Functionalization of polyamide 6 nanofibers by electroless deposition of copper

Polyamide 6 (PA6) nanofibers were prepared via electrospinning. The electrospun PA6 nanofibers were functionalized using electroless deposition technique. Oxygen low temperature plasma treatment was applied to substitute the conventional roughening process using concentrated sulfuric acid-potassium dichromate. The deposition of copper (Cu) on the PA6 nanofibers was characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive X-ray spectroscopy (EDX). The observations revealed the uniform coating of the PA6 nanofibers with thin films of Cu. It was also found that the surface conductivity of the PA6 nanofibers was significantly improved by the Cu deposition. The combination of electrospinning and electroless deposition will provide a new approach to producing the functional nanofibers for various applications.     

静电纺丝法纺制聚乳酸纳米纤维无纺毡

采用静电纺丝法制备了生物降解聚乳酸(PLLA)纳米纤维无纺毡。分析了纺丝液浓度、电压、接收距离、挤出速度等因素对纤维形态的影响。结果表明:纺丝液的浓度和挤出速度对纤维直径的影响较为明显,溶液挤出速度增大,所得纤维微孔含量及尺寸也增大;适当的电压和接收距离有利于收集无液滴纤维;随着纤维直径的减小,无纺毡的孔径呈减小趋势。在PLLA质量分数为5．7％、挤出速度0．8 mL／h、接受距离 15．5 cm、电压8 kV的静电纺丝条件下,可制备纤维直径为200-400 nm的PLLA纳米纤维无纺毡。     

电沉积法制备Bi2S3薄膜及其生长机理

采用阴极恒电压电沉积法在氧化锡铟透明导电玻璃表面沉积了Bi2S3薄膜,用X射线衍射、X射线光电子能谱仪、原子力显微镜、场发射扫描显微镜对制备薄膜的结构和形貌进行了表征。通过对不同沉积时间下制备薄膜的表面形貌分析,初步探讨了电沉积法制备Bi2S3薄膜的生长机理。结果表明:所制备的薄膜由正交相Bi2S3组成,无杂质相;薄膜表面形貌呈现出沿c轴取向的竹笋状的三维结构;随着沉积时间延长,薄膜结晶性能先提高后下降;其生长模式是基于电场力对离子的作用而诱导产生的垂直于基板方向的层状生长。     

The mechanism of the controlled deposition of electrospun fibers

The controlled deposition of electrospun fibers means that the electrospun fibers can be collected in a limited and specified area and can present better applications in the fields of medical treatment, garment making, and 3D printing. In order to study the mechanism of the controlled deposition of electrospun fibers, simulation and experimental methods were used. Specifically, in the electrospinning experiment, circular copper sheets of different diameters were used as collectors. The effect of different collector areas on the morphology of fiber deposition was discussed. The electric field distribution of electrospinning with different specifications of collectors was simulated correspondingly. The experimental results show that, as compared to the traditional large flat collector, the area where the electrospun fibers are deposited is significantly reduced when a smaller circular copper plate was used as a collector. The smaller the area of the collector, the more the fibers tend to deposit at the center area of the collector, and the more likely the morphology of the product formed by the fiber deposition to exhibit a center protrusion shape. The controlled deposition of the electrospun fiber technology can provide more opportunities for the application of the electrospinning technology.     

熔体直写电纺聚己内酯纤维有序沉积工艺

目前聚合物熔体电纺技术制备的纤维大多以杂乱无序的无纺布形式存在,限制了电纺技术在组织工程支架以及机器人等需要有序结构领域的应用。本文将熔体电纺技术与三维运动平台相结合,采用自主设计的熔体电纺可控成型实验装置,对聚己内酯（PCL）进行熔体直写静电纺丝,获得了有序纤维。研究了喷头移动速度、接收距离和纺丝电压对熔体直写电纺纤维沉积形貌的影响。结果表明,纤维直径随着喷头移速、接收距离和纺丝电压的增大而减小,其中接收距离的改变对直径的影响最为显著;接收距离的增大虽然有利于纤维的细化,但是距离过大会使纤维沉积的有序性变差;当射流下落速度与喷头移动速度相匹配时,射流才能实现有序沉积;增大接收距离和纺丝电压会引起射流鞭动,需要相应地增大喷头移动速度才能实现有序沉积。     

