A technique based on viscous polymer processing (VPP) was described, which can produce high ceramic content green fibers. PZT-5 ceramic powders were ball milled to get high dispersibility. The slurry prepared for VPP ...
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A technique based on viscous polymer processing (VPP) was described, which can produce high ceramic content green fibers. PZT-5 ceramic powders were ball milled to get high dispersibility. The slurry prepared for VPP was a composition of PZT-5 powder, PVA binder and glycerin. High ceramic content PZT-5 fibers were extruded with the slurry. The results show that the ceramic powders have fine mean particle size of 0.54 μm, high specific surface area of 3.55 m2/g and zeta potential of 8.81 mV after 16 h milling. The fibers sintered at 1 280 ℃ for 4 h have pure perovskite structure and grains of 2-5 μm in size, with little pores or cracks. The ultimate tensile strength of sintered fibers is up to 13.84 MPa compared with 2.88 MPa of green fibers. The remnant polarization (Pr) and coercive field (Ec) of the fibers are 50.65 μC/cm2 and 2.45 kV/mm, respectively. This fiber can withstand an electric field of 9 kV/mm higher than the ceramic (5 kV/mm), which shows high directional and compact qualities.
Piezoelectricity of composite was simulated by employing Dilute Model and Limit Unit method. The analogizing results recommend that the particle stackers influence the properties of piezo-composite. While fabricating ...
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Piezoelectricity of composite was simulated by employing Dilute Model and Limit Unit method. The analogizing results recommend that the particle stackers influence the properties of piezo-composite. While fabricating piezo-composite, particles stack different with different routine. For thermo-pressing proceeding, stackers trend to take on higher D33 than that processing from forging-membrane.
The organic-inorganic hybrid compounds have attracted much attention for their interesting structures and various properties. In present work, we concentrated on the band structures of the hybrid compound (C4H 9NH3)2G...
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The organic-inorganic hybrid compounds have attracted much attention for their interesting structures and various properties. In present work, we concentrated on the band structures of the hybrid compound (C4H 9NH3)2GeI4 and tried to find out the relations between the geometry structure and the properties. The hybrid's primitive cell was large and including too many atoms, so it was difficult to have a direct and clear analysis on the band structure. The hybrids' DOS and PDOS were analyzed instead, as it was another effective way to analyze the band structure of the hybrid especially when the band structure was complicated. The model of (C4H9NH3)GeI4 was set up, and the program based on the first principle had been employed to calculate its band structure. The difference of iodine's PDOS caused by structure was also discussed.
A systematic research was performed about diffusion kinetics of adsorbing F^- dissolved in water for carbonate hydroxyapatite （CHAP） from the natural hydroxyapatite which was modified by adulterating with CO3^2-. Th...
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A systematic research was performed about diffusion kinetics of adsorbing F^- dissolved in water for carbonate hydroxyapatite （CHAP） from the natural hydroxyapatite which was modified by adulterating with CO3^2-. The result shows that the speed of F^- adsorption is controlled by membrane diffusion when F^- concentration is relatively low, which is expressed by the kinetic equation of diffusion Q=0.0005（Ci-C）（t-ti）＋0.3967, or by vacancy diffusion when F^- concentration is relatively high, which is expressed by the kinetic equation of diffusion In[C（o, t）]=8.4718-0.5048Int. Based on the feature of CHAP for adsorbing F^- dissolved in water and its special channel of the structure of CO3^3- modified hydroxyapatite, models of vacancy diffusion and membrane diffusion were established.
The isothermal oxidation behavior at 900–1300°C for 20 h in air of bulk Ti3AlC2 with 2.8 wt% TiC sintered by means of hot pressing was investigated in the work. The isothermal oxidation behavior generally follow...
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The isothermal oxidation behavior at 900–1300°C for 20 h in air of bulk Ti3AlC2 with 2.8 wt% TiC sintered by means of hot pressing was investigated in the work. The isothermal oxidation behavior generally followed a parabolic rate law. The parabolic rate constants increased from 1.39×10[10] kg[2]·m[4]·s[1] at 900°C to 5.56×10[9] kg[2]·m[4]·s[1] at 1300°C. The calculated activation energy was 136.45 kJ/mol. It was demonstrated that Ti3AlC2 had excellent oxidation resistance due to the continuous, dense; adhesive protect scales consisted of a mass of α-Al2O3; a little of TiO2;/or Al2TiO5. In principle, the oxide scale was grown by the inward diffusion of O[2]; the outward diffusion of Ti[4+]; Al[3+]. The rapid outward diffusion of cations usually resulted in the formation of cracks, gaps,; holes.
