Ultrasonic Pulse Echo Overlap Technique Research Articles

Detection of anomalies in NLO sulphamic acid single crystals by ultrasonic and thermal studies

The ultrasonic pulse echo overlap technique (PEO) has been used to measure the velocities of 10 MHz acoustic waves in sulphamic acid single crystals in the range of 300–400 K. This study evaluated all the elastic stiffness constants, compliance constants and Poisson’s ratios of the crystal. The temperature variations of the elastic constants have been determined. The phase transition studies above room temperature were investigated using ultrasonic PEO technique. This study has suggested new weak elastic anomalies for the crystal around 330 K. The transverse elastic constants C 44 and C 66 have shown clear thermal hysteresis of 2 K. The present differential scanning calorimetric (DSC) studies carried out at a slow heating rate have also suggested weak phase transition around 331 K. The present elastic and thermal studies have been substantiated by already reported DC electrical conductivity studies around 330 K.

Measurement of Elastic Parameters of Lithium Hydroxylammonium Sulphate Single Crystal, by Ultrasonic Pulse Echo Overlap Technique

Ultrasonics is the most established and precise technique to determine the elastic parameters of materials. Elastic constants are important parameters of a crystal which provide valuable infor-mation about the bonding characteristic between adjacent atomic planes and the anisotropic cha-racter of the bonding and structural ability. Second order elastic constants can be measured by measuring the velocity of the ultrasonic pulses of different polarization along different symmetry directions. Elastic Constants of Lithium Hydroxylammonium Sulphate [LHAS] single crystal by ul-trasonic Pulse Echo Overlap [PEO] technique are reported for the first time. Large single crystals of LHAS of size [26×26×10] mm3 have been grown from supersaturated aqueous solution of the salt by slow evaporation technique over a period of 40 - 45 days at 305 K. Absolute velocities at room temperature (303 K) have been measured for the selected direction and modes with McSkimin criterion. The anisotropy in the elastic properties of LHAS is well studied by measuring ultrasonic velocity in the crystal in certain specified crystallographic directions. The elastic stiffness constants C11, C33, C44, C55, and C66, and Acoustic impedance constants and Rao’s constants in specified directions are evaluated.

Ultrasonic Investigation of Elastic Anomalies in Lithium Sodium Sulphate Hexahydrate Single Crystal

An extensive study of the thermal properties of Lithium Sodium Sulphate Hexa hydrate (LSSW) single crystal, with Trigonal structure, has been carried out using ultrasonic Pulse Echo Overlap (PEO) technique, Differential Thermal Analysis (DTA) and Thermo Gravimetric Analysis (TGA). The temperature variation of elastic constants of LiNa3(SO4)2·6H2O single crystal have been reported for the first time. The second order elastic stiffness constants C11, C33, C44, along the various directions in the crystal have been determined in the temperature range 300 - 330 K. The change in velocity with temperature with respect to the room temperature value has been measured using PEO technique. Significant anomalies were observed in C11 and C33 at 316 K. The elastic constant C12 has shown no variation in the temperature range 300 - 319 K. A minor deviation for C44 at 305 K following a parabolic change has been observed. The minor anomalies observed in the elastic constants of LSSW may be due to its dehydration of water of crystallization in the range 304 - 319 K. DTA studies showed an appreciable endothermic change in the range 309 K-369.79 K. TGA curve exhibited a decrease in weight of 1.687 mg in the temperature range 304 K-360 K. The minor anomalies observed in the elastic constants of LSSW may be due to loosing of its water of crystallization in the range 309 - 319 K. On loosing water there will not be any change in chemical structure but there will be physical change associated with loosing of water molecule.

Aniline and Esters-An Ultrasonic Study

Ultrasonic velocity (v), Density (ρ), Refractive index (n) for binary mixtures of Aniline with Methyl Acetate, Ethyl Acetate and Amyl Acetate have been measured at room temperature of about 300.15 K over entire volume component percentage range. The Ultrasonic velocity (v) is measured using Ultrasonic Pulse Echo Overlap (PEO) technique at a frequency of 2MHz. The density measurements have been carried out by using 10ml specific gravity bottle. Refractive index (n) measurements have been carried out by using Abbe Refractometer. Adiabatic Compressibility (βs) and dielectric constant (Є) were computed using measured data of density, ultrasonic velocity and refractive index.

