Magnetization Dynamics of an Individual Single‐Crystalline Fe‐Filled Carbon Nanotube

The magnetization dynamics of individual Fe‐filled multiwall carbon‐nanotubes (FeCNT), grown by chemical vapor deposition, are investigated by microresonator ferromagnetic resonance (FMR) and Brillouin light scattering (BLS) microscopy and corroborated by micromagnetic simulations. Currently, only static magnetometry measurements are available. They suggest that the FeCNTs consist of a single‐crystalline Fe nanowire throughout the length. The number and structure of the FMR lines and the abrupt decay of the spin‐wave transport seen in BLS indicate, however, that the Fe filling is not a single straight piece along the length. Therefore, a stepwise cutting procedure is applied in order to investigate the evolution of the ferromagnetic resonance lines as a function of the nanowire length. The results show that the FeCNT is indeed not homogeneous along the full length but is built from 300 to 400 nm long single‐crystalline segments. These segments consist of magnetically high quality Fe nanowires with almost the bulk values of Fe and with a similar small damping in relation to thin films, promoting FeCNTs as appealing candidates for spin‐wave transport in magnonic applications.     

Formation and mechanical characterisation of SU8 composite films reinforced with horizontally aligned and high volume fraction CNTs

Carbon nanotube (CNT) reinforced composites have been identified as promising structural materials for the mechanical components of microelectromechanical systems (MEMS), potentially leading to advanced performance. High alignment and volume fraction of CNTs in the composites are the prerequisites to achieve such desirable mechanical characteristics. In particular, horizontal CNT alignment in composite films is necessary to enable high longitudinal moduli of the composites which is crucial for the performance of microactuators. A practical process has been developed to transfer CNT arrays from vertical to horizontal alignment which is followed by in situ wetting, realign and pressurized consolidation processes, which lead to a high CNT volume fraction in the range of 46-63%. As a result, SU8 epoxy composite films reinforced with horizontally aligned CNTs and a high volume faction of CNTs have been achieved with outstanding mechanical characteristics. The transverse modulus of the composite films has been characterised through nanoindentation and the longitudinal elastic modulus has been investigated. An experimental transverse modulus of 9.6 GPa and an inferred longitudinal modulus in the range of 460-630 GPa have been achieved, which demonstrate effective CNT reinforcement in the SU8 matrix.     

短纤维橡胶基复合材料模量的理论预测

基于Ｈａｌｐｉｎ－Ｔｓａｉ方程，引入短纤维平均长度和取向因子ｆｐ考虑尼龙短纤维／氯丁橡胶天然橡胶复合材料中短纤维的长度分布和纤维取向对纵向杨氏模量的影响，提出直接用ｆｐ修正ζ来考虑取向影响的新方法，ζθ（ｆｐ）＝Ｌｄ＾－１（ｆｐ＋１）。结果表明，纵向模量的理论预测值和实验值的相关性较好，对横向模量，用ζ＝２＋Ｋｖｆ（Ｋ为决定于体系的常数）考虑取向的影响，预测也较成功。     

纵向拉伸对尼龙帘线-橡胶复合材料横向拉伸力学性能影响的实验研究

采用十字形试件,在双轴拉伸条件下研究了尼龙帘线-橡胶复合材料单层板纵向定载荷对横向力学性能的影响和横向定载荷对纵向力学性能的影响。实验结果表明:纵向拉伸载荷对尼龙帘线-橡胶复合材料的横向拉伸力学性能有很大的影响。随着纵向拉伸载荷的增加,横向应力应变关系发生了很大的变化;横向拉伸强度先上升然后又下降;而其断裂变形和变形能却逐渐减小。横向拉伸载荷对尼龙帘线-橡胶复合材料的纵向拉伸力学性能影响却很小。这可能与材料纵向和横线拉伸性能差异太大有关。     

Quantum Interference in Bismuth Nanowires: Evidence for Surface Charges

We report the results of studies of the transverse magnetoresistance (MR) of single-crystal Bi nanowires with diameter d<80 nm. The single-crystal nanowire samples were prepared by the Taylor-Ulitovsky technique. Due to the semimetal-to-semiconductor transformation and high density of surface states with strong spin-orbit interactions, the charge carriers are confined to the conducting tube made of surface states. The non monotonic changes of transverse MR that are equidistant in a direct magnetic field were observed at low temperatures in a wide range of magnetic fields up to 14 T. The period of oscillations depends on the wire diameter d as for the case of longitudinal MR. An interpretation of transverse MR oscillations is presented.     

