Bi_(3.15)Nd_(0.85)Ti_3O_(12)纳米结构的制备与XPS研究

采用水热法在低温合成了铋层状钙钛矿结构Bi_(3.15)Nd_(0.85)Ti_3O_(12)(BNdT)纳米材料,利用X-射线衍射(XRD)、扫描电子显微镜(SEM)表征产物的晶相和形貌,研究了反应温度和聚乙烯醇(PVA)对水热合成BNdT纳米结构的影响,运用X-射线光电子能谱(XPS)对BNdT纳米结构的化学组分和元素价态进行了表征.结果表明,反应温度和PVA对水热合成BNdT纳米结构的形貌有较大影响;XPS研究显示BNdT纳米结构的表面存在氧空位和轻微的Bi过量.     

Applied Voltage and Near‐Infrared Light Enable Healing of Superhydrophobicity Loss Caused by Severe Scratches in Conductive Superhydrophobic Films

The fabrication of self‐healing/healable superhydrophobic films that can conveniently and repeatedly restore the loss of superhydrophobicity caused by severe mechanical damage, such as deep and wide surface scratches, remains challenging. In the present work, conductive superhydrophobic films that are healable by means of an applied voltage or near infrared (NIR) light irradiation are fabricated by depositing a layer of Ag nanoparticles and Ag nanowires (AgNPs‐AgNWs) on a thermally healable polycaprolactone (PCL)/poly(vinyl alcohol) (PVA) composite film, followed by the deposition of 1H,1H,2H,2H‐perfluorodecanethiol. The AgNPs‐AgNWs layer not only provides micro‐ and nanoscaled hierarchical structures in support of superhydrophobicity but also serves as an electrothermal or photothermal heater to enable healing of the underlying PCL/PVA film under the assistance of a low applied voltage or low‐power NIR light irradiation. Because of the strong adhesion between the PCL/PVA film and the AgNPs‐AgNWs layer, the healability of the PCL/PVA film is successfully conveyed to the conductive superhydrophobic layer, which can rapidly and repeatedly restore the loss of superhydrophobicity caused by cuts several hundreds of micrometers wide. The combined electrothermal and superhydrophobic properties endow the healable conductive superhydrophobic films with improved durability and usefulness as self‐cleaning, antiicing, and snow‐removing surfaces.     

电纺SnO_2纳米纤维的制备及其气敏特性

采用聚乙烯醇(PVA,Mw=80000g/mol)和五水合四氯化锡(SnCl4.5H2O)作为静电纺丝前驱液,着重研究了纺丝电压、前驱液中PVA浓度及煅烧温度等因素对纺丝过程及纤维特性的影响,并用扫描电镜(SEM)和X射线衍射(XRD)等分析手段对纤维的微观结构、表面形貌和结晶状态进行了表征。结果表明,当纺丝电压为4kV、纺丝液中PVA质量分数为7%、退火温度为700℃时,可以得到平均直径为300nm的连续SnO2纳米纤维。该纤维对乙醇的响应恢复时间小于15s,检测极限低于10×10-9。     

Spin-Crossover Grafted Monolayer of a Co(II) Terpyridine Derivative Functionalized with Carboxylic Acid Groups

The synthesis and characterization of a new Co(II) spin-crossover (SCO) complex based on 4′-(4-carboxyphenyl)−2,2′:6′,2″-terpyridine ligand are reported. This complex can be successfully grafted on silver surface maintaining the SCO behavior. Thus, atomic force microscopy (AFM), matrix assisted laser desorption ionization – time-of-flight mass spectrometry (MALDI-TOF MS), Raman spectroscopy, and XPS measurements, upon surface deposition, evidence the formation of a monolayer of intact molecules grafted through carboxylate groups to the Ag surface. Three different techniques: Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS), supported by first-principles calculations, confirm that the deposited molecules undergo a gradual spin transition with temperature. This phenomenon is unprecedented for a monolayer of molecules directly grafted onto a metallic surface from solution.     