Fabrication of nanofibers by a modified air-jet electrospinning method

A modified air-jet electrospinning (MAE) setup was demonstrated for contributing to the large-scale nanofibers production. With this single nozzle air-jet electrospinning device, the productivity of nanofibers can be increased more than forty times as compared with using the single-needle electrospinning (SNE) setup. When compared with other needle-less electrospinning setups, the benefits of this setup include ability to keep stable concentration of electrospun solution and to produce more uniform and thinner fibers, controlling of the jets formed speed and position, higher throughput, lower critical voltage, easier assembling, simpler operation, and so on. Four different parts of the fiber generator were, respectively, charged as electrospun electrodes to produce fibers. The distributions of the electric field with different electrodes were simulated and investigated for explaining the experimental results including the fibers productivity, the deposition area of nanofiber mats, as well as the surface morphology of the fibers. When the whole nozzle was charged, as compared with charging other electrodes, the MAE system produced thinner fibers with larger standard deviation on a much larger scale. By reduction of charged area, the received fibers presented lower productivity and thicker diameter with lower standard deviation. Especially, when a half of the nozzle was charged, the deposition area of nanofiber mats was larger than charging other electrodes. Besides, when a half of the nozzle was charged, the influences of electrospinning parameters such as applied voltage, collecting distance and the flow rate of air on nanofibers morphology were also investigated. Furthermore, based on this spinning unit, multi-nozzle air-jet electrospinning setup can be designed for larger production of nanofibers.     

静电纺丝的研究进展

简述了国内外静电纺丝的研究现状;介绍了静电纺丝的制备原理、静电纺丝装置的改进、影响纤维成形的主要工艺参数及纤维形态;叙述了静电纺丝纳米纤维在过滤材料、生物医学和传感器等方面的应用;展望了静电纺丝的发展方向。指出静电纺丝是纳米纤维的新型生产技术,今后应进一步调整静电纺丝工艺,开发绿色溶剂,以尽早实现静电纺丝的工业化。     

Blow-assisted multi-jet electrospinning of poly-L-lactic acid nanofibers

Regardless the low production rate, electrospinning remains the attractive technique for the nanofibers production in various fields. Thus, the development of a multi-jet technologies for electrospinning gives an opportunity to scale up and increase throughput of the fibers production. However, the multi-jet electrospinning technologies exhibit one major drawback– electrostatic mutual jet repulsion issue. In present research, we propose air blow-assisted multi-jet electrospinning system allowing production of nanofibers with yield, at least, tenfold higher than single jet electrospinning. The system produces nanofibers in two modes: multi-jet electrospinning and blow-assisted multi-jet electrospinning. In case of the latter, the application of sheath air stream allows the system to overcome the electrostatic mutual repulsion issue. These lead to the reduction of deviation of the polymer solution jets, the reduction of instabilities of the jets and the improvement of the control of the nanofibers deposition. Nanofibers morphology and size were investigated based on the scanning electron microscope micrographs. The comparison of the two modes shows changes in nanofibers morphology from beaded structure to fine nanofibers, and the slight increase in fiber mean size when the blowing assistance was applied to the process.     

熔体静电纺丝直写技术在组织工程中的应用进展

熔体静电纺丝直写技术以其纤维直径、沉积形貌可控性高及无溶剂残留等优势,为高强度复杂形貌可控仿生组织工程（TE）支架的制备提供了巨大的空间,成为近年来的研究热点。本文首先简述了熔体静电纺丝直写技术相对于各类其他TE支架制备方法的优势;其次从工艺调控方面综述了熔体静电纺丝直写技术的工艺研究进展,并总结了实现复杂可控形貌TE支架的调控方法;随后从支架材料、形貌表征和细胞培养效果等方面综述了熔体静电纺丝直写技术的TE应用进展,并概括了该技术制备的TE拓扑结构支架的种类及特点;最后指出熔体静电纺丝直写技术具有广阔的研究前景,且该技术应以制备仿生、材料多样化以及复合支架为研究重点。     

静电纺PCL纤维形态与热性能的研究

利用静电纺丝法制备了超细聚ε-己内酯(PCL)纤维;借助扫描电镜仪和差示扫描量热仪表征了PCL纤维的形态与热性能;研究了电纺过程中溶液浓度、电压、接收距离和纺丝速度对纤维形态的影响。结果表明:当纺丝电压为10 kV,接收距离为15 cm,纺丝速度为2 mL/min时,纺丝液中PCL质量分数为6%~12%能获得连续无串珠的纤维;纺丝电压为8~12 kV,电纺过程稳定;接收距离对纤维的直径和形貌无明显影响;与流延成型的PCL膜相比,电纺PCL纤维具有较低的结晶度。     

