticity and acoustic attenuation of actin solutions. Changes in acoustic attenuation of polymerizing actin by far exceed the values expected from calculations based on changes in viscosity and sound velocity. During the lag-phase of actin polymerization, attenuation slightly decreases, depending on actin concentration. After the half-maximum viscosity is accomplished and elasticity turns into steady state, attenuation distinctly rises. Changes in ultrasound attenuation depend on actin concentration, and they are modulated by the addition of alpha-actinin, cytochalasin D and profilin. Thus absorption and scattering of sound on the polymerization of actin is related to the packing density of the actin net, entanglements and the length of the actin filaments. Shortening of actin filaments by cytochalasin D was also confirmed by electron micrographs and falling-ball viscosimetry. In addition to viscosity and elasticity, the attenuation of sound proved to be a valuable parameter in characterizing actin polymerization and the supramolecular associations of F-actin.

Determination of the pre-exponential factor and the activation energy for the low-temperature dislocation relaxation in aluminum

The ultrasonic attenuation and the sound velocity at 10 MHz were measured in deformed Al single crystals in the temperature range between 1.5 and 50 K. In the high purity specimen (RRR=20 000) the change in sound velocity due to deformation shows a step in temperature dependence at 17 K, which corresponds to the 11 K relaxation peak at 50 kHz found by Kosugi and Kino [J. Phys. Soc. Jpn. 58 (1989) 4269], although the change in attenuation due to deformation was masked by the large background attenuation due to phonon–electron interaction. From the present experiment and that of Kosugi and Kino, the activation energy and the attack frequency of the relaxation process are estimated to be 14 meV and 1.0×10 12/s, respectively. If the kink pair formation process of dislocations on the Peierls potential is responsible for this relaxation, the Peierls stress is 5.4×10 −5 G, where G is the shear modulus, and this value does not conflict with the flow stress at low temperatures.

Ultrasonic and magnetic studies ofNd0.5Sr0.5MnO3

The results of systematic ultrasonic and magnetic studies of the magnetoresistive compound ${\mathrm{Nd}}_{0.5}{\mathrm{Sr}}_{0.5}{\mathrm{MnO}}_{3}$ are reported. With decreasing temperature the pronounced acoustic-mode hardening was observed at about ${T}_{\mathrm{CO}}=145$ K. The significant softening of the acoustic mode was observed in the vicinity of the insulator-to-metal transition induced by magnetic field. The $T\ensuremath{-}B$ phase diagram was obtained from the ultrasonic measurements. The change of sound velocity around ${T}_{\mathrm{CO}}$ was explained by a strong coupling between the acoustic phonons and the CO states. The peculiarities of the sound propagation at the phase transition can be attributed to the phase segregation in the ground state in ${\mathrm{Nd}}_{0.5}{\mathrm{Sr}}_{0.5}{\mathrm{MnO}}_{3}.$ An enhancement in magnetic correlations at temperatures below 20 K, as seen by magnetization and ultrasound measurements, was observed in ${\mathrm{Nd}}_{0.5}{\mathrm{Sr}}_{0.5}{\mathrm{MnO}}_{3}.$ We discuss this effect in terms of possible short-range magnetic ordering on the rare-earth sublattice.

Collective modes and sound propagation in ap-wave superconductor:Sr2RuO4

There are five distinct collective modes in the recently discovered p-wave superconductor ${\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4};$ phase and amplitude modes of the order parameter, clapping mode (real and imaginary), and spin wave. The first two modes also exist in the ordinary s-wave superconductors, while the clapping mode with the energy $\sqrt{2}\ensuremath{\Delta}(T)$ is unique to ${\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4}$ and couples to the sound wave. Here we report a theoretical study of the sound propagation in a two-dimensional p-wave superconductor. We identified the clapping mode and study its effects on the longitudinal and transverse sound velocities in the superconducting state. In contrast to the case of ${}^{3}\mathrm{He},$ there is no resonance absorption associated with the collective mode, since in metals $\ensuremath{\omega}{/(v}_{F}|\mathbf{q}|)\ensuremath{\ll}1,$ where ${v}_{F}$ is the Fermi velocity, $\mathbf{q}$ is the wave vector, and $\ensuremath{\omega}$ is the frequency of the sound wave. However, the velocity change in the collisionless limit gets modified by the contribution from the coupling to the clapping mode. We compute this contribution and comment on the visibility of the effect. In the diffusive limit, the contribution from the collective mode turns out to be negligible. The behaviors of the sound velocity change and the attenuation coefficient near ${T}_{c}$ in the diffusive limit are calculated and compared with the existing experimental data wherever it is possible. We also present the results for the attenuation coefficients in both of the collisionless and diffusive limits at finite temperatures.

