High-Performance All-Solid-State Supercapacitor Electrode Materials Using Freestanding Electrospun Carbon Nanofiber Mats of Polyacrylonitrile and Novolac Blends

Herein, this paper reports a facile method to prepare electrospun carbon nanofiber mats (ECNFMs) with high specific surface area and interconnected structure using polyacrylonitrile (PAN) as a precursor and novolac resin (NOC) as a polymer sacrificial pore-making agent. Without additional treatment, the prepared ECNFMs have a highly porous structure because NOC decomposes in a wider temperature range than most polymer activators. The NOC content in the PAN nanofibers shows important effects on porosity. The BET specific surface area of ECNFMs reaches a maximum of 1468 m² g⁻¹ when the precursor nanofibers contained 30 wt% NOC (ECNFM-3) after carbonization at 1000 °C. The supercapacitor device from ECNFM-3 electrode and all-solid-state electrolyte shows excellent cycling durability and high specific capacitance: ≈99.72% capacitance retention after 10 000 charge/discharge cycles and ≈320 mF cm⁻² at 0.25 mA cm⁻². Furthermore, it shows a large energy density of ≈11.1 $\mu$Wh cm⁻² under the power density of 500 mW m⁻². Activation of carbon nanofibers simply by the addition of NOC into precursor nanofibers can offer a handy way to prepare ECNFMs for high-performance all-solid-state supercapacitors and other potential applications.     

A Skin-Inspired Triboelectric Nanogenerator with an Interpenetrating Structure for Motion Sensing and Energy Harvesting

Rapid advancements in wearable electronics impose the challenge on power supply devices. Herein, a flexible single-electrode triboelectric nanogenerator (SE-TENG) that enables both human motion sensing and biomechanical energy harvesting is reported. The SE-TENG is fabricated by interpenetrating Ag-coated polyethylene terephthalate (PET) nanofibers within a polydimethylsiloxane (PDMS) elastomer. The Ag coating and PDMS are performed as the electrode and dielectric material for the SE-TENG, respectively. The Ag-coated PET nanofibers enlarge the electrode surface area, which is beneficial to increase sensing sensitivity. The flexible SE-TENG sensor shows the capability of outputting alternating electrical signals with an open-circuit voltage up to 50 V and a short-circuit current up to 200 nA in response to externally applied pressure. It is used to sense various types of human motions and harvest electric energy from body motion. The harvested energy can successfully power wearable electronics, such as an electronic watch and light-emitting diode. Therefore, the as-prepared SE-TENG sensor with a pressure response and self-powered capability provides potential applications in wearable sensors or flexible electronics for personal healthcare and human–machine interfaces.     

Fabrication and Characterization of Highly Oriented Composite Nanofibers with Excellent Mechanical Strength and Thermal Stability

Here, highly‐oriented poly(m‐phenylene isophthalamide)/polyacrylonitrile multi‐walled carbon nanotube (PMIA/PAN‐MWCNT) composite nanofiber membranes with excellent mechanical strength and thermal stability are successfully produced using electrospinning. It is demonstrated that the cooperation of multi‐walled carbon nanotubes (MWCNT) and high‐speed rotating collection is beneficial to the acquisition of highly oriented fibers and effectively improves the mechanical strength of the membrane along the orientation direction. Specifically, the tensile stress of poly(m‐phenylene isophthalamide)/polyacrylonitrile (PMIA/PAN) membrane is enhanced significantly from 10.6 to 20.7 MPa, benefiting from the highly oriented alignment of the fibers as well as the reinforcing effect of MWCNTs on the fibers. Furthermore, the stressing process of single fiber and fiber aggregates is carefully simulated, and the influence of MWCNTs on the mechanical properties of PMIA/PAN‐MWCNT membranes is analyzed comprehensively, providing a meaningful auxiliary means for the study of mechanical properties. In addition, the composite nanofiber membrane has the advantages of both PMIA and PAN, possessing high temperature resistance, flame‐retardancy, and chemical stability, for an ideal high‐temperature material. In short, the as‐prepared PMIA/PAN‐MWCNT composite membrane with excellent comprehensive property emerges a promising application in many fields, especially in high‐tech.     

