Removal of oil from water using magnetic bicomponent composite nanofibers fabricated by electrospinning

In the present study, a magnetic nanofibrous composite mat composed of polystyrene (PS)/polyvinylidene fluoride (PVDF) nanofibers with selective incorporation of iron oxide (Fe₃O₄) nanoparticles (NPs) on/in PS was successfully prepared via a facile two-nozzle electrospinning process for oil-in-water separation. Field emission scanning electron microscopy and infrared spectroscopy showed the mats to be highly-porous in structure and confirmed the presence of the Fe₃O₄ NPs on/in the nanofibers. Both PS and PVDF nanofibers exhibited oleophilic and hydrophobic properties. The results showed improved mechanical properties when PVDF was added to the composite mat compared to the pristine PS mat. In addition, the incorporation of magnetic Fe₃O₄ NPs in the composite mat helps in the easy recovery of the mats after the oil-in-water sorption process. The composite mats showed good oil sorption capacity (35–46 g/g) and improved mechanical property. The present electrospun magnetic PVDF/Fe₃O₄@PS nanofibers could be potentially useful for the efficient removal of oil in water and recovery of sorbent material.     

Bio-inspired titanium dioxide film with extremely stable super-amphilicity

TiO₂ nanofibers with diameters of 200-550 nm were obtained by high temperature calcinations of the as-electrospun tetrabutyl titanate (Ti(OC₄H₉)₄)/polystyrene (PS) composite fibers prepared by sol-gel processing and electrospinning technique. The fiber films exhibit extremely stable super-amphilicity and self-cleaning properties. The wetting of both watery and oily liquid was observed even after the storage for 240 days in darkness or the contamination of organic compound. And the microstructure of the TiO₂ fibers could be well controlled by different fabrication condition. In addition, the approach shown in this report solved the problem of the stability of the super-amphilicity of titanium dioxide, which very important for the real application.     

The effect of embedded carbon nanotubes on the morphological evolution during the carbonization of poly(acrylonitrile) nanofibers

Hybrid nanofibers with different concentrations of multi-walled carbon nanotubes (MWCNTs) in polyacrylonitrile (PAN) were fabricated using the electrospinning technique and subsequently carbonized. The morphology of the fabricated carbon nanofibers (CNFs) at different stages of the carbonization process was characterized by transmission electron microscopy and Raman spectroscopy. The polycrystalline nature of the CNFs was shown, with increasing content of ordered crystalline regions having enhanced orientation with increasing content of MWCNTs. The results indicate that embedded MWCNTs in the PAN nanofibers nucleate the growth of carbon crystals during PAN carbonization.     

Electrospinning route for α-Fe2O3 ceramic nanofibers and their gas sensing properties

In this paper, α-Fe₂O₃ ceramic nanofibers were prepared by electrospinning poly(vinyl alcohol)/Fe (NO₃)₃·9H₂O composite nanofibers and followed by calcination. The morphologies and structures of the as-prepared samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The gas sensing properties of the sensor based on the as-prepared α-Fe₂O₃ nanofibers were investigated in detail. The experimental results exhibited that our product held rapid response-recovery and high sensitivity characteristics to ethanol vapor. The response and recovery time of the sensor to C₂H₅OH vapor (from 100 to 5000 ppm) are about 3 and 5 s, respectively.     

Catalytic and antibacterial activities of green-synthesized silver nanoparticles on electrospun polystyrene nanofiber membranes using tea polyphenols

An efficient and environmentally friendly method has been developed to prepare Ag nanoparticles (AgNPs) coated tea polyphenols/polystyrene (Ag-TP/PS) nanofiber membrane, which combines electrospinning and in situ reduction of [Ag(NH₃)₂]⁺ using TP as the reductant and stabilizer. In this method, TP/Pluronic/PS nanofiber membranes are fabricated by electrospinning and then immersed in the aqueous solution of [Ag(NH₃)₂]⁺. While TP is being released from TP/Pluronic/PS nanofibers, the surface of TP/Pluronic/PS nanofibers could function as reactive sites for reduction of [Ag(NH₃)₂]⁺ without any extra reagents. XRD results indicate that AgNPs thus formed are in metallic form of Ag⁰. SEM images show that AgNPs can be densely and uniformly coated on the surface of TP/Pluronic/PS nanofibers. The as-prepared Ag-TP/PS nanofiber membranes exhibit excellent catalytic properties for the degradation of methylene blue. Furthermore, the effect of [Ag(NH₃)₂]⁺ concentration on the morphology and catalytic activity of the membrane is investigated. In addition, the antibacterial assays reveal that Ag-TP/PS nanofiber membrane possesses extraordinary antibacterial activity against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli microorganisms. The free-standing membrane is flexible and easy to handle, which is promising for potential applications in catalysis, antibacterial agents and water remediation fields.     

