• Journal of the Korean Ceramic Society
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• v.37 no.1
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• pp.44-49
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• 2000

Silicon nitride powders, were synthesized by the vapor phase reaction using SiH4-NH3 gaseous mixture. The reaction temperature, ratio of NH3 to SiH4 gas and the overall gas quantity were varied. The synthesized powders were characterized using X-ray, TEM, FT-IR and EA. The synthesized silicon nitride powders were in amorphous state, and the average particle size was about 100nm. TEM analysis revealed that the particle size decreased with increasing reaction temperature and gas flow quantity. As-received amorphous powders were annealed in nitrogen atmosphere at 140$0^{\circ}C$ for 2h, then the powders were completely crystallized at 0.2 ratio of NH3 to SiH4.

• Journal of the Korean Ceramic Society
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• v.35 no.11
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• pp.1190-1196
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• 1998

Ultrafine ${\beta}$-SiC powders were synthesized by the vapor phase reaction of TMS[Si(CH3)4] in hydrogen The reaction temperature and TMS concentration were varied from 1000 to 1400$^{\circ}C$ and from 1 to 10% respectively. The average particle size and phase of the powders were analyzed by TEM and XRD. Ultrafine ${\beta}$-SiC powders were synthesized above 1000$^{\circ}C$ and the crystallinity of the powders increased with increasing reaction temperature. Shape of the particles were spherical and had average size of about 20 nm which showed no difference as the reaction temperature and TMS concentration increased. From the FT-IR analysis the absorption bands of Si-C of the powders shifted to higher wavenumber as the reaction temperature increased,. Under the condition of total gas flow above 1500cc/min ${\beta}$-SiC and poly-Si powders were obtained simultaneously. The Si-O bond intensity was increased under the condition of total gas flow rate above 1000cc/min which might be due to oxidation formed on poly-Si.

• Polymer(Korea)
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• v.26 no.3
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• pp.287-292
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• 2002

Graft copolymerization of styrene and glycidyl methacrylate (GMA) to the peroxidized polypropylene (PP) fabric with E-beam in $O_2$ atmosphere was carried out in vapor phase with benzoyl peroxide (BPO) as an initiator. The degree of grafting of copolymers was increased with the increase of the reaction temperature and the highest degree of grafting was obtained at $70^{\circ}C$ with styrene, and at $80^{\circ}C$ with GMA. The highest degree of grafting of styrene grafted PP according to reaction time was higher than that of GMA grafted PP. In vapor phase graft polymerization, the degree of grafting of copolymers according to water composition in monomer mixture was effected by the boiling temperature of monomers.

• Journal of the Korean Ceramic Society
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• v.36 no.8
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• pp.853-858
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• 1999

To investigate the effect of H2 flow rate and TMS[Si(CH3)4] concentration on synthesizing ultrafine ${\beta}$-SiC powder by vapor phase reaction the experiment was performed at 1100$^{\circ}C$ of the reaction temperature under the condition of 200-2000 cc/min of H2 gas flow rate and 1-10% of TMS concentration respectively. The shape of ${\beta}$-SiC particles synthesized was spherical and the size of particles decreased and the distribution of particles was more uniform with increasing H2 gas flow rate. In this case Si powders were coexisted with ${\beta}$-SiC Pure and ultrafine ${\beta}$-SiC powders without Si were obtained under the condition of above 2% of TMS concentration and below 1500 cc/min of H2 gas flow rate.

• Journal of the Korean Ceramic Society
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• v.43 no.6 s.289
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• pp.376-382
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• 2006

In the $Al(OH)_3-SiO_2-AlF_3$ system, leaf-shaped fluorotopaz was first formed at $800^{\circ}C$ and mullite whisker was formed at $1,100^{\circ}C$. The mass transportation of Al and Si as gas phase, the fast reaction and growth, and the absence of liquid phase existence in mullite whisker showed that the formation and growth of mullite was from the solid-vapor reaction.

