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G. Z. Yang - One of the best experts on this subject based on the ideXlab platform.
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Improved dielectric properties and tunability of multiLayered thin films of (Ba0.80Sr0.20)(Ti1−xZrx)O3 with compositionally Graded Layer
Applied Physics Letters, 2004Co-Authors: Can Wang, B. L. Cheng, S. Y. Wang, H. B. Lu, Y. L. Zhou, Z. H. Chen, G. Z. YangAbstract:MultiLayered thin films of (Ba0.80Sr0.20)(Ti1−xZrx)O3 (BSTZ) with compositionally Graded Layer (CGL) have been fabricated by pulsed laser deposition on Pt/TiO2/SiO2/Si substrate. In each CGL, four individual Layers of BSTZ with x=0.36, 0.18, 0.08 and 0 are grown in series with equal thickness. Three kinds of thin-film CGL samples comprising one, two or four CGLs have been elaborated with the final same thickness, and the thickness of each CGL is accordingly varied in different samples to achieve the gradients of composition. The crystalline structures of the CGL thin films are successively characterized using x-ray diffraction and their electrical properties such as ac dielectric properties and polarizations are investigated. Improved dielectric properties and tunability of permittivity have been observed in the multiLayered CGL films compared to single-Layer BSTZ films prepared in the identical condition. Furthermore, with increasing gradients of compositions in the CGL multiLayered films, the dielectric...
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improved dielectric properties and tunability of multiLayered thin films of ba0 80sr0 20 ti1 xzrx o3 with compositionally Graded Layer
Applied Physics Letters, 2004Co-Authors: Can Wang, B. L. Cheng, S. Y. Wang, H. B. Lu, Y. L. Zhou, Z. H. Chen, G. Z. YangAbstract:MultiLayered thin films of (Ba0.80Sr0.20)(Ti1−xZrx)O3 (BSTZ) with compositionally Graded Layer (CGL) have been fabricated by pulsed laser deposition on Pt/TiO2/SiO2/Si substrate. In each CGL, four individual Layers of BSTZ with x=0.36, 0.18, 0.08 and 0 are grown in series with equal thickness. Three kinds of thin-film CGL samples comprising one, two or four CGLs have been elaborated with the final same thickness, and the thickness of each CGL is accordingly varied in different samples to achieve the gradients of composition. The crystalline structures of the CGL thin films are successively characterized using x-ray diffraction and their electrical properties such as ac dielectric properties and polarizations are investigated. Improved dielectric properties and tunability of permittivity have been observed in the multiLayered CGL films compared to single-Layer BSTZ films prepared in the identical condition. Furthermore, with increasing gradients of compositions in the CGL multiLayered films, the dielectric...
Liaoliang Ke - One of the best experts on this subject based on the ideXlab platform.
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thermoelastic contact instability of a functionally Graded Layer and a homogeneous half plane
International Journal of Solids and Structures, 2014Co-Authors: Liaoliang Ke, Yue-sheng WangAbstract:Abstract The conductive heat transfer between two elastic bodies in the static contact can cause the system to be unstable due to the interaction between the thermoelastic distortion and pressure-dependent thermal contact resistance. This paper investigates the thermoelastic contact instability of a functionally Graded material (FGM) Layer and a homogeneous half-plane using the perturbation method. The FGM Layer and half-plane are exposed to a uniform heat flux and are pressed together by a uniform pressure. The material properties of the FGM Layer vary exponentially along the thickness direction. The characteristic equation governing the thermoelastic stability behavior is obtained to determine the stability boundary. The effects of the gradient index, Layer thickness and material combination on the critical heat flux are discussed in detail through a parametric study. Results indicate that the thermoelastic stability behavior can be modified by adjusting the gradient index of the FGM Layer.