Boundary resistance in SC composite wires and cryogenic stability

The measurement of transverse resistivity of NbTi composite wires has shown already the existence of a resistive barrier between SC filaments and the copper matrix. The electric and thermal resistances of this barrier are respectively much higher than those of copper matrix and this barrier is expected to have an influence on the cryogenic stability of composite wires. The transverse and longitudinal resistivities are measured for NbTi composite wires which were heat-treated at different temperatures from 300°C to 600°C. These measurements show that the barrier grows with the heat-treatment temperature. From the experimental results, the effect of the barrier on cryogenic stability is estimated to be negligibly small for the composite wire which is heat-treated under the normal condition. As for Nb₃Sn composite wires, two different structures of composite wires, each of which has a tantalum or niobium diffusion barrier, are studied and the same measurements as on NbTi composite wires are carried out. The results obtained indicate that the transverse resistivity depends appreciably on the structure of composite wires and that the larger transverse resistivity reduces not only the cryogenic stability, but also requires a larger transfer length at a current lead junction.     

Optical transmission measurements of silver, silver-gold alloy and silver-gold segmented nanorods in thin film alumina

Silver nanorods have been grown by electrodeposition into thin film porous alumina. Transmission measurements show two peaks related to the transverse and longitudinal resonance of the nanorods. The behaviour of the longitudinal resonance peak is found to vary with nanorod length and the spectral position to depend on nanorod diameter. As the distance between the nanorods is decreased a small blue-shift of the longitudinal peak is observed. Depositing a small gold cap on top of the silver nanorods causes a red-shift of the longitudinal peak whilst, conversely, the longitudinal peak of gold nanorod arrays is comparatively insensitive to the deposition of a silver cap. Gold-silver alloy nanorods were also deposited from a mixed salt bath and a linear dependence of the transverse peak position on alloy composition was observed.     

Composite nanowire-based probes for magnetic resonance force microscopy

We present a nanowire-based methodology for the fabrication of ultrahigh sensitivity and resolution probes for atomic resolution magnetic resonance force microscopy (MRFM). The fabrication technique combines electrochemical deposition of multifunctional metals into nanoporous polycarbonate membranes and chemically selective electroless deposition of optical nanoreflector onto the nanowire. The completed composite nanowire structure contains all the required elements for an ultrahigh sensitivity and resolution MRFM sensor with (a) a magnetic nanowire segment providing atomic resolution magnetic field imaging gradients as well as large force gradients for high sensitivity, (b) a noble metal enhanced nanowire segment providing efficient scattering cross-section from a sub-wavelength source for optical readout of nanowire vibration, and (c) a nonmagnetic/nonplasmonic nanowire segment providing the cantilever structure for mechanical detection of magnetic resonance.     

Morphology controlled fabrication and ferroelectric properties of vertically aligned one-dimensional lead titanate nanoarrays

Vertically aligned nanowires and highly uniform nanoporous array thin films of PbTiO(3) are synthesized by varying anodic oxidation conditions of Ti foil followed by hydrothermal reaction in an aqueous Pb(II) acetate trihydrate solution. As-synthesized samples have single crystalline nanowire structure and polycrystalline nanoporous structure, although both are pure PbTiO(3) with a tetragonal phase. The structure of intermediate TiO(2) films obtained from different anodic oxidation conditions determines the structure of the product PbTiO(3). The relationships between these morphological structures and ferroelectric properties are investigated. Piezoresponse force microscopy reveals that both these films show ferroelectricity with clear phase contrast and well-defined hysteresis loops. The saturated longitudinal piezoelectric coefficient field (E(c)) of the nanowire sample is smaller than that of nanoporous thin film. Thus, polarization of nanowire thin film is larger in magnitude and easier to flip than that of nanoporous film.     

