静电纺丝纳米纤维研究的最新动向

综述静电纺丝纳米纤维研究的最新动向,有关静电纺丝法制取导电性纳米纤维和聚合物合金型纳米纤维以及静电纺丝装置开发。     

Electrospinning and thermal treatment of yttria doped zirconia fibres

As compared to a bulk material, the fibres exhibit novel physical and chemical properties arising from their unique geometric features such as high surface area, surface to volume ratio and small fibre diameter. This paper is focused on the fabrication of nanosized 8 mol% yttria doped zirconia fibres by electrospinning from propoxide/polyvinylpyrrolidonebased precursors and physical-chemical characterization of the ceramic fibres with an energy application potential. Fully crystalline composition of cubic zirconia was detected after fibre heat treatment at 700 °C. The fibre morphology was changed with increasing temperature from flexible nonsintered nanoparticle system at 700 °C through porous nanograin structure at 900 °C and nonporous structure with coarser nanograins at 1100 °C to fragile chain-like fibre structure formed of elongated submicrometer grains at 1300–1450 °C. The densification and grain growth kinetics were described in two stages in the temperature range from 700 °C up to 1450 °C.     

Facile synthesis and electrochemical properties of conducting SrRuO3-RuO2 composite nanofibre mats

This study reports the facile synthesis of highly conductive SrRuO₃(SRO)-RuO₂ composite nanofibre mats and their potential suitability for application in electrochemical capacitors as an active electrode material. SRO-RuO₂/poly(vinyl acetate) composite nanofibre mats are electrospun on to a Au-coated SiO₂/Si substrate and a Ti substrate, subsequently thermocompressed at 60 °C, and calcined at various temperatures (from 350 to 850 °C). The calcined SRO-RuO₂ nanofibre mats exhibit porous morphologies and bundle shapes composed of multiple-fibrils with a nanoparticle diameter ranging from 20 to 50 nm. Single SRO-RuO₂ nanofibre and multiple SRO-RuO₂ nanofibre mats show high electrical conductivity of 476 and 40.8 S cm⁻¹, respectively. Pseudocapacitors using SRO-RuO₂ nanofibre mats calcined at 350 °C exhibit a high specific capacitance of 192 F g⁻¹ at a scan rate of 10 mV s⁻¹. The superior capacitance retention (83.4%) of the SRO-RuO₂ nanofibre mats is maintained even at rapid scan rate of 1000 mV s⁻¹.     

Characteristics of vitamin E-loaded nanofibres from dextran

In this research, dextran nano?bres were produced as novel carriers for entrapment of vitamin E. Morphological studies indicated that developed fine fibres were in the nano range without spherical beads. Thermal behaviour, chemical structure, and crystalline structure of vitamin E-loaded nanofibres were analysed by differential scanning calorimetry, Fourier transform infrared spectroscopy, and X-ray diffraction which showed that the vitamin was well incorporated within the amorphous structure of fibres without chemical interactions. Nanofibres were used for fortification of cheese. Sensory analysis of the fortified product was performed which showed better acceptability and texture of cheese containing nanofibres in comparison to blank and direct fortified samples. Nanofibres showed the capability of holding water and thus increasing cheese firmness. The release of vitamin E in gastrointestinal media showed that about 14% of vitamin could be released in gastric media and about 30% released in intestinal media. Finally, the results revealed that electrospinning can be used for production of dextran ultrathin fibres to entrap hydrophobic compounds with high potential for design of novel functional foods.     

Effects of porosity gradient of multilayered electrospun nanofibre mats on air filtration efficiency

Performance of the nanofibrous filter media is determined by fibre diameter and pore size distribution of the membranes. In this study, an attempt is made to fabricate a nanofibrous multi-scale filter media by simply varying the layer-by-layer-assisted stacking structure and composition of individual fibres within the single layers. These structural controls of the filter membrane helped to form a skeletal frame-worked membrane with controlled filtration efficiency and pressure drop aerosol particle filtration application. Altering the right electrospinning parameters, layering structure of the membrane resulted in changes in average fibre diameter and pore size distribution, especially in the middle layer of media, while a gradient in pore size and its distribution was created. The results of measurements of pressure drop and filtration efficiency indicated that by changing the gradient in pore size and its distribution in the middle membrane, keeping other layers constant, the pressure drop and filtration efficiency can be effectively tuned. The results suggested that this developed filter media could be used as promising materials for a variety of potential applications in high efficiency particulate air filters with tunable characteristics.     

