Optimal design of sub-wavelength metal rectangular gratings for polarizing beam splitter based on effective medium theory

A novel optimal design of sub-wavelength metal rectangular gratings for the polarizing beam splitter （PBS） is proposed. The method is based on effective medium theory and the method of designing single layer antireflection coating. The polarization performance of PBS is discussed by rigorous couple-wave analysis （RCWA） method at a wavelength of 1550 nm. The result shows that sub-wavelength metal rectangular grating is characterized by a high reflectivity, like metal films for TE polarization, and high transmissivity, like dielectric films for TM polarization. The optimal design accords well with the results simulated by RCWA method.

Ag-modified hydrogen titanate nanowire arrays for stable lithium metal anode in a carbonate-based electrolyte

In the investigation of the next-generation battery anode,Li metal has attracted increasing attention owing to its ultrahigh specific capacity and low reduction potential.However,its low columbic efficiency,limited cycling life,and serious safety hazards have hindered the practical application of rechargeable Li metal batteries.Although several strategies have been proposed to enhance the electrochemical performance of Li metal anodes,most are centered around ether-based electrolytes,which are volatile and do not provide a sufficiently large voltage window.Therefore,we aimed to attain stable Li deposition/stripping in a commercial carbonate-based electrolyte.Herein,we have successfully synthesized hydrogen titanate(HTO)nanowire arrays decorated with homogenous Ag nanoparticles(NPs)(Ag@HTO)via simple hydrothermal and silver mirror reactions.The 3 D cross-linked array structure with Ag NPs provides preferable nucleation sites for uniform Li deposition,and most importantly,when assembled with the commercial LiNi_(0.5)Co0.2Mn_(0.3)O_(2) cathode material,the Ag@HTO could maintain a capacity retention ratio of 81.2% at 1 C after 200 cycles,however the pristine Ti foil failed to do so after only 60 cycles.Our research therefore reveals a new way of designing current collectors paired with commercial high voltage cathodes that can create high energy density Li metal batteries.

Tuning of plasmonic behaviours in coupled metallic nanotube arrays

We theoretically investigate the influence of the shape of nanoholes on plasmonic behaviours in coupled elliptical metallic nanotube arrays by the finite-difference time-domain （FDTD） method. We study the structure in two cases： one for the array aligned along the minor axis and the other for the array aligned along the major axis. It is found that the optical properties and plasmonic effects can be tuned by the effective surface charges as a result of the variation in the minor axis length. Based on the localized nature of electric field distributions, we also clearly show that the presence of localized plasmon resonant modes originates from multipolar plasmon polaritons and a large magnitude of opposing surface charges build up in the gap between adjacent nanotubes.

Effects of a bar on optical transmission through Z-shaped metallic slit arrays

We investigate the effects of a bar on optical transmission through Z-shaped metallic slit arrays by using the finite- difference time domain （FDTD） method. A new hybrid Fabry-Perot （FP） surface plasmon polariton （SPP） mode emerges when changing the geometric parameters of the bar, and this mode can be viewed as a coupling between FP mode and SPP mode. In addition, an obvious dip appears in a featured area when the bar deviates from the central line, and a small displacement of the bar leads to tremendous change of the dip. These behaviors can be attributed to the phase resonance. In short, the structure is very sensitive to the metal bar. Furthermore, it combines photonic device miniaturization with sensitivity, which is useful for making optical switches.

Ultrafast laser dynamics of metal organic frameworks/TiO_2 nano-arrays hybrid composites for energy conversion applications

Herein,we report the victorious synthesis of metal-organic frameworks(MOFs) on TiO_2 nanotubes(NTs)using a layer-by-layer(LbL) approach.Highly crystalline and homogenous thin films of MOFs were grown and characterized using XRD,SEM,FT-IR and UV/Vis spectroscopy.Moreover,the utilization of the MOF films as sensitizers was probed in bespoke Graetzel type liquid junction solar cells.The constructed cell performance revealed an I_(sc) of 1.16 mA cm^(–2),Vocof 0.63 V,FF of 0.33,and E_(ff) of 0.42%.Further,pumpprobe transient laser spectroscopy was performed to investigate the energy and charge transfer dynamics of the MOFs/TiO_2 NTs interface.The results indicated 86% injection efficiency.The ultrafast pump-probe spectroscopy allows the investigation of this process and the differences between MOFs.It also showed that the relaxation of the MOF chromophores is in competition with electron injection in the Ti O2 motif.Thus this study provides a new insight into electron transfer from photoexcited metal-organic frameworks(MOFs) into titanium dioxide.

