共查询到20条相似文献,搜索用时 93 毫秒
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《中国无线电电子学文摘》2002,(6)
TN04 2002060021一维纳米材料的合成、组装与器件/董亚杰,李亚栋(清华大学)11科学通报.一2002,47(9)一641一649一维纳米材料的合成、组装及其物性的测量是制约其在纳米原型器件制作与应用中的关键,评述了这一领域的最新进展.一维纳米材料的组装大致可分为宏观场力组装与微流输助模板限域组装,其中前者是通过控制宏观电场、磁场的方向和大小来对微观的纳米线进行组装,后者则通过控制模板的形状、尺寸、流体的流速、沉积的时间等来实现纳米线网络阵列的制备.纳米线的组装与单根纳米线的物性测量使得纳米线激光器、传感器乃至纳米逻辑电路的制… 相似文献
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介孔TiO2以其独特的结构和优异的性能备受关注,但却存在起始钛源成本高、脱模不理想并易引起孔结构破坏坍塌、骨架晶型差等问题。笔者以钛铁矿酸解得到的工业TiOSO4液作为起始钛源,在复合表面活性剂自组装形成的超分子结构模板诱导作用下进行水解,控制水解产物的结构,形成介孔TiO2前驱体之后,采用氧化、萃取和焙烧相结合的方式脱除前驱体中的表面活性剂模板,制备出比表面积大、结构稳定的锐钛矿型介孔TiO2。重点研究了以下几个与介孔TiO2合成工艺及形成机理有关的问题:(1)合成介孔TiO2前驱体的工艺条件对介孔结构的形成及晶型至关重要,尤其是表面活性剂、反应pH值、温度等。采用复合模板(CTAB/P123)为结构导向剂,由工业TiOSO4液水解合成介孔前驱体,多步焙烧脱除模板,得到孔径分布窄、结构稳定的锐钛型介孔TiO2分子筛,平均孔径为3.0nm,SBET为132.6m2/g。(2)介孔TiO2前驱体合成中引入外场作用能促进产物的晶体结构完善和孔结构形成,使产物的SBET和稳定性均显著提高。超声辐照和微波辐照利于提高介孔结构的有序度;微波辐照所得产物的SBET达146.6m2/g;水热合成强化了无机物种与表面活性剂的相互作用,同时使孔壁缩聚晶化,提高了介孔结构的稳定性。(3)采用臭氧氧化、多次萃取、多步焙烧的综合脱模路线脱除有机复合模板剂CTAB/P123较完全,得到SBET高(133m2/g),平均孔径大(4.65nm)的锐钛矿型介孔TiO2。臭氧氧化使模板剂氧化成短链、小分子有机物,可减小后续脱模过程的阻力;盐酸/无水乙醇的多次萃取使孔道中模板剂的表面活性降低,与骨架结构的作用减弱,有效降低了后期热处理强度;多步焙烧方式可减小因长时间高温焙烧容易造成的无机骨架网络收缩、骨架结构损坏、骨架电荷平衡破坏所致的分子筛孔结构破坏坍塌的负效应。(4)介孔TiO2的锐钛矿晶型,较大的SBET和小的颗粒尺寸,表面吸附和键合的少量SO4使其具有良好的催化活性。介孔TiO2在光氧化分解亚甲基蓝和乙酸乙醇酯化反应中有较高的催化活性,降解率和酯化率分别达98.4%和91%;介孔TiO2对催化高酸值麻疯油与甲醇预酯化反应也表现出一定催化活性。(5)在强酸性水体系中通过CTAB/P123复合模板的超分子诱导自组装合成路线制备出2D六方孔道、SBET大(205.7m2/g)、孔径分布窄的锐钛型介孔TiO2。介孔TiO2前驱体的形成过程属协同作用机理,其特征归纳为如下几点:1)反应体系pH值对钛水解初级粒子与模板剂协同作用影响较大,二者通过静电作用(S+I–)和氢键作用(N0I0)两种方式在界面协同作用;2)调控pH值不仅使钛离子水解缩聚的速率与表面活性剂自组装速率相匹配,且能控制杂质的析出;3)适当提高合成温度有利于大孔径介孔材料的形成;4)增长复合表面活性剂疏水链有助于大孔径介孔材料的合成;5)无机强电解质阴、阳离子的加入有一定的扩孔作用;6)介孔TiO2前驱体合成体系中钛水比和酸钛比对无机钛离子水解速率(H)或抑制速率(p)影响较大,TiOSO4液合成体系大的H/p比值导致钛离子水解加速,胶束尺寸变小,使介孔材料孔径缩小。(6)介孔TiO2脱模过程中,界面作用的变化对晶体结构和微观应变造成一定影响,同时产生原子缺位。萃取脱模对晶体结构影响远弱于焙烧处理,增大萃取脱模量可有效降低焙烧强度,提高介孔TiO2的稳定性。2– 相似文献
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本文根据易引发大风的阵风锋在天气雷达反射率因子图像空间上呈现高度较低、形态呈弧线结构和时间上具有移动特点这3个特征,在低仰角反射率因子、时间差分反射率因子、空间差分反射率因子这3种不同反射率因子图像上,采用模板匹配技术分别对其进行阵风锋图像特征匹配分值处理。融合3种特征匹配结果后,采用区域增长法提取阵风锋弧线图像结构,排除虚假图像。在处理3种得分值结果的过程中,同时采用了风暴抑制模板和放射状回波抑制模板技术来降低非阵风锋回波得分值。结果表明,算法能够有效识别易引发大风的阵风锋图像特征,且识别结果与原阵风锋位置和形状较为一致。本文所设计的阵风锋模板匹配技术为能准确地监测和预警阵风锋灾害性天气过程提供多一种可能。 相似文献
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Kelly N. L. Huggins Alia P. Schoen Manickam Adhimoolam Arunagirinathan Sarah C. Heilshorn 《Advanced functional materials》2014,24(48):7737-7744
The use of biological scaffolds to template inorganic material offers a strategy to synthesize precise composite nanostructures of different sizes and shapes. Proteins are unique biological scaffolds that consist of multiple binding regions or epitope sites that site‐specifically associate with conserved amino acid sequences within protein‐binding partners. These binding regions can be exploited as synthesis sites for multiple inorganic species within the same protein scaffold, resulting in bimetallic inorganic nanostructures. This strategy is demonstrated with the scaffold protein clathrin, which self‐assembles into spherical cages. Specifically, tether peptides that noncovalently associate with distinct clathrin epitope sites, while initiating simultaneous synthesis of two inorganic species within the assembled clathrin protein cage, are designed. The flexibility and diversity of this unique biotemplating strategy is demonstrated by synthesizing two types of composite structures (silver–gold mixed bimetallic and silver–gold core–shell nanostructures) from a single clathrin template. This noncovalent, Template Engineering Through Epitope Recognition, or TEThER, strategy can be readily applied to any protein system with known epitope sites to template a variety of bimetallic structures without the need for chemical or genetic mutations. 相似文献
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Alexandre Finke Philippe Poizot Claude Guéry Driss Mazouzi Jean‐Marie Tarascon 《Advanced functional materials》2008,18(22):3598-3605
