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排序方式: 共有150条查询结果,搜索用时 31 毫秒
1.
Kamalesh Pal Amitava Mukherjee Md. Motin Seikh Parthasarathi Bera Arup Gayen 《Ceramics International》2021,47(10):14798-14808
Synthesis of nanocrystalline pristine and Mn-doped calcium copper titanate quadruple perovskites, CaCu3?xMnxTi4?xMnxO12 (x = 0, 0.5, and 1.0) by modified citrate solution combustion method has been reported. Powder X-ray diffraction patterns attest the phase purity of the perovskite materials. Average particle sizes of all the materials obtained from the Scherrer's formula are in the range of 55–70 nm. The specific surface areas for all the perovskites obtained from BET isotherms are found to be low as expected for the condensed oxide systems and fall in the range of 13–17 m2 g?1. Transmission electron microscopy studies show a reduction in particle size of CaCu3Ti4O12 with increase in Mn doping. Ca and Ti are present in +2 and +4 oxidation states in all the materials as demonstrated by X-ray photoelectron spectroscopy analyses. Cu2+ gets reduced in CaCu3Ti4O12 with higher Mn content. Mn is observed to be present only in +3 oxidation state. All the materials have been examined to be active in CO oxidation as well as H2 production from methanol steam reforming. CaCu3Ti4O12 with ~14 at.% Mn is found to show best catalytic activities among these materials. A comprehensive analysis of the catalytic activities of these perovskites toward CO oxidation and H2 production from MSR reveal the cooperative activity of copper-manganese in the doped perovskites and it is more effective at lower manganese content. 相似文献
2.
涤纶长丝生产喷丝板的选择 总被引:5,自引:1,他引:5
论述了高聚物熔体在喷丝孔区的流变性及粘弹行为。具体分析了喷丝孔直径与剪切速率及喷丝头拉伸倍数之间的关系,提出了喷丝孔直径的选择依据。 相似文献
3.
Polysulfone (PSf) asymmetric hollow‐fiber membranes, which have a dense outer layer but a loose inner layer, were tentatively fabricated by coextrusion through a triple‐orifice spinneret and a dry/wet‐phase inversion process. Two simple polymer dopes were tailored, respectively, for the dense outer layer and the porous inner layer according to the principles of the phase‐inversion process. By adjusting the ratio of the inner/outer extrusion rate, the hollow‐fiber membranes with various thicknesses of outer layers were achieved. The morphology of the hollow‐fiber membranes was exhibited and the processing conditions and the water permeability of the membrane were investigated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 259–266, 2004 相似文献
4.
使用3C型异型多孔喷丝板纺制高性能聚砜中空纤维复合膜基膜,并探讨纺丝液组成和纺丝工艺对基膜性能的影响.结果表明:使用异形板纺丝,对影响纺丝液粘度的料液温度、聚砜及成孔添加剂的浓度要求较高;实验中得到聚砜质量分数为30%、凝固浴温度为50℃、成孔添加剂聚乙二醇-20000质量分数为11%时,所得基膜的纯水通量最高,达到120 L(/m·2h). 相似文献
5.
Rafael A. Amaral Cristiano P. Borges Alberto C. Habert Nicolas R. J.‐D. Mermier 《化学工程与技术》2016,39(6):1171-1176
Emission of sulfur compounds to the atmosphere is universally recognized as one key target to be reduced. For membrane pervaporation which is considered as a potential purification process of fuels, dual‐layer polyurethane (PU)/polyethersulfone hollow‐fiber membranes were prepared. A novel fabrication technique is proposed using a quadruple spinneret to produce the fiber with such morphology by simultaneous spinning of two polymer solutions in the presence of two corresponding precipitation media. Activated carbon was added into the PU solution to improve the transport properties of the selective layer. Resulting hollow‐fiber membranes showed very good adhesion between the selective layer and its support, in addition to an effective removal of a sulfur compound such as 2‐methyl thiophene from a typical model fuel, an indication of good prospects for both the fabrication technique and for sulfur removal by pervaporation of fuels. 相似文献
6.
A novel quadruple spinneret to produce dual-layer hollow fiber membranes by simultaneous spinning of two polymer solutions, using the dual precipitation bath technique is proposed. Hollow fibers aimed at gas separation processes were prepared in extrusion system specifically designed and built for this purpose. A polyurethane polymer was selected as the selective layer (outer-layer), while polyethersulfone was defined as the support (inner-layer). Activated carbon powder was added into the PU solution for further improvement of the transport properties. The hollow fibers showed good adhesion between the polymer layers and a defect-free selective layer. Representative results include a CO2/N2 selectivity of 43. 相似文献
7.
8.
简介了目前国内碳纤维行业所用喷丝头组件的结构优化,着重从组件优化后的效果来分析优化的成果.优化研究表明,改造后的喷丝头组件对原丝的性能几乎没有影响,但却大大降低了原丝的生产成本,提高了原丝生产的稳定性. 相似文献
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