一维NiFe_2O_4纳米丝的制备与磁性能

采用静电纺丝法制备了表面光滑、直径均匀、连续的一维NiFe_2O_4纳米丝。利用傅立叶变换红外光谱仪(FTIR)、X射线电子衍射(XRD)、扫描电子显微镜(SEM)和振动样品磁强计(VSM)对Ni Fe2O4纳米丝的结构、形貌和磁性能进行表征。结果表明,经500~900℃煅烧后均得到直径约为60 nm的纯相尖晶石型NiFe_2O_4纳米丝,且NiFe_2O_4纳米丝具有良好的软磁特性,其饱和磁化强度(Ms)和剩余磁化强度(Mr)随煅烧温度的升高而增大,900℃煅烧后Ms和Mr分别达到最大值35.56、13.29 A·m2/kg。经600℃焙烧后的Ni Fe2O4纳米丝Ms为30.56 A·m2/kg,矫顽力(Hc)达到最大值2.76 A/m,表明NiFe_2O_4的单畴临界尺寸约为28 nm。     

Investigation of dielectric properties of free standing electrospun nonwoven mat

Flexible materials with balanced dielectric as well as conductive characteristics have elucidated considerable demand in field of research where conventional dielectric or insulators can be replaced by recent advances in various electronics appliances. Our work describes the detailed analyses of dielectric properties like dielectric constant, losses, and electric modulus by means of broadband dielectric spectroscopy over frequency ranging from 0.1 Hz to 10 MHz and temperature ranging from 0 to 60 °C for poly(vinyl alcohol)‐polyaniline (PVA‐PANI) free standing electrospinning nonwoven mat. It has been contemplated that the dielectric constant was enhanced by increasing PANI concentration for complete range of frequency at room temperature. The enhanced dielectric constant value (5.14 at 0.1 Hz, 2.66 at 1 KHz, 2.58 at 10 KHz, and 2.19 at 10 MHz) was anticipated for 7 wt % loading of PANI which was attributed to the presence of dipoles and interfacial polarization enclosed by the polymers. The increased dielectric constant with PANI dosing as well as with temperature attributed to favorable interfacial polarization. Shifting of peak is noticed in the spectra of imaginary electric modulus with increase in temperature which indicates increased chain dynamics of polymers in the mat. Three‐dimensional analysis of the field emission scanning electron microscopy images was carried out by SPIP analytical software. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46121.     

竹红菌素-聚(甲基丙烯酸甲酯-co-甲基丙烯酸)纳米纤维的制备及其光敏抗菌性能

针对抗生素类药物在耐药性菌株处理中应用的局限性,在聚(甲基丙烯酸甲酯-co-甲基丙烯酸)纺丝液中添加光敏剂竹红菌素,采用静电纺丝法制备具有光动力广谱抗菌功能的纳米纤维膜。借助扫描电子显微镜、静态接触角测试、傅里叶变换红外光谱仪和热重分析仪等分析添加竹红菌素前后纳米纤维的形貌、润湿性能、化学结构和热稳定性,并研究了添加竹红菌素的纳米纤维膜对金黄色葡萄球菌和大肠杆菌的抗菌能力。结果表明:添加竹红菌素后纳米纤维直径变粗,静态接触角增加约20°,润湿性能下降,热稳定性略有降低;纤维膜在可见光下具有良好的光动力氧化性能,在光照下对金黄色葡萄球菌和大肠杆菌的抑菌率分别达99.97%和54.41%。     

Fabrication of hollow and porous polystyrene fibrous membranes by electrospinning combined with freeze-drying for oil removal from water