An Fe3O4/Cu nanostructured prototype electrode was developed from a 100% bottom‐up approach thanks to an original three‐step electrodeposition procedure that enlists 1) the growth of a ZnO nanocolumnar template, 2) the filling of the template voids by copper prior to the dissolution of the zincite nanopillars, and 3) the plating on the remaining copper nanodots of the Fe3O4 phase. The key technological point is that ZnO readily forms nanorod arrays by self‐assembly when an aqueous solution of ZnII, saturated by dioxygen, is cathodically polarized. The as‐obtained inorganic solid template is sufficiently stable for further deposition steps of any kind (metals, oxides, polymers, and so on) but is easy to remove in both acidic and alkaline media. The self‐supported Fe3O4/Cu nanostructured electrode shows, besides sustained capacity retention, outstanding rate capability when electrochemically tested versus Li. This original and soft process, derived from template‐assisted synthesis, avoids fixing (mechanically) a nanoporous membrane on the substrate, thus, enabling nanostructural design on shapeless surfaces. 相似文献
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交通标志检测技术是交通标志识别系统的重要前提和基础。由于背景的复杂性,在进行颜色分割时部分区域可能会受到干扰,为交通标志的检测带来困难。文中利用HSV颜色空间和RGB颜色空间对不同颜色的交通标志进行粗检测,标记不同的值实现ROI分割。然后利用模板匹配的方法对交通标志进行处理,使用模板在ROI区域上滑动,得到模板相似度的最大值,以此来实现检测过程。实验结果表明该方法能获得较好的检测结果。 相似文献
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T. Xu J. Stevens J.A. Villa J.T. Goldbach K.W. Guarini C.T. Black C.J. Hawker T.P. Russell 《Advanced functional materials》2003,13(9):698-702
Thin films of block copolymers have been used as templates and scaffolds for the fabrication of arrays of nanostructured materials. In general, a chemical modification of the film or the removal of one of the components by photodegradative methods is required to produce a nanoporous film that serves as a template or scaffold. Here, however, the preferential interaction of one of the components with a solvent is shown to produce a reconstruction of the block copolymer film that, upon drying, leads to the generation of a nanoporous template. The area density of the pores is identical to that of the original copolymer thin film. Since no chemical reactions occurr, the process is fully reversible. Upon heating the copolymer film above its glass‐transition temperature, mobility is imparted to the copolymer and the original copolymer film with oriented domains is recovered. The film reconstruction significantly simplifies the generation of nanoporous templates. 相似文献
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A novel method for fabrication of highly oriented polyaniline (PANI) nanowires without removal of the template was developed by combining self‐assembly and template synthesis techniques. By using a self‐assembly process under inhibition conditions, oriented arrays of PANI nanowires growing out of the nanoporous template were obtained, with nanowire diameters ranging from 110 to 190 nm and lengths of several micrometers. The lengths of these wires can be roughly controlled by the polymerization time. 相似文献
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Lateral control of template synthesis in nanoporous alumina membranes (NAMs) was previously shown by us to enable preparation of graded composite materials. Formation of thickness gradients of Cu was demonstrated using electrodeposition (or electrodissolution) of Cu in the NAM template under a lateral voltage drop applied to the working electrode. This approach is extended here to the formation of compositional gradients. The latter are achieved by electrochemical co‐deposition of two metals (Au and Pd) in the membrane pores from a mixed metal‐ion solution under a lateral potential drop, to form an alloy that shows a continuous lateral change of the Au/Pd ratio. Environmental scanning electron microscopy images of cross sections along the line of the applied voltage gradient show that the deposit height changes gradually, while local elemental analysis by energy dispersive spectrometry and X‐ray diffraction measurements confirm a continuous change of the alloy composition along the membrane matrix. 相似文献