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Park S.,Helmut Fischer Korea | Na H.G.,Hanyang University | Choi S.-W.,Korea Institute of Science and Technology | Jin C.,Konkuk University
Synthetic Metals | Year: 2016

Impregnation-dependent nanocomposites, consisting of multi-walled carbon nanotube (MWCNT) and low-density polyethylene (LDPE), were successfully produced by controlling the catalyst-supporter size during catalyst fabrication. The MWCNTs fabricated by the impregnation method with different dimensionalities such as pore density and size were compared with MWCNTs fabricated by the spray drying technique. After mixing MWCNTs with LDPE using an extruder, the individual composite constituents showed different physical and electrical properties related to dispersion and sheet resistance, depending on catalyst-supporter dimensionality. For more detailed dispersion control of the extruded composite, scanning and transmission electron microscopy and sheet-resistance measurement were performed. Furthermore, the electrical properties of MWCNT composites with poly methyl methacrylate (PMMA) instead of LDPE were investigated for comparison. The fabrication of MWCNT composites using the impregnation technique with size-controllable catalyst supporters is regarded as a good synthetic method for realizing optimal MWCNT-based electronic devices. © 2016 Elsevier B.V. All rights reserved.

Park S.,Helmut Fischer Korea | Lee S.,Konkuk University | Jeong H.,Konkuk University | Jin C.,Konkuk University
Bulletin of the Korean Chemical Society | Year: 2016

Four different polymer-coated multi-walled carbon nanotubes (MWCNTs) were prepared under various catalyst-supporter conditions for examining the conductivity of the nanocomposites. The dimensions of the initial Al(OH)3 catalyst supporter, i.e., one of the final ternary catalysts, mainly determined the pristine MWCNT properties. The respective MWCNT-based composites with polycarbonate, high-density polyethylene, polypropylene, and low-density polyethylene generally exhibited remarkable catalyst supportdependent conductivity differences-approximately seven orders of magnitude, from 109.7 to 102.7. The degree of MWCNT dispersion is considered the key factor inducing the significant electrical differences. © 2016 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Park S.,Helmut Fischer Korea | Kim Y.,Samsung | Kim M.,Helmut Fischer Korea | Lee D.,Konkuk University | And 2 more authors.
Materials Science and Engineering B: Solid-State Materials for Advanced Technology | Year: 2015

Catalyst-assisted synthesis of multi-walled carbon nanotube (MWCNT) networks was successfully realized by controlling the catalyst particle size with and without post annealing. The sizes of ternary composite catalyst synthesized from spray pyrolysis method varied with different partial pressures and post-annealing. Various-sized MWCNT networks corresponding to individual catalyst sizes were produced through chemical vapor deposition technique. To investigate the dispersion of MWCNTs with respect to catalyst particle size, particle size analyses, scanning electron microscopy, and transmission electron microscopy were performed. In addition, the sieve shaker with 250 mesh were also used for evaluation of correlation between the MWCNTs networks and catalyst sizes. For electrical properties of the samples, MWCNT sheet resistance values were estimated with a four-point probe. These values were used to establish the optimal dispersion of MWCNTs needed to yield optimal carrier density and mobility. © 2015 Elsevier B.V. All rights reserved.

Na H.G.,Hanyang University | Choi S.-W.,Korea Institute of Science and Technology | Park S.,Helmut Fischer Korea | Hwang S.J.,Inha University | And 5 more authors.
Crystal Growth and Design | Year: 2016

In contrast with conventional thermal evaporation-based semiconducting oxide growth methods, gourd-like SiOx nanotubes (NTs) grown from Si substrates were achieved with incorporated Sn-embedded structures through the precontaminated SnO2 film surroundings. Interestingly, when Sn aggregations assembled as Sn nanoparticles were formed on the surface of the Si substrate, single gourd-like SiOx NTs were grown from the upper local region of the ternary alloy (Si-Sn-O) sphere, maintaining a one-to-one correspondent relationship between the ternary spheres and the Sn-embedded SiOx NTs. Both interfacial reaction-controlled and diffusion-controlled systems occurred stepwise at the smooth and rough surfaces, respectively. In addition, the elemental compositions and sizes of the final Sn-embedded SiOx NTs were influenced by the Sn concentration of the SnO2 film, the rate of In substitution by Sn in the supporting material In2O3, and the degree of carbothermal reduction of additional graphite powders. © 2016 American Chemical Society.

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