Improvement in the mechanical performance of Czochralski silicon under indentation by germanium doping

The mechanical properties of germanium-doped Czochralski (GCz) silicon have been investigated using instrumented nanoindentation combined with an ultrasonic pulse-echo overlap technique. The GCz silicon samples showed higher Young’s modulus and hardness than germanium-free Czochralski silicon samples in nanoindentation tests. We believe this was caused by the enhanced phase transition from the Si-I phase to the stiffer Si-II phase in GCz silicon under contact load during indentation. This scenario was further confirmed by micro-Raman spectroscopy measurements.

Al 3+-modified elastic properties of copper ferrite

Ultrasonic pulse echo-overlap technique at 300 K (9 MHz) has been employed to study the elastic properties of Al 3+-substituted CuFe 2O 4 spinel ferrite system. The longitudinal and transverse wave velocities are used to compute elastic moduli and these are corrected to the zero porosity by employing different models. Contrary to expectation, the magnitude of elastic moduli is found to decrease by 75% with only 30% of Al 3+-substitution for Fe 3+ in the system. The lowering of elastic stiffness is mainly due to residual stress-induced spontaneous cracking and presence of oxygen vacant sites in the material. The lower value of lattice energy for polycrystalline specimens as compared to their single crystalline counterparts have been explained in the light of an increase degree of disorientation at the grain boundary with Al 3+-substitution.

Detection of elastic and electric conductivity anomalies in Potassium Sulphamate single crystal

Elastic anomalies in Potassium Sulphamate, (KNH 2SO 3), above room temperature were detected from temperature variation of elastic constants measured by ultrasonic Pulse Echo Overlap technique. Potassium Sulphamate has been reported to be a ferroelectric and piezo electric material. The elastic constants C 11, C 44, C 55 and C 66 have exhibited weak anomalies around 350 K. The DC conductivity measurement along a, b, and c axes also supports this conclusion.

Elastic study of Potassium Sulphamate crystal using ultrasonic Pulse Echo Overlap technique

Elastic properties of Potassium Sulphamate single crystal with chemical formula, KNH 2SO 3 are studied by ultrasonic Pulse Echo Overlap (PEO) technique. It crystallizes in the orthorhombic symmetry with space group Pbcm The study involves measuring ultrasonic velocity in the crystal in certain specified crystallographic directions; all the nine elastic stiffness constants, compliance constants and Poisson’s ratios are evaluated. The polar plots in a – b , a – c and b – c planes of Phase velocity, Slowness, Young’s modulus and Linear compressibility reveal the anisotropy in elastic properties.

Ultrasonic and sonochemical reaction studies of O-Cresols in different solvent mixtures

Ultrasonic and sonochemical reaction studies have been carried out by measuring ultrasonic velocities (ν) in the mixing of phenols like ortho-cresol with esters like ethyl acetate and iso amyl acetate as solvents. The ultrasonic velocities (ν) were measured using ultrasonic pulse echo overlap technique (model UX4400-M) on mixing of o-cresol with solvents at different temperatures. The results are interesting because increase in the acid content in the binary mixture decreases the ultrasonic velocity (ν). Another important feature is the effect of solvents like isoamyl acetate instead of ethyl acetate on the kinetic process. The reaction rate is larger with ethyl acetate as compared to the kinetic rate in isoamyl acetate. The variation of ultrasonic velocity (ν) in the binary mixtures of o-cresol–isoamyl acetate system with sonic waves is also studied and it has been found that the reaction rate decreases due to the passage of sonic waves through the medium. Arrhenious parameters have been computed for o-cresol–isoamyl acetate system. The free energy of activation (ΔF #) has been computed for o-cresol–ethyl acetate system. It is found that heat of activation (E a), entropy of activation (ΔS #) and free energy of activation (ΔF #) are quite in order for this process.

