C/BN laminated composites were obtained by spark plasma sintering. The relationship between sintering conditions, microstructure and properties were studied. The analysis of micro structure indicated that with increas...
详细信息
C/BN laminated composites were obtained by spark plasma sintering. The relationship between sintering conditions, microstructure and properties were studied. The analysis of micro structure indicated that with increasing the temperature and time of heat preservation the coalescent between graphite and BN was increased gradually. The bonding strength transformed from molecular gravitation to the union of molecular gravitation and mechanical strength. The circulation times of materials reached 40 times at sintering temperature of 1750°C for 5 min. The test of mechanical properties of the materials indicated that the largest tensile strength reached 18.2 MPa.
A single flat-plate Solid Oxide Fuel Cell (SOFC) with Ni-YSZ|YSZ|LSM configuration was developed, the test system and the fuel control system was established. The electrical properties were examined with H2 as the fue...
详细信息
A single flat-plate Solid Oxide Fuel Cell (SOFC) with Ni-YSZ|YSZ|LSM configuration was developed, the test system and the fuel control system was established. The electrical properties were examined with H2 as the fuel and the air as the oxidant in a temperature range of 800 to 1000°C. Results showed that the open-circuit voltage (OCV) was over 1.01 V, the maximum power density at 1000°C reached to 7.73 mW/cm2. It was found that the large ohmic losses of the electrolyte were the main factor responsible for the relative low output power density. The relations of OCV vs. operating temperature and OCV vs. fuel flow rates were also investigated.
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 ...
详细信息
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.
SiCp/Al composites containing high volume fraction of SiC particles were fabricated by spark plasma sintering (SPS), and their thermophysical properties, such as thermal conductivity (TC) and coefficient of thermal ex...
详细信息
SiCp/Al composites containing high volume fraction of SiC particles were fabricated by spark plasma sintering (SPS), and their thermophysical properties, such as thermal conductivity (TC) and coefficient of thermal expansion (CTE), were characterized. High relative density (R-D) of composites was successfully achieved through the optimization of sintering parameters, such as sintering temperature, sintering pressure and heating rate. The measured TCs of SiCp/Al composites fabricated by SPS are higher than 195 W/m k, no matter the volume fraction of SiC particles is high or low as long as the R-D is higher than 95%. The measured CTEs of SiCp/Al composites are in good agreement with the estimated values based on Kerners model. The high volume fraction of SiCp/Al composites are a good candidate material to substitute for conventional thermal management materials in advanced electronic packages due to its tailorable thermophysical properties.
By using of high temperature XRD data, the high temperature structure behavior of corundum (α-Al2O3) with different crystal morphologies was studied by comparative crystal chemistry. It was revealed that cell paramet...
详细信息
By using of high temperature XRD data, the high temperature structure behavior of corundum (α-Al2O3) with different crystal morphologies was studied by comparative crystal chemistry. It was revealed that cell parameter (a, c) and Al-O bond length (LAl-O) of grain corundum were logarithmically increased because of thermal expansion, but that of the whisker corundum was linearly increased. The crystal lattice coefficient of thermal expansion (M) of the grain corundum was logarithmically increased almost in uniformity tendency, which was isotropy. On the contrary, that of the whisker corundum was linearly increased in whole tendency, the value M of cell parameter (a) is greater than cell parameter (c), which was anisotropy.
The effect of particle morphology of α-Al2O3 on sintering property of its compact is investigated in this paper. The morphology of α-Al2O3 particles and its compact were studied by SEM and TEM, and line-shrinkage ra...
详细信息
The effect of particle morphology of α-Al2O3 on sintering property of its compact is investigated in this paper. The morphology of α-Al2O3 particles and its compact were studied by SEM and TEM, and line-shrinkage rate, density and water absorption rate were measured respectively. The results showed that the expansion of compact at elevated temperature brought harm to densification and formation of homogenous structure of the compact and the sintering property of compact was influenced by the morphology of α-Al2O3 particles in different degrees.
Permittivity and dielectric strength determine the energy storage density of a material. Although a composite can be molded easier, its lower energy storage density prevents the material from applications since the po...
详细信息
In the present study, the processing-properties relationships of the ZrO2/(Ni+Al2O) 3) composites are examined. Dense composites were prepared either by pulse electrical current sintering (PECS) at 1350C for 5 minutes...
详细信息
In the present study, the processing-properties relationships of the ZrO2/(Ni+Al2O) 3) composites are examined. Dense composites were prepared either by pulse electrical current sintering (PECS) at 1350C for 5 minutes or by pressureless sintering (PLS) at 1600C for 1 h. The size of Ni particles is as small as 30 nm to 50 nm. Though the size of ZrO2 grains in the matrix increases as alumina and nickel particles are added, the strength of the ZrO2/(Ni+Al2O3) composites is significantly higher than that of monolithic ZrO2.
After combining the PVDF and BST powders with different particle sizes, the anti-voltage strengths of composites was tested. Although the concentrates of ceramic were all the same, their anti-voltage strengths were di...
详细信息
Highly oriented plate-like rod/tube arrays of ZnO are synthesized by a solution-based approach at low temperature. The ZnO rod/tube arrays grow oriented vertically on silicon substrate and the intersectant ZnO nanoshe...
Highly oriented plate-like rod/tube arrays of ZnO are synthesized by a solution-based approach at low temperature. The ZnO rod/tube arrays grow oriented vertically on silicon substrate and the intersectant ZnO nanosheets stand on the backbones of ZnO rods/tubes. The constructions of plate-like rod or tube arrays depend on the processing conditions. The growth mechanisms are investigated based on the nucleation and growth process. The initial ZnO film formed on substrate is crucial for the growth of ZnO rods/tubes perpendicular to the substrate. The nanosheets grow around the ZnO rods/tubes by the secondary nucleation and growth process. The ZnO tubes are formed by the etching of the ZnO polar faces. The novel ZnO structures are expected to have great potential for electronics, photoelectronics, sensors, and catalysis etc.
暂无评论