Effect of aqueous electrolyte on pseudocapacitive behavior of chemically synthesized La2S3 electrode

Lanthanum sulfide electrode (La₂S₃) is prepared by a low cost, simple and room temperature chemical route for energy storage. The surface morphology of La₂S₃ film is revealed through field emission scanning electron microscopy. For the energy storage purpose, the pseudocapacitive behavior of La₂S₃ electrode is studied in 1 M aqueous Na₂SO₄ and 1 M KOH electrolytes. La₂S₃ electrode achieved maximum specific capacitance of 358 F g⁻¹ at 5 mV s⁻¹ scan rate with 78% electrochemical cyclic stability over 1000 cycles in 1 M Na₂SO₄ electrolyte. The galvanostatic charge–discharge study demonstrated the energy density of 35 Wh kg⁻¹ at power density of 1.26 kW kg⁻¹. The electrochemical impedance study showed field assisted charge transfer process with relaxation time of 32 ms in 1 M Na₂SO₄ electrolyte ensuring fast redox reaction.     

Preparation and luminescent properties of Tb3+ doped Y2O2SO4 microflakes

Abstract

Tb³⁺ doped Y₂O₂SO₄ (Y₂O₂SO₄:Tb³⁺) microflakes were prepared by a combination method of electrospinning and calcination. The two-dimensional microflakes had smooth surface and high radial/axial ratio. Crystal structures of the Y₂O₂SO₄:Tb³⁺ microflakes resulted in layer by layer growth in axial direction. A possible formation mechanism was proposed on the basis of experimental results, which indicated that poly(vinyl pyrrolidone) played the role of the nanostructure directing template and revealed the growth priority in radial direction. The microflakes showed a favourable fluorescent property symbolised by the characteristic green emission (541 nm) resulting from the ⁵D₄→⁷F₅ transition of Tb³⁺ ions under 229 nm ultraviolet excitation. The maximum intensity of Tb³⁺ emission of the Y₂O₂SO₄:Tb³⁺ microflakes was 2·3 times stronger than that of the Y₂O₂SO₄:Tb³⁺ bulk powders with the same doping concentration.     

Encapsulation of vanillin/cyclodextrin inclusion complex in electrospun polyvinyl alcohol (PVA) nanowebs: Prolonged shelf-life and high temperature stability of vanillin

We produced functional nanowebs, containing vanillin, having prolonged shelf-life and high temperature stability facilitated by cyclodextrin (CD) inclusion complexation. Polyvinyl alcohol (PVA) nanowebs incorporating vanillin/cyclodextrin inclusion complex (vanillin/CD-IC) were produced via electrospinning technique. The vanillin/CD-IC was prepared with three types of CDs; α-CD, β-CD and γ-CD to find out the most favourable CD type for the stabilization of vanillin. PVA/vanillin/CD-IC nanofibres, having fibre diameters around ∼200 nm, were successfully electrospun from aqueous mixture of PVA and vanillin/CD-IC. Our results indicated that vanillin with enhanced durability and high temperature stability was achieved for PVA/vanillin/CD-IC nanowebs due to complexation of vanillin with CD, whereas the PVA nanofibres without CD-IC could not effectively preserve the vanillin. Additionally, we observed that PVA/vanillin/γ-CD-IC nanoweb was more effective for the stabilization and slow release of vanillin suggesting that the strength of interaction between vanillin and the γ-CD cavity is stronger when compared to α-CD and β-CD.     

Toward the integration of a single carbon nanofibre as via interconnect

The use of carbon nanotube/nanofibres as via interconnects is widely studied. As the vias dimensions decrease below 50 nm, the number of carbon nanotubes could be close to the unity in each via hole. In the present study we show the integration processes to obtain interconnects made of one single vertically free standing carbon nanofibre. Two different catalyst integrations are detailed and tested.     

Fabrication of tin-filled carbon nanofibres by microwave plasma vapour deposition and their in situ heating observation by environmental transmission electron microscopy

Sn-filled carbon nanofibres (CNFs) are fabricated by microwave plasma chemical deposition. Scanning electron microscopy observations revealed the existence of a Sn island under the CNFs. The structure of the CNFs is investigated, and the behaviour of Sn in the internal space of CNFs is revealed by performing in situ heating observations by environmental transmission electron microscopy (ETEM). ETEM observations reveal that they have low-crystallized carbon wall and Sn occupies not only the CNF’s internal space but also its carbon wall. The Sn inside the CNF is completely covered by the carbon wall. Further, the in situ heating observations reveal that Sn within the internal space and the carbon wall of the CNFs diffused to the outside during heating. Moreover, it is found that higher membered carbon rings and defects in the graphite layer act as diffusion routes between disordered carbon layers.