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Stress Analysis for an Elastic Semispace with Surface and Graded Layer Coatings under Induced Torsion
Mechanics Based Design of Structures and Machines, 2014Co-Authors: Liaoliang Ke, Yue-sheng Wang, Yong-ming XingAbstract:In this paper, the axisymmetric torsional problem of a coating structure consisting of a surface coating, a functionally Graded Layer and a substrate under a rigid cylindrical punch is investigated. The coating and substrate are homogeneous materials with distinct physical properties while the intermediate Layer is inhomogeneous with its shear modulus changing exponentially along the thickness direction. The Hankel integral transform technique is employed to reduce the torsional problem to a singular integral equation with a Cauchy kernel. The circumferential shear stress and displacement fields in the coating structure are calculated by solving the integral equation numerically. The results show that the stiffness ratio has significant effect on the distribution of the circumferential stress and displacement at the interface.
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two dimensional contact problem for a coating Graded Layer substrate structure under a rigid cylindrical punch
International Journal of Mechanical Sciences, 2008Co-Authors: Jie Yang, Liaoliang KeAbstract:The two-dimensional frictionless contact problem of a coating structure consisting of a surface coating, a functionally Graded Layer and a substrate under a rigid cylindrical punch is investigated in this paper. The coating and substrate are homogeneous materials with distinct physical properties, while the intermediate Layer is inhomogeneous with its shear modulus changing arbitrarily along the thickness direction. To approximate the through-thickness variation, a piecewise linear multi-Layer model is used and the Graded Layer is divided into a number of sub-Layers whose shear modulus is assumed to vary linearly. Poisson's ratio, however, is taken as a constant within the structure for simplicity. By using the transfer matrix method and Fourier integral transform technique, the governing equations are reduced to a Cauchy singular integral equation which is numerically solved to determine the normal contact pressure, contact region, the through-thickness stress fields and longitudinal stress distributions at interfaces. A parametric study is conducted, showing that both normal contact pressure and stress fields in the structure are significantly influenced by the shear modulus ratio and the thickness ratio of the exponentially Graded Layer but are less sensitive to the gradient index of the Graded Layer whose shear modulus follows a power law variation.
Kang L. Wang - One of the best experts on this subject based on the ideXlab platform.
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Experimental study of a surfactant-assisted SiGe Graded Layer and a symmetrically strained Si/Ge superlattice for thermoelectric applications
Thin Solid Films, 2000Co-Authors: Kang L. Wang, C. D. Moore, Mark S. Goorsky, Theodorian Borca-tasciuc, Gang ChenAbstract:Abstract A method to grow high-quality SiGe Graded buffer Layer is presented. The main concept of the method is to use Sb as a surfactant when growing SiGe Graded Layers. Compared with a Si 0.5 Ge 0.5 Graded sample without Sb surfactant, the Sb-assisted Si 0.5 Ge 0.5 Graded Layer has much smoother surface and a significantly lower threading dislocation density. Thermal conductivity of a symmetrically strained Si/Ge superlattice grown on Sb-assisted Si 0.5 Ge 0.5 Graded Layer is also presented.
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a surfactant mediated relaxed si0 5ge0 5 Graded Layer with a very low threading dislocation density and smooth surface
Applied Physics Letters, 1999Co-Authors: C. D. Moore, Mark S. Goorsky, G D Uren, Y Lu, Shawn G Thomas, Kang L. WangAbstract:A method to grow a relaxed Si0.5Ge0.5 Graded Layer with a very smooth surface and a very low threading dislocation density using solid-source molecular-beam epitaxy is reported. This method included the use of Sb as a surfactant for the growth of a 2 μm compositionally Graded SiGe buffer with the Ge concentration linearly Graded from 0% to 50% followed by a 0.3 μm constant Si0.5Ge0.5 Layer. The substrate temperature was kept at 510 °C during the growth. Both Raman scattering and x-ray diffraction were used to determine the Ge mole fraction and the degree of strain relaxation. Both x-ray reflectivity and atomic force microscopy measurements show a surface root mean square roughness of only 20 A. The threading dislocation density was determined to be as low as 1.5×104 cm−2 as obtained by the Schimmel etch method. This study shows that the use of a Sb surfactant and low temperature growth is an effective method to fabricate high-quality Graded buffer Layers.
