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浓差极化的介电模型——复合膜/溶液体系的数值模拟 总被引:1,自引:0,他引:1
提出了具有电导率和介电常数线性分布的介质的介电模型, 并导出了其内部电的和结构性质的参数与宏观测量的电容和电导之间定量关系的理论表达式, 以模拟复合膜中的多孔层部分的介电弛豫行为. 大量的模拟计算描述并解释了多孔层介电谱随介电常数分布、厚度等性质而变化的规律. 进一步对具有层状构造的复合膜以及复合膜和溶液相组成的多层体系的弛豫行为进行了数值模拟, 比较了三个体系(多孔层、复合膜、复合膜/液相层状体系)的介电谱, 结果揭示了介电谱对各层性质的依赖关系. 所提出的电导率和介电常数线性分布的多孔层的介电模型, 也可用于具有其他电导率、介电常数分布规律的体系. 相似文献
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采用铝阳极氧化法制备了Al2O3-Al-体型多孔氧化铝载体,再采用电沉积技术将TiO2沉积到氧化铝多孔的纳米孔道内,制备了催化精馏专用SO42-/TiO2-Al2O3-Al型固体酸催化剂,并以乙酸乙酯合成为模型反应,考察了水封条件,电沉积电压、电沉积时间等制备工艺条件对催化剂活性的影响.实验结果表明,适宜的制备条件为水封温度为50℃,水封时间为1 h,电沉积电压为6V,电沉积时间为30 min,在此制备条件下,醋酸转化率为31.34%.采用扫描电镜(SEM),X射线衍射分析(XRD)手段对所制备催化剂进行了表征.结果表明:阳极氧化铝膜的结构为无定型结构,TiO2在载体上呈高度分散状态. 相似文献
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用改进的介电松弛谱仪(精度2‰)测定了VDF/TrFE(7/27、65/35、52/48mol%)共聚物溶液成膜、液氮淬火、熔融慢冷和热处理试样在-120—130℃、10-2一104Hz范围的复数介电常数.介电松弛研究结果显示低结晶度的淬火试样较高结晶度的熔融慢冷和热处理试样的Tc高.结晶度上升,居里点处的介电常数增大.室温以下的介电频率谱分别由代表非晶区分子运动的β松弛(低频部)和局域运动的γ松弛(高频部)叠合而成.随结晶度提高,β松弛峰减小,γ松弛峰增大;非晶松弛强度减弱.晶区松弛强度增强. 相似文献
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应用循环伏安法和直流恒流充放电研究了以离子液体1-乙基-3-甲基咪唑三氟乙酸盐([EMIm]CF3COO)和高比表面活性炭电极构成的电化学双电层电容器的电化学性能.实验表明,[EMIm]CF3COO具有高的比电容、良好的循环特性以及高的充放电效率.在离子液体稳定的电化学窗口内,比电容随电化学窗口的增加而增大.能量密度随电流和电化学窗口的增加逐渐提高,功率密度随电流的增加而减小、随电化学窗口的增加而增加,是一种优良的电化学双电层电解液. 相似文献
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化石燃料的使用排放了大量CO2,对气候和环境造成了日益严重的危害.固体氧化物电解池(SOEC)能够利用可再生能源产生的电能将CO2高效转化成CO,降低CO2排放的同时,又能减少化石燃料的使用,近年来受到研究者的广泛关注.相比于低温液相CO2电还原,SOEC高的运行温度保证了其较高的反应速率,即较高的电流密度.典型的SOEC单电池由多孔阴极、致密电解质和多孔阳极以三明治的方式组装而成.CO2分子在阴极得到两个电子解离成CO和一个O2–;生成的O2–通过致密电解质传导至阳极,在阳极失去四个电子发生析氧反应(OER)生成一个O2.相比于两电子的阴极反应,阳极四电子的析氧反应更难进行,可能是整个电极过程的速控步,因此开发高性能的阳极材料有望显著提高SOEC的CO2电还原性能.La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF)因具有较高的混合离子-电子导电性而被用作SOEC阳极材料,但受LSCF-气体两相界面的限制,其OER性能较低.研究表明,LSCF-掺杂的CeO2-气体所构成的三相界面相比于LSCF-气体两相界面具有更高的电化学反应活性,即OER反应更易在三相界面进行.因此,本文将Gd0.2Ce0.8O1.9(GDC)纳米颗粒浸渍到SOEC LSCF阳极来提高其OER活性,考察了纳米颗粒浸渍量(3,5,10和20 wt%)对SOEC电化学性能的影响.结果表明,SOEC的电化学性能随浸渍量的增加而逐渐升高,当GDC纳米颗粒浸渍量为10 wt%时(10GDC/LSCF),SOEC的电化学性能达到最高,在800 oC和1.6 V的电流密度为0.555 A cm–2,是LSCF阳极SOEC性能的1.32倍.继续增加浸渍量到20 wt%,电化学性能反而开始下降.电化学阻抗谱测试结果表明,GDC纳米颗粒的加入减小了SOEC的极化电阻.对应的弛豫时间分布函数解析结果表明10GDC/LSCF阳极上的OER由四个基元反应构成.电镜和O2-程序升温脱附结果表明,GDC纳米颗粒的加入显著增加了10GDC/LSCF阳极三相界面和表面氧空位的数量以及体相氧的流动性,从而促进了OER四个基元反应的反应速率,降低了这几个过程的极化电阻,因而降低了OER反应的极化电阻,提高了SOEC电还原CO2的电化学性能. 相似文献
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MnO2超级电容器充放电过程研究 总被引:1,自引:0,他引:1
采用机械化学法,在高锰酸钾和乙酸锰摩尔配比为1/1的条件下制备了弱结晶性α-MnO2。采用循环伏安、交流阻抗等方法对MnO2电极进行测试;对MnO2超级电容器在6mol/L KOH溶液中以1.2V放电窗口、200mA/g电流密度下进行充放电过程研究。结果表明,超级电容器在低电位范围表现出双电层电容,在高电位范围表现为法拉第假电容;Mn3O4电化学惰性物质主要在初始40次充放电过程中生成,其使循环伏安图中氧化还原峰逐渐消失、高电位法拉第假电容逐渐减小、放电曲线逐渐接近直线,表现为双电层电容特征。电极最大比容量为416F/g,200次循环后为240F/g,等效串联电阻由17Ω逐渐增到41Ω。 相似文献
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Shun Koyama Yoshitaka Aoki Shinji Nagata Hiroki Habazaki 《Journal of Solid State Electrochemistry》2011,15(10):2221-2229
Zr–Al alloys containing up to 26 at.% aluminum, prepared by magnetron sputtering, have been anodized in 0.1 mol dm−3 ammonium pentaborate electrolyte, and the structure and dielectric properties of the resultant anodic oxide films have been
examined by grazing incidence X-ray diffraction, transmission electron microscopy, Rutherford backscattering spectroscopy,
