Longitudinal Ultrasonic Velocity Research Articles

The compressibility of silicate liquids containing Fe2O3 and the effect of composition, temperature, oxygen fugacity and pressure on their redox states

Ultrasonic longitudinal acoustic velocities in oxidized silicate liquids indicate that the pressure derivative of the partial-molar volume of Fe2O3 is the same in iron-rich alkali-, alkaline earth- and natural silicate melt compositions at 1 bar. The dV/dP for multicomponent silicate liquids can be expressed as a linear combination of partial-molar constants plus a positive excess term for Na2O−Al2O3 mixing. Partial-molar properties for FeO and Fe2O3 components allow extension of the empirical expression of Sack et al. (1980) to permit the calculation of Fe-redox equilibrium in a natural silicate liquid as a function of composition, temperature, fo2 and pressure; a more formal thermodynamic expression is presented in the Appendix. The predicted equilibrium fo2 of natural silicate melts, of fixed oxygen content, closely parallels that defined by the metastable assemblage fayalite+magnetite+β-quartz (FMQ), in pressure-temperature space. A silicate melt initially equilibrated at 3 GPa and FMQ, will remain within approximately 0.5 log10 units of FMQ during its closed-system ascent. Thus, for magmas closed to oxygen, iron-redox equilibrium in crystal-poor pristine glassy lavas represents an excellent probe of the relative oxidation state of their source regions.

Use of longitudinal ultrasonic velocity as a predictor of elastic moduli and density of sintered uranium dioxide

Nondestructive characterization of sintered uranium dioxide using ultrasonics is addressed. The values of elastic moduli and ultrasonic velocity of uranium dioxide as a function of pore volume fraction are compared with the predicted values of elasticity and self-consistent scattering theories. Analysis of data shows that the longitudinal ultrasonic velocity may be used as a predictor of density and elastic moduli and that the relationship between the elastic moduli and longitudinal velocity is linear over a change of Young's modulus by 50%

Phase diagram of UPt3 from ultrasonic velocity measurements.

We present measurements of longitudinal ultrasonic velocity on single crystals of the heavy-fermion superconductor ${\mathrm{UPt}}_{3}$. The measurements show clear signatures of second-order phase transitions in the superconducting state, with the velocity anomalies well accounted for by Ginzburg-Landau theory. From these signatures we construct a phase diagram for ${\mathrm{UPt}}_{3}$ that reveals all the boundary lines that have been identified as possible phase transitions. We are able to track the phase transition lines to a tetracritical point, located on the upper-critical-field curve, to within the width of the normal-superconducting transition.

Elastic properties and thermal expansion of the UNi 5− xCu x system

Measured values of longitudinal and transverse ultrasonic velocities are given between 10 and 300 K for polycrystalline samples of UNi 5− x Cu x after correction for thermal expansion.

Nondestructive evaluation of elastic parameters of sintered iron powder compacts

A systematic study of the variation of elastic moduli and Poisson's ratio of sintered iron compacts of porosity (up to 21.6%) has been carried out by measuring longitudinal and shear ultrasonic velocities. The variation of these parameters with porosity is compared with predictions of elasticity and scattering theories. Further, a linear relationship was observed between the elastic moduli and the ultrasonic velocities and the use of ultrasonic velocity as a predictor of elastic moduli is therefore recommended for porous materials.

Ultrasonic techniques in evaluation of metal matrix particulate composites

Gravity- and pressure-die-cast aluminium alloy-ceramic particle composites containing dispersions of alumina and zircon particles were characterized using a pulse echo ultrasonic technique. Good agreement was obtained between the experimental and theoretical values of longitudinal ultrasonic velocities and moduli in the case of low (less than 1%) porosity composites. By suitably controlling the casting conditions to reduce porosity levels below 1%, these ultrasonic measurements can be used for rapid determination of the volume percentage of particles in a production unit.

Ultrasonic investigation of phase transition and relaxational phenomena in superionic nasicon

Longitudinal ultrasonic wave velocity and attenuation and also complex electric conductivity temperature and frequency dependencies have been measured in superionic Na 3Zr 2Si 2PO 12. At phase transition near T c=450 K the minimum of ultrasonic velocity and attenuation peak as well as two regions of ultrasonic relaxation in room temperature phase have been observed. The comparison of acoustic and electric measurements indicated that one of the relaxations is caused by acoustoionic interaction inside crystallites and the other by modulation of intercrystalline barriers.