Quantificational Etching of AAO Template

Ni nanowires were prepared by electrodeposition in porous anodized aluminum oxide （AAO） template from a composite electrolyte solution. Well-ordered Ni nanowire arrays with controllable length were then made by the partial removal of AAO using a mixture of phosphoric acid and chromic acid （6 wt pct H3PO4：1.8 wt pct H3CrO4）. The images of Ni nanowire arrays were studied by scanning electron microscopy （SEM） to determine the relationship between etching time and the length of Ni nanowire arrays. The results indicate that the length of nanowires exposed from the template can be accurately controlled by controlling etching time.     

Large-scale, reliable and robust SERS-active nanowire substrates prepared using porous alumina templates

nanowire arrays for surface-enhanced Raman scattering applications. These nanowire films were synthesized via electrodeposition using porous alumina templates of varying order, thickness and pore diameters. Mechanical polishing has been shown to be a very effective method to prepare nanowire arrays with monodisperse length over comprehensively large dimensions. On the other hand, a convenient synthesis route has been suggested that allows the formation of nanoparticle rrays using very thin and/or large area porous alumina films. It is reckoned that even films with the smallest obtainable pore sizes can be utilized to prepare large area, fine nanoparticle arrays. Such arrays may also find use in other areas, such as solar cells and electrochemistry. Preliminary Raman experiments indicated that the nanowire/nanoparticle arrays are indeed surface-enhanced Raman scattering-active. Finally, the potentials offered by the reported processing methods for fabricating substrates with predictable and high Raman amplifications are discussed.     

Quantiflcational Etching of AAO Template

Ni nanowires were prepared by electrodeposition in porous anodized aluminum oxide (AAO) template from a composite electrolyte solution. Well-ordered Ni nanowire arrays with controllable length were then made by the partial removal of AAO using a mixture of phosphoric acid and chromic acid (6 wt pct H3PO4: 1.8 wt pct H3CrO4). The images of Ni nanowire arrays were studied by scanning electron microscopy (SEM) to determine the relationship between etching time and the length of Ni nanowire arrays. The results indicate that the length of nanowires exposed from the template can be accurately controlled by controlling etching time.     

Large scale, highly conductive and patterned transparent films of silver nanowires on arbitrary substrates and their application in touch screens

The application of silver nanowire films as transparent conductive electrodes has shown promising results recently. In this paper, we demonstrate the application of a simple spray coating technique to obtain large scale, highly uniform and conductive silver nanowire films on arbitrary substrates. We also integrated a polydimethylsiloxane (PDMS)-assisted contact transfer technique with spray coating, which allowed us to obtain large scale high quality patterned films of silver nanowires. The transparency and conductivity of the films was controlled by the volume of the dispersion used in spraying and the substrate area. We note that the optoelectrical property, σ(DC)/σ(Op), for various films fabricated was in the range 75-350, which is extremely high for transparent thin film compared to other candidate alternatives to doped metal oxide film. Using this method, we obtain silver nanowire films on a flexible polyethylene terephthalate (PET) substrate with a transparency of 85% and sheet resistance of 33 Ω/sq, which is comparable to that of tin-doped indium oxide (ITO) on flexible substrates. In-depth analysis of the film shows a high performance using another commonly used figure-of-merit, Φ(TE). Also, Ag nanowire film/PET shows good mechanical flexibility and the application of such a conductive silver nanowire film as an electrode in a touch panel has been demonstrated.     