Electric potential distribution near nanocone arrays on metal substrates

Based on the nanostructured surface model,where conical nanoparticle arrays grow out symmetrically from a plane metal substrate,a theoretical model of the local electric potential near nanocones is built when a uniform external electric field is applied.In terms of this model,the electric potential distribution near the nanocone arrays is obtained and given by a curved surface using a numerical computation method.The computational results show that the electric potential distribution near the nanocone arrays exhibit an obvious geometrical symmetry.These results could serve as a basis for explaining many abnormal phenomena,such as the abnormal infrared effects（AIREs） which are found on nanostructured metal surfaces,as well as a reference for investigating the applications of nanomaterials,such as nanoelectrodes and nanosensors.

Detection of Trace Heavy Metals Ions by Arrays of Titania Nanotubes Annealed in Nitrogen

Redox response of trace heavy metals ions（THMIs） has better performance on highly ordered vertically oriented titania nanotube arrays（TNA） annealed in nitrogen. Experimental data showed that different THMIs possess different reaction peak shapes and charge and discharge capacities. Therefore, the TNA will become an important tool used for environmental protection and facilitating the rapid determination of THMIs. THMIs of 5×10^4 mol/L concentration were measured at a scan rate of 100 mV/s. The analytical utility of TNA is demonstrated in a neutral 0.5 mol/L Na2SO4 solution. The results sufficiently show that titania nanotube arrays electrodes（TNAE） will be used to measure THMIs.

Homogenous metallic deposition regulated by abundant lithiophilic sites in nickel/cobalt oxides nanoneedle arrays for lithium metal batteries

Although lithium(Li)metal delivers the highest theoretical capacity as a battery anode,its high reactivity can generate Li dendrites and"dead"Li during cycling,resulting in poor reversibility and low Li utilization.Inducing uniform Li plating/stripping is the core of solving these problems.Herein,we design a highly lithiophilic carbon film with an outer sheath of the nanoneedle arrays to induce homogeneous Li plating/stripping.The excellent conductivity and 3D framework of the carbon film not only offer fast charge transport across the entire electrode but also mitigate the volume change of Li metal during cycling.The abundant lithiophilic sites ensure stable Li plating/stripping,thereby inhibiting the Li dendritic growth and"dead"Li formation.The resulting composite anode allows for stable Li stripping/plating under 0.5 mA cm^(-2) with a capacity of 0.5 mA h cm^(-2) for 4000 h and 3 mA cm^(-2) with a capacity of3 mA h cm^(-2) for 1000 h.The Ex-SEM analysis reveals that lithiophilic property is different at the bottom,top,or channel in the structu re,which can regulate a bottom-up uniform Li deposition behavior.Full cells paired with LFP show a stable capacity of 155 mA h g^(-1) under a current density of 0.5C.The pouch cell can keep powering light-emitting diode even under 180°bending,suggesting its good flexibility and great practical applications.

Manipulating d-d orbital hybridization induced by Mo-doped Co_(9)S_(8) nanorod arrays for high-efficiency water electrolysis

Precisely refining the electronic structure of electrocatalysts represents a powerful approach to further optimize the electrocatalytic performance.Herein,we demonstrate an ingenious d-d orbital hybridization concept to construct Mo-doped Co_(9)S_(8) nanorod arrays aligned on carbon cloth(CC)substrate(abbreviated as Mo-Co_(9)S_(8)@CC hereafter)as a high-efficiency bifunctional electrocatalyst toward water electrolysis.It has experimentally and theoretically validated that the 4d-3d orbital coupling between Mo dopant and Co site can effectively optimize the H_(2)O activation energy and lower H^(*)adsorption energy barrier,thereby leading to enhanced hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)activities.Thanks to the unique electronic and geometrical advantages,the optimized Mo-Co_(9)S_(8)@CC with appropriate Mo content exhibits outstanding bifunctional performance in alkaline solution,with the overpotentials of 75 and 234 mV for the delivery of a current density of 10 mA cm^(-2),small Tafel slopes of 53.8 and 39.9 mV dec~(-1)and long-term stabilities for at least 32 and 30 h for HER and OER,respectively.More impressively,a water splitting electrolylzer assembled by the self-supported Mo-Co_(9)S_(8)@CC electrode requires a low cell voltage of 1.53 V at 10 mA cm^(-2)and shows excellent stability and splendid reversibility,demonstrating a huge potential for affordable and scalable electrochemical H_(2) production.The innovational orbital hybridization strategy for electronic regulation herein provides an inspirable avenue for developing progressive electrocatalysts toward new energy systems.

