Alok Kumar Gupta

Ultrasonic properties of nanoparticles-liquid suspensions ☆

A polymer colloidal solution having dispersed nanoparticles of Cu and Au metals have been developed using a novel chemical method. Average size of the nanoparticles could be varied in the 4-10 nm range by conducting the reaction at an elevated temperature of 50-70 degrees C. Colloidal solutions of representative concentrations of 0.1-2.0 wt% Cu/Au contents in the primary solutions are used to study the modified ultrasonic attenuation and ultrasonic velocity in PVA polymer molecules on incorporating the Cu/Au particles. A characteristic behaviour of the ultrasonic velocity and the attenuation are observed at the particular temperature/particle concentration. The results demonstrate that the primary reaction during the nanoparticles-PVA colloidal formation occurs in divided groups in small micelles. The results are analyzed predicting the enhanced thermal conductivity of the samples.

ULTRASONIC WAVE PROPAGATION IN SEMI-METALLIC SINGLE CRYSTALS

In this paper, ultrasonic attenuation due phonon–phonon interaction and thermoelastic loss mechanisms has been computed for longitudinal and shear waves along 〈100〉, 〈110〉 and 〈111〉 crystallographic directions in the temperature range 100 K to 300 K using modified Masons approach in gadolinium monopnictides GdX (X: P, As, Sb and Bi). For the evaluation of ultrasonic attenuation with allied factors, the second and third order elastic constants were also evaluated using Coulomb and Born–Mayer type potential considering interaction up to second nearest neighborhood. The thermoelastic loss is not so important in present case due to lesser free electrons than metallic material. GdP is found to be ductile, more perfect, flawless in comparison to GdAs, GdSb and GdBi in this temperature regime and the direction 〈111〉 is more suitable for wave propagation in these B1 structured materials due to low value of attenuation. The mechanical properties of GdP are better than other monochalcogenides because of higher valued elastic constants. The thermal conductivity is the leading factor to study ultrasonic attenuation in these monopnictides. The characteristic features are discussed in correlation with other physical properties like thermal conductivity, specific heat etc.

Study of Elastic and Acoustic Properties of TiN

This work is totally focused on three types of ultrasonic velocities (V1, V2, V3) in TiN single crystals. They are determined by using the SOEC (second order elastic constant) and TOEC (third order elastic constant) at room temperature. TiN possesses rock slats structure and the atoms in the unit cell is equally located in all the direction. Therefore ultrasonic waves are supposed to be propoagted alongany direction with the crystals axis. Finally ultrasonic attenuationdue to phonon-phonon interaction and thermoelastic relaxation phenomena in TiNis evaluated for longitudinal and shear waves along , and crystallographic directions at the different temperature (temperature varies from 150 to 400K) by utilizing the SOEC and TOEC of the materials. The SOEC and TOEC, ultrasonic velocities, thermalrelaxation, anisotropic and acoustical coupling constant have been computedfor the evaluation of ultrasonic attenuation in this temperature range. The crystallographic direction is responsible for propogating the longitudinal ultrasonic wave while , direction is the best direction for propogating the shear waves due to lowest values of ultrasonic attenuationdue to phonon-phonon vibration in these direction.

Ultrasonic properties in Au nanoparticles reinforced PVA solution

Abstract A polymer colloidal solution with dispersed nanoparticles of gold metal has been developed using a novel chemical reaction between Au3+ cations and polymer molecules of reactive surfaces of polyvinyl alcohol (PVA). Average size of Au particles could be varied in the range of 4–10 nm by conducting the reaction at an elevated temperature of 50–70°C. Colloidal solutions at representative concentrations of 0·1–1·0 wt-%Au contents in the primary solutions are used to study the modified ultrasonic attenuation and ultrasonic velocity in PVA polymer molecules on incorporating the Au particles using pulse echo technique. A characteristic minimum in velocity and maximum in attenuation are observed at the same temperature. The results demonstrate that the primary reaction during the Au–PVA colloidal formation occurs in divided groups in small micelles. The Au particles are encapsulated in PVA polymer molecules. The results are analyzed and discussed in correlation with the optical and electrical properties.

Temperature Dependent Ultrasonic Study in Scandium Antimonide Semiconductor

In this paper analysis of wave propagation of elastic wave in scandium antimonide semiconductor was investigated. In scandium antimonide semiconductor, NaCl structure was found. Ultrasonic properties like ultrasonic attenuation, sound velocities, acoustic coupling constants, and thermal relaxation time have been investigated in cubic scandium antimonide semiconductor. Second and third order elastic constant have been computed for the evaluation of above said ultrasonic properties. Second and third elastic constant was studied at the various temperatures. Longitudinal and shear velocity was calculated by using the elastic constant. Longitudinal and shear velocity increase with increase the temperature. Ultrasonic attenuation either from longitudinal or shear wave propagation in cubic materials increase with increase the temperature.