Can Wang - One of the best experts on this subject based on the ideXlab platform.
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Improved dielectric properties and tunability of multiLayered thin films of (Ba0.80Sr0.20)(Ti1−xZrx)O3 with compositionally Graded Layer
Applied Physics Letters, 2004Co-Authors: Can Wang, B. L. Cheng, S. Y. Wang, H. B. Lu, Y. L. Zhou, Z. H. Chen, G. Z. YangAbstract:MultiLayered thin films of (Ba0.80Sr0.20)(Ti1−xZrx)O3 (BSTZ) with compositionally Graded Layer (CGL) have been fabricated by pulsed laser deposition on Pt/TiO2/SiO2/Si substrate. In each CGL, four individual Layers of BSTZ with x=0.36, 0.18, 0.08 and 0 are grown in series with equal thickness. Three kinds of thin-film CGL samples comprising one, two or four CGLs have been elaborated with the final same thickness, and the thickness of each CGL is accordingly varied in different samples to achieve the gradients of composition. The crystalline structures of the CGL thin films are successively characterized using x-ray diffraction and their electrical properties such as ac dielectric properties and polarizations are investigated. Improved dielectric properties and tunability of permittivity have been observed in the multiLayered CGL films compared to single-Layer BSTZ films prepared in the identical condition. Furthermore, with increasing gradients of compositions in the CGL multiLayered films, the dielectric...
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improved dielectric properties and tunability of multiLayered thin films of ba0 80sr0 20 ti1 xzrx o3 with compositionally Graded Layer
Applied Physics Letters, 2004Co-Authors: Can Wang, B. L. Cheng, S. Y. Wang, H. B. Lu, Y. L. Zhou, Z. H. Chen, G. Z. YangAbstract:MultiLayered thin films of (Ba0.80Sr0.20)(Ti1−xZrx)O3 (BSTZ) with compositionally Graded Layer (CGL) have been fabricated by pulsed laser deposition on Pt/TiO2/SiO2/Si substrate. In each CGL, four individual Layers of BSTZ with x=0.36, 0.18, 0.08 and 0 are grown in series with equal thickness. Three kinds of thin-film CGL samples comprising one, two or four CGLs have been elaborated with the final same thickness, and the thickness of each CGL is accordingly varied in different samples to achieve the gradients of composition. The crystalline structures of the CGL thin films are successively characterized using x-ray diffraction and their electrical properties such as ac dielectric properties and polarizations are investigated. Improved dielectric properties and tunability of permittivity have been observed in the multiLayered CGL films compared to single-Layer BSTZ films prepared in the identical condition. Furthermore, with increasing gradients of compositions in the CGL multiLayered films, the dielectric...
Seyed Rasoul Atashipour - One of the best experts on this subject based on the ideXlab platform.
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reduction of the stress concentration factor in a homogeneous panel with hole by using a functionally Graded Layer
Composites Part B-engineering, 2014Co-Authors: Roberta Sburlati, Seyed Rasoul AtashipourAbstract:This work aims at understanding the effect of a radially heterogeneous Layer around the hole in a homogeneous plate on the stress concentration factor. The problem concerns a single hole in a plate under different far-field in-plane loading conditions. By assuming a radial power law variation of Young's modulus and constant value for Poisson's ratio, the governing differential equations for plane stress conditions, and general in-plane loading conditions are studied. The elastic solutions are obtained in closed form and, in order to describe localized interface damage between the ring and the plate, two different interface conditions (perfectly bonded and frictionless contact) are studied. The formulae for the stress concentration factors are explicitly given for uniaxial, biaxial and shear in-plane loading conditions and comparisons with interface hoop stress values are performed. The solutions are investigated to understand the role played by the geometric and Graded constitutive parameters. The results are validated with numerical finite element simulations in which some simplified hypotheses assumed in the analytical model, are relaxed to explore the range of validity of the elastic solution presented. In this way the results obtained are useful in tailoring the parameters for specific applications.
