Ultrasonic measurement of viscoelastic shear modulus development in hydrating cement paste

A test procedure for measuring changes in amplitude and phase of SH ultrasonic waves from the interface between fused-quartz and cement paste samples is presented. The phase change is determined from the temporal shift in the reflected signal relative to the incident signal. The sensitivity of the measured parameters to changes in acoustic impedance of the materials in contact with fused-quartz is evaluated for different angles of incidence. It is shown that a reflection measurement at normal incidence at nano-second temporal resolution does not provide sufficient sensitivity to measure the viscous component of shear modulus of low viscosity fluids and cannot be applied to cement paste while it is in a fluid state. Monitoring the measured amplitude and phase at oblique angle of incidence allows for measuring fluids with acoustic impedance comparable to cement paste. The reflection measurements are used to determine the evolution of elastic and viscous components of shear modulus cement paste with time. Influence of sampling rate and temperature effects on the phase measurements are evaluated and shown to be significant. It is shown that the initial loss of workability of cement paste through setting process is associated with a larger relative increase in the viscous component of shear modulus. Following the initial rapid rise of the viscous component of shear modulus, there is a larger relative increase in the elastic component, which can be related to the emergence of a solid structure capable of retaining an imprint.     

Determination of physicochemical properties of diacylglycerol oil at high pressure by means of ultrasonic methods

The purpose of the paper is to address, using ultrasonic methods, the impact of temperature and pressure on the physicochemical properties of liquids on the example of diacylglycerol (DAG) oil. The paper presents measurements of sound velocity, density and volume of DAG oil sample in the pressure range from atmospheric pressure up to 0.6 GPa and at temperatures ranging from 20 to 50 °C.     

Ultrasonic study of the phase diagram of methanol

The phase diagram of methanol is studied by an ultrasonic technique over the temperature range 90–290 K at pressures up to 1.2 GPa. The pressure and temperature dependence of the velocity of longitudinal ultrasonic waves and the density of crystalline and liquid phases has been determined. Weak anomalies in the velocity of ultrasound in the liquid phase of methanol and the corresponding anomalous additional compression of the liquid at 230–250 K and 0.2–0.6 GPa have been found, and they are likely attributable to structural changes in the liquid phase.     

Pressure-sensitive paint as a distributed optical microphone array

Pressure-sensitive paint is presented and evaluated in this article as a quantitative technique for measurement of acoustic pressure fluctuations. This work is the culmination of advances in paint technology which enable unsteady measurements of fluctuations over 10 kHz at pressure levels as low as 125 dB. Pressure-sensitive paint may be thought of as a nano-scale array of optical microphones with a spatial resolution limited primarily by the resolution of the imaging device. Thus, pressure-sensitive paint is a powerful tool for making high-amplitude sound pressure measurements. In this work, the paint was used to record ensemble-averaged, time-resolved, quantitative measurements of two-dimensional mode shapes in an acoustic resonance cavity. A wall-mounted speaker generated nonlinear, standing acoustic waves in a rigid enclosure measuring 216 mm wide, 169 mm high, and 102 mm deep. The paint recorded the acoustic surface pressures of the (1,1,0) mode shape at approximately 1.3 kHz and a sound pressure level of 145.4 dB. Results from the paint are compared with data from a Kulite pressure transducer, and with linear acoustic theory. The paint may be used as a diagnostic technique for ultrasonic tests where high spatial resolution is essential, or in nonlinear acoustic applications such as shock tubes.     

Acoustic cavitation in 1-butyl-3-methylimidazolium bis(triflluoromethyl-sulfonyl)imide based ionic liquid

In this work, a comparison between the temperatures/pressures within acoustic cavitation bubble in an imidazolium-based room-temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium bis(triflluoromethyl-sulfonyl)imide ([BMIM][NTf₂]), and in water has been made for a wide range of cavitation parameters including frequency (140–1000 kHz), acoustic intensity (0.5–1 W cm⁻²), liquid temperature (20–50 °C) and external static pressure (0.7–1.5 atm). The used cavitation model takes into account the liquid compressibility as well as the surface tension and the viscosity of the medium. It was found that the bubble temperatures and pressures were always much higher in the ionic liquid compared to those predicted in water. The valuable effect of [BMIM][NTf₂] on the bubble temperature was more pronounced at higher acoustic intensity and liquid temperature and lower frequency and external static pressure. However, confrontation between the predicted and the experimental estimated temperatures in ionic liquids showed an opposite trend as the temperatures measured in some pure ionic liquids are of the same order as those observed in water. The injection of liquid droplets into cavitation bubbles, the pyrolysis of ionic liquids at the bubble-solution interface as well as the lower number of collapsing bubbles in the ionic liquid may be the responsible for the lower measured bubble temperatures in ionic liquids, as compared with water.     

