Composite nanofibers produced by modified needleless electrospinning

A needleless electrospinning method was used to prepare poly(vinyl alcohol) nanofibers with a content of single walled (SWCNTs) and multi walled carbon nanotubes (MWCNTs). The needleless process of electrospinning from free surface of polymeric solution requires perfect solutions of polymers and additives (carbon nanotubes in the case). The solutions were prepared by sonication method and by usage of surface modified carbon nanotubes. The presence of carbon nanotubes inside the electrospun nanofibrous materials were proved by means of Raman spectroscopy. This process example can be modified for other polymer solutions to produce nanocomposite fibrous structures by electrospinning in mass scale.     

Characterization and tensile strength of HPC-PEO composite fibers produced by electrospinning

Hydroxypropylcellulose (HPC) and polyethylene oxide (PEO) were dissolved in water in order to be electrospun. The electrospun membranes showed porous structure with fibers having diameter of 255 ± 65 nm. Synthesized silver nanoparticles of 5-8 nm were embedded into the HPC/PEO matrix to improve the strength. It was seen that the embedding of silver particles into the polymer matrix improved the membrane strength ∼ 4 times.     

Fabrication of polycrystalline lanthanum manganite (LaMnO3) nanofibers by electrospinning

Lanthanum manganite (LaMnO₃) nanofibers were successfully fabricated by electrospinning utilizing sol-gel precursors. Polycrystalline cubic-perovskite structure LaMnO₃ fibers of 50-100 nm were obtained by calcination of the inorganic/organic hybrid fibers at 600 °C for 1 h. The XRD results showed that the grain size of the fibers increased significantly with the increase of calcinations temperature. The average diameter of crystal grains was 17 nm after calcined at 400 °C for 2 h, then grew to 20 nm after heated up to 600 °C for 1 h. The morphology, microstructure, crystal structure and thermal analysis were investigated by SEM, TEM, XRD and TG-DSC, respectively.     

Fabrication of TiO2/ZnO composite nanofibers by electrospinning and their photocatalytic property

TiO₂/ZnO composite nanofibers with diameters in the range of 85–200 nm were fabricated via the electrospinning technique using zinc acetate and titanium tetra-isopropoxide as precursors, cellulose acetate as the fiber template, and N,N-dimethylformamide/acetone 1:2 (v/v) mixtures as the co-solvent. After treated with 0.1 mol/L NaOH aqueous solution, TiO₂/zinc acetate/cellulose acetate composite nanofibers were transformed into TiO₂/Zn(OH)₂/cellulose composite nanofibers. TiO₂/ZnO composite nanofibers were obtained by calcinating the hydrolyzed composite fibers at 500 and 700 °C for 5 h. The structure and morphology of composite nanofibers were characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. With the blending of ZnO into TiO₂, a new crystallite ZnTiO₃ was formed in addition to the ZnO and TiO₂ crystallites, and the ultraviolet light absorption efficiency was enhanced according to the UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of TiO₂/ZnO composite nanofibers toward the decomposition of Rhodamine B and phenol was investigated. Almost 100% Rhodamine B and 85% phenol were decomposed in the presence of TiO₂/ZnO composite nanofibers under mild conditions. The results demonstrated that the blending of ZnO in the TiO₂/ZnO composite nanofibers increased the photocatalytic efficiency. The optimum ZnO content in the TiO₂/ZnO composite nanofibers was 15.76 wt% to reach the most efficient photocatalytic activity. A schematic diagram of photocatalytic mechanism of TiO₂/ZnO composite nanofibers was also presented.     

Morphology and conductivity of polyaniline sub-micron fibers prepared by electrospinning

Sub-micron fibers of pure polyaniline (PANI) doped with sulfuric acid or hydrochloric acid were prepared by electrospinning PANI with suitable molecular weight dissolved in hot sulfuric acid. A modified electrospinning setup was employed with a coagulation bath as a collector, where dilute sulfuric acid was used as coagulation bath. The factors influencing the morphology and conductivity of the synthesized PANI fibers were investigated, including the concentration of dilute H₂SO₄ solution in the coagulation bath, the doped PANI concentration in H₂SO₄ solution, the type of doping acid and the voltage applied to the solution. The morphologies of doped PANI fibers were characterized by scanning electron microscope (SEM). The structure of the resulting fibers was analyzed by Fourier transform infrared spectroscopy and UV–vis spectrometer. The conductivity of PANI fibers were characterized by I–V characteristics. Homogeneous PANI fibers with a diameter of 370 nm and a high conductivity of 52.9 S/cm were prepared. The possible mechanisms of different morphology formation and conductivity of PANI fibers were also discussed.     

