scholarly journals Investigation of Deuteration Effect on Sound Attenuation in Hydrogen Bonded Ferroelectric Crystals

2011 ◽  
Vol 8 (1) ◽  
pp. 137-141 ◽  
Author(s):  
S. C. Deorani ◽  
P. Singh ◽  
M. S. Yadav
Keyword(s):  
Curie Temperature ◽  
Longitudinal Wave ◽  
Strong Interaction ◽  
Soft Mode ◽  
Ultrasonic Attenuation ◽  
Frequency Range ◽  
Longitudinal Waves ◽  
Crystal Potential ◽  
Frequency Variations ◽  
Curie Temperature Tc

The anomalous ultrasonic attenuation of longitudinal wave propagated in KDP and DKDP have been discussed and calculated near Curie-temperature (Tc) in Para- electric phase in the frequency range 5 to 50 MHz. The attenuation of longitudinal waves is primarily due to a strong interaction with thermally excited phonon in the coupled-soft mode. Temperature and frequency variations of attenuation are discussed. Anharmonicity in the crystal potential is essential to discuss (observe) critical attenuation.

The temperature dependence of the photoinduced soft mode in Sn2P2S6 crystal

2019 ◽  
Vol 33 (08) ◽  
pp. 1950061
Author(s):  
K. A. Brekhov ◽  
N. A. Ilyin ◽  
E. D. Mishina ◽  
P. A. Prudkovskii ◽  
G. Kh. Kitaeva
Keyword(s):  
Phase Transition ◽  
Femtosecond Laser ◽  
Curie Temperature ◽  
Temperature Dependence ◽  
Oscillation Frequency ◽  
Phonon Mode ◽  
Soft Mode ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Curie Temperature Tc

In this paper, we present the results of the temperature dependence studies of the photoinduced phonon mode which appears in a ferroelectric-semiconductor Sn2P2S6 (SPS) crystal under the influence of femtosecond laser pulses. We show that its behavior reminds the soft mode one near the phase transition. However, the observed decrease in the oscillation frequency in the vicinity of Curie temperature Tc is much weaker than previously reported. This can be explained by the shadowing of the pure soft mode by its interaction with other photoinduced modes.

Ultrasonic Testing for Vulcanization Inspection of Natural Rubber

2003 ◽  
Author(s):  
Mongkol Seenawat ◽  
Asa Prateepasen ◽  
Cherdpong Jomdecha
Keyword(s):  
Natural Rubber ◽  
Longitudinal Wave ◽  
Frequency Spectrum ◽  
Ultrasonic Testing ◽  
Ultrasonic Attenuation ◽  
Longitudinal Waves ◽  
Transmission Technique ◽  
Frequency Domains ◽  
Novel Method ◽  
Pulse Echo

This paper presents a novel method to inspect the levels of vulcanization of natural rubber by ultrasonic testing. In the research, test specimens are natural rubbers of type ‘cis-1,4-polyisoprene’ vulcanized at different durations. Piezoelectric contact transducers were used to transmit and receive ultrasonic to/from each sample. Longitudinal waves at nominal frequency of 2, 2.25 and 5 MHz were used to investigate the samples. Experiments were conducted using two techniques: pulse echo and through transmission. The pulse echo technique was applied to inspect the ultrasonic attenuation and the velocity of longitudinal wave of natural rubber. The through transmission technique was implemented to identify the shape and amplitude of the frequency spectrum. The results from both time and frequency domains can be employed to classify the levels of the vulcanization. From the experiments, this ultrasonic testing provides an effective way to inspect the vulcanization of natural rubber with repeatability and allows faster inspection rate than other methods.

Temperature Dependent Raman Scattering in CsTiOAsO4 Single Crystal

1995 ◽  
Vol 398 ◽  
Author(s):  
A.R. Guo ◽  
C.-S. Tu ◽  
Ruiwu Tao ◽  
R.S. Katiyar ◽  
Ruyan Guo ◽  
...  
Keyword(s):  
Soft Mode ◽  
Low Frequency ◽  
High Mobility ◽  
Vibrational Modes ◽  
Frequency Range ◽  
Temperature Dependent ◽  
Higher Symmetry ◽  
Phonon Spectra ◽  
Symmetry Structure ◽  
Increasing Temperature

ABSTRACTThe longitudinal (LO) and transverse (TO) A1 vibrational modes have been measured between 30-1200 cm−1 as a function of temperature (30–1240 K) for CsTiOAsO4 (CTA). The frequencies for all corresponding Raman components shifted to lower frequencies on increasing the temperature, however, there is no typical soft-mode like behavior observed in the measured frequency range. The relative intensities of the low frequency bands increase dramatically with increasing temperature due to high mobility of Cs+ ion. A higher symmetry structure taking place above 940K has been confirmed by changes in the phonon spectra.

scholarly journals An efficient control of Curie temperature TC in Ni–Mn–Ga alloys

2004 ◽  
Vol 272-276 ◽  
pp. 2067-2068 ◽  
Author(s):  
V.V. Khovailo ◽  
V.A. Chernenko ◽  
A.A. Cherechukin ◽  
T. Takagi ◽  
T. Abe
Keyword(s):  
Curie Temperature ◽  
Efficient Control ◽  
Curie Temperature Tc

scholarly journals Effect of Ca-substitution on the Magnetic and Dielectric Properties of Mn-Zn Ferrites

2012 ◽  
Vol 4 (2) ◽  
pp. 297 ◽  
Author(s):  
M. M. Rahman ◽  
P. K. Halder ◽  
F. Ahmed ◽  
T. Hossain ◽  
M. Rahaman
Keyword(s):  
Dielectric Constant ◽  
Curie Temperature ◽  
Loss Tangent ◽  
Sintering Temperature ◽  
Initial Permeability ◽  
Q Factor ◽  
Dielectric Polarization ◽  
Ca Substitution ◽  
Magnetic And Dielectric Properties ◽  
Curie Temperature Tc