Wear Studies on Metal Matrix Composites: a Taguchi Approach

An attempt has been made to study the influence of wear parameters like applied load, sliding speed, sliding distance and percentage of reinforcement on the dry sliding wear of the metal matrix composites. A plan of experiments, based on techniques of Taguchi, was performed to acquire data in controlled way. An orthogonal array and the analysis of variance were employed to investigate the influence of process parameters on the wear of composites. The objective is to establish a correlation between dry sliding wear of composites and wear parameters. These correlations were obtained by multiple regressions. Finally, confirmation tests were conducted to verify the experimental results foreseen from the mentioned correlations.

In-situ design and construction of lithium-ion battery electrodes on metal substrates with enhanced performances：A brief review

For the ever-growing demand of advanced lithium-ion batteries, it is highly desirable to grow self-supported micro-/nanostructured arrays on metal substrates as electrodes directly. The in-situ growth of electrode materials on the conducting substrates greatly simplifies the electrode fabrication process without using any binders or conductive additives. Moreover, the well-ordered arrays closely connected to the current collectors can provide direct electron transport pathways and enhanced accommodation of strains arisen from lithium ion lithiation/delithiation. This article summarizes our recent work on design and construction of lithium-ion battery electrodes on metal substrates. An aqueous solution-based process and a microemulsion-mediated process have been respectively presented to control the kinetic and thermodynamic processes for the micro-/nanostructured array growth on metal substrates, with particular attention to CuO nanorod arrays and microcog arrays successfully prepared on Cu foil substrates. They can be directly used as binder-free electrodes to build advanced lithium-ion batteries with high energy, high safety and high stability.

Modified method of surface plasmons in metal superlattices

We present a modified method to solve the surface plasmons （SPs） of semi-infinite metal/dielectric superlattices and predicted new SP modes in physics. We find that four dispersion-equation sets and all possible SP modes are determined by them. Our analysis and numerical calculations indicate that besides the SP mode obtained in the original theory, the other two SP modes are predicted, which have either a positive group velocity or a negative group velocity. We also point out the possible defect in the previous theoretical method in accordance to the linear algebra principle.

Tribological Behaviour of Aluminium/Alumina/Graphite Hybrid Metal Matrix Composite Using Taguchi’s Techniques

Tribological behaviour of aluminium alloy (Al-Si10Mg) reinforced with alumina (9%) and graphite (3%) fabricated by stir casting process was investigated. The wear and frictional properties of the hybrid metal matrix composites was studied by performing dry sliding wear test using a pin-on-disc wear tester. Experiments were conducted based on the plan of experiments generated through Taguchi’s technique. A L27 Orthogonal array was selected for analysis of the data. Investigation to find the influence of applied load, sliding speed and sliding distance on wear rate, as well as the coefficient of friction during wearing process was carried out using ANOVA and regression equations for each response were developed. Objective of the model was chosen as ‘smaller the better’ characteristics to analyse the dry sliding wear resistance. Results show that sliding distance has the highest influence followed by load and sliding speed. Finally, confirmation tests were carried out to verify the experimental results and Scanning Electron Microscopic studies were done on the wear surfaces.

Ultrasound Imaging in Nuclear Reactors Cooled by Liquid Metals

In nuclear reactors cooled by liquid metals, ultrasound is the only type of field that allows obtaining images of the reactor cores and diagnostics of the integrity of the fuel assemblies. The article discusses the features of the practical realization of ultrasonic imaging systems based on phased arrays and offers an alternative solution of imaging on the basis of the acoustic lenses of refractive and diffraction types. Using lenses eliminates many of the technical and technological problems associated with the development of multi-element phased arrays. It is shown that lens systems allow using traditional methods of transformation of acoustic fields into the visible images by 2D piezo matrix and a more promising way of acoustooptical transformation based on coherent optical interferometry.