Insight into the Solid Electrolyte Interphase Formation in Bis(fluorosulfonyl)Imide Based Ionic Liquid Electrolytes

The formation of the solid electrolyte interphase (SEI) in an ionic liquid electrolyte of 0.5 m lithium bis(fluorosulfonyl)imide (LiFSI) in 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide at high cell voltages (1.7–1.9 V) is investigated in ordered mesoporous carbon (OMC) based Li metal cells using an operando small-angle neutron scattering (SANS) technique coupled with electrochemical impedance spectroscopy and ex situ X-ray photoelectron spectroscopy (XPS). It is demonstrated that discharging the OMC Li metal cells to ≈2 V and holding the cell voltage constant induces a rapid current increase with time, confirming extensive reduction and SEI formation. XPS analysis reveals that LiF is formed at open cell voltage (OCV), which is attributed to the carbenes generated at the lithium negative electrode because of its reaction with EMIm cation diffusing to and initiating the reaction with FSI⁻ anions at the carbon positive electrode. It is confirmed that the chemical reaction at OCV and electrochemical reduction at high cell voltage of the FSI⁻ anion plays a protective role against EMIm cation co-intercalation into the carbon positive electrode during the initial discharge. Operando SANS studies also suggest that slight differences occur in the surface composition and reaction mechanism as a function of cell voltage.     

聚乙烯醇(PVA)在氢醌(H_2Q)存在下的氧化降解

本文应用电子显微镜研究了PVA在H_2Q存在下的氧化降解机理,并对PVA降解前后的微观结构变化进行了观察。结果表明:高聚物PVA在有光敏剂(H_2Q)存在下,能引发PVA产生降解,其降解机理是按自由基连锁反应过程进行的,降解后的低聚合度PVA的微结构形态也与降解前不同。     

KNN基无铅压电陶瓷材料制备的研究进展

碱金属铌酸盐系的(K,Na)NbO_3(KNN)因其具有高压电常数(d_(33)),高机电耦合系数,高品质因数及高居里温度(T_C)而成为无铅压电材料研究的热点。为了探索高性能KNN无铅压电陶瓷材料制备及应用,该文综述了其相关制备工艺、性能特点,重点阐述了KNN系无铅压电材料的掺杂、烧结、极化及其对性能的影响,指出了KNN无铅压电陶瓷的掺杂改性及工艺优化研究是其有效的研究方向。     

Silver metallization for advanced interconnects

Silver metal has the highest room-temperature electrical conductivity of any substance; however, it has found limited acceptance in the electronic industry (e.g., silver filled epoxy) due to the high rate of metal corrosion and migration causing dendrites and electrical failures. With decreasing transistor feature sizes, device-operating voltages have scaled down considerably. In this paper, the reliability of silver and potential benefits of silver metallization are discussed in terms of future trends in microelectronic interconnections. Experimental data supports existing reliability models indicating that electrochemical migration failure modes may not be operative at low voltages. Silver metal corrosion and migration are studied under accelerated test conditions to obtain a qualitative understanding of the failure mechanism     

Impact of Morphology on Printed Contact Performance in Carbon Nanotube Thin‐Film Transistors

Silver nanoparticles (NPs) are the most widely used conductive material throughout the printed electronics space due to their high conductivity and low cost. However, when interfacing with other prominent printed materials, such as semiconducting carbon nanotubes (CNTs) in thin‐film transistors (TFTs), silver is suboptimal when compared to more expensive or less conductive materials. Consequently, there would be significant value to improving the interface of printed silver to CNT films. In this work, the impact of nanostructure morphology on the electrical properties of printed silver and nanotube junctions in CNT‐TFTs is investigated. Three distinct silver morphologies (NPs, nanoflakes – NFs, and nanowires – NWs) are explored with top‐ and bottom‐contact configurations for each. The NF morphology in a top‐contact configuration is found to yield the best electrical interface to CNTs, resulting in an average contact resistance of 1.2 MΩ ? µm. Beyond electrical performance, several trade‐offs in morphology selection are revealed, including print resolution and process temperature. While NF inks produce the best interfaces, NP inks produce the smallest features, and NW inks are compatible with low processing temperatures (<80 °C). These results outline the trade‐offs between silver contact morphologies in CNT‐TFTs and show that contact morphology selection can be tailored for specific applications.     