and AC impedance spectroscopy. The anodic oxide film formed on zirconium consists of monoclinic and tetragonal ZrO2 with the former being a major phase. Two-layered anodic oxide films, comprising an outer thin amorphous layer and an inner
main layer of crystalline tetragonal ZrO2 phase, are formed on the Zr–Al alloys containing 5 to 16 at.% aluminum. Further increase in the aluminum content to 26 at.%
results in the formation of amorphous oxide layer throughout the thickness. The anodic oxide films become thin with increasing
aluminum content, while the relative permittivity of anodic oxide shows a maximum at the aluminum content of 11 at.%. Due
to major contribution of permittivity enhancement, the maximum capacitance of the anodic oxide films is obtained on the Zr–11 at.%
Al alloy, being 1.7 times than on zirconium at the formation voltage of 100 V. 相似文献
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High-resolution transmission electron microscopy and electron energy loss spectroscopy (EELS) were performed on electrochemically anodized niobium and niobium oxide. Sintered anodes of Nb and NbO powders were anodized in 0.1 wt% H3PO4 at 10, 20, and 65 V to form surface Nb2O5 layers with an average anodization constant of 3.6 +/- 0.2 nm/V. The anode/dielectric interfaces were continuous and the dielectric layers were amorphous except for occurrences of plate-like, orthorhombic pentoxide crystallites in both anodes formed at 65 V. Using EELS stoichiometry quantification and relative chemical shifts of the Nb M4,5 ionization edge, a suboxide transition layer at the amorphous pentoxide interface on the order of 5 nm was detected in the Nb anodes, whereas no interfacial suboxide layers were detected in the NbO anodes. 相似文献
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M. Sunada H. Takahashi T. Kikuchi M. Sakairi S. Hirai 《Journal of Solid State Electrochemistry》2007,11(10):1375-1384
Highly pure aluminum specimens (99.99%) after electropolishing and DC-etching were covered with SiO2 films by electrophoretic sol-gel coating and were anodized in neutral boric acid/borate solutions. Time-variations in cell
voltage during electrophoretic sol-gel coating and in anode potential during anodizing were monitored. Structure and dielectric
properties of the anodic oxide films were examined by scanning electron microscopy (SEM), transmission electron microscopy
(TEM), energy-dispersive X-ray (EDX), and electrochemical impedance spectroscopy (EIS). It was found that electrophoretic
sol-gel coating forms uniform SiO2 films on the surface of both electropolished and DC-etched specimens. Anodizing of specimens after electrophoretic coating
lead to the formation of anodic oxide films consisting of two layers: an inner alumina layer and an outer Al–Si composite
oxide layer. The anodic oxide films formed, thus, had slightly higher capacitances than those formed on aluminum without any
coating. Higher heating temperatures after electrophoretic deposition caused the increase in capacitance of anodic oxide films
more effectively. Anodizing in a boric acid solution after SiO2 coating on DC-etched foil allowed the anode potential to reach a value higher than 1,000 V, resulting in 39% higher capacitances
than those on specimens without SiO2 film.