A novel method was proposed to fabricate hollow and surface porous polystyrene (PS) fibrous membranes for the removal of oil from water. Spinning solutions were prepared by using camphene and tetraethoxysilane (TEOS) as pore-forming agents, and hollow PS fibers with 100–400 nm pores on the surface were fabricated by electrospinning and freeze-drying. The distribution and volatilization of camphene and TEOS, as well as the drying behavior of solvents in high relative humidity, were important factors in forming the porous structure of PS fibers. The specific surface area of obtained PS fibrous membranes was twice that of conventional electrospun PS fibrous membranes and displayed superhydrophobic properties. Moreover, the large adsorption storage space was formed due to the hollow structure and porous surface of PS fibers. The maximum oil adsorption capacity of the porous PS fibrous membrane was 105.4 g g⁻¹, and was larger than that of the conventional PS fibrous membrane after repeated five times, thus making it a promising tool for oil spill cleanups. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47262.     

一种壳聚糖基敷料的制备及其性能研究

近年来,临床上由于压疮、溃足等现象而导致伤口感染病例日益增加,而目前尚未有好的解决方法或是存在对应的"金标准"产品。在选用伤口敷料上具有潜力的天然高分子材料——壳聚糖,将其与一种力学性能优良、生物相容性好的聚合物P (LLA-CL)复合,通过静电纺丝技术制备了纳米纤维膜。经过一系列表征,该纳米纤维膜被证实具有纳米级的结构、微小的空隙、良好的力学性能以及较好的生物相容性,有望运用于伤口敷料。     

Structure and Properties of PET Nano‐Porous Luminescence Fibers for Fluorescence‐Indicating to Acid Gases

This work describes the fluorescence‐indicating function to trace acid gases of polyethylene terephthalate (PET) nano‐porous luminescence fibers (PNPLFs) through the analysis of correlation between the concentration of acid gas and fluorescence intensity of organic rare earth complexes dispersed uniformly in the PET nano‐porous structured fibers. The porous structure and large specific surface area of the PET nano‐fibers prepared through electrospinning technology offer the strong adhesive force and good absorption efficiency of PET nano‐porous fibers to acid gases. The fast response ability of benzoic acid organic rare earth complexes to pH value gives the PET nano‐porous luminescence fibers fluorescence‐indicating function to acid gas. Under dry state and in situ conditions, the fluorescence‐indicating to acid gases of PET nano‐porous luminescence fibers can be completed in 10 s. The precise value is 1 ppm. At the same time, repeated cycling experiments show that the PET nano‐porous luminescence fibers have good recycling property, and the recycling life can increase 40‐fold. Coupled with the good mechanical performances that the breaking strength achieves 121.6 cN, the PET nano‐porous luminescence fibers have better potential in the fluorescence‐indicating to acid gases.     

Effective modeling and optimization of PVDF–PTFE electrospinning parameters and membrane distillation process by response surface methodology

Ploy(vinylidene fluoride)–polytetrafluoroethylene nanofibrous membrane fabrication and direct contact membrane distillation (DCMD) process were simulated and optimized by response surface methodology (RSM). Analysis of variance was applied to develop and verify the models that predict the objectives. The three-dimensional response surfaces of different objectives were obtained. Results showed that the membrane with thickness of 70.7 μm, contact angle of 146.2°, and liquid entry pressure of 53.5 kPa was obtained within investigated experimental range under the optimum electrospinning conditions. Rejection rate of 99.99% and the permeate flux of 67.5 kg m⁻² h⁻¹ were gained under the optimum membrane distillation (MD) process parameters. The actual and predicted values show good consistency verifying the accuracy of the models. In addition, an overall investigation of the influence of heat-press temperature on the morphological and mechanical properties of electrospun membrane was carried out. Results indicated that electrospinning process and MD performance can be enhanced after the corresponding variables were optimized by RSM. This study provides a scientific way to optimize the electrospinning and DCMD parameters. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47125.