• Carbon letters
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• v.12 no.4
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• pp.185-193
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• 2011

Carbon nanotubes (CNTs) have developed into one of the most competitively researched nano-materials of this decade because of their structural uniqueness and excellent physical properties such as nanoscale one dimensionality, high aspect ratio, high mechanical strength, thermal conductivity and excellent electrical conductivity. Mass production and structure control of CNTs are key factors for a feasible CNT industry. Water and ethanol vapor enhance the catalytic activity for massive growth of vertically aligned CNTs. A shower system for gas flow improves the growth of vertically aligned single walled CNTs (SWCNTs) by controlling the gas flow direction. Delivery of gases from the top of the nanotubes enables direct and precise supply of carbon source and water vapor to the catalysts. High quality vertically aligned SWCNTs synthesized using plasma enhance the chemical vapor deposition technique on substrate with suitable metal catalyst particles. This review provides an introduction to the concept of the growth of vertically aligned SWCNTs and covers advanced topics on the controlled synthesis of vertically aligned SWCNTs.

• Journal of the Korean Ceramic Society
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• v.40 no.6
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• pp.519-524
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• 2003

Porous carbon with high surface area and pore volume was prepared by a reverse replication process and its toluene equilibrium adsorption behavior was investigated. The preparation process of the porous carbon was composed of fellowing sub-processes in series: synthesis and template preparation of silica gel, impregnation and polymerization of DVB monomer in silica template, carbonization of DVB polymer in a silica-polymer composite, and HF-assisted selective etching of silica in carbon-silica composite. The prepared porous carbon was nano porous and had ultrahigh specific surface area (2007 ㎡/g) and large pore volume (3.07 ㎤/g). The nanoporous carbon showed rapid toluene adsorption rate and good toluene adsorption capacity, compared with a commercial Y-type zeolite. In the present study, a reverse replication process to prepare nanoporous carbons will be introduced and its application potential as a gas adsorbent will be discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.236.1-236.1
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• 2014

Compounds of Ga, such as gallium oxide (Ga2O3) and gallium nitride (GaN), are of interest due to its unique properties in semiconductor application. In particular, GaN has the potentially application for optoelectronic device such as light-emitting diodes (LEDs) and laser diodes (LDs) [1]. Nanoparticle is an interesting material due to its unique properties compared to the bulk equivalents. In this report, we develop a synthesizing method for gallium nitride nanoparticle using non-thermal plasma. For gallium source, the gallium is heated by thermal conduction of tungsten boat which is heated by eddy current induced from RF current in antenna. Nitrogen source for nanoparticle synthesis are from inductively coupled plasma with N2 gas. The synthesized nano particles are analyzed using field-emission scanning microscope (FESEM), transmission electron microscope (TEM) and x-ray photoelectron spectroscopy (XPS). The synthesized particles are investigated and discussed in wide range of experiment conditions such as flow rate, pressure and RF power.

• Journal of Powder Materials
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• v.20 no.6
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• pp.411-424
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• 2013

In this study, the synthesis of nickel nanoparticles and copper nanospheres for the potential applications of MLCC electrode materials has been studied by plasma arc evaporation method. The change in the broad distribution of the size of nickel and copper nanopowders is successfully controlled by manifesting proper mixture of gas ambiance for plasma generation in the size range of 20 to 200 nm in diameter. The factors affecting the mean diameter of the nanopowder was studied by changing the composition of reactive gases, indicating that nitrogen enhances the formation of larger particles compared to hydrogen gas. The morphologies and particle sizes of the metal nanoparticles were observed by SEM, and ultrathin oxide layers on the powder surface generated during passivation step have been confirmed using TEM. The metallic FCC structure of the nanoparticles was confirmed using powder X-ray diffraction method.

• Korean Journal of Materials Research
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• v.23 no.1
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• pp.1-6
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• 2013

A simple thermal oxidation of Cu thin films deposited on planar substrates established a growth of vertically aligned copper oxide (CuO) nanorods. DC sputter-deposited Cu thin films with various thicknesses were oxidized in environments of various oxygen partial pressures to control the kinetics of oxidation. This is a method to synthesize vertically aligned CuO nanorods in a relatively shorter time and at a lower cost than those of other methods such as the popular hydrothermal synthesis. Also, this is a method that does not require a catalyst to synthesize CuO nanorods. The grown CuO nanorods had diameters of ~100 nm and lengths of $1{\sim}25{\mu}m$. We examined the morphology of the synthesized CuO nanorods as a function of the thickness of the Cu films, the gas environment, the oxidation time, the oxidation temperature, the oxygen gas flow rate, etc. The parameters all influence the kinetics of the oxidation, and consequently, the volume expansion in the films. Patterned growth was also carried out to confirm the hypothesis of the CuO nanorod protrusion and growth mechanism. It was found that the compressive stress built up in the Cu film while oxygen molecules incorporated into the film drove CuO nanorods out of the film.

