Absorption Coefficient Of Ultrasonic Waves Research Articles

Velocity and Absorption Coefficient of Ultrasonic Waves for Silicate Melts

Velocity and Absorption Coefficient of Ultrasonic Waves for Silicate Melts

Acoustic properties of PEG biocompatible magnetic fluid under perpendicular magnetic field

Biocompatible magnetic fluids of nanoparticles coated with polyethylene glycol show stable acoustic properties up to a field intensity of H = 70 kA / m . In higher fields, the ultrasonic wave absorption coefficient significantly increases and is strongly dependent on temperature, magnetic field intensity, magnetic field sweep rate and time of exposure to magnetic field. Adjustment of these parameters leads to control of the acoustic properties of the magnetic ferrofluids.

Thermochemical and thermophysical property measurements in slag systems

This paper reviews developments on experimental methods and results of thermochemical and thermophysical property measurements of molten silicate slag systems and its theoretical achievements. Several selected topics are focused on, including experimental procedure and measurements of viscosity, density, surface-interfacial tension, thermal conductivity, thermal diffusivity and velocity and absorption coefficient of ultrasonic waves. Thermal conductivity and diffusivity of slags have been mainly measured by the transient techniques such as the laser flash and hot wire methods. Most of the measurements for velocity and absorption coefficient of ultrasonic waves are carried out using a pulse technique. The reliable data for thermochemical and thermophysical properties are required for the optimisation of metallurgical processes and the data is needed in order to improve the numerical models of processing. For academic interest, the results were discussed from the viewpoint of slag structure, as these properties are closely related to the slag structure.

The Effect of a Magnetic Field on the Absorption Coefficient of Ultrasonic Wave in Biocompatible Ferrofluid

In this paper acoustic and magnetic properties of water-based biocompatible fluid MF BSA (bovine serum albumin) are presented. The changes in the ultrasonic wave absorption coefficient show that MF had a good structural stability up to 100 kA/m. The measurements of magnetic susceptibility enabled to estimate the mean magnetic moment and mean size of magnetic particles. The obtained values are promising for future biomedical applications of such magnetic fluids.

The effect of temperature on the anisotropy of ultrasound attenuation in a ferrofluid

This paper reports results of a study on the acoustic properties of a ferrofluid, APG-513A. The anisotropy of the ultrasonic wave absorption coefficient was determined in a sample subjected to an external magnetic field. The measurements were performed in a strong magnetic field HDC = 125 kA m−1, for temperatures of 1–60°C. The dependence of the absorption coefficient of the ultrasonic wave (f = 3.6 MHz) on the angle between the direction of measurement and that of the magnetic field provided important information on the ferrofluid structure in a magnetic field. A comparison of the experimental results with the predictions of the Taketomi theory allowed a determination of the cluster radius and the number density of the colloidal particles. These data allowed us to draw conclusions about the changes in the parameters describing the structure of the ferrofluid at different temperatures. The per cent contribution of the magnetic particles in the cluster structures was estimated. On the basis of the measurements performed, it was possible to establish the proportion of the ultrasonic wave used for excitation of the translational and rotational degrees of freedom. The results revealed a significant effect of temperature on the translational and rotational components of the absorption coefficient. Moreover, the magnetic susceptibility was measured versus the external magnetic field intensity.

The influence of the concentration of ferroparticles in a ferrofluid on its magnetic and acoustic properties

This paper reports results of a study of magnetic and acoustic properties of a ferrofluid, EMG-605. The measurements were performed for three samples of the same ferrofluid differing in concentration. The magnetic susceptibility was measured as a function of an external magnetic field for each sample, which allowed us to determine the magnetization curves and saturation magnetization. The results provide information on the mean magnetic moment and the mean radius of the magnetite grain. In the samples subjected to an external magnetic field, the anisotropy of the ultrasonic wave absorption coefficient was determined. The mechanisms of ultrasonic wave energy dissipation through the translational and rotational degrees of freedom were established for some ferrofluid concentrations.

Hysteresis of changes of ultrasonic wave absorption coefficient in a magnetic fluid caused by the magnetic field

The magnetic fluids change their structure under the influence of an external magnetic field and do not return to the initial state after the magnetic field removal. It is supposed that the cluster formed in the fluid subjected to a magnetic field remains after the field has been removed. The resulting dependence of the ferrofluid properties on its magnetic history has been studied by the analysis of changes in the ultrasonic wave absorption coefficient.

The effect of the rate of magnetic field and temperature changes on the ultrasonic wave absorption coefficient in a magnetic fluid

The rate of external magnetic field changes as well as temperature influences the structure of a magnetic fluid. This work presents experimental results on changes in the ultrasonic wave absorption coefficient of EMG-605 water-based magnetic fluid as a function of the external magnetic field intensity for different rates of magnetic field changes, at different temperatures. On the basis of these studies, radii of spherical clusters formed in the fluid under the influence of an external magnetic field have been determined.

