Ga dopping GaxPb1-xTe(x=0.01-0.05) compounds were prepared by melting reaction method, and the in-c fluence of Ga content on the thermoelectric properties were investigated. The results showed that temperature dopende...
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Ga dopping GaxPb1-xTe(x=0.01-0.05) compounds were prepared by melting reaction method, and the in-c fluence of Ga content on the thermoelectric properties were investigated. The results showed that temperature dopendent carrier concentration increased and the hall mobility decreased with increasing Ga content, which indicated that the carrier scattering mechanism gradually changed from an acoustical scattering to the interaction between an acoustical phone and an ionized impurity scattering as x increased. All samples show n-type conduct and the absolute Seebeck coefficient values and the electric conductivity increase significantly with increasing Ga content.
The layered perovskite-type organic-inorganic hybrids (CnH2n+1NH3)2 MnCl4 (n=2, 4, 6, 8, 10, 12) were synthesized in solution and their structures were characterized. The results showed that the structures of the prod...
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The layered perovskite-type organic-inorganic hybrids (CnH2n+1NH3)2 MnCl4 (n=2, 4, 6, 8, 10, 12) were synthesized in solution and their structures were characterized. The results showed that the structures of the products were independent on the reaction initial temperature. The X-ray diffraction (XRD) patterns and the scanning electron microscopy (SEM) images of the products demonstrated that the hybrids crystallize very well and had typical layered structures. The interlayer distance of each hybrid was obtained from the XRD patterns. It was linear dependent on the carbon atom number in the organic chain and the organic chains interdigitated between the two adjacent inorganic sheets.
The solubility of layered perovskite-type organic-inorganic hybrids (CnH2n+1 NH3)2MCl4 (where M = Mn, Co, Cu, Zn;n = 2, 4, 6, 8, 10, 12) in seven kinds of solvent are obtained by atomic absorption spectrometry and tit...
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The solubility of layered perovskite-type organic-inorganic hybrids (CnH2n+1 NH3)2MCl4 (where M = Mn, Co, Cu, Zn;n = 2, 4, 6, 8, 10, 12) in seven kinds of solvent are obtained by atomic absorption spectrometry and titration method. The solvents are sherwood oil, cyclohexane, acetone, trichloromethane, DMF, methanol and water. The results show that the hybrids are prone to dissolve in polar solvent. This is attributed to the polarity of the hybrids. The hybrids disassembly dissolve when the interaction between the ammonium and the electron-donating group of the solvent is stronger than that between the organic and the inorganic parts in the hybrids. The series of M = Zn and Co have better solubility in the polar solvent than that of M = Mn and Cu and this is presumably because there are weaker interactions between the organic and inorganic parts in hybrids of M = Zn and Co.
In this study, K3Li2-xNb5+xO 15+2x (KLN) thin films were prepared by laser-ablated a sintered ceramic target. For an optimum deposition condition, in-situ post annealing method was employed on as-deposited films. XRD ...
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In this study, K3Li2-xNb5+xO 15+2x (KLN) thin films were prepared by laser-ablated a sintered ceramic target. For an optimum deposition condition, in-situ post annealing method was employed on as-deposited films. XRD measurements showed that KLN films with (310) preferred orientation were obtained on fused quartz substrate. Surface morphology studies indicated mat in-situ post annealing could improve the surface quality of KLN thin films. The average transmittance of as-deposited and annealed films in the visible range was nearly 80% to 90%.
Sodium potassium bismuth titanate (KNBT) slurry with high plasticity was prepared by the viscous polymer processing. The effects of milling time, bonding agent content, dispersant content, and pH value on the rheologi...
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Sodium potassium bismuth titanate (KNBT) slurry with high plasticity was prepared by the viscous polymer processing. The effects of milling time, bonding agent content, dispersant content, and pH value on the rheological properties were investigated by rheograms, and the optimal technological parameters were investigated. The KNBT fibers with improved properties were fabricated via an extruding machine. The results show that the slurry has optimal rheological behavior when the milling time is 16 h, the pH value is 7, the bonding agent content is 1.22% (in mass, the same below), and the dispersant content is 0.4%.
A modification analytical model is presented for the thermal elastoplastic stresses of functionally graded materials subjected to thermal loading. The presented model follows the analytical scheme presented by Y. L. S...
