摘要 :
We synthesized the isomeric polyimides, 6FDA-m-DDS and 6FDA-p-DDS, and investigated the gas selectivity of the asymmetric polyimide membranes with an oriented surface skin layer. Particularly, we focused on the effect of the chemi...
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We synthesized the isomeric polyimides, 6FDA-m-DDS and 6FDA-p-DDS, and investigated the gas selectivity of the asymmetric polyimide membranes with an oriented surface skin layer. Particularly, we focused on the effect of the chemical structure of the polyimide on the molecular orientation. The asymmetric membranes with the oriented skin layer were prepared by a dry-wet phase inversion process at different shear stresses. The gas permeances of the asymmetric polyimide membranes were measured using a high vacuum apparatus with a Baratron absolute pressure gauge at 76 cmHg. The molecular orientation in the asymmetric polyimide membranes was measured using polarized ATR-FTIR spectroscopy. The gas selectivity of the asymmetric 6FDA-m-DDS membrane increased with an increased in the shear stress and were greater than that of the dense membrane. In contrast, the gas selectivities of the asymmetric 6FDA-p-DDS membrane did not depend on the shear stress and were similar to those of the dense membrane. We clarified that a parallel oriented surface formed on the asymmetric 6FDA-m-DDS membrane caused the enhanced gas selectivity of the membrane.
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We developed an automatic feedback control system of the crystal-melt interface position to keep the temperature at the interface constant during growth, and demonstrate its successful application to grow Ge-rich SiGe bulk crystal...
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We developed an automatic feedback control system of the crystal-melt interface position to keep the temperature at the interface constant during growth, and demonstrate its successful application to grow Ge-rich SiGe bulk crystals with uniform composition. In this system, the position of the crystal-melt interface was automatically detected by analyzing the images captured using in situ monitoring system based on charge-coupled-devices camera, and the pulling rate of the crucible was corrected at every 1 min. The system was found to be effective to keep the crystal-melt interface position during growth even when the variation of the growth rate is quite large. Especially, the interface position was kept for 470 h during growth of Ge-rich SiGe bulk crystal when we started with a long growth melt of 80mm. As a result, a 23mm-long Si_(0.22)Ge_(0.78) bulk crystal with uniform composition was obtained thanks to the constancy of the growth temperature during growth through the control of the interface position. Our technique opens a possibility to put multicomponent bulk crystal in a practical use.
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The use of misch-metal is widely spread among the stainless steel producers. Casting problems like clogging are common when using these additions. Information about Ce-La-Al-O particles formed due to the addition of misch-metal in...
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The use of misch-metal is widely spread among the stainless steel producers. Casting problems like clogging are common when using these additions. Information about Ce-La-Al-O particles formed due to the addition of misch-metal in the ladle is scarce in the open literature. The aim of this study is to increase the knowledge of the particle behavior and the particle characteristics in two stainless steels resulting from the addition of misch-metal. The in situ particle behavior has been studied using a Confocal Laser Scanning Microscope.
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Studies of inclusion behavior at the metal-slag interface are of great importance for the steel industry in order to obtain better control of the size and of inclusions as well as improving the steel quality and casting process. I...
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Studies of inclusion behavior at the metal-slag interface are of great importance for the steel industry in order to obtain better control of the size and of inclusions as well as improving the steel quality and casting process. In this work the agglomeration of liquid Al_2O_3-CaO particles at the liquid steel-liquid slag interfaces are studied with a confocal scanning laser microscope. In addition, the agglomeration of liquid Al_2O_3-CaO inclusions already transferred to the slag is investigated. It is found that agglomeration of the liquid inclusions at the steel-slag interface could only take place when the inclusions were forced towards each other, while the agglomeration of liquid particles was seen to be noticeably enhanced when the particles were already in the slag.
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We have observed, by use of low-energy electron microscopy, the first direct evidence of self-driven polycrystallization evolved from a single nucleus in the case of epitaxial pentacene growth on the Si(lll)-H terminated surface. ...
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We have observed, by use of low-energy electron microscopy, the first direct evidence of self-driven polycrystallization evolved from a single nucleus in the case of epitaxial pentacene growth on the Si(lll)-H terminated surface. In this Letter we demonstrate that such polycrystallization can develop in anisotropic systems (in terms of crystal structure and/or the intermolecular interactions) when kinetic growth conditions force the alignment of the intrinsic preferential growth directions along the density gradient of diffusing molecules. This finding gives new insight into the crystallization of complex molecular systems, elucidating the importance of nanoscale control of the growth conditions.
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摘要 :
The phase relationship between ZrO_2 and PuO_2 was examined in a low PuO_2 content region, from 3.1 to 11.2 mol/100 PuO_2,a temperatures between 1273 K and 1473 K, the samples in this composition range consisted of two phases, mon...
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The phase relationship between ZrO_2 and PuO_2 was examined in a low PuO_2 content region, from 3.1 to 11.2 mol/100 PuO_2,a temperatures between 1273 K and 1473 K, the samples in this composition range consisted of two phases, monoclinic and cubic. Another phase, tetragonal, was observed at 1373 K.
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