纸基PVA无芯片RFID湿度传感器

传统湿度传感器制造工艺复杂、需有线连接信号,对此,文中提出一种纸基无芯片射频识别(Radio Frequency Identification, RFID)湿度传感器。为提升传感器谐振特性,选择非对称开口环内部分布式加载金属碎片作为传感器结构,聚乙烯醇(PVA)作为湿敏材料,使用遗传算法和HFSS射频仿真软件来设计并优化传感器结构。以喷墨打印技术制作传感器样品,采用滴涂法在传感器表面分别制备了5%、10%、15%三种质量浓度比的PVA薄膜。湿敏特性仿真及测试结果一致表明：PVA与纸基底协同作用可显著提高传感器灵敏度。随PVA浓度增加灵敏度增加,15%PVA传感器灵敏度最高,高湿灵敏度达到12.22 MHz/%RH,但随PVA浓度增加恢复特性变差,5%PVA湿度传感器具有良好的恢复特性,恢复度达83.87%。通过长期多次实验验证了PVA纸基湿度传感器具有良好的温度稳定性与中长期稳定性。与同类研究成果对比,文中设计在感湿范围及灵敏度方面有优势且制造工艺更简单,为低成本湿度传感器的大规模使用提供了可能。     

内外相结构的粉浆法制备白光LED

为了获得白光LED芯片表面上优质性能的荧光粉层,提出一种内外相结构的粉浆法。基于水溶性感光胶的平面涂层技术,采用四氢呋喃将硅胶均匀分散后,通过有机硅消泡剂乳化形成以聚乙烯醇(PVA)为外相,以憎水性粘合剂硅胶为内相的乳液。实验结果表明,这种粉浆具备硅胶的优良特性,提高了荧光粉层的物化性能,显影后在芯片表面得到均匀且厚度可控的平面涂层,改善了白光的均匀性,提高了芯片的出光效率。     

Laser-induced implantation of silver particles into poly(vinyl alcohol) films and its application to electronic-circuit fabrication on encapsulated organic electronics

In this study, we propose a new laser-induced implantation based approach for embedding electronic interconnects in this study. Direct implantations of silver particles, vaporized by a pulsed laser from a silver film initially pre-coated on a transparent glass substrate, into poly(vinyl alcohol) (PVA)-encapsulated organic electronic devices as electronic conducting circuits are demonstrated. Two test carriers are the devices of organic thin-film transistors and polymeric light-emitting diodes. Device property characterizations indicate the implanted circuits can work smoothly. The implantation process is driven by the high-energy ejected particles that soften and melt the PVA layer and penetrate into it until their momentums are totally lost. The penetration depth increases with the number of laser pulses and is becoming saturated as the pulse number is getting high. A conducting circuit, with length of 2 μm, can be completely embedded within 3 laser pulses. Due to its flexibility in embedding metals into an encapsulated device, this technique can be used for repairing internal circuit damage. Besides, all steps can be executed in the ambient environment and at room temperature that is suitable for plastic substrate processing.     

用于超宽带探地雷达的新型功率纳秒级开关

将高速断路开关与电感储能元件结合应用于功率脉冲产生系统中非常有前景,短时间内负载上产生的脉冲电压是储能元件电压的好几倍.在20世纪末期.发现了一种当电流从正向转至反向时,硅半导体PN结中出现高电压快速恢复现象,由此产生了一种新型固态等离子体断路开关漂移阶跃恢复二极管.这种开关具有长寿命、低抖动、高重频等优点.详细地分析了这种开关快恢复的物理特性,设计了基于此开关的发射机,可应用于探地雷达系统中.     