Some nonlinear and linear elastic properties of Ni40Ti50Cu10 near the martensitic transformation

Abstract Linear and nonlinear elastic effects occuring in a single crystal of the ternary alloy Ni 40 Ti 50 Cu 10 were determined with a modified ultrasonic pulse echo-overlap technique at different temperatures. All linear elastic coefficients could be measured above and below the martensitic transformation supplementing the results of [A. Alippi (Ed.), Proceedings of the International Conference on Acoustics, Rome, 2001]. A large jump of the elastic stiffness c 44 could be detected. First nonlinear elastic measurements were performed. No substantial increase of anharmonicity could be found. The maximum stress amplitude was held far below the yield stress of the material.

Ultrasonic measurement of the elastic constants of potassium hydrogen phthalate single crystals

Many organic crystals with orthorhombic symmetry exhibit electro-optic, ferroelectric, and triboluminescence properties. The potassium salt of phthalic acid (KAP), with the formula C8H5O4K, finds application in soft x-ray spectroscopy due to its large d spacing and has been reported to be piezoelectric as well. KAP crystallizes into orthorhombic structure with space group Pca21 All nine elastic constants of KAP have been determined by measuring the velocity of longitudinal and transverse ultrasonic waves propagating along different symmetry directions. Velocities have been measured by the ultrasonic pulse echo overlap technique by injecting waves generated by quartz transducers through a suitable bonding medium into the crystal. The McSkimin Δt correction has been applied to determine the velocities accurately. The temperature variation of selected elastic constants over the range 300–420 K has also been measured and reported.

Elastic properties of bismuth borate glasses

The elastic properties of the vitreous system Bi2O3-B2O3 have been measured by ultrasonic pulse echo overlap technique at a frequency of 10 MHz and at room temperature. For the purpose of measuring the ultrasonic velocity with high accuracy, the McSkimin criterion for determining the correct cyclic overlap between echoes is used. The elastic properties of the present glass system as a function of composition are discussed on the basis of the elastic internal energy due to the deformation. Also presented is a full discussion of the Poisson's ratio; which is found to be rather sensitive to the glass composition.

Ultrasonic investigations of PbO–V2O5–P2O5 glass

The velocity and attenuation of longitudinal and transverse ultrasonic waves in (PbO)x–(V2O5)y–(P2O5)1−x−y glass systems of different compositions have been measured at temperatures between 80 and 300 K using the ultrasonic pulse echo overlap technique at 10 MHz. For each sample the velocity data have been used to find the elastic moduli and Debye temperature at different temperatures. The results indicate that for each sample, the velocities decrease slowly and steadily with increasing temperature. The temperature dependence of ultrasonic attenuation has been explained in terms of a thermally activated relaxation process. On the other hand, the combined effect of relaxation, anharmonicity, and the effect due to frozen-in fluctuation is taken into consideration to explain the variation of velocity with temperature.

Ultrasonic measurement of the elastic constants of LiKSO 4 between 300 and 370 K

All five independent elastic constants of LiKSO 4 have been determined from absolute velocity measurements on single crystal samples using ultrasonic pulse echo overlap technique. The constant C 13 is reported for the first time. Measurement of the temperature variation of elastic constants between 300 and 370 K indicates no anomaly near 333 K, ruling out a phase transition occurring in the sample at this temperature reported in an earlier Brillouin scattering work.

Ultrasonic investigations of CuOP2O5 glass

The ultrasonic velocity and attenuation in four different samples of the (CuO)x(P2O5)1 − x glass system (x = 0.1500, 0.3030, 0.3768, 0.5106) have been measured at temperatures between 80 and 300 K using the ultrasonic pulse echo overlap technique at 10 MHz. The samples were prepared by the melt-quench method. The velocity data have been used to find the elastic moduli and Debye temperature for each composition. The results indicate that, for each composition, the velocities decrease slowly and steadily with increasing temperature and there is no indication of a minimum in the variation of velocity with temperature unlike many other glasses. The dependence of ultrasonic velocity and attenuation with temperature has been interpreted in terms of a thermally activated relaxation process. The model is based on an asymmetric double-well potential having distribution of both the barrier height and the asymmetry between the two wells. Attempts have been made to explain the apparent discrepancy found in the velocity variation between the theory and experiment.

