Super-fine mesophase powder (SFMP) was prepared from a coal tar pitch accompanying mesocarbon microbeads (MCMB) and then was manufactured into high density and isotropic carbon (HDIC) bulks. The influence of ß-re...
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ISBN:
(纸本)9781605600390
Super-fine mesophase powder (SFMP) was prepared from a coal tar pitch accompanying mesocarbon microbeads (MCMB) and then was manufactured into high density and isotropic carbon (HDIC) bulks. The influence of ß-resin content in SFMP precursors and sintering conditions has been studied on the performance of derived HDIC. It has found that, to obtain HDIC with excellent mechanical performance, suitable ß-resin content in SFMP and sintering rate are required. In the sintering range of 470°C-1000°C, higher temperature facilitate the formation of compact HDIC with high flexural strength. Volume shrinkage during sintering can be adopted to val-ate approximately the mechanical performance.
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.
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 paper presents results on the mechanism of spark plasma sintering (SPS). First, the temperature distribution in the sample and the die in SPS were studied. Under certain conditions, the difference may reach a few ...
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ISBN:
(纸本)0470081562
The paper presents results on the mechanism of spark plasma sintering (SPS). First, the temperature distribution in the sample and the die in SPS were studied. Under certain conditions, the difference may reach a few hundreds of degrees of centigrade. Controlling of processing parameters can decrease the temperature difference. Second, the process of atomic diffusion due to the effect of the current was also studied. It was found that the atomic diffusion is enhanced at the interface between specimens in the SPS relative to hot pressing (HP). Third, we have utilized the SPS process to form transparent ceramics, porous metals and ceramics, and to effect welding of alloys.
Dynamic response and fracture of high strength boride/alumina ceramic composite were investigated by split Hopkinson pressure bar (SHPB) experiment in this paper. The compressive stress-strain curves and dynamic compr...
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Dynamic response and fracture of high strength boride/alumina ceramic composite were investigated by split Hopkinson pressure bar (SHPB) experiment in this paper. The compressive stress-strain curves and dynamic compression strength of the composites were tested. The surface's microstructure of fractured composites were examined by using scanning electron microscope (SEM) to investigate the fracture mechanism. The results show that boride/alumina has high dynamic compressive strength and high Young's modulus. The main fracture mode of the material is the fracture of the ceramic grains. The micro-voids and flaws, generated during the sintering and manufacturing of material and mechanical process of specimen, decrease the strength of the material because they provide the source of crack expansion when the material undergoes the dynamic loadings.
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.
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...
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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...
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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...
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