Spark or not in insulator materials sintered by pulse electric current or spark plasma sintering is still in dispute. In this paper, the electric field in the graphite die was calculated by Maxwell theory. The calcula...
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ISBN:
(纸本)0470081562
Spark or not in insulator materials sintered by pulse electric current or spark plasma sintering is still in dispute. In this paper, the electric field in the graphite die was calculated by Maxwell theory. The calculated results indicate that the distribution of electric field is in heterogeneous. The intensity of electric field is enhanced at the centre area contacting with punch surface, weakened in circumference contacting with the die. It is deduced from the calculated results that the most possible area to generate spark lies on the punch surface if any spark could be generated in the sintered sample. Some experimental results are accordance with the calculated distribution of electric field and the spark of punch surface.
TiB2-Si3N4-BN composite was fabricated by hot press, and the influence of the content of additive and sintering temperature on the property is also discussed. The results show that content of the additive and the sint...
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TiB2-Si3N4-BN composite was fabricated by hot press, and the influence of the content of additive and sintering temperature on the property is also discussed. The results show that content of the additive and the sintering temperature play an important role on the materials properties, TiB2-Si3N4-BN composite is of better properties at sintering temperature 2073 K with the additive of 1 wt%.
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.
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.
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...
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ISBN:
(纸本)0470081562
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. The principle of the fabrication was analyzed. Spark can be generated by electric field if the cavity in the green body is large enough. The melted Al by spark densify the compact which is similar to the pressure infiltration but with simple method. High relative density (R-D) of composites was successfully achieved through the optimization of sintering parameters. The measured TCs of SiCp/Al composites fabricated by SPS are higher than 195W/m·k.
Aluminum borate whiskers with TiB2 as borate source were prepared in this paper. The phase transformation process was analyzed by XRD and TG-DSC. The results indicate that TiB2 was decomposed into TiO 2 and B2O3 in th...
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Aluminum borate whiskers with TiB2 as borate source were prepared in this paper. The phase transformation process was analyzed by XRD and TG-DSC. The results indicate that TiB2 was decomposed into TiO 2 and B2O3 in the calcining process in the active [O] atmosphere. 2Al2O3.B2O3 was formed in the lower temperature with reaction of Al2O3 and B2O3, while 9Al2O3.2B 2O3 whiskers were grown by compensation of 2Al 2O3.B2O3 at higher temperature (above 1050°C).
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...
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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...
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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.
BaCO3 whiskers exhibiting different morphologies were fabricated by a simple precipitation reaction of barium chloride with sodium carbonate in the absence and presence of poly-（styrene-alt-maleic acid） （PSMA） as ...
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BaCO3 whiskers exhibiting different morphologies were fabricated by a simple precipitation reaction of barium chloride with sodium carbonate in the absence and presence of poly-（styrene-alt-maleic acid） （PSMA） as a crystal growth modifier at room temperature. The as-prepared products were characterized by scanning electron microscopy （SEM）,transmission electron microscopy （TEM）,and X-ray diffraction （XRD）. The influences of experimental parameters on the size and morphology of BaCO3 whiskers were investigated and discussed. It was found that the as-prepared BaCO3 whiskers are single crystals with diameter ranging from 100 to 300?nm,and grow along the crystallographic a-axis or [100] direction. BaCO3 whiskers with different morphologies,such as branching and dendritic structure,can be obtained depending on the experimental conditions. With increasing PSMA concentration,the diameter of BaCO3 whiskers decreases.
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