Anomalies of ultrasonic velocity in high-T c ceramics YBa 2Cu 3O y and BiSrCaCu 2O y

Ultrasonic longitudinal velocity and adsorption have been measured in ceramic superconductors YBa 2Cu 3O y with various porosity and also in BiSrCaCu 2O y . A velocity drop of about 400 ppm was found at T c only in the measurements on cooling. The magnitude of the velocity drop is anomalously large compared with the value expected from the thermodynamics. A hysteresis of velocity with respect to temperature was observed in all the samples studied. It is suggested that some structural change at pore size level is responsible for this phenomenon.

Determination of ultrasonic velocity in human enamel and dentine

Acoustic velocity data have been obtained preparatory to investigation of high frequency ultrasound as a non-invasive imaging technique for dental hard tissues and their pathology. In vitro studies were conducted on extracted human permanent teeth. Pulse-echo ultrasound of 18 MHz centre frequency and approx. 150 ns pulse duration successfully detected the front and back surfaces of 0.45 – 1.07 mm thick sections of enamel and of dentine. Water was used as the coupling agent. The oscilloscope traces of the echoes from pure enamel and pure dentine were similar. The longitudinal ultrasonic velocities for pure enamel and dentine were experimentally determined for a number of teeth in different planes of section. For enamel in longitudinal and transverse sections, the mean ultrasonic velocities were 6150 ± 140 and 6500 ± 190m/s respectively. For dentine in longitudinal section, the mean ultrasonic velocity was 4050 ± 30m/s.

A remote laser system for ultrasonic velocity measurement at high temperatures

The temperature dependence of the longitudinal ultrasonic velocity in iron and Dural has been obtained using a totally remote laser technique. The ultrasound is generated by irradiation of one face of a sample with a Q-switched Nd:YAG laser pulse and is detected on the opposite face using a modified Michelson laser interferometer. The system has proved capable of measurements up to temperatures in excess of 1000 °C, with an absolute accuracy in velocity of ±1%, and relative accuracies of better than 0.1%. Anomalies in the data for iron have been discerned at the Curie temperature of ∼768 °C, due to the ferromagnetic to the paramagnetic phase transition, and at 910 °C due to the crystallographic phase transition from ferrite to austenite.

Use of ultrasonic velocity for nondestructive evaluation of ferrite content in duplex stainless steels

The possibility of using ultrasonic velocity measurements for the nondestructive estimation of the ferrite content in duplex stainless steels has been explored. The variation of the longitudinal ultrasonic velocity in specially prepared duplex stainless steel coupons having a ferrite content in the range 40–55 vol% has been studied using an ultrasonic thickness/velocity meter. The longitudinal wave velocity has been correlated to the ferrite content of the samples estimated by X-ray diffraction and quantitative image analysis.

Brillouin spectrum of Ca(OH) 2

Brillouin spectrum of several directions, such as [0,0,1], [0,1,1]/✓2, [0,1,0] and [1,/✓2,1/2,1/2] of Ca(OH) 2 crystals were measured. The elastic stiffness coefficients c 11, c 33, c 44, c 66 and c 13 are estimated to be (in N/m 2 × 10 10): 9.928±0.15, 3.260±0.2, 0.985±0.2, 3.155±0.15 and 2.965±1.5, respectively. Large dispersion of ultrasonic and hypersonic longitudinal velocities is noted.

Measurement of small elastic anisotropy in solids using laser-induced ultrasonic pulses

Nondestructive laser-induced short ultrasonic pulse generation (duration ≊10 ns) together with broadband detection is used to detect and measure the small elastic anisotropy in opaque solids quickly and precisely. This is demonstrated for an extruded aluminum alloy type 6061-T6. A single laser-induced acoustic pulse propagation measurement over a path length of 47 mm provides a longitudinal ultrasonic velocity measurement accuracy of 0.02%. The longitudinal velocities at ±45° from the extruding direction Z are found to be 2% larger than the velocity along Z, indicating that most of the aluminum crystallites are oriented with a principal axis parallel to Z. Thermal annealing of the sample results in a small increase in ultrasonic veolcity in all directions with the observed acoustic anisotropy remaining essentially unchanged.