High performance polyimide composite films prepared by homogeneity reinforcement of electrospun nanofibers

Highly aligned polyimide (PI) and PI nanocomposite fibers containing carbon nanotubes (CNTs) were produced by electrospinning. Scanning electron microscopy showed the electrospun nanofibers were uniform and almost free of defects. Transmission electron microscopy indicated that the CNTs were finely dispersed and highly oriented along the CNT/PI nanofiber axis at a relatively low concentration. The as-prepared well-aligned electrospun nanofibers were then directly used as homogeneity reinforcement to enhance the tensile strength and toughness of PI films. The neat PI nanofiber reinforced PI films showed good transparency, decreased bulk density and significantly improved mechanical properties. Compared with neat PI film prepared by solution casting, the tensile strength and elongation at break for the PI film reinforced with 2 wt.% CNT/PI nanofibers were remarkably increased by 138% and 104%, respectively. The significant increases in the overall mechanical properties of the nanofibers reinforced polyimide films can be ascribed to good compatibility between the electrospun nanofibers and the matrix as well as high nanofiber orientation in the matrix. Our study demonstrates a good example for fabricating high performance and high toughness polyimide nanocomposites by using this facile homogeneity self-reinforcement method.     

Templated synthesis of polyaniline nanotubes with Pd nanoparticles attached onto their inner walls and its catalytic activity on the reduction of p-nitroanilinum

In this paper, polyaniline (PANI) nanotubes with palladium nanoparticles (NPs) attached onto their inner walls were synthesized via a templating method which contains three steps. First, electrospun polystyrene (PS) nanofibers were coated with nearly monodispersed Pd NPs (d = 3.411 nm, σ = 0.687 nm, d is the average diameter of Pd NPs and σ is the standard deviation of their diameters) through in situ reduction of Pd²⁺ ions on the surface of sulfonated PS nanofibers. Then we used a self-assembly method to coat the composite with a PANI layer. The final product was obtained after the removal of PS nanofibers by diluting them in tetrahydrofuran. The morphology of samples was analyzed by scanning electron microscopy and transmission electron microscopy and the structure was characterized by Fourier transform infrared, ultraviolet–visible spectra, X-ray diffraction patterns and X-ray photoelectron spectroscopic patterns. Inductively coupled plasma atomic spectra were used to show the weight percentage of Pd nanoparticles. Its catalytic activity on the reduction of p-nitroanilinum was also investigated and compared to Pd/C catalyst and Pd/MWNTs.     

Anomalous transfer phenomenon of carbon nanotube in the blend of polyethylene and polycarbonate

A contradict interphase transfer of multi-walled carbon nanotubes (MWCNT) is detected in the immiscible polymer pair of polyethylene (PE) and polycarbonate (PC). When laminated sheets composed of PE with MWCNTs and PC are annealed in the molten state of both polymers, MWCNTs are found to move from PE to PC. This transfer phenomenon is originated from the difference in the interfacial tension with the aid of Brownian motion. On the contrary, MWCNTs prefer to reside in the PE phase in the blend of PE, PC and MWCNTs, even when MWCNTs are first dispersed in PC. This result indicates that MWCNTs transfer from PC to PE. The opposite direction of the transfer is attributed to the PE molecules being adsorbed on the surface of MWCNTs, which are generated during mixing.     

Multi-walled carbon nanotubes fabricated by electrospinning of acrylonitrile/nylon solution and subsequent carbonization

The poly(acrylonitrile) (PAN) nanofiber web interpenetrated nylon-6 nanofiber supporters were prepared by electrospinning of an acrylonitrile (AN)/nylon-6 solution. It was realized that the average diameters of PAN and nylon-6 nanofiber were 20 and 100 nm, respectively, and that the PAN nanofibers constructed spider-mat networks which were supported by the robust nylon-6 nanofiber pillars. After stabilization and carbonization above 600 degrees C, both hollow-shaped and bamboo-shaped multi-walled carbon nanotubes (MWCNTs) were formed with the diameter range from 5 to 20 nm. The morphology and structure of MWCNTs had been further investigated by the combination techniques of transmission electron microscopy (TEM), electron diffraction (ED), X-ray diffraction (XRD) and elemental analyzer (EA).     