Theoretical analysis of an ultrasonic interferometer for precise measurements at high pressures

Expressions making it possible to calculate the transmission coefficient of an ultrasonic interferometer, its Q factor and errors of interferometric measurements are presented. These expressions are obtained on the basis of a one-dimensional model which takes into account the non-ideal reflection of acoustic waves from the transducers, diffraction losses and electromechanical properties of transducers. Fixed path ultrasonic interferometers which are widely used for high precision measurements of ultrasound absorption and velocity in liquids, include air-backed transducers. Air-backing limits the application of these interferometers for the measurements under the high pressures. The influence of non-gaseous backing of transducers on the characteristics of an interferometer is theoretically analysed by means of suggested expressions. Frequency dependences of main parameters of the interferometer are obtained. The possibility of high precision measurements of velocity and absorption of ultrasound in liquids under the high pressures by means of fixed path interferometers with liquid-backed transducers is shown.     

Phase transition in a NaBi(MoO<Subscript>4</Subscript>)<Subscript>2</Subscript> crystal: Acoustic investigations

This paper reports on the results of acoustic investigations of a NaBi(MoO₄)₂ crystal in the temperature range from 20 to 70°C. The temperature dependences of the velocity of longitudinal ultrasonic waves propagating along the crystallographic axes z and x are measured at a frequency of 4 MHz. The results obtained demonstrate that a structural phase transition occurs in the NaBi(MoO₄)₂ crystal at a temperature of 309 K. The experimental findings are consistent with the assumption that the observed phase transition is either a second-order ferroelastic transition or a first-order ferroelastic transition that is very close to being a second-order phase transition.     

基于自发瑞利-布里渊散射的氮气体黏滞系数的测量

体黏滞系数是从微观角度认识气体分子黏滞性的重要参数,传统的兆赫兹声频范围的声波吸收方法无法直接应用于声波弛豫效应在千兆赫兹范围的高频领域,而瑞利-布里渊散射则能实现对声波弛豫效应在千兆赫兹的气体体黏滞系数的测量.本文测量了532 nm激光激发的常温下压强分别为1-9 bar的氮气的自发瑞利-布里渊散射光谱,利用已知温度和压强的理论模型对测量光谱进行了比较,获得了准确的散射角.利用该散射角并结合χ~2值最小原理反演得到不同压强(4—9 bar)下氮气的平均体黏滞系数为(1.46±0.14)×10~(-5)kg·m~(-1)·s~(-1),该结果与文献中利用自发瑞利-布里渊散射获得的结果和理论计算结果相近,但与相干瑞利-布里渊散射的测量结果相差明显.利用该平均体黏滞系数对氮气在不同压强下的温度进行了反演,得到各压强下的温度与实际温度的绝对误差小于2.50 K,反演温度的平均值与实际温度误差小于0.15 K,该结果证明了实验测量得到的氮气的体黏滞系数具有较高的准确性,同时也说明利用瑞利-布里渊散射反演气体参数具有较高的准确性和可靠性.     

X-Ray Diffraction Investigation of Oleic Acid under High Pressure

Pressure has a specific influence on the light scattering in those liquids in which all molecules have an unsaturated double bond C=C. Strong changes of intensity of transmitted and scattered light in oleic acid were observed during its transition to the high-pressure phase. In this paper, local order in liquid of oleic acid has been studied using the X-ray diffraction photographic Laue method. Experiments were run at room temperature under atmospheric pressure as well as under pressures up to 0.25 GPa. At pressures above 0.2 GPa a strong increase of ordering of molecules, similar to a smectic liquid crystal phase, has been observed. This confirms results obtained previously by studies of light scattering under high pressure.     

Applications of Acoustic Wave Devices for Sensing in Liquid Environments

Abstract

Acoustic wave devices such as thickness shear mode (TSM) resonators and shear horizontal surface acoustic wave (SH‐SAW) devices can be utilized for characterizing physical properties of liquids and for chemical sensor applications. Basic device configurations are reviewed and the relationships between experimental observables (frequency shifts and attenuation) and physical properties of liquids are presented. Examples of physical property (density and viscosity) determination and also of chemical sensing are presented for a variety of liquid phase applications. Applications of TSMs and polymer‐coated guided SH‐SAWs for chemical sensing and uncoated SH‐SAWs for “electronic tongue” applications are also discussed.     