溶剂与表面活性剂对醋酸丁酸纤维素静电纺丝的影响

应用静电纺丝法制备了醋酸丁酸纤维素纳米纤维。利用扫描电子显微镜探讨了不同的溶剂体系和表面活性剂对纺丝过程及纳米纤维形态的影响。试验结果表明:醋酸-丙酮混合溶剂体系有利于纺丝过程的顺利进行和获得平滑无珠节的纳米纤维,而添加表面活性剂则有助于减小纤维直径和获得粗细均匀的纤维形态。     

Electrospinning of thermoplastic polyurethane microfibers and nanofibers from polymer solution and melt

Electrospinning technique was used to produce ultrafine fibers from thermoplastic polyurethane (TPU). A direct comparison between melt and solution electrospinning of TPU was provided for the evaluation of process–structure relationship. It was found that the deposition rate of melt electrospinning (0.6 g h^?1) is four times higher than that of solution electrospinning (0.125 g h^?1) for TPU under the same processing condition. However, the average fiber diameters of solution electrospun TPUs (220–280 nm) were much lower than those of melt electrospun TPUs (4–8 μm). The effect of processing variables including collection distance and electric field strength on the electrospun fiber diameter and morphology was also studied. The findings indicate that increasing the electric field strength yielded more electrical forces acting on polymer jet and resulted in a decrease in fiber diameter as a result of more fiber drawing in both solution and melt electrospun fibers. It was also demonstrated that increasing the collection distance led to an improvement in the solidification of melt electrospun fibers and thus less fused fibers were obtained. Finally, a close investigation of fiber structures revealed that melt electrospun TPU fibers had smooth surface, whereas solution electrospun TPU fibers showed high intensity of cracks on the fiber surface. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

溶剂对电纺聚酯纳米纤维可纺性的影响

利用静电纺丝法制备聚酯(PET)纳米纤维,选择苯酚和四氯乙烷,三氟乙酸,三氟乙酸和二氯甲烷3种溶剂分别溶解PET切片进行静电纺丝,通过扫描电子显微镜(SEM)对纤维表面形态进行观察,结果表明:三氟乙酸和二氯甲烷混合溶剂溶解PET制备的电纺纤维较好。使用视频光学接触角测定仪测试PET电纺纤维膜与其流延膜的接触角,通过分析两者表面结构,证明PET电纺纤维膜能产生较强的疏水功能。     

Lyotropic self-assembly in electrospun biocidal polyurethane nanofibers regulates antimicrobial efficacy

Electrospinning of a series of soft segment-free biocidal polyurethanes was undertaken to facilitate examination of the influence of fiber size and morphology on resulting biocidal activity. Although the fibrous nanomaterials greatly outperformed films of the same composition, tunability of resulting activities was also accomplished by controlling crystallization of the nanofibers through electrospinning parameter modulation. While inaccessibility of quaternary ammonium biocides driven by extensive fiber crystallization limited overall antimicrobial activity, biocide structure and electrospinning parameters were utilized to overcome material limitations in order to generate highly antimicrobial materials. Overall, processing conditions were shown to be decisive elements in dictating activities as specific polymer compositions were characterized as having antimicrobial activities spanning over 4 orders of magnitude depending on electrospinning conditions and up to 7 orders of magnitude when compared to films of the same composition.     

Multi‐jet nozzle electrospinning on textile substrates: observations on process and nanofibre mat deposition

Electrospinning is a simple and versatile process for producing small‐diameter fibres (nanofibres). However, in spite of the many potential applications of electrospun nanofibres, further process developments are still necessary to achieve a decisive productivity breakthrough for electrospinning plants. Increasing knowledge of multi‐jet electrospinning is crucial for developing industrial devices for large‐scale nanofibre production. This paper reports on the effect of a non‐conducting textile substrate placed between a jet‐emitting source (nine‐nozzle arrangement) and collector. Shielding the electric field changes the electrospinning conditions, nanofibre morphology, stability of jets and fibre deposition on the collecting surface. Various perturbation phenomena of the electrically driven jets were recorded and are described. The intensity of the perturbations increases as the weight of the non‐woven substrate increases resulting in defects in the nanofibrous mat (i.e. beaded nanofibres), production of tick fibres or failure to produce fibrous materials (e.g. films, droplets). The paper also reports an objective image‐processing procedure to enhance the evaluation of the collector after nanofibre deposition. Copyright © 2010 Society of Chemical Industry     

Microstructure,Surface Morphology and Photoluminescence Properties of Al-Doped ZnO Thin Films Prepared by Plasma Focus Method