Calculation of sound velocity in U2D2 solid 3He

Because of its large Gruneisen constant, U2D2 solid 3He is a very appropriate system to study the magnon–phonon coupling in a nuclear spin system. I calculate the sound velocity changes caused by magnon–phonon coupling with the second quantization method. The Hamiltonian is expanded with magnon operators by using the Holstein–Primakoff transformation for antiferromagnets. The attenuation of the sound is also calculated. The results are compared with the measurements of Nomura et al.

Applications of nonlinear ultrasonics to the NDE of material degradation

Nonlinear ultrasonics is suggested as a new approach for the effective evaluation of material degradation. As its quantification, the parameter beta is introduced on the basis of nonlinear elasticity, and a new method to measure the parameter beta using bispectral analysis is proposed. Then, the correlation between beta and material degradation is investigated. From the results for several mild steel (SS41, SS45) specimens that were degraded by stretching and cyclic loads, it was confirmed that the parameter beta has a strong correlation with material degradation. As another practical application, the evaluation of the aging degradation in a high temperature material is tried. For this, Cr-Mo-V specimens that are generally used in turbine rotors in power plants were prepared, and the variation of beta caused by aging time was investigated. For comparison, the fracture appearance transition temperature (FATT) of the specimen was measured, and its behavior showed good agreement with beta. In addition, for all of the experiments, no noticeable change in attenuation and sound velocity in the same specimens with change of degradation were observed. From these results, it may be concluded that nonlinear ultrasonics could be applied to the quantitative evaluation of material degradation.

Role of low-frequency vibrations on sound propagation in glasses at intermediate temperature

We report measurements of the temperature dependence of the sound attenuation and the fractional change in sound velocity for the glass (G) and orientational-glass (OG) phases of polymorphic ethanol. Strikingly similar behaviors are found for both phases despite the OG's underlying crystal (bcc) lattice. Such similarity, which is also revealed in dielectric spectroscopy and inelastic neutron scattering measurements, suggests whole molecule small-angle librations as a common microscopic origin for a wide variety of ``glassy'' phenomena.

A novel phase locked cavity resonator for B/ A measurements in fluids

A new technique for the measurement in fluids of the acoustic non-linearity parameter B/ A is presented, together with measured B/ A values for several fluids. The non-linearity parameter is measured by phase locking radial modes within a PZT cylinder. The system, which implements the isentropic phase technique, uses continuous wave phase locking to measure the change in sound velocity that is typically associated with a change in ambient pressure under constant entropy. The method provides a means of measuring B/ A in vitro both accurately and simply without the typical problems involved in time-of-flight systems. Fluid samples can remain small due to the nature of the cavity resonator, so the system is well suited to small volume, biological samples.

Stress dependence of sound velocity in Fe-based amorphous wires

The dependence of the longitudinal sound velocity on the bias magnetic field and tensile stress in Fe/sub 77.5/Si/sub 7.5/B/sub 15/ amorphous wires are presented, The measurements were made using the magnetostrictive delay line principle. The results show that changes in longitudinal sound velocity with bias magnetic field and tensile stress applied along the length of amorphous wires are strongly dependent on the thermal treatment. In the as-cast state, the change of the longitudinal sound velocity is negligible. There is a monotonic dependence of the sound velocity value on the tensile stress up to about 12 MPa. For about 16 MPa and 600 A/m tensile stress and bias magnetic field magnitude, respectively the saturation value of the longitudinal sound velocity is reached.

Detonation type waves in phase (chemical) transformation processes in condensed matter

Fast self sustained waves (autowaves) associated with chemical or phase transformations are observed in many situations in condensed matter. They are governed neither by diffusion of matter or heat (as in combustion processes) nor by a travelling shock wave (as in gaseous detonation). Instead, they result from a coupling between phase transformation and the stress field, and may be classified as gasless detonation autowaves in solids. We propose a simple model to describe these regimes. The model rests on the classical equations of elastic deformations in a 1-dimensional solid bar, with the extra assumption that the phase (chemical) transformation induces a change of the sound velocity. The transformations are assumed to occur through a chain branched mechanism, which starts when the mechanical stress exceeds a given threshold. Our investigation shows that supersonic autowaves exist in this model. In the absence of diffusion (dissipation factor, losses), a continuum of travelling wave solutions is found. In the presence of diffusion, a steady state supersonic wave solution is found, along with a slower wave controlled by diffusion.