Pressure-induced structural transformations and the anomalous behavior of the viscosity in network chalcogenide and oxide melts

It is known that a number of compressed melts undergo structural phase transitions. Data on the structural changes at high pressures in chalcogenides (AsS, As₂S₃) and oxide (B₂O₃) melts with a network structure have been reviewed. Viscosity is one of the fundamental physical properties of a liquid. For various melts, it varies in a very wide range. Structural transformations in melts induce the corresponding changes in all physical properties, in particular viscosity. The measurements of the viscosity of a number of melts at high pressures and temperatures by the radiographic method have been reported. Changes in the viscosity by several orders of magnitude have been detected when the pressure is varied by several gigapascals. The diffusion mechanism in network-structure melts at various pressures has been analyzed. The prediction of the behavior of the viscosity of various melts at superhigh pressures is of high importance for the physics of glass transition, geophysics, and materials science.     

Contact and non-contact ultrasonic diagnostics of shock waves driven by single-shot femtosecond laser ablation of titanium

Initial pressures and expansion speeds of air shock waves, driven by single-shot femtosecond laser ablation of titanium surface at fluences up to 6 J/cm², were acquired by means of front-side non-contact time-of-flight ultrasonic measurements. Similar contact ultrasonic measurements on the rear side of the titanium target demonstrate general correlation of ultrasonic amplitudes the measured in the contact and non-contact modes at high ablative pressures (above 100 GPa, superelastic propagation regime), and strong deviation of these dependences at lower ablative pressures (strong dissipation regime) without any indications of new titanium phases, besides the initial α-Ti phase.     

Modeling cavitation in a rapidly changing pressure field – Application to a small ultrasonic horn

Ultrasonic horn transducers are frequently used in applications of acoustic cavitation in liquids. It has been observed that if the horn tip is sufficiently small and driven at high amplitude, cavitation is very strong, and the tip can be covered entirely by the gas/vapor phase for longer time intervals. A peculiar dynamics of the attached cavity can emerge with expansion and collapse at a self-generated frequency in the subharmonic range, i.e. below the acoustic driving frequency. The term “acoustic supercavitation” was proposed for this type of cavitation Žnidarčič et al. (2014) [1].We tested several established hydrodynamic cavitation models on this problem, but none of them was able to correctly predict the flow features. As a specific characteristic of such acoustic cavitation problems lies in the rapidly changing driving pressures, we present an improved approach to cavitation modeling, which does not neglect the second derivatives in the Rayleigh–Plesset equation. Comparison with measurements of acoustic supercavitation at an ultrasonic horn of 20 kHz frequency revealed a good agreement in terms of cavity dynamics, cavity volume and emitted pressure pulsations.The newly developed cavitation model is particularly suited for simulation of cavitating flow in highly fluctuating driving pressure fields.     

Acoustical investigations of a La<Subscript>0.75</Subscript>Sr<Subscript>0.25</Subscript>MnO<Subscript>3</Subscript> single crystal

The acoustical, resistive, and magnetic properties of a La_0.75Sr_0.25MnO₃ lanthanum manganite single crystal are investigated in the temperature range involving the second-order magnetic phase transition. The acoustical measurements are performed by the pulse-echo method in the frequency range 14–90 MHz. It is found that, as the temperature decreases, the velocity of a longitudinal acoustic wave propagating along the [111] axis in the single crystal drastically increases at temperatures below the critical point of the magnetic phase transition. No dispersion of the acoustic velocity is revealed. A sharp increase in the acoustic velocity is accompanied by the appearance of an acoustical absorption peak. The observed effects are discussed with due regard for the interaction of acoustic waves with the magnetic moments of the manganese ions.     

Experimental investigations on ultrasound mediated particle breakage

This paper investigates the effect of high-intensity ultrasound on the breakage characteristics of particles suspended in water. A continuous sonicated flow experimental apparatus is used involving a 24 kHz horn type transducer and continuous in-line particle chord length measurement. The effects of sonication power (150-350 W) and temperature (10-50 degrees C) on the breakage characteristics are investigated. Higher breakage is favored at higher sonication power. An optimum temperature in the range tested is observed to exist between 25 degrees C and 37 degrees C. The acoustic cavitation field is influenced by temperature through a complex interplay of vapor pressure, surface tension and viscosity leading to the optimum observed in particle breakage. The efficiency of ultrasound energy conversion to particle breakage is calculated using calorimetry and found along with the net breakage efficiency to initially increase with temperature followed by a decrease after the optimum. It is found to be independent of input ultrasonic power. The effects of contact time is also investigated.     