Preparation of poly (vinyl alcohol)/silica composite nanofibers membrane functionalized with mercapto groups by electrospinning

Membranes of poly vinyl alcohol (PVA)/silica functionalized with mercapto groups are synthesized by electrospinning. Scanning electron microscopy (SEM) studies showed that the fiber diameters are in the range of 200-300 nm. The thickness of nanofiber decreases with an increase in calcination temperature. The results of Fourier transform infrared (FTIR) indicated that PVA/silica nanofibers are functionalized by mercapto groups via the hydrolysis poly-condensation method. N₂ adsorption-desorption showed that organic molecules can be removed completely when the PVA/silica composite fibers are calcinated at 800 °C. The fibers calcinated at 800 °C were pure inorganic silica species with a mesoporous structure. These mercapto groups functionalized PVA/silica nanofibers have a great potential application in the field of adsorption of heavy metal ions.     

The fabrication of PPV/C60 composite nanofibers with highly optoelectric response by optimization solvents and electrospinning technology

We have successfully loaded C60 into a PPV precursor using CS2 and ethanol as mixed solvents and fabricated uniform PPV/C60 composite nanofibers by electrospinning for the first time. C60 was homogeneously distributed in nanofibers. The PL spectra analysis confirmed the formation of a composite and revealed the obvious fluorescent quenching comparing with pure PPV nanofibers. Countable electrospun composite nanofibers on a Au interdigitated electrode showed a fast and highly optoelectric response under 100 mW/cm² light irradiation by a Xe lamp. The results showed that photo induced charge transfer took place at the interface of PPV and C60 and suggested the great potential in the field of micro/nano organic optoelectric devices, especially in micro/nano organic photoswitches.     

Preparation and electrical characterization of polyamide-6/chitosan composite nanofibers via electrospinning

We report on the preparation and electrical characterization of polyamide-6/chitosan composite nanofibers. These composite nanofibers were prepared using a single solvent system via electrospinning process. The resultant nanofibers were well-oriented and had good incorporation of chitosan. Current-voltage (I-V) measurements revealed interesting linear curve, including enhanced conductivities with respect to chitosan content. The electrical conductivity of the polyamide-6/chitosan composite nanofibers increased with increasing content of chitosan which was attributed to the formation of ultrafine nanofibers. In addition, the sheet resistance of composite nanofibers was decreased with increasing chitosan concentration.     

静电纺丝法制备多孔纳米炭纤维及其电化学性能研究

分别以聚乙烯醇(PVA)/热固性酚醛树脂(PF)/碳酸钾(K2CO3)和PVA/PF的水溶液为纺丝原液,通过静电纺丝、固化和炭化处理制得多孔纳米炭纤维。利用扫描电子显微镜(SEM)、低温氮气吸脱附等对所制多孔炭纳米纤维进行表征,并将所制多孔炭纤维作为模拟电容器电极材料,利用循环伏安和恒电流充放电进行了电化学性能测试。结果表明:纺丝原液中加入K2CO3后所制多孔纳米炭纤维的比表面积增大(从564 m.2g-1提高到668 m.2g-1),电化学性能提高(在电流密度为0.2 A.g-1的情况下,比电容由165 F.g-1提高到178 F.g-1)。     

Ultrafine polyacrylonitrile/silica composite fibers via electrospinning

Polyacrylonitrile (PAN)/silica composite nanofibers, in the diameter of 200-300 nm, were prepared by a one-step electrospinning method. The PAN/silica nanofibers were characterized by SEM, TEM, ATR-FTIR and DSC. SEM and TEM images show that beads are formed and silica nanoparticles start to aggregate when the silica content is higher than 2 wt.% in nanofibers. ATR-FTIR spectra and DSC results indicate that there may exist interactions between silica nanoparticles and PAN. The addition of silica nanoparticles also changes the thermal properties of PAN/silica nanofibers.     

PP／s-1，2PB共混物的非等温结晶动力学

用DSC方法研究了聚丙烯(PP)、PP与间同1,2-聚丁二烯(s-1,2 PB)共混物的非等温结晶行为,结果表明:Mo法处理PP及PP/s-1,2 PB(90/10)共混物是非常适宜的,而用Ozawa法处理则存在缺陷.用Jeziorny法处理共混物也是适宜的,但对PP处理存在缺陷;s-1,2 PB对PP有加速结晶的作用; s-1,2 PB使PP的结晶活化能降低,s-1,2 PB在PP结晶过程中起到异相成核的作用.     