Use of ultrasonic velocity for measurement of density of sintered fuel pellets

The possibility of using ultrasonic wave velocity measurements for monitoring sintered density of nuclear fuel pellets has been explored. The variation of longitudinal ultrasonic velocity in sintered uranium dioxide pellets in the range of 89-96% of theoretical density has been studied using an ultrasonic thickness/velocity meter. The longitudinal wave velocity has been correlated with the density of sintered uranium dioxide pellets. The possible applications of this nondestructive evaluation technique in the quality control of nuclear fuels is discussed.

Acoustic characterization of changes in viscoelastic properties of epoxy during cure

The transformation of an epoxy during cure from a viscoelastic liquid to a viscoelastic solid is characterized by the change in the shear and longitudinal ultrasonic velocities and attenuations. The measurement of these ultrasonic properties is reported for several different resins cured at room temperature. The velocities are used to calculate the bulk and shear moduli as a function of cure time. The results indicate a parallel development during cure of the shear and bulk moduli. Measurements of the longitudinal attenuation at several different frequencies indicate the viscoelastic response can be characterized by a single relaxation time which increases as the cure progresses.

Alkali treatment of coir fibres for coir-polyester composites

Coir fibres were subjected to alkali treatment with a view to improving the wettability of coir fibres by a commercially available resin such as polyester. Tensile strength of the fibres increases by 15% when the fibres are soaked in 5% aqueous solution of NaOH at 28±1° C for 72 to 76 h after which it shows a gradual decrease. This decrease is much more pronounced when the alkali is replenished after every 24 h. SEM observations showed the removal of cuticle and tyloses from the surface of coir as a result of alkali treatment, resulting in a rough fibre surface with regularly spaced pits. The debonding stress of alkali-treated fibres from polyester matrix was 90% higher than that of untreated fibres from the same matrix. Untreated fibres tended to float in the polyester whereas alkali-treated fibres were uniformly dispersed in polyester. Incorporation of 0.30 volume fraction of untreated and treated fibres in polyester resulted in composites having 11% and less 5% porosity, respectively. Flexural strength, modulus and impact strength of composites containing alkali-treated fibres were 40% higher than those containing the same volume fractions of untreated fibres. Longitudinal ultrasonic velocity and sound attenuation measurements indicated less fibre segregation and better fibre-matrix bonding in composites containing alkali-treated fibres.

Magnetic behaviour of dilute Cr-Al alloys from sound velocity measurements

Measurements of the longitudinal ultrasonic wave velocity in a series of dilute Cr-Al alloys as a function of temperature have shed new light on the magnetic behaviour of compositions in the range 2 ≲ c ≲ 4 at% al.

Use of neutron diffraction texture measurements to establish a model for calculation of ultrasonic velocities in highly oriented austenitic weld material

Neutron diffraction has been used to measure the crystallite orientation distribution function for a cubic test sample of highly textured austenitic weld material. The longitudinal and transverse ultrasonic velocities in three orthogonal directions in the sample have been calculated from this function and compared with measured values for the sample. The Voigt approximation is found to give good agreement with experiment and appears to be the most useful approach for the calculation of ultrasonic velocities in highly textured materials.

On magnetoelastic dispersion in a nickel single crystal at high frequencies

The longitudinal ultrasonic velocity dispersion due to domains (Δ E effect) in a nickel single crystal has been measured in the frequency range 8 to 270 MHz. The velocity decreases with the increase of frequency but remains finite upto a frequency of 270 MHz. A relaxational approach with two relaxation frequencies, one at lower MHz region and the other at higher MHz region, fit the data well. The results for [111] and [1 1 0 directions of propagation require different relaxation frequencies.

High temperature acoustic bond compatible with fluoride fluorites

In order to study metal fluorides of the fluorite structure at temperatures greater than 650 °K using ultrasonic techniques, several previously reported acoustic bonds were found to be inadequate. DuPont 9770 silver–platinum paste has been found to act as an effective acoustic bond for longitudinal ultrasound in contrast to the usual high temperature oxide acoustic bonds which break because they interact strongly with fluoride materials. Measurements of longitudinal ultrasonic velocities have been made up to 796 °K in [110] oriented CdF2 and up to 850 °K in [100] oriented BaF2. In neither of these measurements did the bonds break at the highest temperatures.