Optimization of Friction and Wear Behaviour in Hybrid Metal Matrix Composites Using Taguchi Technique

Al-7075 alloy-base matrix, reinforced with mixtures of silicon carbide (SiC) and boron carbide (B4C) particles, know as hybrid composites have been fabricated by stir casting technique (liquid metallurgy route) and optimized at different parameters like sliding speed, applied load, sliding time, and percentage of reinforcement by Taguchi method. The specimens were examined by Rockwell hardness test machine, Pin on Disc, Scanning Electron Microscope (SEM) and Optical Microscope. A plan of experiment generated through Taguchi’s technique is used to conduct experiments based on L27 orthogonal array. The developed ANOVA and the regression equations were used to find the optimum wear as well as co-efficient of friction under the influence of sliding speed, applied load, sliding time and percentage of reinforcement. The dry sliding wear resistance was analyzed on the basis of “smaller the best”. Finally, confirmation tests were carried out to verify the experimental results.

Ordered silicon nanorod arrays with controllable geometry and robust hydrophobicity

Highly ordered silicon nanorod（Si NR） arrays with controllable geometry are fabricated via nanosphere lithography and metal-assisted chemical etching. It is demonstrated that the key to achieving a high-quality metal mask is to construct a non-close-packed template that can be removed with negligible damage to the mask. Hydrophobicity of Si NR arrays of different geometries is also studied. It is shown that the nanorod structures are effectively quasi-hydrophobic with a contact angle as high as 142°, which would be useful in self-cleaning nanorod-based device applications.

大型双板导波天线对核电磁脉冲传输损耗和畸变特性

大型导波核电磁脉冲模拟器可为系统级装备试验提供自由空间辐照环境。针对此类模拟器常用的双板导波天线可能存在的传输损耗和波形畸变问题,以电磁仿真软件和算例对比分析研究了3种主要的影响因素,包括土壤的介电损耗及其抑制、前锥板向平行板转折的结构不连续、线栅阵列代替金属板的缝隙泄漏。研究结果表明:对上下极板等宽的情形,土壤损耗可使电压传输效率降低25%以上;适当展开下极板宽度可屏蔽土壤损耗;上极板转折处的结构不连续可导致平行段试验空间内电场呈现双峰交叠、幅度降低、波形畸变等特征;最大线间距0.3 m不会导致前沿显著变化。作为工程应用案例,设计了前锥长度60 m、顶高15 m、下极板拓宽3 m、由100根线栅阵列构成上极板的导波天线,试验空间超过20 m×20 m×10 m,实现了前沿2.5~3.0 ns双指数脉冲的无损耗、无畸变传输。

金属氧化物半导体MEMS气体传感器研究进展

随着物联网的快速发展,各领域对气体监测的需求越来越大,基于先进微机电系统(Micro-electro-mechanical systems, MEMS)技术的金属氧化物半导体(Metal oxide semiconductor, MOS)气体传感器在过去几十年里取得了很大发展。MEMS微热板的多样化设计、MOSs纳米结构的多样化以及机器学习算法的出现为MEMS的传感性能以及智能传感系统的构建提供了很大助力。本文从MEMS气体传感器的分类、制备和应用以及传感器阵列的构建等方面综述了金属氧化物半导体MEMS气体传感器的最新研究进展,并对MEMS基气体传感器的发展前景进行了总结和展望。

特殊螺纹油管密封面相控阵超声图像特征分析

特殊螺纹油管密封面的接触状况对密封性能有重要影响。超声反射幅值应力技术仅依靠反射系数单一参数,难以全面评估密封面不同接触状况。为此,通过采集不同扭矩及无螺纹脂情况下油管密封面相控阵超声图像,提取图像的纹理特征,分析纹理特征参数与不同接触状况下的定性及定量关系。研究结果表明:随着油管扭矩的增大,超声图像灰度均值、灰度方差及偏度均减小;油管密封面超声图像灰度共生矩阵对比度,随着油管扭矩的增大,在45°、90°及135°方向上呈线性减小;在0°方向上不含螺纹脂的超声图像是同扭矩下含螺纹脂对比度的2.19倍;油管密封面超声图像灰度共生矩阵熵值,随着油管扭矩的增加,在0°、45°、90°及135°方向上呈线性减小。研究结果可为油管密封面不同接触状况下超声检测图像定性及定量表征提供数据支撑。

基于平面线圈阵列的电动汽车无线充电金属异物检测方法研究

针对电动汽车无线充电,有效检测充电区域内的金属异物对保障电动汽车的充电安全和充电效率具有重要意义。因此,文中提出了一种基于平面线圈阵列的金属异物检测新方法。利用4×4结构的平面线圈阵列作为主要感测元件,结合电磁层析成像技术重建充电区域的电导率分布图像,对重建图像进行后处理获得金属异物的轮廓、位置和数量信息。有限元仿真与实物实验结果表明,此方法能有效检测数种常见金属异物。