高强瓦楞复合纸板侧压性能实验研究

为了了解高强瓦楞复合纸板侧压性能,采用夹层结构材料侧压性能的测试方法对其进行了实验测试。实验选用了10,15,20和30 mm 4种厚度的高强瓦楞复合纸板样品,分别按照横向和纵向进行了测试。结果表明:相同厚度纸板纵向的侧压强度大于横向;不同厚度纸板随着纸板厚度的增加,横向和纵向侧压强度都呈降低趋势。研究结果对于提高高强瓦楞复合纸板托箱的堆码承载能力,具有很强的实践应用价值。     

单向复合材料的应力集中系数

本文计算了实心纤维及空心纤维单向增强复合材料在横向、纵横剪切、纵向载荷形式下的应力集中系数,着重对单向增强复合材料受纵向载荷时的纵向应力集中现象进行了分析讨论。      

Dielectric Properties and Hysteresis Loops of a Ferroelectric Nanoparticle System Described by the Transverse Ising Model

In this work, we use the effective field theory based on the probability distribution method to investigate the longitudinal and transverse polarizations, susceptibility, pyroelectric coefficient, and the hysteresis behavior of a ferroelectric cubic nanowire. The effects of the core–shell exchange interaction and the core–shell transverse fields on the longitudinal and transverse polarizations, the susceptibility, the pyroelectric coefficient, and the hysteresis loops of the system are examined. Some characteristic phenomena are found in the thermal variations, depending on the physical parameters in the shell and in the core.     

Surface plasmon resonance imaging using a high numerical aperture microscope objective

We designed, constructed, and tested a surface plasmon resonance (SPR) microscope using a high numerical aperture objective from a commercially available inverted optical microscope. Such a configuration, combined with various methods to shorten the surface plasmon propagation length, achieves diffraction-limited spatial resolution in the transverse direction and near-diffraction-limited resolution in the longitudinal direction. A virtue of the objective-type SPR imaging is that we achieve distortion-free angle-resolved SPR imaging, allowing the angle-dependent reflectivity of the sample to be examined on a pixel-by-pixel basis, thus offering high-resolution information about surface properties.     

Proximity and interaction effects in arrays of I-bars

Calculations have been made of interactions and fields in two-dimensional periodic arrays of I-bars. The results of the study shed light on several questions of interactions among bubble propagation elements. We have calculated interaction effects in arrays of I-bars as a function of both longitudinal and transverse spacing between bars. Three different geometries of I-bar show similar effects; the transverse and longitudinal interactions have opposing signs and are stronger in the transverse direction. We also have calculated local and average fields for an array of I-bars of geometries chosen to facilitate comparison with recent measurements. The local field in the gap between elements is found to be highly nonuniform but with an average value that obeys a simple relationship as the gap length is varied. The field profile is also nonuniform in the transverse direction, and exhibits a proximity enhancement that depends upon gap dimension. These results support the interpretation that bar-bar interactions can influence the magnetization in propagation arrays.     

Controlled fabrication and electrical properties of long quasi-one-dimensional superconducting nanowire arrays

We report a general method for reliably fabricating quasi-one-dimensional superconducting nanowire arrays, with good control over nanowire cross section and length, and with full compatibility with device processing methods. We investigate Nb nanowires with individual nanowire cross sectional areas that range from bulklike to 10 x 11 nm, and with lengths from 1 to 100 microm. Nanowire size effects are systematically studied. In particular, a comprehensive investigation of influence of nanowire length on superconductivity is reported for the first time. All results are interpreted within the context of phase-slip models.     

Analysis of optical absorption in silicon nanowire arrays for photovoltaic applications

This paper presents analysis of the optical absorption in silicon nanowire arrays that have potential applications in solar cells. The effects of wire diameter, length, and filling ratio on the absorptance of nanowire arrays are simulated. The study reveals that nanowire arrays with moderate filling ratio have much lower reflectance compared to thin films. In a high-frequency regime, nanowire arrays have higher absorptance than their thin film counterparts. In low-frequency regime, nanowire arrays absorb less but can be designed to approach that of the film by changing the filling ratio.