Fabrication and texture evolution of hexagonal YMnO3 nanofibers by electrospinning

Hexagonal YMnO₃ nanofibers were successfully fabricated by sol-gel preparation based on electrospinning. The as-spun fibers dried at 125 °C were round and had a rather uniform diameter around 0.7 μm-2 μm over its length. In order to get pure hexagonal YMnO₃ nanofibers, crystalline structures and microstructures of fibers at various temperatures for 6 h were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The reasonable evaluations for the change of morphology with the increasing temperature were proposed. After being heated at 1100 °C for 6 h, the pure hexagonal YMnO₃ nanofibers were obtained with a reduced diameter ranging from 200 nm to 800 nm and the fibers were homogenous in chemical constitution over its length.     

Molecularly imprinted polyimide nanofibers prepared by electrospinning

An estrone imprinted polyimide nanofiber mat was prepared by using an electrospinning method. The diamine monomer-template complex was synthesized by the reaction of the diamine monomer having an isocyanate group and estrone (template) having a phenol moiety, in which the template was attached to the monomer via a thermally reversible urethane bond. A poly(amic acid) was synthesized by polymerization of the diamines (1:19 mole ratio of the diamine monomer-template complex to 4,4′-oxydianiline) and pyromellitic dianhydride in N,N-dimethylformamide and the reaction solution was used for electrospinning. The poly(amic acid) fibers were thermally imidized and then heated in 1,4-dioxane in the presence of water to remove the template molecules. The imprinted polyimide nanofibers showed the specific recognition ability and fast kinetic adsorption for estrone.     

Synthesis of ultrafine lanthanum ferrite (LaFeO3) fibers via electrospinning

Ultrafine one-dimensional LaFeO₃ nanofibers were synthesized by electrospinning utilizing sol-gel precursors. The surface morphology, microstructure and crystal structure were investigated by scanning electron microscopy, X-ray diffraction and transmission electron microscopy. The nanofibers with smaller diameter were continuous and uniformly distributed. Typical fiber diameter was between 180 nm and 220 nm and the average diameter was 200 nm. The fibers consisted of many single-crystal LaFeO₃ grains and the grain size was about 20-50 nm. The relationship between the diameter of as-synthesized fibers and the PVP concentration of the precursor was investigated. The experimental results indicated that the PVP concentration had a great impact on the fiber size and 5.89 wt.% PVP concentration in sol-gel precursors was advantageous to the formation of more uniform electrospun composite fibers with smaller diameter.     

Preparation of porous polyacrylonitrile fibers by electrospinning a ternary system of PAN/DMF/H2O

Polyacrylonitrile (PAN) porous fibers were prepared in one step by electrospinning a ternary system of PAN/N, N-dimethylformamide (DMF)/water at ambient environment. The formation of porous structures was mainly due to the spinodal decomposition phase separation occurred during the electrospinning process. The concentration of PAN varied from 3 to 10 wt.% with the water content changing from 2 to 8 wt.%. When PAN concentration was above 5 wt.%, the composition of the ternary system was close to the “cloud point” and fibers with porous structures were obtained. In addition, the surface tension and viscosity of PAN solutions increased with water which may lead to the diameter increase of the fibers. The Brunauer-Emmett-Teller (BET) surface area of porous PAN nanofibers obtained from 8 wt.% PAN solution containing 7 wt.% of water was 46.4 m² g⁻¹, which was 3 times higher than that of nonporous PAN nanofibers prepared under the same conditions from a solution without water.     

Electrospun Er:TiO2 nanofibrous films as efficient photocatalysts under solar simulated light

TiO₂ nanofibrous films with variable amounts of erbium were prepared via electrospinning. Analytical results demonstrated that the doping of erbium inhibited the phase transformation and the crystallite growth of TiO₂. The doped samples were more efficient for degradation of methylene blue than TiO₂, and an optimal dosage of erbium at 0.5% activated at 773 K achieved the highest degradation rate. The higher photoactivity might be attributable to the transition of 4f electrons of erbium, particle size, phase composition and the increase of the separating rate of photogenerated charges by erbium doping.     

Effect of fiber diameter on the deformation behavior of self-assembled carbon nanotube reinforced electrospun Polyamide 6,6 fibers

High precision electrospinning technique was used to obtain self-assembled carbon nano-tube (CNT) reinforced polyamide (PA) 6,6 fibers. The reinforcement factors were critically evaluated with respect to the effects of fiber diameter and inclusion of CNTs. The average fiber diameter ranged from 240 to 1400 nm and the CNT contents were 0, 1 and 2.5 wt%. A sharp increase in modulus and strength of the fibers was demonstrated when the size of the fiber was decreased below ∼500 nm, which could be attributed to ordered arrangement of crystals and the spatial confinement effect of the fibers. Also, investigation of the deformation behavior of fibers as a function of CNT content revealed that tensile fiber modulus and strength improved significantly with increase of CNTs. Addition of CNTs restricted the segmental motion of polymer chains and provided the confinement effect to the neighboring molecules.