Results 1 - 8 of 8
Results 1 - 8 of 8. Search took: 0.015 seconds
|Sort by: date | relevance|
[en] The preparation of high performance separation membrane is the key technology for developing efficient oil/water separation system. In this paper, hydrophilic/oleophilic Polystyrene (PS)/Polyacrylonitrile (PAN) bi-component membranes were prepared via electro-blown spinning (EBS) technique and exhibited extremely high oil flux. The addition of PAN component significantly enhanced the tensile strength of the PS based fibrous membranes and PS/PAN membrane with the weight ratio of 5:3 achieved a tensile strength of 2.1 MPa which was 3 times higher than pure PS membrane. The PS/PAN membranes demonstrated a high light oil flux up to 18000 l·m-2·h-1 and could remain the oil flux recovery ratio of 94.09 % after 10 cycles. The as-prepared membranes exhibited the superior oil/water separation performance with the separation efficiency higher than 99.5 % and have a great potential to deal with the oily waste water in the near future.
[en] The plasma screening effects on the energy levels and wave functions of hydrogen-like ions were estimated by using Debye model. The effects on n l(n=1-4, l=0-3) energy levels and wave functions of hydrogen and Fe25+ ion versus screening lengths λ have been analyzed. Furthermore, the screening effects versus quantum number n and l has been analyzed. The results show that the screening effects increasing as n increasing and decreasing as l increasing. Last, the Eigenergies of isoelectronic series change against screening parameter λ has been discussed, it's shown that the plasma screening effects are decreasing as nuclear charge increasing. (authors)
[en] A highly sensitive and fast sensor for gaseous hydrogen chloride (HCl) is described. It is based on the use of the optical probe 5,10,15,20-tetraphenylporphyrin contained in a poly(lactic acid) nanoporous fiber membrane that was fabricated via electrospinning. With its porous structure, the sensor overcomes the slow gas absorption and diffusion of other sensing materials. Field emission SEM was employed to characterize the morphology of the sensing membrane. The exposure to HCl gas causes a color change from pink to green that is due to the protonation of the central nitrogen atoms of the porphyrin, and fluorescence is quenched. The largest increase in absorbance occurs at 442 nm. HCl gas can be detected in this way even at sub-ppm levels. The detection limit is 34 ppb, and the response time is as short as 5 s. The sensor is highly stable after ten cycles of tracing HCl gas and recovery, and response is fully reversible. (author)
[en] Highlights: • A novel PVDF tree-like nanofiber membrane was fabricated. • A possible mechanism for the formation of the tree-like nanofibers was proposed. • Tree-like structure decreased the pore size of membrane. • Tree-like structure improved the mechanical properties of membrane. A novel polyvinylidene fluoride (PVDF) tree-like nanofiber was controllably fabricated via one-step electrospinning by adding certain amount of salt into PVDF solution. A possible mechanism for the formation of the tree-like nanofibers was proposed by analyzing high speed camera photos of the spin jet and the result showed that the formation of tree-like nanofibers was due to the splitting of jets. The effects of salt type, salt content and processing parameter on the content of tree-like branches were investigated. The electrospun nanofibers were characterized by field emission scanning electron microscopy (FE-SEM), energy disperse spectroscopy (EDS), X-ray diffraction (XRD), pore size meter and mechanical properties measurement. It was found that the PVDF/TBAC tree-like nanofibers with improved crystallinity and mechanical strength. The decreased average pore size caused by the tree-like structure and the resistance to organic solvent, can make it as a potential candidate for membrane separation.
[en] In this study, the MnO2 & carbon composite porous nanofibers (CPNF) were prepared via electro-blown spinning and in-situ hydrothermal synthesis. The MnO2 nano-sheets were uniformly growing on carbon skeleton and filling in honeycomb-like carbon porous nanofibers, and the clear CPNFs were formed. The different hydrothermal parameters including the mass ratios of honeycomb-like porous carbon nanofiber and potassium permanganate, hydrothermal times and temperatures were discussed to obtain optimizing reaction conditions. The CPNFs were investigated by scanning electron microscopy (SEM), transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and low temperature nitrogen adsorption, respectively, and the supercapacitor performance of CPNF was preliminary tested. The discharge capacity was 421.5 F g−1 at 0.5 A g−1, and it retained ∼81.2% after 3000 cycles at the current densities of 1.0 A g−1. Moreover, this CPNF owned special structure and a great industrialization potentiality which could realize the applications in absorption and catalyst fields.
