Synthesis of C–N nanotube blocks and Y-junctions in bamboo-like C–N nanotubes

We report the observations made on the synthesis and characterization of C–N nanotube blocks and Y-junctions in bamboo-like C–N nanotubes. The C–N nanotube Blocks have been synthesized by pyrolyzing the mixture of silver nitrate acetonitrile solution and ferrocene benzene solution. The structural/microstructural characterization of the as-synthesized material has been done using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray photoelectron spectroscopic (XPS) analysis has been carried out to confirm the presence of nitrogen in nanotubes. These investigations reveal the formation of blocks of bamboo-like nanotubes having the dimension 300 × 200 × 30 μm and the diameter is 20–50 nm. We also observe the formation of Y-junctions in bamboo-like nanotubes as we spray the acetonitrile ferrocene and AgNO₃ mixture. The length of the synthesized Y-junction nanotube bundles is ~2 μm. Some more complex Ψ-shaped junctions are also found to be present. The diameters of the Y-junction nanotubes is ~80 nm at the junction and 25–50 nm at the branches.     

Y型微通道两相流内部流动特性刘

利用显微粒子图像测速技术、高速度数码显微系统及数值模拟方法研究了Y 型微通道内液滴的形成. 主要考虑了Y 型角度（45°,90°,135°,180°）、两相流量大小等因素的影响. 发现在挤压机制中,Y 型微通道内分散相液滴的形成主要受到来自连续相的剪切作用,Y 型角度越小,分散相所受到的剪切作用越大. 在液滴生成过程中,连续相速度剖面呈非对称抛物线型分布. 当Y 型角度小于180°时,角度的变化对液滴直径大小影响较小,但角度的减小会加快液滴的生成时间. 当Y 型角度为180°时,生成的液滴体积最大且生成时间最长. 毛细数对液滴直径和生成时间的变化同时产生影响,连续相毛细数的增大使得连续相在两相交汇位置处对分散相的作用力更集中,导致分散相更易破裂.     

Nanotubes and nanowires

Synthesis and characterization of nanotubes and nanowires constitute an important part of nanoscience since these materials are essential building units for several devices. We have prepared aligned carbon nanotube bundles and Y-junction nanotubes by the pyrolysis of appropriate organic precursors. The aligned bundles are useful for field emission display while the Y-junction nanotubes are likely to be useful as nanochips since they exhibit diode properties at the junction. By making use of carbon nanotubes, nanowires of metals, metal oxides and GaN have been obtained. Both the oxide and GaN nanowires are single crystalline. Gold nanowires exhibit plasmon bands varying markedly with the aspect ratio. GaN nanowires show excellent photoluminescence characteristics. It has been possible to synthesise nanotubes and nanowires of metal chalcogenides by employing different strategies.     

Effect of PVA functionalization on hydrophilicity of Y-junction single wall carbon nanotubes

Hydrophilic surface of carbon nanotubes (CNTs) are of great interest for various applications including chemical and biological sensing. Surface functionalization of single wall carbon nanotubes (SWNTs) mats with a biocompatible polymer polyvinyl alcohol (PVA) was studied. PVA modification induced a drastic change in water wettability of the SWNT surface transforming it from hydrophobic to highly hydrophilic. These PVA modified SWNTs mats have also demonstrated increasing impedance variation in relative humidity compared to the pristine nanotubes. An appreciable change in conductivity of Y-junction SWNT mats as a function of relative humidity indicates its potential application as humidity sensor. This higher sensitivity for humidity variation shown in Y-junction SWNT mats could be attributed to the greater portion of semiconducting nanotubes in these mats revealed by Raman analysis. A possible conductance changing mechanism of surface modified SWNTs mats is discussed.     

Effect of Residual Resist on Performance of Single-Mode 1 × 4 Optical Splitter in Photosensitive Polymer

Abstract

Polymer residues are generally left in the Y-junctions of the conventional splitters. Besides increased insertion loss, the Y-junction residue results in asymmetric distribution of power at device outputs. An analysis of the device performance in the presence of junction residue is presented and a design to overcome the non-uniformities in output power distribution brought about by the presence of the residue is proposed.     

