• DEVRAJ SINGH

      Articles written in Pramana – Journal of Physics

    • Ultrasonic investigations in intermetallics

      Devraj Singh D K Pandey

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      Ultrasonic attenuation for the longitudinal and shear waves due to phonon–phonon interaction and thermoelastic mechanism have been evaluated in B2 structured in-termetallic compounds AgMg, CuZr, AuMg, AuTi, AuMn, AuZn and AuCd along $\langle 1 0 0 \rangle, \langle 1 1 1 \rangle and \langle 1 1 0 \rangle crystallographic directions at room temperature. For the same evaluations, second- and third-order elastic constants, ultrasonic velocities, Grüneisen parameters, non-linearity parameter, Debye temperature and thermal relaxation time are also computed. Although the molecular weight of these materials increases from AgMg to AuCd, the obtained results are affected with the deviation number. Attenuation of ultrasonic waves due to phonon–phonon interaction is predominant over thermoelastic loss. Results are compared with available theoretical and experimental results. The results with other well-known physical properties are useful for industrial purposes.

    • A study of nanosized zinc oxide and its nanofluid

      D K Singh D K Pandey R R Yadav Devraj Singh

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      The synthesis and characterization of nanosized zinc oxide and its nanofluid in a polyvinyl alcohol (PVA) matrix have been done in the present investigation. Crystalline zinc oxide nanoparticles are synthesized using single-step chemical method while the nanofluids are prepared by the dispersion of nanoparticles in PVA solution using an ultrasonicator. The prepared nanoparticles are characterized using X-ray diffraction, SEM–EDX and UV–visible spectrum. The particle size distribution measurement is carried out by acoustic particle sizer. The ultrasonic velocities are measured in the synthesized nanofluid under different physical conditions using an ultrasonic interferometer. It is found that the degree of crystallinity of nanoparticles depends on the evaporation rate during its synthesis and ultrasonic velocity has non-linear relation with temperature for the present nanofluid.

    • Study of elastic, mechanical, thermophysical and ultrasonic properties of divalent metal fluorides XF2 (X = Ca, Sr, Cd and Ba)

      GAURAV SINGH SHAKTI PRATAP SINGH DEVRAJ SINGH ALOK KUMAR VERMA D K PANDEY R R YADAV

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      This paper described the behaviours of four divalent metal fluorides (CaF$_2$, SrF$_2$, CdF$_2$ and BaF$_2$) in terms of their superior elastic, mechanical and thermophysical properties. Initially, higher-order elastic constants of the chosen divalent metal fluorides have been calculated using the Coulomb and Born–Mayer interaction potential in the temperature regime 100–300 K.With the help of these constants, other elastic moduli, such as Young’s modulus (Y ), bulk modulus (B), shear modulus (G), Poisson’s ratio (σ ) and Pugh’s ratio (B/G) have been computed using Voigt–Reuss–Hill approximation. The Born stability criteria and Vicker’s hardness parameter ( ) have been used for analysing the nature and strength of the materials. Later on, ultrasonic velocities including Debye average velocities were evaluated using calculated values of second-order elastic constants and density in the samephysical conditions. Thermal properties such as the lattice thermal conductivity, thermal relaxation time, thermalenergy density and acoustic coupling constant have also been computed at the same physical conditions and along $\langle$100$\rangle$. The temperature-dependent ultrasonic properties have been correlated with other thermophysical propertiesto extract important information about the microstructural quality and the nature of the materials. The obtained results have been analysed to explore the inherent properties of the chosen divalent metal fluorides, which are useful for numerous industrial applications.

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