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排序方式: 共有855条查询结果,搜索用时 31 毫秒
1.
《Journal of the European Ceramic Society》2022,42(6):2879-2891
In this study, seven different filler materials in different proportions were added to a Ba-Ca-Si glass matrix “H” to investigate new sealant with higher thermal expansion coefficient (CTE) value and good sealing performance for application in oxygen transport membrane (OTM). SrTi0.75Fe0.25O3-δ (STF25) was used as an OTM, and the sealing partners were ferritic steel Aluchrom and pre-oxidized Aluchrom. Compatibility tests were carried out to investigate the feasibility of the composites. Higher CTE values were found in dilatometer tests on composite samples by adding 40 wt% Ag (HAg40) and 30 wt% Ni-Cr (HNC30). Gas-tightness measurements of sandwiched samples produced appropriate helium leakage rates in the range of 10?6 mbar·l·s?1. Sealing behaviour of sealants HAg40 and HNC30 were investigated by joining STF25 and as-delivered/pre-oxidized Aluchrom together. Scanning electron microscopy (SEM) on cross-sections of the joints revealed a homogeneous microstructure and good adherence of the glass sealants to support metals and STF25. 相似文献
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碳纳米管膜的场致发射电流密度仅由它表面的宏观电场决定,无论其表面形状是平的还是半球状的。对于理想的平行板电极系统,其表面电场强度均匀(UId),发射电流密度、总电流与发射面积成正比:对于半球一平面电极系统半球形的阴极存在一个宏观场增强因子ks,一个与两极距离和球半径之比(d/r)相关的函数,其表面的平均场强为ks U/d。对于d/r=0,ks=1,d≥r的情况,ks接近于常数。对于10〈d/r〈100的情况,存在一个经验的表达式:ks=1+0.15d/s=0.005(d/r)^2。在引入ks后,不同作者给出的平面电极系统和半球一平面电极系统碳纳米管膜的场致发射电流I与宏观表面电场强度E的关系都可以近似用-经验公式描述:I=a(E-Eo)^b,a,b为常数。该经验公式可为稳定生产的CNT膜片应用产品设计提供方便。 相似文献
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Polycrystalline Ti3SiC2 suffered from serious hot corrosion attack in the mixture of 75wt.%Na2SO4 + 25wt.%NaCl melts at 850 °C. In order to improve the hot corrosion resistance of this material, pre-oxidation treatment was conducted at 1200 °C in air for 2 h. A duplex oxide scale with an outer layer of TiO2 and an inner layer of a mixture of TiO2 and SiO2 was formed during the pre-oxidation. Because the outer oxide layer of the pre-oxidation treated specimens could inhibit hot corrosion process, they exhibited good hot corrosion resistance in the mixture of 75wt.%Na2SO4 + 25wt.%NaCl melts at 850 °C for 50 h. However, during the hot corrosion the outer layer of TiO2 would degrade gradually. Once the outer layer damaged, the hot corrosion rate increased sharply, the corrosion behavior was similar to Ti3SiC2 corroded under the same conditions. The microstructure and phase compositions of the hot corrosion samples were investigated by SEM/EDS and XRD. 相似文献
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Effects of Austempering after Hot Deformation on the Mechanical Properties of Hot Rolled Si-Mn TRIP Steel Sheets 总被引:1,自引:0,他引:1
LIZhuang ZHANGPing-li WUDi 《材料热处理学报》2004,25(5):248-251
Excellent mechanical properties are obtained by austempering after hot deformation without subsequent heat treatment in the present Si-Mn TRIP steel sheets. Isothermal holding time after finishing rolling has affected the mechanical properties of this steel. The results show that the sample exhibits a good combination of ultimate tensile strength and total elongation when it is held at the bainite transformation temperature after hot deformation. The stability of retained austenite increases with an increase of isothermal holding time, and a further increase in the holding duration results in a decrease of it. The tensile strength, total elongation and strength ductility reach the maximum values (774MPa, 33% and 25542MPa% respectively) for this sort of hot rolled Si-Mn TRIP steel using the optimal technology. 相似文献
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To solve the difficulty in describing the generic bill of material (GBOM) with the conventional tabular structure in a relational database system,a novel XML-based approach is presented to represent GBOM. It can represent and maintain one generic structure that encompasses all variants of a product. With the combination of product-oriented notation,this approach further gives a high degree of flexibility to support the user in the product variant specification task. The generic BOM system is then introduced for the particular product variant,and a prototype system has been developed. It is indicated that the presented approach is feasible. 相似文献
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The corrosion behavior of polycrystalline Ti3SiC2 was studied in the presence of Na2SO4 deposit and water vapor at 900°C and 1000°C. The mass gain per unit area of the samples superficially coated with Na2SO4 exposed to water vapor was slightly lower than that of the samples corroded without water vapor. The microstructure and composition of the scales were investigated by SEM/EDS and XRD. Pores were observed in the corroded sample surfaces. The main corrosion phases on the sample surface were identified by XRD as TiO2, Na2Si2O5 and Na2TiO3. After Ti3SiC2 corroded in the presence of the Na2SO4 deposit and water vapor, the scale had a three-layer microstructure, which was different from the duplex corrosion scale formed on Ti3SiC2 beneath the Na2SO4 film without water vapor. Because water vapor penetrated the corrosion layer and then reacted with SiO2 to form volatile Si(OH)4, an intermediate porous and TiO2-enriched layer formed in the corrosion layer. 相似文献