Flexible Cu(In,Ga)Se2 solar cells with reduced absorber thickness

Reduction of the absorber thickness combined with deposition on a flexible substrate is a technically viable strategy to allow lower cost manufacturing of Cu(In,Ga)Se₂ solar modules. Flexible plastic substrates, however, require a low‐temperature deposition process and appropriate control of the band gap grading for achieving high efficiencies. In this work, we developed solar cells on polyimide films using evaporated Cu(In,Ga)Se₂ absorbers with thickness of 0.8–1.3 µm. The double Ga‐grading profile across the absorber thickness was modified by varying the maximum Cu excess at the end of the second stage or by adapting the In and Ga evaporation flux profiles during the growth process. By minimizing the Cu excess during the intermediate stage of the growth process, no loss in open circuit voltage and fill factor is observed compared with a device having a thicker absorber. Efficiency of 16.3% was achieved for cells with an absorber thickness of 1.25 µm. Insufficient absorption of photons in the long wavelength region is mainly responsible for current loss. By changing the In and Ga evaporation profiles, the shape and position of the Ga notch were effectively modified, but it did not lead to a higher device performance. Modifications of the Ga compositional profile could not help to significantly reduce absorption losses or increase charge carrier collection in absorbers with thickness below 1 µm. Changes of open circuit voltage and fill factor are mostly related to differences in the net acceptor density or the reverse saturation current rather than changes of the double Ga grading. Copyright © 2013 John Wiley & Sons, Ltd.     

Evaluation of Electrochemical Migration on Flexible Printed Circuit Boards with Different Surface Finishes

This study investigated the influence of three parameters, the distance between electrodes, bias voltage, and surface finish material, on the electrochemical migration (ECM) in flexible printed circuit boards (FPCBs) during water drop testing. The ECM rate increased when the distance between electrodes of opposite polarity was decreased and the bias voltage was increased. Irrespective of the distance between the electrodes and the bias voltage, the growth rate of dendrites from the cathode to the anode decreased with the following order of surface finish material: Cu, electroless Ni, and electroless nickel-immersion gold. The order of the corrosion rate in distilled water with pH 6.5 was the same. Therefore, the ECM rate on the FPCB increased with increasing corrosion rate of the FPCB surface finish material.     

Effect of deposition power in fabrication of highly efficient CdS:O/CdTe thin film solar cell by the magnetron sputtering technique

Polycrystalline II–VI semiconductor materials such as oxygenated CdS have a wide and tunable band gap (≥2.5 eV) which plays an important role in increasing the light absorption capacity of CdTe absorber. In this study, the ultra-thin CdS:O and CdTe films were deposited by the sputtering technique and the optimum condition of deposition power is investigated. The prepared ultra-thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray photoelectron spectroscopy (XPS), UV–vis spectrometry, Hall Effect and current–voltage measurements techniques. The complete cell was then fabricated by the sputtering technique with a novel configuration of ‘glass/FTO/ZnO:Sn/CdS:O/CdTe/C:Cu/Ag’. To avoid the pin hole effect, the high resistive ZnO:Sn layer was deposited as a buffer layer in between the FTO and CdS:O films. It has been observed that the cell performance parameters are found to be varied with deposition power of CdO:S films and an overall conversion efficiency of 10.27% was achieved.     