[en] Herein, the composite carbon material of porous carbon nanofiber and carbon nanotube is developed via electro-blown spinning and one-step simultaneous carbonization and chemical vapor deposition without injecting every kind of reaction gas in proportion and removing catalyst in secondary processing. The carbon nanotubes are uniformly growing on carbon skeleton which dramatically improve the performances such as specific surface area (from 334.066 to 644.589 m2 g−1) and electrical conductivity (from 42.22 to 146.20 S cm−1) comparing with porous carbon nanofibers. The different spinning parameters are investigated to optimize parameters, and the porous carbon nanofiber and carbon nanotube are studied and used as electrode for supercapacitors. The results showed that it possesses excellent electrochemical properties, including high specific discharge capacity (216.5 F g−1 at 1.0 A g−1) and good cycle performance (retains ~ 98.68% after 5000 cycles). Moreover, the convenient one-step prepared method special throughout pores structure and superior performance provide a novel approach for designing new types of carbon composite materials which also possess potential application prospect in fields of catalyst, adsorption, etc.
[en] In this study, the F-doped poly-m-phenyleneisophthalamide (PMIA) solution was synthesized by low temperature polymerization method and spun to be three-dimensional nanofibrous membranes by electrospinning. The Energy Dispersive X-Ray Spectroscopy and Fourier Transform Infrared Spectroscopy investigations verified that F was successfully doped in PMIA membrane. The X-ray diffraction patterns showed the crystallinity degree of PMIA membrane decreased with the addition of F. The morphology, pore size and aperture distribution tests manifested that the average diameter of F-PMIA fibers became finer and their distribution was more uniform than these of PMIA fibers. The electrolyte uptake, preserving liquid electrolyte, thermal stability and shrinkage resistance of the F-dopoed membrane were also significantly enhanced than that of pure PMIA membrane. The F-PMIA membrane could be acted as matrix to prepare gel polymer electrolyte. Finally, the F-doped PMIA membrane was used in the assembled coin cells to test the properties including the electronic conductivity, battery interfacial characteristics, electrochemical stability windows and cycle performances of battery. The lower electronic conductivity and interfacial resistance, higher electrochemical stability window (5.7 V) of F-doped PMIA membranes were obtained when comparing to the pure PMIA and commercial polyethylene membrane. The cell exhibited high first-cycle discharge capacity with 145 mAh g−1 and excellent cycling stability with good capacity retention of 93.1% and coulombic efficiency of 99.3% after 100 cycles.
[en] In this study, we prepared a novel type of biofunctionalized poly(vinylidene fluoride) (PVDF) nanofibers. Cysteine, a natural amino acid, was grafted onto the surfaces of PVDF nanofibers, The −SH groups of cysteine were then oxidized to −SO3H. The formation of proton-conducting pathways was induced by the −SO3H and COOH groups of the oxidized cysteine chains on the surfaces of the biofunctionalized PVDF nanofibers. Composite membranes were fabricated by impregnating the biofunctionalized PVDF nanofibers with Nafion. Then, the effects of incorporating nanofibers grafted with different amounts of oxidized cysteine on the thermal stability, water uptake dimensional stability, proton conductivity, and single-cell performance of Nafion composite membranes were investigated. The properties of the composite membranes were superior to those of the Nafion membrane. Furthermore, Nafion/PVDF–Cys-30 exhibited the highest proton conductivity of 0.22 S cm−1 (80 °C), and the maximum power density of 108.42 mW cm−2 which was twice than the values of Nafion 117 membrane (51.2 mW cm−2) at 60 °C under 100% RH. The introduction of biofunctionalized nanofibers significantly improved cell performance, proton conductivity, dimensional stability, and methanol permeability of the membrane.