A modification analytical model is presented for the thermal elastoplastic stresses of functionally graded materials subjected to thermal loading. The presented model follows the analytical scheme presented by Y. L. Shen and S. Suresh [6]. In the present model, the functionally graded materials are considered as multilayered materials. Each layer consists of metal and ceramic with different volume fraction. The ceramic layer and the FGM interlayers are considered as elastic brittle materials. The metal layer is considered as elastic‐perfectly plastic ductile materials. Closed‐form solutions for different characteristic temperature for thermal loading are presented as a function of the structure geometries and the thermomechanical properties of the materials. A main advance of the present model is that the possibility of the initial and spread of plasticity from the two sides of the ductile layers taken into account. Comparing the analytical results with the results from the finite element analysis, the thermal stresses and deformation from the present model are in good agreement with the numerical ones.
The high intensity of thermal stress was generated during fabrication of 6063 aluminum/60SiC‐35Al‐5Si double‐layer material. In order to decrease the thermal stress, graded materials of Al/60SiC‐35Al‐5Si was fabr...
The high intensity of thermal stress was generated during fabrication of 6063 aluminum/60SiC‐35Al‐5Si double‐layer material. In order to decrease the thermal stress, graded materials of Al/60SiC‐35Al‐5Si was fabricated by spark plasma sintering. The CTE in the graded layer was controlled by SiC fraction and particle sizes. The calculation results indicate that the net stress of more than 800 MPa was generated in the double‐layer materials, but it decreased to 170 MPa or less in the graded materials. So the stability can be guaranteed in the graded composites. The graded layers also have the potential for high thermal conductivity, more than 180W/Mk for every layer, which satisfies the application.
A study of silicon nitride ceramic radomes, which includes preparation of the material and optimal design of the radome wall structure, is presented in this paper. Multilayer radome wall structure with high dielectric...
A study of silicon nitride ceramic radomes, which includes preparation of the material and optimal design of the radome wall structure, is presented in this paper. Multilayer radome wall structure with high dielectric constant skins and a low dielectric constant core layer is used for broadband application. As a candidate material for both the skins and core layer, silicon nitride ceramics of controlled dielectric constant in the range 3.0∼7.5 were prepared by adding different content of sintering aids such as magnesia, alumina, silica and zirconium phosphate binder and choosing suitable sintering methods. A computer aided design (CAD) for the wall structure of silicon nitride multilayer ceramic radome based on microwave equivalent network method is carried out according to design requirements. By optimizing the thickness of skins and core layer, the power transmission efficiency of such a multilayer Si3N4 ceramic radome is calculated. The calculated results suggest that when the dielectric constant of skins lies in the range 6∼7.5 and core layer in the range 3.5∼4, the power transmission efficiency is above 85% with frequency of 2∼18 GHz while the thickness of skins is less than 0.03λ and the thickness ratio of skins to core layer is less than 1:15.
In the present study, Si3N4 ceramics with pore gradient structure were prepared by spark plasma sintering (SPS) technique. Silicon nitride ceramics with different controlled porosities were prepared by using ZrP2O7 as...
In the present study, Si3N4 ceramics with pore gradient structure were prepared by spark plasma sintering (SPS) technique. Silicon nitride ceramics with different controlled porosities were prepared by using ZrP2O7 as a binder material and heat treated at 1100 °C in a pressureless nitrogen atmosphere. Si3N4 ceramics with controlled porosity of 34–47% were obtained. The distribution of porous structure was homogenous. Fully dense Si3N4 ceramics could be sintered at 1400∼1600 °C by using MgO and alumina Al2O3 as the sintering aids. Pore gradient structure was formed by laminating the Si3N4 porous ceramics and powder mixture was used to obtain fully dense ceramics, and then sintering at 1400–1600 °C. Microstructure of sintered samples was observed by scanning electronic microscope (SEM) and the change of phase compositions was analyzed by X‐ray diffraction (XRD). The results showed that these samples exhibited a good porous graded structure with a highly porous layer and a dense surface layer. The major phase of the Si3N4 ceramics was still α phase.
An analytical model of normal ballistic impact on the ceramic/metal gradient armor, which is based on modified Alekseevskii‐Tate equations, has been developed. The process of gradient armour impacted by the long rod ...
An analytical model of normal ballistic impact on the ceramic/metal gradient armor, which is based on modified Alekseevskii‐Tate equations, has been developed. The process of gradient armour impacted by the long rod can be divided into four stages in this model. First stage is projectile's mass erosion or flowing phase, mushrooming phase and rigid phase; second one is the formation of comminuted ceramic conoid; third one is the penetration of gradient layer and last one is the penetration of metal back‐up plate. The equations of third stage have been advanced by assuming the behavior of gradient layer as rigid‐plastic and considering the effect of strain rate on the dynamic yield strength.
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