Elastic constants of b.c.c. Li-Mg alloys

Abstract Single crystal elastic constants of Li–Mg alloys with 45–69 at.% Mg were measured using the ultrasonic pulse echo-overlap technique. Results were obtained in the temperature range 4–293 K. A nonlinear variation in elastic constants with temperature is found. A comparison of the experimental values with theoretically calculated elastic constants shows reasonable agreement.

The elastic behaviour of indium under pressure and with temperature up to the melting point

Abstract The ultrasonic pulse-echo overlap technique has been used to measure pressure and temperature dependences of elastic wave propagation velocities along various crystallographic directions in single-crystal indium. The results provide a complete set of the pressure derivatives of the elastic constants of indium between room temperature and the melting point (429·7 K). This in turn has allowed the long-wavelength acoustic mode Gruneisen parameters to be determined over that temperature range. The values obtained for acoustic mode Gruneisen parameters show that there is a significant increase in vibrational anharmonicity as the melting temperature is approached. To allow determination of the thermal Gruneisen parameters γth up to the melting point, the thermal expansion tensor components α11 and α33 have also been measured. The mean zone-centre acoustic mode Gruneisen parameter γe1 is found to be larger than γth owing mainly to the contributions from the more anharmonic slow shear modes (k[110], e[11...

The elastic behaviour of Ce3S4 and La3S4

The hydrostatic pressure and temperature dependences of the elastic stiffnesses of the cubic, Th3P4 structure compounds Ce3S4 and La3S4 have been measured using the ultrasonic pulse echo overlap technique. Although Ce3S4, unlike La3S4 (T c = 103 K), does not undergo a phase transition when its temperature is lowered to 16 K, its elastic stiffnesses (C11-C12)/2 and C11 soften with decreasing temperature (in a similar manner but less markedly than those of La3S4); this lattice instability indicates an incipient phase transition. In both compounds the elastic constants increase under pressure: the long-wavelength acoustic-mode Gruneisen parameters are all positive, and the application of pressure does not induce acoustic phonon-mode softening.

Elastic behavior under hydrostatic pressure and acoustic-mode vibrational anharmonicity of single-crystal berlinite.

The set of the second-order elastic constants and their hydrostatic-pressure derivatives have been obtained for the rhombohedral single-crystal berlinite (${\mathrm{AlPO}}_{4}$) using the ultrasonic pulse echo overlap technique. To quantify the vibrational anharmonicity, the acoustic-mode Gr\"uneisen parameters in the long-wavelength limit have been derived in the quasiharmonic approximation. The results extend previous observations that the elastic and physical behavior of berlinite is quite similar to that of quartz. The hydrostatic-pressure derivative \ensuremath{\partial}${C}_{66}$/\ensuremath{\partial}P has a negative value indicating that the corresponding transverse-acoustic mode softens under pressure; this is in accord with the anomalous positive temperature dependence of ${C}_{66}$. The anomalous behavior of ${C}_{66}$ indicates that there may be even at room-temperature influence of the zone-center optic phonon, whose softening is associated with the \ensuremath{\alpha}-\ensuremath{\beta} structural transformation, on long-wavelength transverse-acoustic phonons propagating in the same crystallographic direction.

The characteristics of abrupt change on elastic constants C33 of LiKSO4 crystal at 60°C

Using the ultrasonic pulse echo overlap technique, we have measured the temperature dependence of the elastic constant C33 of LiKSO4 crystal. The abrupt change of C33 occurs at 60°C, and there is a large temperature hysteresis. On repeated experiments, this abrupt peak of C33 reduces successively. But after a certain time of "seasoning", it appears again.