Temperature Dependence Of Ultrasonic Attenuation Research Articles

Mechanical, Thermophysical, and Ultrasonic Properties of Thermoelectric HfX2 (X = S, Se) Compounds

In the present study, ultrasonic and thermophysical behaviour of thermoelectric hexagonal structured HfX2 (X = S, Se) compounds have been analysed by the theoretical evaluation of second and third order elastic constants (SOECs and TOECs) using many body interaction potential model. The computed SOECs have been used to determine the temperature dependent specific heat, thermal energy density, elastic coupling constants, Gruneisen parameters, ultrasonic velocities, Debye average velocity, ultrasonic attenuation, and thermal relaxation time. We have observed that the temperature dependent ultrasonic attenuation and thermal relaxation time for HfX2 are mainly affected by thermal conductivity. The elastic properties of the material are compared with existing data in literature for the validation of the work. The obtained values of elastic stiffness are found very large in comparison to that of other material from transition metal dichalcogenides of group IVB indicating better mechanical properties than the same group materials. Calculated elastic, thermal, and ultrasonic properties are correlated for better characterization of the materials which are useful for thermoelectric and energy transport applications.

Ultrasonic wave propagation in ternary intermetallic CeCuGe compound

The elastic and ultrasonic properties of the hexagonal intermetallic CeCuGe ternary compound have been evaluated along unique axis at room temperature. Higher order elastic constants have been calculated for CeCuGe compound using Lennard–Jones interaction potential model. The ultrasonic velocity, Debye average velocity, thermal relaxation time and acoustic coupling constant are evaluated along unique axis of the crystal and the temperature dependent ultrasonic velocities are evaluated along different angles with unique axis of the crystal. Finally temperature dependent ultrasonic attenuation is evaluated to extract important information about the material.

Effect of thermal cycling on ferroelectric phase transition of PVDF-TrFE based composites as investigated by ultrasonic spectroscopy

ABSTRACTIn this paper we report on the investigation of longitudinal ultrasonic wave attenuation, velocity and ultrasonically induced piezoelectric voltage in P(VDF-TrFE) composites with fillers of conductive carbon nanotubes (CNT). Moreover, temperature dependences of ultrasonic attenuation in the composites were shown to be sensitive to thermal cycling over the ferroelectric phase transition.

Ultrasonic attenuation anomalies of n-type superconductor Pr2−xCexCuO4

Pr[Formula: see text]Ce[Formula: see text]CuO4 ([Formula: see text] = 0 and 0.15) samples were prepared via solid state reaction. Pr2CuO4 sample is insulating while Pr[Formula: see text]Ce[Formula: see text]CuO4 sample exhibited an onset critical temperature, [Formula: see text] of 21 K. The temperature dependences of ultrasonic attenuation in these polycrystalline n-type superconductor Pr[Formula: see text]Ce[Formula: see text]CuO4 ([Formula: see text] = 0 and 0.15) samples have been measured between 80 K and 300 K using longitudinal and shear waves by pulse-echo-overlap method with frequencies between 5 MHz and 10 MHz. For the longitudinal mode, a pronounced attenuation peak around 200 K was observed in Pr2CuO4, but it is not observed in the superconducting material Pr[Formula: see text]Ce[Formula: see text]CuO4. For the shear mode, no pronounced attenuation peaks were observed in the samples. It is suggested that the attenuation peak in the [Formula: see text] = 0 sample at 200 K is due to the weak structural distortion induced by the magnetic transition.

Dielectric Spectroscopy of Polymer Based PDMS Nanocomposites with ZnO Nanoparticles

Dielectric spectroscopy results of organic polymer Polydimethylsiloxane (PDMS) with different ZnO nanoparticle concentrations are presented in wide temperature range. Dielectric loss was measured as a function of electromagnetic field frequency at various temperatures. Our measurements have shown that the value and position of dielectric loss peak on a temperature scale depends on the concentration of ZnO nanoparticles within PDMS. The temperature behaviour of dielectric losses was compared with temperature dependencies of ultrasonic attenuation in the samples. It is shown that the maximum of dielectric losses in PDMS nanocomposite is described according to the Vogel-Fulcher law and the glass transition increases with ZnO concentration.