Light-Induced Increase in Two-Level Tunneling States in Hydrogenated Amorphous Silicon

AbstractWe observe an increase of the low-temperature internal friction of hydrogenated amorphous silicon prepared by both hot-wire and plasma-enhanced chemical-vapor deposition after extended light-soaking at room temperature. This increase, and the associated change in sound velocity, can be explained by an increase of the density of two-level tunneling states, which serves as a measure of the lattice disorder. The amount of increase in internal friction is remarkably similar in both types of films although the amount and the microstructure of hydrogen are very different. Experiments conducted on a sample prepared by hot-wire chemical-vapor deposition show that this change anneals out gradually at room temperature in about 70 days. Possible relation of the light-induced changes in the low-temperature elastic properties to the Staebler-Wronski effect is discussed.

Ultrasonic measurement of stress in pin and hanger connections

Pin and hanger connections are used in bridges to suspend an interior span from the outer spans. The connections can sometimes lock up due to corrosion. If lockup occurs the stresses in the connection are cycled due to thermal expansion and contraction of the bridge: fatigue cracking and failure may occur. We constructed an apparatus to simulate a locked-up pin and hanger connection. We performed proof-of-concept tests of a method to detect stresses in pin and hanger connections. The method uses the stress-induced changes in sound velocity of shear waves polarized parallel and perpendicular to the hanger axis. The birefringence is the normalized difference in these shear wave velocities. We measured the birefringence at opposite sides of the hangers, at midsection. We simulated three scenarios: continuous monitoring of hanger status; intermittent monitoring from a known initial state; measurement with no a priori knowledge of hanger status. Good agreement with strain gauge data was obtained for all three scenarios.

Effect of particle size distribution upon specific surface area and ultrasonic velocity in sintered ceramic powders

The changes in ultrasonic sound wave velocity and specific surface area which occur as a result of sintering have been correlated for several zinc oxide and alumina powder systems. Particle size distribution is shown to have a significant effect upon the nature of this correlation. Powders with narrow particle size distributions exhibit a nearly linear relationship between the surface area reduction and the longitudinal wave velocity over much of the initial and intermediate stages of sintering. In contrast, powders with broad particle size distributions exhibit a significant reduction in the specific surface area, with little increase in the ultrasonic velocity, during the early stages of sintering. This behavior is attributed to the differences in the thermodynamic driving forces for sintering of the different sized particles. These data also indicate that in powder compacts containing broad particle size distributions, the apparent elastic moduli, as manifested in the ultrasonic velocity, are dominated by the larger particles. The present work contributes to the understanding of the dynamic behavior of sintering powder compacts in terms of the ultrasonic velocity, which may be determined non-intrusively during processing. This understanding may facilitate the use of ultrasonic techniques for real-time monitoring and controlling of the sintering process in ceramic power compacts.

New Developments in Diamond-Cell Research.

Melting of the compressible alkali halides (KBr, KCl, CsI, NaCl, LiF) have been measured up to 1 Mbar. Their melting slopes approach values between 1 and 2 K/kbar at high pressures, a trend similar to almost all other materials measured thus far. Based on this trend and the close agreement in the melting temperatures between the diamond cell and shock wave experiments for the alkali halides and aluminum, and based on systematics in the magnitude of the change in sound velocity upon melting, we reinterpret the shock sound velocity measurements on iron as indicating onset of melting at 2 Mbar instead of 2. 4 Mbar as previously reported. This may reconcile the assumed discrepancies between static and shock experiments for iron. A new method for analyzing samples from laser heated diamond cells using an ion probe is presented. Chemical diffusion profiles were measured on samples with dimensions of order 10 μm by depth profiling with a radial resolution of about 2μm and a depth resolution of about 100 nm. We present first results on the partitioning and diffusion of nickel and cobalt in Mg-Si-perovskite at pressures up to 800 kbar and temperatures up to 2500 K.

ULTRASONIC MEASUREMENTS ON QUENCH-CONDENSED NOBLE GAS FILMS

Quench–condensed noble gas films are a simple model system for studying the elastic properties of polycrystalline or amorphous solids at low temperatures. We have investigated the temperature dependence of the sound velocity δv/v and attenuation α of quench–condensed polycrystalline Ar, Ne, and HD films using surface acoustic waves at 800 MHz. Up to 0.7 K the sound velocity of all samples increases logarithmically in temperature and decreases above 1 K. This behavior is similar to what is found in glasses and is indicative of the presence of tunneling systems with a wide distribution of energies. Despite the qualitative similarities between the samples, remarkable quantitative differences were observed: Compared to argon the changes of sound velocity and of attenuation in neon are reduced by almost one order of magnitude and in HD even by approximately two orders of magnitude.

