Temperature and Orientation Dependence of Ultrasonic Parameters in Americium Monopnictides

The temperature dependence of the ultrasonic parameters like ultrasonic velocities and Grüneisen parameters in americium monopnictides AmY (Y: N, P, As, Sb and Bi) have been studied for longitudinal and shear waves along , and crystallographic directions in the temperature range 100 K - 500 K. The second- and third- order elastic constants have also been evaluated for these monopnictides using Coulomb and Born-Mayer potential. The values of elastic constants are the highest for AmN. Hence the mechanical properties of AmN are better than other monopnictides AmP, AmAs, AmSb and AmBi. Ultrasonic velocity is found large for AmP. So the ultrasonic wave propagation will be much better than others in AmP. Obtained results are compared with available results of same type of materials.

Synthesis and Ultrasonic Characterization of Cu/PVP Nanoparticles-Polymer Suspensions

A polymer colloidal solution having dispersed nanoparticles of Cu metal has been developed using a novel chemical method. Colloidal solutions of representative concentrations of 0.2 to 2.0 wt% Cu-nanoparticles con-tents in the primary solutions were prepared to study the modified ultrasonic attenuation and ultrasonic velocity in polyvinyl alcohol (PVP) polymer molecules on incorporating the Cu-nanoparticles. The synthesized copper metal nanoparticles dispersed in the polymer solutions were characterized by UV-Visible absorption spectros-copy, X-ray diffraction (XRD) and Transmission electron microscopy (TEM). The nanofluid sample showed a symmetrical peak at 592 nm due to the surface plasmon resonance of the copper nanoparticles. XRD results confirmed that copper nanoparticles were crystalline in the colloidal solution. The TEM micrograph revealed spherical copper nanoparticles having diameter in the range 10 - 40 nm. A characteristic behaviour of the ultra-sonic velocity and the attenuation are observed at the particular temperature/particle concentration. It reveals that the colloidal suspension occurs in divided groups in the small micelles. The results are discussed in correlation with the thermophysical properties predicting the enhanced thermal conductivity of the samples.

Ultrasonic Wave Propagation in Californium Monopnictides

In this paper, we have investigated the temperature dependence of the ultrasonic parameters like ultrasonic velocities and Grüneisen parameters in californium monopnictides CfY (Y: N, As and Sb) for longitudinal and shear waves along , and crystallographic directions in the temperature range 100–500K. For the same evaluation the second- and third- order elastic constants have also been computed for these monopnictides using Coulomb and Born-Mayer potential upto second nearest neighborhood. The mechanical properties and stability of CfN is best, because of its high valued elastic constants. Ultrasonic velocity is found to be highest for CfAs along all chosen directions, so CfAs will be most suitable compound for wave propagation. The obtained results of present investigation are discussed in along with identified thermophysical properties.

Ultrasonic Attenuation in Calcium Oxide

Ultrasonic attenuation studies can be used to characterize material not only after production but during processing as well. The most important causes of ultrasonic attenuation in solids are electron-phonon, phonon-phonon interaction and that due to thermo elastic relaxation. The two dominant processes that will give rise to appreciable ultrasonic attenuation at higher temperature are the phonon-phonon interaction also known as Akhiezer loss and that due to thermo elastic relaxation are observed in calcium oxide crystal. At frequencies of ultrasonic range and at higher temperatures in solids, phonon-phonon interaction mechanism is dominating cause for attenuation. Ultrasonic attenuation due to phonon-phonon interaction (α/f2)p-p and thermo elastic relaxation (α/f2)th are evaluated in Calcium Oxide crystal up to an elevated temperature from 100 K - 1500 K along , and crystallographic directions. Temperature dependence of ultrasonic attenuation along different crystallographic direction reveals some typical characteristic features.

Sensitivity of Nanostructured Iron Metal on Ultrasonic Properties

The present investigation is focused on the influence of the nanocrystalline structure of pure iron metal on the ultrasonic properties in the temperature range 100 - 300 K. The ultrasonic attenuation due to phonon- phonon interaction and thermoelastic relaxation phenomena has been evaluated for longitudinal and shear waves along , and crystallographic directions. The second-and third-order elastic constants, ultrasonic velocities, thermal relaxation, anisotropy and acoustic coupling constants were also com- puted for the evaluation of ultrasonic attenuation in this temperature scale. The direction is most ap- propriate to study longitudinal sound waves, while , direction are best to propagate shear waves due to lowest values of attenuation in these directions. Other physical properties correlated with obtained results have been discussed.

Acoustic Wave Propagation in Nanocrystalline RuCo Alloys

The ultrasonic properties like elastic constant, ultrasonic velocity in the hexagonal structured nanocrystalline RuCo alloys have been studied along unique axis at room temperature. The second and third order elastic constants (SOEC & TOEC) have been calculated for these alloys using Lennard-Jones potential. The orientation dependent ultrasonic velocity has been also evaluated to study the anisotropic behaviour of these alloys. The velocities VL and VS1 have minima and maxima, respectively at 45° with unique axis of the crystal, while VS2 increases with the angle from unique axis. The inconsistent behaviour of angle-dependent velocities is associated to the action of second order elastic constants. Debye average ultrasonic velocities of these alloys are increasing with the angle and has maximum at 55° with unique axis at room temperature. Hence, when a ultrasonic wave travels at 55° with unique axis of these alloys, then the average ultrasonic velocity is found to be maximum. Elastic constants and density are mainly the affecting factor for anomalous behaviour of ultrasonic velocity in these alloys. The mechanical and ultrasonic properties of Co0.75Ru0.25 alloy will be better than the other compounds due to their high SOEC, ultrasonic velocity and low ultrasonic attenuation. Co0.75Ru0.25 alloy is more suitable for industrial and other uses, as it has the highest elastic constants and lowest ultrasonic attenuation in comparison to other of these alloys. The results of this investigation are discussed in correlation with other known thermophysical properties.