CYCLIC DEFORMATION OF FACE CENTERED CUBIC CRYSTALS AND ITS DISLOCATION INTERACTION MODEL——Ⅱ.DISLOCATION INTERACTION MODEL OF CYCLIC DEFORMATION

A dislocation interaction model has been proposed for cyclic deformation of fcc crystals.Ac- cording to this model,cyclic stress-strain responses and saturation dislocation structures of a crystal are associated with the modes and intensities of dislocation interactions between slip systems active in the crystal; and,hence,may be predicted by the location of its tensile axis in the crystallographic triangle.This model has successfully explained the different behaviours of double-slip crystals and multi-slip behaviours of some crystals with orientations usually con- sidered as single-slip ones.

Response of loose bonding on reflection and transmission of elastic waves at interface between elastic solid and micropolar porous cubic crystal

The problem of reflection and transmission of plane periodic waves incident on the interface between the loosely bonded elastic solid and micropolar porous cubic crystal half spaces is investigated. This is done by assuming that the interface behaves like a dislocation, which preserves the continuity of traction while allowing a finite amount of slip. Amplitude ratios of various reflected and transmitted waves have been depicted graphically. Some special cases of interest have been deduced from the present investigation.

Propagation of plane waves in thermoelastic cubic crystal material with two relaxation times

A problem concerned with the reflection and refraction of thermoelastic plane waves at an imperfect interface between two generalized thermally conducting cubic crystal solid half-spaces of different elastic and thermal properties with two relaxation times has been investigated. The generalized thermoelastic theory with two relaxation times developed by Green and Lindsay has been used to study the problem. The expressions for the reflection and refraction coefficients which are the ratios of the amplitudes of reflected and refracted waves to the amplitude of incident waves are obtained for an imperfect boundary and deduced for normal stiffness, transverse stiffness, thermal contact conductance, slip and welded boundaries. Amplitude ratios of different reflected and refracted waves for different boundaries with angle of emergence have been compared graphically for different incident waves. It is observed that the amplitude ratios of reflected and refracted waves are affected by the stiffness and thermal properties of the media.

Rayleigh-Type Wave in A Rotated Piezoelectric Crystal Imperfectly Bonded on a Dielectric Substrate

Propagation characteristics of Rayleigh-type wave in a piezoelectric layered system are theoretically investigated.The piezoelectric layer is considered as a cubic crystal with finite thickness rotated about Y-axis and is imperfectly bonded onto a semi-infinite dielectric substrate.The imperfect interface between the two constituents is assumed to be mechanically compliant and dielectrically weakly conducting.The exact dispersion relations for electrically open or shorted boundary conditions are obtained.The numerical results show that the phase velocity of Rayleigh-type wave is symmetric with respect to the cut orientation of 45°and can achieve the maximum propagation speed in this orientation.The mechanical imperfection plays an important role in the dispersion relations,further the normal imperfection can produce a significant reduction of phase velocity comparing with the tangential imperfection.Comparing with the mechanical imperfection the electrical imperfection makes a relatively small reduction of phase velocity of Rayleigh-type wave.The obtained results can provide some fundamentals for understanding of piezoelectric semiconductor and for design and application of piezoelectric surface acoustic wave devices.

Growth and Optical Spectra of Tb^(3+)/Eu^(3+) Co-doped Cubic NaYF_4 Single Crystal for White Light Emitting Diode

High quality Tb^3＋/Eu^3＋ co-doped cubic NaYF 4 single crystal in the size of Φ1.0 cm×6.6 cm was grown by a modified Bridgman method using KF as assistant flux for NaF-YF 3 system under the condition of completely closed Pt crucible.A white light emission from the combination of the violet-blue,blue,green,orange,and red lights with chromaticity coordinates of x = 0.3107,y = 0.3274,correlated color temperature of T c = 6637 K,color rendering index of R a = 83,and color quality scale of Q a = 82 could be obtained from 1.51 mol%Tb^3＋ and 1.42 mol%Eu^3＋ co-doped cubic NaYF 4 single crystal when being excited by a 369 nm light.This indicates that Tb^3＋/Eu^3＋）co-doped cubic NaYF 4 single crystal has a potential application in white light emitting diode excited by ultraviolet light.

Effect of rare earth(Nd^(3+))metal doping on structural,morphological,optical and magnetic traits of Zn-Mg nano-ferrites

Herein,we report the synthesis of Zn_(0.7)Mg_(0.3)Nd_(x)Fe_(2-x)O_(4)(where,x=0,0,0,01,0,02)ferrite nanoparticles by employing the sol-gel auto-combustion technique.The X-ray diffraction(XRD)pattern suggests the formation of a pure cubic structure,without any impurity phase,with an Fd3m space group at room temperature.With increasing doping amount,the crystallite size is reported as 35-41 nm,while the lattice parameters rise from 0.8381 to 0.8395 nm.Field emission scanning electron microscopy(FESEM)images show the formation of spherical grains with agglomerated morphology in all the samples,with grain sizes ranging from 49 to 103 nm.Energy dispersive X-ray spectroscopy(EDX)and elemental mapping investigation confirm the chemical purity of all the samples.Fourier transform infrared(FTIR)analysis shows the presence of two prominent peaks around 440 and 560 cm^(-1)that correspond to the octahedral and tetrahedral positions.In addition,the existence of five Raman active vibratio nal modes in all produced specimens again confirms the structural purity of all the samples.The M-H curve shows that saturation magnetization(M_(s))first increases from 14.98 to 28.22 emu/g and then decreases to 18.98emu/g with increasing doping amount.This is due to the A-B type super-exchange interaction for the synthesized samples.The variation in coercivity(H_(c))and magnetic anisotropy(K_(1))suggest the thermal stability of all the samples and can be utilized in transformers and solenoids.