Dedicated to Professor Su-Il Pyun on the occasion of his 65th birthday. 相似文献
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由二乙醇胺与H6P2W18O62·nH2O合成了[(HOCH2CH2)2NH2]6·P2W18O62·6H2O(I).单晶结构解析结果表明晶体属三方晶系,空间群为R-3,晶胞参数:a=b=c=1.36298(16)nm,α=β=γ=106.490(17)°,Z=1,V=2.1374(4)nm3,R=0.0837,Rw=0.2219.化合物分子由一个P2W18O626 阴离子、六个质子化的二乙醇胺、六个结晶水组成.标题化合物具有可逆光色性.热分析表明,化合物阴离子在463℃左右分解. 相似文献
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由MoO3和(CH3)3N或(C2H5)3N反应合成了两种分子组成分别为[(CH3)3NH]4Mo8O26·2H2O(1)和[(C2H5)3NH]4Mo8O26·2H2O(2)的化合物.单晶X衍射结构分析表明,化合物(1)属三斜晶系,空间群为P1,晶胞参数a=1.0500(2)nm,b=1.0533(2)nm,c=1.0765(2)nm,α=100.21(3)°,β=101.93(3)°,γ=118.47(3)°,V=0.9698(3)nm3,R1=0.0524.化合物(2)属单斜晶系,空间群为P21,晶胞参数a=1.1512(2)nm,b=1.3097(3)nm,c=1.7610(4)nm,β=101.40(3)°,V=2.6028(9)nm3,R=0.0428.结构分析表明,两种化合物中Mo8O264-阴离子均发生畸变,有机阳离子增大,Mo-O键键长缩短,阴离子畸变增大. 相似文献
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通过固相反应,合成了新的配合物六亚甲基四胺锑(Ⅲ)、铋(Ⅲ):SbCl3(C6H12N4)2·H2O(1)、BiCl3(C6H12N4)2·H2O(2).经元素分析、X 射线粉末衍射、远红外光谱和差热 热重分析进行表征,确定了配合物的组成和结构.对XRD谱指标化,确定其晶系和晶胞参数.SbCl3(C6H12N4)2·H2O(1):a=1.2490nm,b=1.4583nm,c=1.6870nm,β=91.78°,V=3.0706nm3;BiCl3(C6H12N4)2·H2O(2):a=1.3250nm,b=1.3889nm,c=1.7449nm,β=98.94°,V=3.1725nm3. 相似文献
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吡啶-2-甲酸镍的合成及其晶体结构 总被引:1,自引:0,他引:1
以吡啶 2 甲酸和Ni(ClO4)2·6H2O为原料反应制得配合物[Ni(C5H4NCOO)2(H2O)2]2H2O,并通过X 射线衍射法测定其晶体结构.该化合物属于单斜晶系,空间群P21/n,晶胞参数:a=0.97351(15)nm,b=0.52254(8)nm,c=1.4483(2)nm,β=90.119(3)°,V=0.7367(2)nm3,Z=2,Dc=1.690g/cm3,μ=1.362mm 1,F(000)=388,结构偏离因子R1=0.0316,wR2=0.0902,共收集到4771个强度数据,其中1700个独立衍射点,1489个(I>2σ(I))可观测点.X 射线分析表明晶体是由分子间氢键和π π弱相互作用堆积而成的二维层状结构. 相似文献