Interconnected multi-walled carbon nanotubes reinforced polymer-matrix composites

A modified method for interconnecting multi-walled carbon nanotubes (MWCNTs) was put forward. And interconnected MWCNTs by reaction of acyl chloride and amino groups were obtained. Scanning electron microscopy shows that hetero-junctions of MWCNTs with different morphologies were formed. Then specimens of pristine MWCNTs, chemically functionalized MWCNTs and interconnected MWCNTs reinforced epoxy resin composites were fabricated by cast moulding. Tensile properties and fracture surfaces of the specimens were investigated. The results show that, compared with pristine MWCNTs and chemically functionalized MWCNTs, the chemically interconnected MWCNTs improved the fracture strain and therefore the toughness of the composites significantly.     

Preparation and characterization of electrospun poly(2,5-dicyclohexylphenylene-1,4-ethynylene) (C<Subscript>24</Subscript>H<Subscript>30</Subscript>)<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>/poly(ethylene oxide) (PEO) hybrid nanofibers

We report the preparation of poly(2,5-dicyclohexylphenylene-1,4-ethynylene) (PDE)/poly(ethylene oxide) (PEO) hybrid nanofibers by electrospinning technique. The hybrid nanofibers were characterized by a host of characterization techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, atomic force microscopy, optical and scanning electron microscopy. The results showed a successful preparation of PDE/PEO composite nanofibers. The diameter of the hybrid nanofibers ranges between 500 and 1000 nm. The results showed that this kind of hybrid nanofibers could be a possible candidate in color display devices.     

Multi-walled carbon nanotube/nanostructured zirconia composites: Outstanding mechanical properties in a wide range of temperature

Multi-walled carbon nanotube (MWCNT)/nanostructured zirconia composites with a homogenous distribution of different MWCNT quantities (ranging within 0.5-5 wt.%) were developed. By using Spark Plasma Sintering we succeeded in preserving the MWCNTs firmly attached to zirconia grains and in obtaining fully dense materials. Moreover, MWCNTs reduce grain growth and keep a nanosize structure. A significant improvement in room temperature fracture toughness and shear modulus as well as an enhanced creep performance at high temperature is reported for the first time in this type of materials. To support these interesting mechanical properties, high-resolution electron microscopy and mechanical loss measurements have been carried out. Toughening and creep hindering mechanisms are proposed. Moreover, an enhancement of the electrical conductivity up to 10 orders of magnitude is obtained with respect to the pure ceramics.     

TiO2-MWCNT rice grain-shaped nanocomposites—Synthesis, characterization and photocatalysis

Titanium dioxide (TiO₂)-multiwalled carbon nanotube (MWCNT) nanocomposites with a novel morphology of rice-grains are prepared by electrospinning method. Anatase-MWCNT composites (with a negligibly small percentage of rutile and brookite) are obtained by high temperature sintering of the as-spun (polymer-TiO₂-MWCNT) composite fibers. The nanocomposites are characterized using spectroscopy and microscopy. The results show that the functionalized MWCNTs are integrated into the TiO₂ rice grain structures. The enhanced photocatalysis of the nanocomposites in comparison to TiO₂ rice grains and commercially available P-25 is demonstrated in photodegradation of Alizarin Red dye.     

Fabrication of TiO2 hollow fibers with surface nanostructure

Polyvinyl alcohol-TiO₂ (PVA-TiO₂) core sheath nanofibers were fabricated by electrospinning an aqueous solution of PVA and introducing the thread-like droplets directly into a titanium tetraisopropoxide (TTIP)/hexane solution. Rod-like and sheet-like structures of lepidocrocite-type layered titanate formed on the surface of the TiO₂ sheath of the nanofibers by alkaline treatment in 1 mol L⁻¹ aqueous NaOH solution at 363 K. The nanofibers were converted to hollow TiO₂ nanofibers with surface nanostructure and anatase crystallinity by acid treatment to remove sodium ions and heat treatment at 773 K. The surface nanostructures enhanced the crystallinity and external surface area of the nanofiber and contributed to the improvement of photocatalytic oxidation activity.     