Elastic and ultrasonic properties of single crystalline nickel nanowires

In the present paper, we have theoretically calculated the non linear elastic constants of single crystalline Ni NWs at very broad temperature range 20–300K validating simple interaction potential model. The temperature dependent ultrasonic attenuation and other related properties are determined using their second and third order elastic constants (SOECs/TOECs). Where possible, the results are compared with experiments from literature. There is a correlation between the thermal conductivity and ultrasonic attenuation in the temperature range 100–300K. Also, a correlation between the resistivity and ultrasonic attenuation in the temperature range 40–100K has been established validating the theoretical approach.

Size and temperature dependent ultrasonic properties of thermoelectric nanowires

Hicks and Dresselhauss proposed that conversion of bulk materials into low dimensional size might significantly enhance thermoelectric performance. PbTe nanowires have been suggested as promising thermoelectric materials. In the present paper, nonlinear second and third order elastic constants (SOECs/TOECs) for PbTe nanowires (NWs) are calculated using a simple interaction potential model. Finally, the temperature dependent ultrasonic attenuation is determined for different diameters of the PbTe NWs. Good correlation between the size and temperature dependent thermophysical properties and the ultrasonic attenuation has been established. The studies are important for the development of NWs for energy and thermoelectric cooling applications.

Temperature Dependent Elastic and Ultrasonic Properties of Iron Aluminide

The anisotropic elastic constants of a B2 structured iron aluminide FeAl (Fe-40 at. % Al) alloy at different temperatures are computed using Coulomb and Born Mayer model. The temperature dependent ultrasonic properties of the alloy along with other associated parameters are determined using the elastic constants. The correlation between the mechanical and thermal properties makes ultrasonic properties a suitable, nondestructive tool to study the physical state of FeAl alloy. The results of present investigation are discussed in correlation with the microstructural phenomenon like phonon-phonon interaction and the other thermophysical properties. Temperature dependence of ultrasonic attenuation along different crystallographic directions reveals some typical characteristic features.

Study of ultrasonic attenuation for the Kondo and magnetic effects in heavy fermion systems

The heavy fermion (HF) systems draw considerable attention due to their cooperative phenomena and anomalous properties arising out of the huge effective mass. A heavy fermion system is described by a model Hamiltonian consisting of the Kondo lattice model in addition to the Heisenberg-type spin-spin interaction among the localised electrons. The Hamiltonian is treated in the mean-field approximation to find the Kondo singlet parameter λ and the short-ranged f-electron correlation parameter Γ. In order to investigate ultrasonic absorption in the system, we consider the phonon interaction with the bare f-electrons, and the phonon coupling to the Kondo singlets. Further, the phonon Hamiltonian is considered in the harmonic approximation. The phonon Green’s function is calculated in closed form. The imaginary part of the phonon self-energy describes the ultrasonic attenuation for the HF systems. The calculated ultrasonic attenuation clearly displays the f-electron correlation region separated by the Kondo singlet state at low temperatures. The correlation transition temperature and the Kondo temperature are located at dips in the temperature-dependent ultrasonic attenuation. The parameter dependence of the attenuation is investigated by varying the physical parameters of the HF systems and the wave frequency, and the experimental observations are explained on the basis of the model calculations.

Behavior of Ultrasonic Attenuation in MnO

Temperature dependence of ultrasonic attenuation and allied parameters are investigated for manganese oxide in the temperature range 300-500 K. These calculations are made for longitudinal and shear waves along the , and crystallographic directions of propagation. If the values of second order elastic constants and density at a particular temperature are known for any substance, one may obtain ultrasonic velocities for longitudinal and shear waves which give an important information about its internal structure, inherent and anharmonic properties. The non-linearity coupling parameters and thermal relaxation time have also obtained for this crystal. In the present investigation, it has been found that phonon-phonon interaction is the dominant cause for ultrasonic attenuation. This study will be useful in characterisation of the material and it will give a clear picture of the behaviour of ultrasonic attenuation in MnO.