• Journal of Magnetics
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• v.14 no.2
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• pp.75-79
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• 2009

Nickel (Ni) and ferrite ($Fe_3O_4$, $NiFe_2O_4$) nanoparticles were synthesized by LGC using both wire feeding (WF) and micron powder feeding (MPF) systems. Phase evolution and magnetic properties were then investigated. The Ni nanopowder included magnetic-ordered phases. The LGC synthesis yielded spherical particles with large coercivity while the abnormal initial magnetization curve for Ni indicated a non-collinear magnetic structure between the core and surface layer of the particles. Since the XRD pattern cannot actually distinguish between magnetite ($Fe_3O_4$) and maghemite (${\gamma}-Fe_2O_3$) as they have a spinel type structure, the phase of the iron oxide in the samples was unveiled by $M{\ddot{o}}ssbauer$ spectroscopy. The synthesized Ni-ferrite consisted of single domain particles, including an unusual ionic state. The synthesized nanopowder bore an active surface due to the defects that affected abnormal magnetic properties.

• Journal of the Korean Institute of Gas
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• v.18 no.4
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• pp.27-34
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• 2014

In this study, we evaluated an effect of the tempered materials on the thermal runaway characteristics in the resol resin synthesis reaction using the adiabatic calorimetry of vent sizing package 2(VSP2). The kinetic parameters, such as an activation energy and heat of reaction, were estimated using the test results. As the results, the instantaneous characteristics to express the intensity of runaway reaction decreased at the low solid content. However, the sudden loss of the tempered materials triggered the second runaway reaction rapidly. In this condition, the heat of reaction and the activation energy of phenol and p-formaldehyde were about 157 kJ/mol and 60 kJ/mol, respectively.

• Elastomers and Composites
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• v.49 no.4
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• pp.313-322
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• 2014

Among many types of flame retardants, the most available halogen-containing flame retardants were put under environmental restrictions in their use, so non-halogen type phosphorus-based flame retardants have come into the spotlight. When added to resins, flame retardants commonly bring about thermal degradation and decrease in mechanical properties of resins. Studies of new flame retardants were carried out in an attempt to minimize degradation of physical properties and require enough flame retardancy. In this study, three types of non-halogen phosphorus-based flame retardants were synthesized with diaryl alkyl phosphate esters, aromatic phosphate esters and phosphonium nitron flame retardants, which were then identified for the synthesis and thermal properties by gas chromatography (GC), IR and thermal gravimetric analysis (TGA).

• Journal of the Korean Society of Safety
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• v.11 no.3
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• pp.126-136
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• 1996

Synthesis of perfluoromethanesulfonyl fluoride(PFMSF) which is a valuable precursor of perfluoro-chemicals such as surface modifier and fine chemicals was studied by electrochemical fluorination (ECF). In order to determine the termination of preelectrolysis, it was carried to monitor the variation of current during preelectrolysis by means of constant cell voltage operation. In a batch cell, chronopotentiometric electrolysis and various chemical analysis such as GC, GC/MS and If were used to understand the potential change of electrode and synthesis and control of hazardous gases products. Termination of preelectrolysis was determinated by measurement the current and/or detection of $F_2$ gas generation. And during the preelectrolysis, an amount of generated $OF_2$ was shown that a lot of moisture was absorbed from air when a cell was filled with anhydrous hydrogen fluoride( AHF ). Above 4V cell voltage, $F_2$ gas was generated and acted on any form of fluorinating agents. In the ECF of MSC (methane sulfonyl chloride) by constant current operation, the potential of anode was intimately relation with generation of $SO_2F_2$. Exchange of Cl to F was dominatly occured in a initial stage. There were various gaseous products including PFMSF as main product and $C_4$ compounds.

• Journal of the Korean Institute of Gas
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• v.2 no.2
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• pp.40-47
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• 1998

This study describes a synthesis of spinel-type $Fe_3O_4$ for decomposition of carbon dioxide, using $Fe_3O_4$ $7H_2O$ and NaOH, at $40^{\circ}C$ for 20 h. with change of their chemical equivalent ratio from 0.50 to 0.75, 1.00, 1.25 and 1.50, respectively. Addition of 0.1-1.00 mole percentage $NiCl_2,\;RhCl_3$ to the particles of $Fe_3O_4$, Prepared by reacting chemical equivalent ratio 1.00, afforced spinel $Fe_3O_4$. The structure of $Fe_3O_4$ and $NiCl_2,\;RhCl_3$-added $Fe_3O_4$ was investigated with XRD and SEM, respectively.