Solvothermal synthesis has been explored to prepare Sb2Te3 material in the solvent of DMF. The effect of reaction temperature and time on the phase composition and micro-structure have also been studied. The structure...
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Solvothermal synthesis has been explored to prepare Sb2Te3 material in the solvent of DMF. The effect of reaction temperature and time on the phase composition and micro-structure have also been studied. The structure and morphologies of nano-powders were investigated by XRD, SEM, TEM, and EDS observations. The growth mechanism of Sb2Te3 crystal has been researched. The results indicate that the particle size of the powders significantly increase with the escales temperature and the increasing time. At the temperature of 180 degree and maintaining for 24 hours, Sb2Te3 powder of hexagonal crystal was yielded.
ZnO whiskers were grown by a simple vapor-phase approach by using microwave energy without any catalyst in a very short time. The result of the XRD indicates that the production structure was wurtzite. The SEM shows s...
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ZnO whiskers were grown by a simple vapor-phase approach by using microwave energy without any catalyst in a very short time. The result of the XRD indicates that the production structure was wurtzite. The SEM shows some are rod crystals, the other are tubes with 50 μm diameter and 500 μm length. The photoluminescence (PL) exhibits strong ultraviolet emission (wavelength is 360 nm) and blue emission (wavelength is 470 nm) at room temperature. Experiments indicate that the temperature gradient is very important for the ZnO whiskers growth by using vapor phase. The temperature gradient between conventional and microwave heating is different.
The carbonyl iron/Al2O3 core-shell composite particles with different morphologies of nanoshells were prepared and the influences of the Al2O3 nanoshell morphologies on the properties of the carbonyl iron/Al2O3 core-s...
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The carbonyl iron/Al2O3 core-shell composite particles with different morphologies of nanoshells were prepared and the influences of the Al2O3 nanoshell morphologies on the properties of the carbonyl iron/Al2O3 core-shell composite particles were investigated. The results show that the shell morphologies of the carbonyl iron/Al2O3 core-shell composite particles strongly depend on the species of acid and pH value. Compared to the carbonyl iron particles, the anti-oxidation property, microwave electromagnetic parameters and mechanical properties of the composite particles are significantly improved, and the particles, uniform, compact and grain-like Al2O3 nanoshells are beneficial to improving the anti-oxidation property and decreasing permittivity with the retention of permeability, while fiber-like Al2O3 nanoshells are more advantageous to improving the interface compatibility between the particles and the matrix of the polymers, resulting in obvious increase of mechanical properties of their based absorbing coatings.
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.
Spark plasma sintering was used to fabricate the LaPO4 ceramics and the effect of SPS holding time and sintering temperature on the densification and texture of LaPO4 ceramics were studied. The results revealed that h...
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Spark plasma sintering was used to fabricate the LaPO4 ceramics and the effect of SPS holding time and sintering temperature on the densification and texture of LaPO4 ceramics were studied. The results revealed that holding time had no obvious influence on the densification of LaPO4 ceramics under the present process. The density increases with the increase of sintering temperature, when it reached 1350C, the relative density kept nearly constant of 98.6 %. The preferred orientation of LaPO 4 ceramics approximately increases with the increase of sintering temperature, but contrary impact in holding time.
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 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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