• Journal of Powder Materials
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• v.10 no.1
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• pp.1-5
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• 2003

Nano-sized WC powders were synthesized by vapor phase reaction using the precusor of tungsten ethoxide under helium and hydrogen atmosphere. The phases of the powder were varied with reaction Bone and gas flow rate. The powder size was about 30nm in diameter, and the tungsten carbide powder was coated by carbon layer. The synthesis of nano-sized WC powders was promoted as the hydrogen gas flow rate became higher. Inversely, tungsten oxide was formed by increasing the flow rate of helium gas. The synthesized powders were analyzed by XRD, FE-SEM, carbon analyzer etc.

• Macromolecular Research
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• v.11 no.6
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• pp.495-500
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• 2003

UV-induced graft polymerization of glycidyl methacrylate (GMA) to a polypropylene (PP) membrane was carried out in the vapor phase with benzophenone (BP) as a photoinitiator. Attenuated total reflection Fourier transform infrared spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM) were utilized to characterize the copolymer. The degree of grafting increased with increasing reaction time, increased UV irradiation source intensity, and increased immersion concentration of the BP solution. The optimum synthetic condition for the PP-g-GMA membrane was obtained with a reaction time of 2 hrs, a UV irradiation source intensity of 450 W, and an immersion concentration of the BP solution of 0.5 mol/L. The pure water flux decreased upon increasing the degree of grafting and increasing the amount of diethylamino functional group introduced. The analysis of AFM and SEM images shows that the graft chains and diethylamino groups of PP-g-GMA grew on the PP membrane surface, resulting in a change in surface morphology.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.1
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• pp.97-104
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• 2001

Decomposition of trichloroethlyene(TCE) in electron beam irradiation was examined on order to obtain information on the treatment of VOC in air. Air containing vaporized TCE has been studied in a flow reactor with different reaction environments, at various initial TCE concentration and in the presence and absence of water vapor. Maximum decomposition was observed in oxygen reaction environment and the degree of decomposition was about 99% at 20kGy for 2,000ppm initial TCE. The concentration of TCE exponentially decreased with dose in air and pure oxygen. The effect of water vapor on TCE decomposition efficiency was examined. The decomposition rate of TCE in the presence of water vapor (5,600 ppm) was approximately 10% higher than that in the absence of water vapor. Dichloroacetic acid, dichloroacethyl chloride and dichloroethyl ester acid were identified as primary products of this reaction adn were decomposed and oxidized to yield CO and $CO_2$. Perchloroethylene, hexachloroethane, chloroform and carbon tetrachloride were also observed as highly chlorinat-ed by products.

• Bulletin of the Korean Chemical Society
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• v.16 no.6
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• pp.507-511
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• 1995

Catalytic chlorination of chlorobenzene was studied in vapor phase using various solid-acid catalysts such as silica-alumina, alumina, zeolite and a modified clay prepared by impregnating bentonite with ferric chloride. The conversions of both chlorine gas and chlorobenzene showed high over silica-alumina, alumina and modified clay catalysts. However relatively large amounts of polychlorinated benzene derivatives were also observed. The active species of catalytic activity in chlorination of chlorobenzene in vapor phase were proved to be as Lewis acid sites by in-situ IR experiments. The strength of Lewis acid sites which were effective for the vapor-phase chlorination seemed to be having Hammett acidity Ho >-3.0. The selectivity to dichlorobenzenes was proved to be high over the zeolite catalyst due to their shape-selective properties. p-Dichlorobenzene or dichlorobenzene selectivities were improved more or less by changing the reaction conditions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.123-126
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• 2001

Multiwalled carbon nanotubes were massively produced by the catalytic reaction of C$_2$H$_2$ - Fe(CO)$\sub$5/ mixture at 750 - 950$^{\circ}C$ in a quartz tube reactor and over quartz substrates. Well-aligned MWNT array grows perpendicular to the quartz tube reactor and the quartz substrates at an average of 60 nm in diameter and up to several thousands of micrometers in length. This method does not require any pretreatment of substrates and CNTs are grown at atmospheric pressure. It could be suitable for mass production of multiwalled nanotubes. Scanning electron microscope and transmission electron microscope images of the nanotubes deposited on the substrates allowed us to monitor the quality of MWNTs grown under different operating conditions.