Heterojunction of SrTiO3/TiO2 nanotubes with dominant (001) facets: Synthesis,formation mechanism and photoelectrochemical properties

Controllable growth of anatase TiO₂ with dominant high reactive crystal facets has attracted intense interest in the past few years due to their unique structure-dependent properties. In this work, SrTiO₃/TiO₂ heterostructure nanotubes (SrT) arrays films with high reactive dominant (001) facets of anatase TiO₂ were successfully prepared through the part conversion of TiO₂ by a hydrothermal method. Various characterizations were used to investigate the morphologies, crystal phases and chemical compositions of the prepared samples. Structure analyses using X-ray diffraction and a high-resolution transmission electron microscope revealed that, the treatment sequence of hydrothermal reaction and annealing was a crucial influence factor on controlling the growth of preferred orientation of (001) facets of TiO₂ in SrTiO₃/TiO₂ heterojunction, whereas the inverse treatment sequence yielded randomly oriented facets. The formation mechanism of dominant (001) facets of TiO₂ in the heterojunction was related to crystal structures of TiO₂ and SrTiO₃. The heteroepitaxial growth on (001) plane of SrTiO₃ led to dominant (001) facets of anatase TiO₂ attributing to their excellent surface lattices match. The photoelectric performances of pure TiO₂ nanotubes and SrT were investigated by photoluminescence, UV–visible diffuse reflectance, photocurrent and current–voltage response. The semiconductor characteristics of them were studied by electrochemical impedance spectroscopy and Mott–Schottky analysis in detail. The results demonstrated that the heterostructure of SrT not only increased light absorption, but also effectively shifted the Fermi level and promoted charge transfer. Among all the samples, the SrTiO₃/TiO₂ heterojunction prepared by 1 h hydrothermal treatment (1SrT) exhibited the best photoelectrochemical performances due to the synergetic contributions of the high active (001) facets of anatase TiO₂ and the charge transport properties of the heterostructure.     

Preparation and characterization of size controllable spherical silver nanoparticles

By adjusting pH values of reactant system, the mass ratio of stabilizer/water and aging temperature, size controllable spherical silver nanoparticles （NPs） were synthesized. The properties of silver NPs are characterized by X-ray diffrac- tion （XRD）, transmission electron microscope （TEM） and ultraviolet visible （UV-VIS） absorption spectra. Within the pH values of 7.0-11.0, the aging temperature of 80℃ is better to improve silver NPs in shape to nearly sphere, con- centrate size distribution and reduce aggregation than the aging temperature of 25 ℃. The shape and dispersibility of silver NPs are the best when the pH of the reactant system is within 7.0---8.0. With pH of 7.5, aging at 80 ℃, and sta- bilizer/water mass ratio of 1%, the spherical silver NPs with sizes of 50---70 nm were synthesized. The results are promising to be used to synthesize core/shell NPs when silver NPs are as core.     

Patterned Color and Fluorescent Images with Polydiacetylene Supramolecules Embedded in Poly(vinyl alcohol) Films

Poly(vinyl alcohol) (PVA) films embedded with functional polydiacetylene (PDA) are efficiently prepared for color and fluorescence imaging. Intensely blue films are obtained by mixing and drying solutions containing PDA vesicles and PVA. A blue‐to‐red color transition is observed upon heating the polymer films. In addition, selective UV irradiation (through a photomask) of PVA films containing diacetylene monomer results in the generation of micropatterned color (without heating) and both color and fluorescent images (after heating the films at 120 °C for 10 s). Patterned two‐color (blue and red) images in the polymer film are readily obtained by a sequential process of photomasked irradiation, heating, and unmasked irradiation.     

叠层片式ZnO压敏电阻器配方研究

研究了以ZnO-Bi2O3-SiO2系为基础,适当添加Co、Mn、Sb、Cr、Ni等金属氧化物的叠层片式ZnO压敏电阻器配方。通过严格控制Bi2O3及SiO2的含量,较好地解决了瓷料与银鈀内电极的共烧问题,且电性能优良。其瓷料的特点是烧结温度低(<1050℃),产品非线性系数高(≥25),泄漏电流小(<5μA),限制电压低(V1A/V1mA<1.70),通流能量大(≥1800A/cm2)。