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Author: search.filters.author.Wongwiriyapan, WinaddaSubject: search.filters.subject.Carbon nanotube

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    Field emission properties of a DWCNT bundle and a single MWCNT
    (2018-02-01)
    Fujishige, Masatsugu
    ;
    Wongwiriyapan, Winadda
    ;
    Muramatsu, Hiroyuki
    ;
    Takeuchi, Kenji
    ;
    Arai, Susumu
    The field emission properties of a bundle of double-walled carbon nanotubes (DWCNTs) and a single multiwalled carbon nanotube (MWCNT) were investigated. A DWCNT bundle or a single MWCNT was attached to the head of sharpened tip of tungsten by electrophoresis; the tungsten tip was dipped into a drop of a carbon nanotube/1,2-dichloroethane suspension on a stainless plate, and a high-frequency AC voltage (20 V peak to peak with a frequency of 15 MHz) was applied between the tungsten tip and the stainless steel plate. The turn-on fields of the DWCNT and MWCNT tips for 1 nA/cm<sup>2</sup> were 0.05 and 0.48 V/μm, respectively. From the Fowler-Nordheim plots, the field enhancement factor (β) of the tips was estimated to be 109,600 (DWCNT) and 6780 (MWCNT). The present DWCNT emitter is characterized by a very small turn-on field and large β. The field emission performance is discussed in terms of the sizes of the bundle of DWCNTs and a single MWCNT.
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    Facile growth of carbon nanaotube electrode from electroplated Ni catalyst for supercapacitor
    (2015-01-01)
    Yordsri, Visittapong
    ;
    Wongwiriyapan, Winadda
    ;
    Thanachayanont, Chanchana
    A facile growth of carbon nanotubes (CNTs) was facilitated by the use of direct-current plating technique for catalyst preparation. Ni nanoparticles (NPs) were deposited on Cu foil at different applied voltages of 1.0, 1.5 and 2.0 V. The Ni-deposited foil was subsequently used as catalyst for CNTs synthesis by chemical vapour deposition (CVD) method. CVD was carried out at 800 °C using ethanol as carbon source. A voltage of 1.5 V was the optimum condition to deposit uniform Ni NPs that had a narrow size distribution of 55±3 nm, which in turn, yielded synthesized CNTs with a uniform diameter of approximately 60±5 nm with graphitic layers parallel to the CNTs axis. On the other hand, electroplated Ni at 1.0 V produced CNTs with graphitic layers at an angle to the CNTs axis, while electroplated Ni at 2.0 V produced curly CNTs with a wide distribution of diameters. These results show that Ni NPs size distribution could be controlled by electroplated voltage. Our observation was that Ni NPs with a narrow distribution of sizes and a uniform diameter is a key to uniform CNT synthesis. Furthermore, the synthesized CNTs electrode shows a faradic pseudo capacitance property, which can be attributed to the existence of oxidized Ni NPs. These results propose that the synthesized CNTs are promising materials for future super capacitor application. The optimization of ratio of Ni NPs and CNTs may improve the supercapacitors performance.
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    Synthesis of carbon nanotube and carbon nanofiber in nanopore of anodic aluminum oxide template by chemical vapor deposition at atmospheric pressure
    (2012-10-15)
    Kasi, Jafar Khan
    ;
    Kasi, Ajab Khan
    ;
    Wongwiriyapan, Winadda
    ;
    Afzulpurkar, Nitin
    ;
    Dulyaseree, Paweena
    Carbon nanotube (CNT) is one of the most attractive materials for the potential applications of nanotechnology due to its excellent mechanical, thermal, electrical and optical properties. We demonstrated the fabrication of carbon nanotube and carbon nanofiber (CNF) inside the pore and at the surface of anodic aluminum oxide (AAO) membrane by chemical vapor deposition method at atmospheric pressure. Ethanol was used as a hydrocarbon source and Co-Mo as catalyst. CNT was synthesized at different temperature. High graphitic multiwall carbon nanotube (MWCNT) was found at 750°C, while CNF was found at 800oC and above temperature analyzing by Raman spectroscopy. © (2012) Trans Tech Publications, switzerland.