Effect of temperature on non-destructive wave propagation in potassium halides

Temperature dependence of ultrasonic attenuation is investigated for potassium halides in the temperature range 100–400K. These calculations are done for KCl, KBr and KI for longitudinal and shear waves along the 〈111〉 direction. The non-linearity coupling parameters and thermal relaxation time have also been obtained for these crystals. In the present investigation, it has been found that phonon–phonon interaction is the dominant cause for ultrasonic attenuation.

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.

Acoustical investigation of lead chalcogenides

Temperature dependence of ultrasonic attenuation due to phonon–phonon interaction and thermo-elastic loss have been studied in NaCl-type lead monochalcogenides (PbS, PbSe and PbTe) in the temperature range 100–500 K for longitudinal and shear modes of propagation along 〈1 0 0〉, 〈1 1 0〉 and 〈1 1 1〉 directions. Second and third order elastic constants have been evaluated using electrostatic and Börn repulsive potentials and taking interactions up to next nearest neighbours. These values have been utilized to obtain attenuation coefficient for lead compounds. In the present investigation, it has been found that phonon–phonon (p–p) interaction is the dominant cause for ultrasonic attenuation. The possible implications of the results have been discussed.

Temperature dependent physical effects of ultrasonic wave in beryllium chalcogenides

Temperature dependent physical effects of ultrasonic wave viz. ultrasonic attenuation due to interaction of sound wave and thermal phonons, thermoelastic loss and dislocation damping have been studied in beryllium chalcogenides (BeX, X = S, Se and Te) in the temperature range 50–500 K, along three crystallographic directions of propagation viz. [1 0 0], [1 1 0] and [1 1 1] for longitudinal and shear modes of propagation. Second and third order elastic moduli have been obtained using electrostatic and Born repulsive potentials and taking hardness parameter and nearest neighbour distance as input data. Gruneisen numbers, acoustic coupling constants and drag coefficients have been evaluated for longitudinal and shear waves along different directions of propagation and polarization. The results have been discussed and compared with the available data. It has been found that the temperature dependence of ultrasonic attenuation follows the temperature variation of diffusion coefficient and is mainly dominated by phonon–phonon interaction.

Characterization of II–VI: 3d crystals with the help of ultrasonic technique

The temperature dependence of ultrasonic attenuation is proposed to use for determining concentration of dopand in a diluted magnetic semiconductor. This non-destructive method can be used for the crystal in which attenuation is caused by relaxation in the Jahn―Teller system. Attenuation coefficient per the impurity ion β obtained at a fixed frequency was introduced as a parameter characterizing sensitivity of the method. This parameter was determined for a number of II―VI: 3d semiconductors: ZnSe:Ni 2+ , ZnTe:Ni 2+ , ZnSe:V 2+ , ZnSe:Cr 2+ , and ZnSe:Fe 2+ at 54 MHz. Anomalously large value of β = 23 × 10 ―18 dB cm 2 was found for Cr 2+ in ZnSe.

Measurement of Broadband Temperature-Dependent Ultrasonic Attenuation and Dispersion Using Photoacoustics

The broadband ultrasonic characterization of biological fluids and tissues is important for the continued development and application of high-resolution ultrasound imaging modalities. Here, a photoacoustic technique for the transmission measurement of temperature-dependent ultrasonic attenuation and dispersion is described. The system uses a photoacoustic plane wave source constructed from a polymethylmethacrylate substrate with a thin optically absorbent layer. Broadband ultrasonic waves are generated by illuminating the absorbent layer with nanosecond pulses of laser light. The transmitted ultrasound waves are detected by a planar 7-microm high-finesse Fabry-Perot interferometer. Temperature-induced thickness changes in the Fabry-Perot interferometer are tracked to monitor the sample temperature and maintain the sensor sensitivity. The measured -6 dB bandwidth for the combined source and sensor is 1 to 35 MHz, with an attenuation corrected signal level at 100 MHz of -10 dB. The system is demonstrated through temperature-dependent ultrasound measurements in castor oil and olive oil. Power law attenuation parameters are extracted by fitting the experimental attenuation data to a frequency power law while simultaneously fitting the dispersion data to the corresponding Kramers-Krönig relation. The extracted parameters are compared with other calibration measurements previously reported in the literature.