纳米纤维素/碳纳米管/纳米银线柔性电极的制备

目的以竹粉为原料制备纳米纤维素,并将其作为基底材料制备纳米纤维素/碳纳米管/纳米银线复合电极,应用于柔性超级电容器。方法采用化学机械处理法,将竹粉通过化学处理以及研磨、超声等处理,制备成纳米纤维素悬浮液;分别将多壁碳纳米管和纳米银线超声分散于溶剂中;最后,通过层层自组装制备纳米纤维素/碳纳米管/纳米银线复合电极,同时,作为对照组,制备纳米纤维素/碳纳米管复合电极。结果纳米纤维素纤丝的直径大约为30~100 nm,相互之间缠绕成网状结构,是很好的支撑材料,纳米纤维素/碳纳米管/纳米银线复合电极具有很好的成膜性和电化学性能,在扫描速率为30 m V/s时,面积比电容达到77.95 m F/cm~2。结论以纳米纤维素为基底,通过层层自组装方法制备的纳米纤维素/碳纳米管/纳米银线复合电极具有较好的电化学性能,可作为柔性超级电容器的电极。     

Effect of multi-walled carbon nanotubes on mechanical,thermal and electrical properties of phenolic foam via in-situ polymerization

In this study, phenolic foam (PF)/multi-walled carbon nanotubes (MWCNTs) composites were fabricated by in-situ polymerization, and carbonized foams based on these PF foams were prepared and the electrical property was investigated. TEM results indicated excellent dispersion of MWCNTs in the phenolic resin matrix. Scanning electron microscope results indicated that PF composites exhibited smaller cell size, thicker cell wall thickness, and higher cell density, compared with pure PF. The incorporating of MWCNTs significantly improved the mechanical properties of PF. All PF composites showed a lower thermal conductivity versus pure PF. Moreover, the carbonized pure and composites PF exhibited open-cell three-dimensional skeleton carbon structure and the MWCNTs were well-dispersed on the surface of the skeletons. It is noteworthy that the introduction of MWCNTs significantly improved the electrical performances of foams and carbonized foams by construction of conductive MWCNTs network.     

Fabrication of aligned ferrite nanofibers by magnetic-field-assisted electrospinning coupled with oxygen plasma treatment

This paper describes a simple and effective approach to fabrication of aligned magnetic ferrite nanofibers by magnetic-field-assisted electrospinning coupled with oxygen plasma treatment. Large and flexible magnetic hybrid membranes of aligned Fe₃O₄/PVP composite nanofibers were fabricated readily by electrospinning mixtures of Fe₃O₄/PVP in a magnetic field. The PVP matrix could be removed either by calcination or by oxygen plasma treatment. Oxygen plasma treatment retained the original crystalline phase of Fe₃O₄, and large inorganic membranes of aligned ferrite nanofibers were obtained. The ferrite nanofibers showed ferromagnetic behaviors, and are promising in flexible magnetic membranes, magnetic separation, drug delivery, and magnetic sensors.     

Nanoparticles assembly of boehmite nanofibers without a surfactant

Self-assembly of aluminum hydrate particles into larger boehmite (γ-AlOOH) nanofibers was illustrated by a facile hydrothermal method without using any surfactants. The size and morphology of boehmite nanofibers could be controlled by adjusting the pH value of the reaction mixture. The resulting products were characterized by XRD (X-ray diffraction), FTIR (Fourier transform infrared spectra), SEM (scanning electron microscopy), and TEM (transmission electron microscopy). The specific surface area and pore-size distribution of the obtained product as determined by gas-sorption measurements show that the boehmite nanofibers possess high-surface area and porosity properties. A possible formation mechanism of nanofibers via a nanoparticle assembly procedure is proposed based on the experiments under the different conditions.     

Fracture toughness and creep performance of PMMA composites containing micro and nanosized carbon filaments

Chopped carbon fiber (CCF), multiwall carbon nanotubes (MWCNTs) and carbon nanofibers (CNFs) were introduced to polymethylmethacrylate (PMMA) via melt compounding. Fracture toughness and creep performance of these composites are presented. A constant volume concentration of 1 vol.% was used. Dispersion was evaluated on both micro- and nano-scales. Flexural modulus was also measured.     

Fabrication and characterization of Fe-Ni alloy/nickel ferrite composite nanofibers by electrospinning and partial reduction

A novel synthetic process has been developed to fabricate the magnetic alloy/spinel ferrite composite nanofibers. By employing the electrospinning technique and subsequent partial reduction, Fe-Ni alloy/nickel ferrite composite nanofibers with an average diameter of around 170 nm were successfully prepared. The synthesized composite nanofibers consist of the face centered cubic and body centered cubic phases of Fe-Ni alloy and the spinel phase of nickel ferrite, and have novel magnetic properties with much enhanced coercivity and saturation magnetization as compared with the pristine nickel ferrite nanofibers.