Influence of hydrostatic pressure on the thermal properties of polymers at low temperatures

The thermal conductivity λ of polycarbonate (PC) has been measured in the temperature range 3–150 K under hydrostatic pressure up to 1.3 GPa [Geilenkeuser, R., Weise, F. and Jäckel, M., Czech. J. Physics, 1996, 46, 2251 ( Proc. LT 21, Prag, August 1996)]. A strong influence of pressure on λ has been observed over the entire temperature range. Additional measurements of the pressure dependence of the density showed that the density of PC, polystyrene (PS), epoxy resin and PTFE (Teflon) increased considerably with pressure (Jäckel, M., Weise, F. and Geilenkeuser, R. In Proc. ICEC16/ICMC, Kitakyushu, May 1996, in press). At a pressure of 1.3 GPa the relative increase of the density amounts to 25%. The thermal conductivity data were corrected for the changes of density, sample geometry and sound velocity. The corrected data show an increase of λ with pressure only in the plateau region of thermal conductivity. Similar results were measured for vitreous silica (Jäckel, M., Wagner, K. and Hegenbarth, E., Physica B, 1996, 219&220, 308) and epoxy resin (Grace, J.M. and Anderson, A.C., Phys. Rev. B, 1989, 40, 1901).

Measurements of Sound Velocities and Freezing Pressures in Neon-Argon Mixed Gases.

The sound velocities in neon-argon mixed gases have been measured using a piston-cylinder gas apparatus up to 3 GPa at 295 K. The sound velocities increase smoothly with pressure up to the freezing pressure of mixed gas. Although the slopes of velocity with respect to the molar concentration of argon are negative in the lower pressure region, they are positive in the higher one. The gas-solid phase equilibrium is observed by both sound velocity and volume changes.

Melting curve of aluminum in a diamond cell to 0.8 Mbar: implications for iron

The melting curve of aluminum was measured in a laser-heated diamond cell up to a pressure of 0.8 Mbar in order to test the agreement between this technique and shock wave measurements, which has been lacking in the case for iron. At this pressure, which is over an order of magnitude higher than in previous experiments [1, 2], the melting temperature is 3800 K, comparable to that measured for iron at 2 Mbar [3]. The present results for aluminum extrapolate smoothly to the previous melting measurements in a multi-anvil apparatus to 60 kbar and to the calculated shock melting point of 4750 K at 1.25 Mbar. They are also in excellent agreement with theoretical calculations. A review of the shock data reported for Al, Ta and Mo, close-packed metals, in which a break in the sound velocity-pressure curve is used to determine the melting pressure, shows that the change in velocity at melting is about 10% for all three metals. In the case of iron, the sound velocity data have been used to infer two transitions: a solid-solid transition at 2.0 Mbar and melting at 2.4 Mbar, each of these transitions having about a 5% change in sound velocity. It is unlikely that a phase transition between close-packed cubic structures will have a 5% velocity change, the same as is found in the melting transition. We therefore suggest that for iron there exists only a single transition, starting at 2.0 Mbar, a region of incomplete shock melting between 2 and 2.4 Mbar, and a total change in sound velocity of about 10%, which is closer to the value of the other metals studied. This interpretation introduces a very good agreement between the shock melting results of Brown and McQueen [4] and diamond cell measurements for iron [3] which has up to now been lacking.

Constraints on core chemistry from the pressure dependence of the bulk modulus

A simple method for evaluating the compatibility of different alloying constituents with the elastic properties of the outer core is presented. This approach depends primarily on the value of the pressure derivative of the bulk modulus ( K′) of possible alloying phases, and has the advantages of being largely independent of temperature and being based on observable parameters: the sound speed as a function of depth in the outer core, and the sound speed of molten iron at high pressures. Accurate constraints on the K′ values of light alloying element containing phases are, however, crucial in deriving purely geophysical constraints on the geochemistry of the core. Our results emphasize that the present bounds on K′ of S, O and H-rich iron alloys are compatible with the change in sound velocity as a function of depth in the outer core. Alloying constituents with K′ values less than or equal to about 4 are unable to satisfy this depth-dependence. Both shock and static compression data on Si-rich alloys indicate that the K′ of Si-rich iron alloys fall in this range; moreover, other lighter alloying phases have values of K′ which are unable to compensate for the effect of significant Si within the outer core. It thus appears that Si cannot be the primary light alloying element of the outer core. Our results indicate that dramatically reducing conditions and resultant reduction of silicates is unlikely to have occurred during core formation.