Acoustic wave propagation in barium monochalcogenides in the B1 phase

Temperature dependence of ultrasonic attenuation due to phonon-phonon interaction and thermoelastic loss have been studied in (NaCl-type) barium monochalcogenides [BaX, X = S, Se, Te], in the temperature range 50–500 K; for longitudinal and shear modes of propagation along 〈100〉, 〈110〉, 〈111〉 directions. Second and third order elastic constants have been evaluated using electrostatic and Born repulsive potentials and taking interactions up to next nearest neighbours. Gruneisen parameters, nonlinearity constants, nonlinearity constants ratios and viscous drag due to screw and edge dislocations have also been evaluated for longitudinal and shear waves at 300 K. In the present investigation, it has been found that phonon-phonon interaction is the dominant cause for ultrasonic attenuation. The possible implications of results have been discussed.

Ultrasonic attenuation due to phonon–phonon interaction, thermoelastic loss anddislocation damping in transition metal carbides

Temperature dependent ultrasonic attenuation due to phonon–phonon (p–p) interaction,thermoelastic loss and dislocation damping due to screw and edge dislocations have beeninvestigated in fcc (NaCl B1 type) structured group IVb and Vb monocarbides (transitionmetal carbides, namely TiC, ZrC, HfC, VC, NbC and TaC) in the temperature range50–500 K, along the three crystallographic directions of propagation, namely [100], [110] and[111] for longitudinal and shear modes of propagation. The second- and third-order elasticmoduli (SOEM and TOEM) obtained at different temperatures using the electrostatic andBorn repulsive potentials and taking interactions up to next-nearest neighbours, have beenused to obtain Gruneisen numbers, acoustic coupling constants and their ratios alongdifferent directions of propagation and polarization for longitudinal and shear modes ofwave propagation. Temperature variation of the phonon relaxation time showsexponential decay. The results have been discussed and compared with availabledata.

Physical properties of ferromagnetic-superconducting coexistent system from a mean-field model

We study the nuclear relaxation rate $1∕{T}_{1}$ of a ferromagnetic-superconducting system from the mean field model proposed by Karchev et al. [Phys. Rev. Lett. 86, 846 (2001)]. This model predicts the existence of a set of gapless excitations in the energy spectrum which will affect the properties studied here, such as the density of states and, hence, $1∕{T}_{1}$. The study of the temperature variation of $1∕{T}_{1}$ (for $T<{T}_{c}$) shows that the usual Hebel-Slichter peak exists, but will be reduced because of the dominant role of the gapless fermions and the background magnetic behavior. We have also presented the temperature dependence of ultrasonic attenuation and the frequency dependence of electromagnetic absorption within this model. We are successful in explaining certain experimental results.

Internal friction and Young’s modulus of a carbon matrix for biomorphic silicon carbide ceramics

The amplitude, temperature, and time dependences of the Young’s modulus and internal friction (ultrasonic attenuation) of a eucalyptus-based carbon biomatrix intended for preparing biomorphic silicon carbide ceramics were studied. Adsorption and desorption of molecules of the ambient medium (air) was shown to determine, to a considerable extent, the effective Young’s modulus and acoustic vibration decrement of a specimen. A doublet maximum in the temperature dependence of ultrasonic attenuation was observed at a temperature close to the sublimation temperature of solid CO2. The microplastic properties of the material were estimated from acoustic measurement data.