Y型微通道内双重乳液流动破裂机理

基于体积分数法建立了Y型微通道中双重乳液流动非稳态理论模型,数值模拟研究了Y型微通道内双重乳液破裂情况,详细分析了双重乳液流经Y型微通道时的流场信息以及双重乳液形变参数演化特性,定量地给出了双重乳液流动破裂的驱动以及阻碍作用,揭示了双重乳液破裂流型的内在机理.研究结果表明:流经Y型微通道时,双重乳液受上游压力驱动产生形变,形变过程中乳液两端界面张力差阻碍双重乳液形变破裂,两者正相关;隧道的出现将减缓双重乳液外液滴颈部收缩速率以及沿流向拉伸的速率,并减缓了内液滴沿流向拉伸的速率,其对于内液滴颈部收缩速率影响不大;隧道破裂和不破裂工况临界线可以采用幂律关系式l~*=βCa~b进行预测,隧道破裂和阻塞破裂工况临界线可以采用线性关系l~*=α描述;与单乳液运动相图相比,双重乳液运动相图各工况的分界线关系式系数α和β均相应增大.     

A flattop PLC polymer waveguide interleaver based on folded two-stage-cascaded Y-junction Mach-Zehnder interferometers

We demonstrate realization of a flattop Y-Junction Planar Optical Waveguide Interleaver (YJPOWI) with a channel spacing of 100 GHz through a novel scheme of folded cascaded two-stage unbalanced Mach-Zehnder interferometers (MZI) fabricated on a polymer Planar Lightwave Circuit (PLC) platform. The characteristic 0.5 dB passbands of the interleaver centered at ITU wavelength grids at its two output ports were 50 and 45 GHz, respectively. The operating bandwidth of the device spanned the entire C band of a fiber amplifier and it is compact in size (1.3 × 1.4 cm²). In addition, the device is easy to fabricate and do not require any individual heater to trim its performance.     

Photonic crystal optical switch using a new slow light waveguide and heterostructure Y-junctions

In this paper we propose a photonic crystal Mach-Zehnder interferometer (MZI) based on a new coupled-cavity waveguide, where its advantage over the previous type of photonic crystal coupled-cavity waveguide is discussed. A heterostructure Y-junction is comprised of square and hexagonal lattices of the new coupled-cavity waveguide. It is designed by applying the temporal coupled-mode theory and is optimized, where an overall throughput efficiency of more than 90% is achieved at the wavelength of 1.55 μm. The design of the Y-junction is performed using finite-difference time-domain method. The designed heterostructure Y-junction is used in the structure of a MZI, where its arms are approximately as short as 24 μm. Finally, the transient response of the proposed optical switch is investigated.     

Novel composite beam splitter with directional coupler and Y-junction using photonic crystal

We propose and analyze a novel multiway high efficiency composite beam splitter based on propagation properties of the light waves in directional coupler and Y-junction. The splitting properties of the beam splitter have been numerically simulated and analyzed using the PWE and FDTD methods. Then in order to obtain equal distribution of power, we place and adjust some additional rods in the output waveguides to optimize the devices. It was shown that a large separating angle, a high beam rate, high flexibility, has been extended to have more light output channels in the beam splitter.     

Size effect of quantum conductance in carbon nanotube Y-Junctions

This paper studies the quantum conductance properties of three-terminated carbon nanotube Y-junctions, which are built by connecting three (5,5) single-walled carbon nanotubes. The results show that the quantum conductance at the Fermi energy oscillates periodically with the junction's size, and the number of oscillating periodic layers is 3 which is the same as that in the two terminated $(10,0)/m(5,5)/(10,0)$ junctions. Moreover, this Y-junction with different size exhibits obvious different distribution of electron current in the two drain branches, called shunt valve effect of electronic current. Thus the degree of this effect can be controlled and modulated directly by constructing the three branches' sizes or the distribution of defect. The results show in detail that the difference between the two drain currents can be up to two times for some constructions with special sizes. In addition, the uniform distribution of defects in the Y-junction leads to lower quantum conductance than that of other defect configurations.