The processes of the coupling graft of -Si(OCH3)3 groups between 7-aminopropyl trimethoxysilane molecules and iron microparticles and the preparation of Fe/SiO2 core-shell composite particles in the alcohol-alkali-wat...
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The processes of the coupling graft of -Si(OCH3)3 groups between 7-aminopropyl trimethoxysilane molecules and iron microparticles and the preparation of Fe/SiO2 core-shell composite particles in the alcohol-alkali-water solution were investigated in the paper. The as-prepared and heat-treated composite particles were characterized with XRD, SEM, and pickling tests. The results showed that the formation of free SiO2 could be effectively prevented by decreasing the rate of adding ammonia, and that Fe/SiO2 core-shell composite particles almost without free SiO2 were successfully fabricated with a controlling rate about 5 drops of ammonia per minute. The optimal temperature range for the densification of SiO2 nanoshell is about 600 [similar to] 700 °C. The SiO2 nanoshells were badly melt and dropped off when the composite particles were heat-treated at 900 °C. The acid resistance of the composite particles increases as the temperature rose from 200 °C to 700 °C.
The microstructure and microwave dielectric properties of the CuO-doping CaTiO3-Ca(Zn1/3Nb2/3)O3 ceramics prepared by the conventional solid-method were investigated. XRD results indicate the ceramics with orthorhombi...
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Mullite-based nanocomposite powders with embedded iron nanoparticles were synthesized by reduction of sol-gel prepared Al5.4Fe 0.6Si2O13 solid solution in hydrogen. Structural characterization studied by TEM revealed ...
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ISBN:
(纸本)0470080337
Mullite-based nanocomposite powders with embedded iron nanoparticles were synthesized by reduction of sol-gel prepared Al5.4Fe 0.6Si2O13 solid solution in hydrogen. Structural characterization studied by TEM revealed that the intra-granular iron nanoparticles along with inter-type iron grains were obtained in mullite matrix. The magnetic properties of nanocomposite powders after reduction at 1200°C were measured by SQUID. It suggests that the intergranular and intragranular α-iron nanoparticles had the ferromagnetic and superparamagnetic behavior at room temperature, respectively. Dense Mullite-based iron composites were prepared from the nanocomposite powders reduced at different temperatures by hot pressing. The mechanical and magnetic properties were strongly affected by the reduction temperature. Flexural strength of mullite based iron nanocomposite reduced at 1200°C and successively hot pressed at 1650°C is one times higher than monothetic mullite. Furthermore, dense composites also behave ferromagnetic property at room temperature.
Aluminum nitride-boron nitride (AlN/BN) composite ceramics were prepared by spark plasma sintering (SPS). The sintering behaviors of AlN/BN composites with 5-15% volume fraction of BN were studied. The influences of B...
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Aluminum nitride-boron nitride (AlN/BN) composite ceramics were prepared by spark plasma sintering (SPS). The sintering behaviors of AlN/BN composites with 5-15% volume fraction of BN were studied. The influences of BN content, as well as the sintering temperature on the density, microstructure, mechanical strength, thermal conductivity and machinability of the composites were also investigated. The results showed that the full densification of AlN/BN composite ceramics could be realized by SPS technique at the temperature no higher than 1800°C for 3 minutes. The thermal conductivity of AlN/BN composites is in the range of 66-79W/mK, and AlN/BN composites can be cut or drilled by carbides or even steel tools when BN content is 15% volume fraction. The mechanical strength of AlN/BN composites is about 330MPa and is not remarkably affected by the addition of BN. The improvement of mechanical properties of AlN/BN composite ceramics is due to the fine and homogenous microstructure developed in the SPS process.
In this paper, the effect of imperfect inner interface on the stress fields in the coated inclusion composite is investigated, the spring-layer of vanishing thickness model is introduced to simulate the imperfect inte...
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In this paper, the effect of imperfect inner interface on the stress fields in the coated inclusion composite is investigated, the spring-layer of vanishing thickness model is introduced to simulate the imperfect interface, assuming that across the interface between the inclusion and the coating the interfacial traction is continuous while displacement discontinuities are permitted through interfacial traction-displacement jump relations. Numerical examples corresponding to the composites containing single coated spherical and fibrous inclusion, respectively, under shear loading at infinity, are calculated, which indicate that the imperfect inner interfaces have significant effect on stress fields of the composites.
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