Acoustic anomalies near phase transitions in manganite

The behavior of the velocities and attenuation of ultrasonic waves propagating in La_1?x Sr_xMnO₃ (x=0.175) manganite at frequencies of 700–800 MHz is studied in the temperature interval from 320 to 180 K, and the effect of magnetic field on the acoustic parameters is investigated. The transformation of acoustic modes in the vicinity of the magnetic phase transition is observed. The changes in the acoustic parameters near the structural and magnetic phase transitions are shown to be related to the strong spin-phonon and electron-phonon interactions.     

Investigation of thermal and deformation properties of quartzite in a temperature range of polymorphous α-β transition by neutron diffraction and acoustic emission methods

The results of combined application of the neutron diffraction and acoustic emission methods for investigation of the physical properties of synthetic quartz and natural quartzite in a temperature range of α-β transition are given. In experiments, the quartzite sample was exposed to heating and uniaxial compression. Changes of the lattice spacings in quartzite were measured in a temperature range 540–620°C. On the basis of these measurements, the inner inner stresses are evaluated and found to exceed the applied stresses by several times. It is found that after the phase transition is finished, short bursts of acoustic emission (AE) occur which are two orders of magnitude more intense than the acoustic emissions produced by thermal cracking of the sample while the sample is heating up to the transition temperatures. An assumption is made that the anomalous behavior of the physical properties of quartz-containing rocks under relatively low pressures near the transition temperature can cause the formation of strong concentrators of local stresses comparable with the breaking point of the material, thereby initiating microcracking.     

Suitability of laser Doppler velocimetry for the calibration of pressure microphones

The details of a new approach for absolute calibration of microphones, based on the direct measurement of acoustic particle velocity using laser Doppler velocimetry (LDV), are presented and discussed. The calibration technique is carried out inside a tube in which plane waves propagate and closed by a rigid termination. The method developed proposes to estimate the acoustic pressure with two velocity measurements and a physical model. Minimum theoretical uncertainties on the estimated pressure and minimum measurable pressure are calculated from the Cramer Rao bounds on the estimated acoustic velocity amplitude and phase. These uncertainties and the minimum measurable pressure help to optimize the experimental set up. Acoustic pressure estimations performed with LDV are compared with acoustic pressures obtained with a reference microphone. Measurements lead to a minimum bias of 0.006 dB and a minimum uncertainty of 0.013 dB on the acoustic pressure estimation for frequencies 1360 Hz and 680 Hz.     

Comparison of phase behavior between water soluble and insoluble surfactants at the air-water interface

The surface phase behavior of 2-hydroxyethyl myristate (2-HEM) has been studied in Langmuir monolayers by measuring surface pressure (π)-area (A) isotherms with a film balance and observing monolayer morphology with a Brewster angle microscope (BAM). These results are compared with the phase behavior of 2-hydroxyethyl laurate (2-HEL) in Gibbs monolayers studied by measuring π-time (t) curves and observing monolayer morphology. The π-A isotherms of 2-HEM show a first-order phase transition from a liquid expanded (LE) phase to a liquid condensed (LC) phase in the temperature range between 5 and 35 °C whereas the π-t curves of 2-HEL represent a similar phase transition in the temperature range between 2 and 25 °C. The critical surface pressure, π_c necessary for the phase transitions increases with increasing temperature in both the cases. The LC domains formed in 2-HEM show circular shapes, which are independent of the temperature. In contrast, the circular domains having stripe texture formed at lower temperatures show a shape transition to fingering domains with uniform brightness at 15 °C. The amphiphile, 2-HEM having 13-carbon chain has higher line tension than 2-HEL that has 11-carbon chain as tail. Thus, for 2-HEM, this high line tension always dominates over other factors giving rise to circular domains at the all studied temperatures.     

Propagation and Diagnostic of Ion Acoustic Waves in a Low Pressure Argon Discharge

In a dc argon discharge column of pressure 5 × 10^?4 torr, ion acoustic waves are studied experimentally. Plasma parameters obtained from the phase velocity of waves are compared with the Langmuir probe measurements. The wave diagnostic method yields the electron temperature lower than the probe method by a factor of 3…?5, if the atomic argon ion is assumed as a dominant ion species. The axial profiles of ion drift velocity show the presence of ions flowing toward the anode along the potential drop in flont of it. Also it is found that the surface condition of the cathode sensitively affects the propagation of ion acoustic waves through the changes in discharge parameters.