Spinel Mn-Zn ferrites with composition MnxZn0.4Ca0.6-2xFe2+xO4, where x = 0.10, 0.15, 0.20, 0.25 and 0.30 have been prepared by conventional ceramic technique sintered at    1300 °C for 4 hours. The influence of Ca-substitution on various properties of Mn-Zn ferrites have been studied in this work. Investigations were carried out by the measurements of Curie temperature, permeability, loss tangent, Q-factor, dielectric constant and AC resistivity of the samples. Curie temperature (Tc), the real part of initial permeability (µ´), loss tangent (tan ?), and AC resistivity have been found to be decreased while the Q-factor increases with the increase in Ca-content. The frequency characteristics of the dielectric constant and AC resistivity have been found to be decreased as the frequency increases. Maxwell-Wagner interfacial type of dielectric polarization was observed with the addition of Ca-content over the entire range of frequency considered. Keywords: Spinel ferrites; Sintering temperature; Initial permeability; Dielectric constant.© 2012 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi: http://dx.doi.org/10.3329/jsr.v4i2.9752 J. Sci. Res. 4 (2), 297-306 (2012)

Magnetic Properties and Magnetostriction of ZnxNi1-x MnSb Alloys

2005 ◽  
Vol 475-479 ◽  
pp. 1715-1718
Author(s):  
S.K. Ren ◽  
G.B. Ji ◽  
Song Ling Huang ◽  
Q.Q. Cao ◽  
Feng Ming Zhang ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Curie Temperature ◽  
Structural Phase ◽  
Solid State Reaction Method ◽  
Experimental Result ◽  
Xrd Pattern ◽  
Zn Concentration ◽  
Magnetostriction Coefficient ◽  
The Relationship ◽  
Curie Temperature Tc

We have investigated the magnetic properties and magnetostriction of ZnxNi1-xMnSb compounds prepared by solid state reaction method. It is found that for x less than 0.6 the magnetization of ZnxNi1-xMnSb almost remains unchanged. However, when x is larger than 0.6 the magnetization starts to drop linearly. Experimental result indicates that at low Zn concentrations, x < 0.7, the Curie temperature (TC) decreases with increasing Zn concentration x. However, when x > 0.7, the Curie temperature increases distinctly with increasing x. The Zn concentrartion dependence of magnetostrictive ceofficient is also studied. The experimental curve shows that when x < 0.6 the value of magnetostriction coefficient for ZnxNi1-xMnSb decreases linearly with the increasing Zn concentration x. However, when x is above 0.6, the magnetostrictive ceofficient raises distinctly. By analyzing the XRD pattern, the structures of the materials are examined and the relationship between the properties and the structures are discussed. A structural phase transition is observed. It has been indicated that the structure plays an important role in the magnetic and magnetostrictive properties of the system.

Numerical simulation of internal defect imaging with the longitudinal wave generated by laser induced ultrasonic array

2020 ◽  
pp. 2150103
Author(s):  
Hao Sui ◽  
Kesi Li ◽  
Zhenyu Zhu ◽  
Le Cheng ◽  
Xiaorong Gao ◽  
...  
Keyword(s):  
Longitudinal Wave ◽  
Phased Arrays ◽  
Synthetic Aperture ◽  
Wave Component ◽  
The Finite Element Method ◽  
Internal Defect ◽  
Longitudinal Waves ◽  
Synthetic Aperture Focusing ◽  
Synthetic Aperture Focusing Technique ◽  
Defect Imaging

To verify the performance of longitudinal waves induced by laser phased arrays (LPA) for detection and quantitative evaluation in internal defects, the finite element method (FEM) is utilized to establish the models of LPA scanning processing. The interaction of longitudinal wave and internal defect is analyzed. Besides, the two components of the reflected longitudinal waves (the longitudinal wave component [Formula: see text] and the shear wave component [Formula: see text] are focused on the imaging of defects with the synthetic aperture focusing technique (SAFT) and total focusing method (TFM) algorithms. It shows that the imaging of internal sub-millimeter defect is obtained using the LPA. The defect size and location are simultaneously calculated, with the relative error being 6.7% and 2.9%, respectively. The proposed longitudinal wave-based LPA is a promising method for the imaging and evaluation of internal micro defects.

scholarly journals A Study on Fatigue State Evaluation of Rail by the Use of Ultrasonic Nonlinearity

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2698
Author(s):  
Bo Zhu ◽  
Jaesun Lee
Keyword(s):  
Longitudinal Wave ◽  
Second Harmonic ◽  
Early Stage ◽  
Wave Mixing ◽  
Third Harmonic ◽  
Longitudinal Waves ◽  
Testing Method ◽  
State Evaluation ◽  
Stress Fatigue ◽  
Train Safety

Nonlinear ultrasonic testing has been accepted as a promising manner for evaluating material integrity in an early stage. Stress fatigue is the main threats to train safety, railways examinations for stress fatigue are more significant and necessary. A series of ultrasonic nonlinear wave experiments are conducted for rail specimens extracted from railhead with different degree of fatigue produced by three-point bent loading condition. The nonlinear parameter is the indicator of nonlinear waves for expressing the degree the fatigue. The experimental results show that the sensitivity of a third harmonic longitudinal wave is higher than second harmonic longitudinal wave testing. As the same time, collinear wave mixing shows strong relative with fatigue damages than a second longitudinal wave nondestructive testing (NDT) method and provides more reliable results than third harmonic longitudinal waves nonlinear testing method.

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