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Yang T.L.,National Sun Yat - sen University | Yang T.L.,National Science Cncl Core Facilities Laboratory For Nano Science And Nano Technology In Kaohsiung Pingtung Area | Pan C.T.,National Sun Yat - sen University | Pan C.T.,National Science Cncl Core Facilities Laboratory For Nano Science And Nano Technology In Kaohsiung Pingtung Area | And 13 more authors.
Optical Materials

In this study, polyol process was used to synthesize anisotropic silver nanowires (AgNWs). The ranges of synthesis temperature from 100 to 200 degrees were explored, and the ranges from 4.53 to 13.75 wt% Polyvinylpyrrolidone (PVP) were investigated. The lengths and diameters of AgNWs from 15 to 30 μm and from 10 to 50 nm can be obtained, respectively. Then, the AgNWs embedded in PVP fibers (PVP/AgNWs) were fabricated by the near-field electrospinning (NFES) process. The AgNWs were broken down into nanoparticles when the applied electric field was over 1.4 × 107 V/m. However, the AgNWs could remain undamaged when the electric field was controlled between 8 × 106 and 1.2 × 107 V/m. Therefore, the threshold electric field can be determined and the diameter of the PVP/AgNWs fibers from 500 nm to 10 μm can be obtained. Next, the characteristics of the PVP/AgNWs were examined by N&K analyzer, four-point probe, EDS and FTIR. The transmittance of PVP/AgNWs films was 51.29-68.97% and the sheet resistance of purified AgNWs was 0.125 Ω/sq which was superior to that of commercial ITO. In addition, the haze of PVP/AgNWs with 30-90 nm thick was from 11.5% to 13.3%. In the near future, the PVP/AgNWs fibers can be used as transparent conductive electrodes. © 2014 Elsevier B.V. Source

Liu Z.H.,National Sun Yat - sen University | Liu Z.H.,National Science Cncl Core Facilities Laboratory For Nano Science And Nano Technology In Kaohsiung Pingtung Area | Liu Z.H.,Metal Industries Research and Development Center | Pan C.T.,National Sun Yat - sen University | And 6 more authors.
Applied Surface Science

The mechanical characterization of the electrospinning polyvinylidene fluoride (PVDF) nonwoven fiber fabrics (NFFs) doped with multi-walled carbon nanotubes (MWCNTs) was investigated. Piezoelectric composite nanofibers of the PVDF/MWCNTs were directly electrospun by the hollow cylindrical near-field electrospinning (HCNFES) without any post-poling treatment. We have made the HCNFES NFFs consisted of high-orderly arranged nanofiber assemblies for further characterizing the effect of MWCNTs filling PVDF nanofibers. An in situ electrical poling and high uniaxial stretching imparted on the polymer jet during the HCNFES process, which naturally align the dipoles in the PVDF crystals and promote the formation of the polar β-crystalline phase within the fibers. Moreover, the reinforcement of the HCNFES PVDF nanofibers indicated the improvement in mechanical properties and the degree of high oriented extended-chain crystallites through adding adequate contents of MWCNTs. In the case of alignment of the all-trans polymer chains in the vicinity of MWCNTs along the fiber axis, X-ray diffraction (XRD) patterns showed the strongest diffraction peak of the β-crystalline phase. In the comparison of the near-field electrospinning (NFES), the HCNFES nanofibers with smooth surface and smaller diameter can easily form high density structural NFFs. After nano-indentation and tensile strength measurements, the results indicated that the mechanical properties of the HCNFES NFFs are better than the NFES ones. When 16 wt% PVDF solution doped with 0.03 wt% MWCNTs, the results reveal that Young's modulus, hardness, yield stress, yield strain, ultimate tensile strength, and strain at break of the HCNFES composite NFFs are obviously enhanced to 1.39 GPa, 39.6 MPa, 28 MPa, 48.17 MPa, 3.3%, and 32.5%, respectively. Finally, a flexible wearable sensor made of three-dimensional piezoelectric NFFs was actually experimented. Outstanding mechanical properties with highly deformable of PVDF/MWCNTs composite nanofibers would maintain it to represent great challenges during practical implementation. © 2015 Elsevier B.V. All rights reserved. Source

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