Results 1 - 10 of 14
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[en] To improve the stress transfer and distribution of carbon fiber/epoxy interface, a gradient interphase reinforced by graphene oxide (GO) was designed in the composites. GO was introduced onto the surface of carbon fibers by physical adsorption, forming a gradient interphase in composite interface during the procedure of resin wetting. In order to improve the dispersion of GO in gradient interphase and chemical adhesion between GO and epoxy, GO was covalently functionalized with silane coupling agents and the silanized graphene oxide (SGO) was introduced into the gradient interphase as well. Compared with the base composites without nanosheets, the interfacial shear strength (IFSS), interlaminar shear strength (ILSS), flexural and tensile properties of hierarchical composites decreased seriously when 0.5 wt% GO was introduced on carbon fiber surface. However, hierarchical composites containing 0.5 wt% SGO showed a significant increase 60% in IFSS, 19% in ILSS, 15% in flexural strength and 16% in flexural modulus. A new stiffness phase between carbon fibers and matrix was found in the stiffness distribution curve of hierarchical composites by atomic force microscope in force mode. In addition, the stiffness of interphase was proved to change gradually from carbon fibers to epoxy, indicating the gradient dispersion of nanosheets in interphase. - Graphical abstract: Display Omitted - Highlights: • Graphene oxide was covalently functionalized with silane coupling agents. • Gradient interphase composed of SGO and epoxy was designed in fiber/matrix. • A new stiffness phase between fiber and matrix was found by AFM in force mode. • Interfacial properties of composites containing SGO/epoxy interphase were increased
[en] Two transition metal ions (Fe"3"+ and Cu"2"+) and a rare earth metal ion (Ce"3"+) were selected to coordinate with amidoximated polyacrylonitrile (PAN) nanofibrous membrane for preparing three metal modified PAN nanofibrous membrane complexes (M-AO-n-PANs, M = Fe, Cu, or Ce) as the heterogeneous Fenton catalysts for the dye degradation in water under visible irradiation. The coordination kinetics of three metal ions with modified PAN nanofibrous membranes was studied and the catalytic properties of the resulting complexes were also compared. The results indicated that increasing metal ion concentrations in solution or higher coordination temperature led to a significant increase in metal content, particularly in Fe and Cu contents of the complexes. Their coordination process could be described using Langmuir isotherm and pseudo-second-order kinetic equations. Moreover, Fe-AO-n-PAN had the best photocatalytic efficiency for the dye degradation in acidic medium, but a lower photocatalytic activity than Cu-AO-n-PAN in alkali medium
[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] 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 work, an affinity nanofiber membrane was successfully prepared by solution blowing of arginine-modified chitosan (CS-Arg) for bovine serum albumin (BSA) adsorption. CS-Arg was firstly synthesized by coupling L-arginine onto chitosan backbone. Then, CS-Arg nanofiber membranes (CANFs) were fabricated using solution blowing process with Polylactide (PLA) as assistant polymer. The results showed that CANFs effectively adsorbed BSA, and the adsorption capacities were influenced by the degrees of substitution (DS) of arginine in CS, pH value, contact time, and initial protein concentration. The highest adsorption capacity of 445.19 mg/g was achieved uvnder the following conditions: DS of 43.7 %, pH of 7.14, and initial concentration of 3.0 mg/ml. BSA adsorbed on the CANFs membrane conformed to Langmuir model, and the adsorption rate was consistent with the second-order kinetics model. This work implies that an arginine-modified chitosan nanofiber-based novel biomaterial has a potential application in adsorption of BSA.
[en] A new type of hydrophobic polyacrylonitrile (PAN) nanofiber is fabricated by solution blowing of a blend solution of fluorine-containing polyacrylate (FPA) and PAN. The nanofibers’ surface composition, hydrophobicity, and protection ability were evaluated to clarify the effects of FPA addition. Results revealed that FPA addition increased the nanofiber diameter, as well as enhanced the hydrophobicity and transport properties of the nanofiber mats. The mats had average water contact angles of 123.44°, 132.11°, and 137.11° for FPA contents of 0.66 wt%, 1.98 wt%, and 3.30 wt%, respectively. All these results suggested the potential of the solution blowing nanofiber mats as protection materials.
[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 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] Here we reported a two-step procedure for preparing a novel polymeric based solid-solid phase change heat storage material. Firstly, a copolymer monomer containing a polyethylene glycol monomethyl ether (MPEG) phase change unit and a vinyl unit was synthesized via the modification of hydrogen group of MPEG. Secondly, by copolymerization of the copolymer monomer and phenyl ethylene, a novel polymeric based solid-solid phase change heat storage material was prepared. The composition, structure and properties of the novel polymeric based solid-solid phase change material were characterized by IR, 1H NMR, DSC, WAXD, and POM, respectively. The results show that the novel polymeric based solid-solid phase change material possesses of excellent crystal properties and high phase change enthalpy.