Investigation of Adiabatic Compressibility and Ultrasonic Relaxation in Aqueous Solutions of N, N-Diisopropylacetamide and Zinc Acetate

Measurements of velocity at frequency of 1 MHz and absorption coefficient of ultrasonic waves within the range 3-50 MHz in aqueous solutions of N,N-diisopropylacetamide (D-i-PA) and zinc acetate ((CH3COO)2Zn) were made. Additionally, the density of the solutions was measured. The adopted method for making the solutions helped to change the ratio of the number of non-electrolyte molecules to that of electrolyte molecules, with a constant number of water molecules. Measurements of the velocity of ultrasonic waves in the solutions under study were conducted by means of an impulse-phase interferometer. Measurements of the absorption coefficient of ultrasonic waves were conducted by means of an ultrasonic high frequency system, type Matec Instruments (USA) Model 7700. All the measurements were conducted at a constant temperature of 20°C. On the basis of the analysis of excess functions of the molar volume and the adiabatic compressibility, the formation of solvatomers composed of [(D-i-PA)2Zn(H 2 O) 2 ] 2+ and [(D-i-PA)Zn(H2O)3] 2 + was found. Also the complex [Zn(CH3COO)4] 2— can be recognised. The results of measurements of sound absorption indicate the occurrence of the relaxation process in the solutions under study and the frequency range used. On the basis of the relaxation theory, relaxation parameters of the process under study were calculated. The relaxation processes discovered in the system (D-i-PA)-H2O(CH3COO)2Zn were assigned to the formation and disintegration of solvatomers composed of [(D-i-PA)Zn(H2O)3] 2+ and probably complexes mentioned before.

Absorption of ultrasonic waves in aqueous solutions of N-methylacetamide and zinc chloride

Measurements of the absorption coefficient of ultrasonic waves have been made within the frequency range of 10–100 MHz in aqueous solutions of N-methylacetamide (NMAA) and zinc chloride (ZnCl2). The method used to prepare quasi-two-component solutions permitted a change in the ratio of the number of amide molecules to electrolyte molecules, given a constant number of water molecules. The results indicate the occurrence of a single relaxational process in the solutions under investigation and the frequency range adopted. On the basis of the theory of relaxational absorption of sounds, relaxation parameters as well as the enthalpy of activation of the solution in question, which was 16.4 kJ/mol, have been calculated. The character of the relaxational process observed was determined on the basis of the analysis of relaxational curves. The discovered relaxational process in H2O–NMAA–ZnCl2 was ascribed to the formation and disintegration of ‘‘solvatomers’’ composed of [NMAA Zn(H2O)3]2+.

Velocity and absorption coefficient of ultrasonic waves in molten and glassy silicates and borates

The velocity and absorption coefficient of longitudinal ultrasonic waves with 5 and 10 MHz in molten and glassy silicates and borates have been measured by means of the pulse-echo method in 300 to 1600 K. The silicate and borate were Na2O−SiO2, K2O−SiO2, PbO−SiO2, Na2O−B2O3, and PbO−B2O3. The velocity of sound decreased with increasing temperature and decreased rapidly near the transition temperature of glasses. The product of the one-third power of velocity of sound and the molar volume of the oxide melt was constant and independent of temperature. The absorption coefficient of ultrasonic waves in the oxide melts increased with an increase in viscosity. The absorption mechanisms of ultrasonic waves and the mean free path of phonons in the oxide melts were discussed.

On the magnitude of ultrasonic volume viscosity

Measurements of the absorption coefficient of ultrasonic waves is in all cases larger than can be explained by viscosity and heat conduction. The benchmark paper by Herzfeld and Rice [Phys. Rev. 31, 691 (1928)] introduced a third factor, namely vibrational relaxation, which for many substances accounted for most of the excess absorption. The remaining excess absorption has led to the concept of a volume viscosity, which has been historically associated with structural and other relaxation mechanisms. We have observed that when accurate absorption data is available for such diverse substances as gases, liquids, and polymers in which there is an absence of vibrational and structural (e.g., water) relaxation mechanisms, the ratio of volume to shear viscosity is exactly 2/3. We present numerous data to support this. The consistency of this ratio, and its temperature independence, suggests that the viscous counterpart to the Lame constant λ″ is negligibly small. That is, ηv = λ″ + 2ηs/3, ηv/ηs ≈ 2/3, therefore...

On a new variation of the echoimpulse method for measuring the absorption coefficient of ultrasonic waves: Stojanov, Z., Giceski, A. Faculty of Science, Skopje University, Vol 16 (1965) pp 107–116 (In Russian) (1086)

On a new variation of the echoimpulse method for measuring the absorption coefficient of ultrasonic waves: Stojanov, Z., Giceski, A. Faculty of Science, Skopje University, Vol 16 (1965) pp 107–116 (In Russian) (1086)

Real and Apparent Absorption Coefficient of Ultrasonic Waves in Liquids

IT has been suggested that the generally accepted high absorption coefficient of ultrasonic waves1 in carbon disulphide and also, to some extent, in benzene, are not in accord with some experimental observations made by us2. This problem has now been studied more critically.

Temperature Variation of Velocity and Absorption Coefficient of Ultrasonic Waves in Heavy Water (D2O)

The coefficient of absorption and velocity of propagation were measured in D2O at 50.22 Mc/sec as functions of temperature. Velocity values are lower than those in H2O at corresponding temperature by about 100 m/sec but measurements extended to 90° show a striking qualitative similarity between velocity vs temperature curves for D2O and H2O. The value of the frequency-free absorption coefficient 2α/ν2 varies from 124×10−17 to 27×10−17 cm−1 sec2 over the temperature range of 5° to 50°C. The mean value of the ratio of measured value to classical value is 2.87 against 3.12 for H2O.