Al-doped ZnO (AZO), as one of the most promising transparent conducting oxide (TCO) materials, has now been widely utilized in thin film solar cells. In this research the optimization process of AZO thin films deposited by plasma focus device was carried out by investigation of its physical properties under different deposition conditions for its utilize as a front contact for the Cadmium Telluride (CdTe) based thin film solar cell applications. The effects of number of focus shots and angular position of substrate on the microstructure, surface morphology and photoluminescence properties of the thin films have been systematically studied. X-ray diffraction (XRD) study confirmed the polycrystalline nature of the all deposited AZO thin films. XRD analysis also revealed that crystal structure characteristics of obtained samples strongly depend on deposition conditions (number of shots and angular position). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses revealed the structure growth and enhancement of surface roughness, with increasing of focus shots or decreasing of angular position. From Photoluminescence (PL) emission spectra, the variations of structural defects and band gap energy for all the AZO thin films prepared under different deposition conditions were also discussed.     

Electrospinning of poly(hydroxybutyrate‐co‐hydroxyvalerate) fibrous tissue engineering scaffolds in two different electric fields

Poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) was electrospun into ultrafine fibrous nonwoven mats. Different from the conventional electrospinning process, which involves a positively charged conductive needle and a grounded fiber collector (i.e., positive voltage (PV) electrospinning), pseudo‐negative voltage (NV) electrospinning, which adopted a setup such that the needle was grounded and the fiber collector was positively charged, was investigated for making ultrafine PHBV fibers. For pseudo‐NV electrospinning, the effects of various electrospinning parameters on fiber morphology and diameter were assessed systematically. The average diameters of PHBV fibers electrospun via pseudo‐NVs were compared with those of PHBV fibers electrospun via PVs. With either PV electrospinning or pseudo‐NV electrospinning, the average diameters of electrospun fibers ranged between 500 nm and 4 μm, and they could be controlled by varying the electrospinning parameters. The scientific significance and technological implication of fiber formation by PV electrospinning and pseudo‐NV electrospinning in the field of tissue engineering were discussed. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Plasma enhanced aerosol–gel deposition of Al2O3 coatings

The new plasma enhanced aerosol–gel technique has been used for alumina films preparation, in this work. This process integrates aerosol–gel deposition of films and their plasma treatment in one reactor. The alumina films deposited by aerosol–gel method on Si substrate were plasma or thermally treated. The influence of deposition and condensation conditions on properties of the films was studied. Produced coatings were characterized in terms of surface morphology (SEM, AFM) as well as crystalline and chemical structure (FTIR, XRD). Plasma discharge used for modification of the substrates prior to the deposition process improved homogeneity of produced coatings. Coatings obtained at room temperature exhibit boehmite structure which was transformed into γ-Al₂O₃ after annealing. A similar transformation was induced by low temperature oxide plasma discharge treatment for sufficiently thin coatings.     

电沉积法制备纳米SnO_2薄膜

采用一种电沉积法室温下制备纳米SnO2薄膜。经研究得到了电沉积SnO2薄膜的最佳工艺条件:电流密度、电沉积时间、主盐浓度、游离酸浓度分别为i=8 mA.cm-2,t=120 m in,c(SnC l2)=0.02 mol/L,c(HNO3)=0.03 mol/L。用X射线衍射、红外光谱和扫描电镜、透射电镜等对薄膜的物相和微观结构、表面形貌等进行了研究。结果表明,室温下干燥得到的薄膜由SnO2.xH2O组成,但经过400℃热处理后,逐渐转变成结晶较为完整的四方结构SnO2薄膜,薄膜的表面较为平整、呈多孔状,薄膜粒径大小为8~20 nm。     

Synthesis and characterization of sol gel derived nontoxic CZTS thin films without sulfurization

Recently, great attention has been paid to the development of earth rich and nonhazardous Copper Zinc Tin Sulfide (CZTS–Cu₂ZnSnS₄) thin films for application in photovoltaic devices owing to its high absorption coefficient over the visible and infrared region. However, sulfurization process is an indispensable step in growing stoichiometric thin film using conventional physical vapor deposition. Hence, it is imperative to devise a liquid based technique without intentional sulfurization for the optimum quality growth of CZTS thin films. In the current work, layer-by-layer sol-gel deposition technique was utilized to grow high quality CZTS thin films without sulfurization and their structural and optical characteristics were investigated using XRD studies and UV-visible spectroscopy respectively. The morphology and chemical composition of the prepared CZTS films are estimated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis respectively. Highly absorbing and crystalline CZTS films have been successfully grown in the present work which could be further utilized as an absorber layer in photovoltaic applications.