• Bulletin of the Korean Chemical Society
• /
• v.34 no.12
• /
• pp.3767-3770
• /
• 2013

Potassium methylselenite ($KSeO_2(OCH_3)$) was reduced to elemental selenium, Se(0), and then doped onto montmorillonite K 10 (MK10) clay to examine the interaction between elemental mercury (Hg(0)) vapor and Se(0) in an effort to understand the possible heterogeneous reaction of Hg(0) vapor and Se(0) solid. The clay was used as a cost-effective support material for uniform dispersion of Se(0). The Se(0)-doped MK10 showed an excellent reaction performance with Hg(0) under an inert nitrogen gas at 70 and $140^{\circ}C$ in our lab-scale fixed-bed system. However, the precursor, $KSeO_2(OCH_3)$-doped MK10 showed a negligible reaction performance with Hg(0), suggesting that the oxidation state of selenium plays a key role in the reaction of Hg(0) vapor and selenium compounds.

• Journal of Industrial Technology
• /
• v.2
• /
• pp.13-19
• /
• 1982

Polycrystalline silicon layers have been deposited by a chemical vapor deposition technique using $SiCl_4$, $H_2$ gas mixture on single crystal silicon substrates. In this work, the effects of depostion temperature and total flow rate on the deposition rate of polycrystalline silicon are investigated. From the experimental results it was found that the formation reaction of polycrystalline silicon was limited by surface reaction and mass transfer controlled as the deposition temperature was increased. The morphology of polycrystalline silicon layer changed from a fine structure to a coarse one as the deposition temperature was increased.

• Journal of the Korean Ceramic Society
• /
• v.34 no.12
• /
• pp.1199-1204
• /
• 1997

SiC conversion layer was fabricated by the chemical vapor reaction between graphite substrate and silica powder. The CVR process was carried out in nitrogen atmosphere at 175$0^{\circ}C$ and 185$0^{\circ}C$. From the reduction of silica powder with graphite substrate, the SiO vapor was created, infiltrated into the graphite substrate, then, the SiC conversion layer was formed from the vapor-solid reaction of SiO and graphite. In the XRD pattern of conversion layer, it was confirmed that 3C $\beta$-SiC phase was created at 175$0^{\circ}C$ and 185$0^{\circ}C$. Also, in the back scattered image of cross-sectional conversion layer, it was found that the conversion layer was easily formed at 185$0^{\circ}C$, the interface of graphite substrate and SiC layer was observed. It was though that the coke particle size and density of graphite substrate mainly affect the XRD pattern and microstructure of SiC conversion layer. In the oxidation test of 100$0^{\circ}C$, the SiC converted graphites exhibited good oxidation resistance compared with the unconverted graphites.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.7
• /
• pp.1573-1578
• /
• 2009

A computational study of the reactions between Zn-containing species, the products of the thermal decomposition of diethylzinc (DEZn) and water was investigated. The Zn-containing species – $C_2H_5)_2,\;HZnC_2H_5,\;and\;(ZnC_2H_5)_2$ – were assumed to react with water during ZnO metal organic chemical vapor deposition (MOCVD). Density functional theory (DFT) calculations at the level of B3LYP/6-311G(d) were employed for the geometry optimization and thermodynamic property evaluation. As a result dihydroxozinc, $Zn(OH)_2$, was the most probable reaction product common for all three Zn-containing species. A further clustering of $Zn(OH)_2$ was investigated to understand the initial stage of ZnO film deposition. In experiments, the reactions of DEZn and water were examined by in-situ Raman scattering in a specially designed MOCVD reactor. Although direct evidence of $Zn(OH)_2$ was not observed, some relevant reaction intermediates were successfully detected to support the validity of the gas phase reaction pathways proposed in the computational study.

• Korean Journal of Materials Research
• /
• v.12 no.11
• /
• pp.850-855
• /
• 2002

Silica powders were prepared from $SiCl_4$-$H_2$O system by chemical vapor deposition process, and investigated on size control of the products with reaction conditions. The products were amorphous and nearly spherical particles with 130nm~50nm in size. The size distribution became narrow with the increase of [$H_2$O]/[SiCl$_4$] concentration ratio. The particle size decreased with the increase of reaction temperature, [$H_2$O]/[SiCl$_4$] concentration ratio and total flow rate. The specific surface area measured by BET method was about three times larger than that of electron microscope method.

• Bulletin of the Korean Chemical Society
• /
• v.25 no.5
• /
• pp.681-686
• /
• 2004

Ti-ZSM-5 prepared by secondary synthesis, from the reaction of H-ZSM-5 with vapor phase $TiCl_4$, was characterized with several physicochemical techniques including FT-IR and UV/VIS-DRS. It was found that zeolite structure, surface area and pore volume did not change, and the framework aluminum could not be replaced by titanium atom during the secondary synthesis of Ti-ZSM-5. The incorporation of titanium into the framework might be due to reaction of $TiCl_4$with the silanol groups associated with defects or surface sites. The formation of extra-framework titanium could not be avoided, unless the samples were further treated by water vapor at 550 $^{\circ}C$ or higher temperature. High temperature steam treatment of Ti-ZSM-5 prepared by chemical vapor deposition with $TiCl_4$was efficient to prevent the formation of non-framework titanium species. Ti-ZSM-5 zeolites prepared in this work contained only framework titanium species and exhibited improved catalytic property close to TS-1 prepared by hydrothermal synthesis.

• Bulletin of the Korean Chemical Society
• /
• v.27 no.2
• /
• pp.219-223
• /
• 2006

The thermal decomposition of tetrakis(ethylmethylamido) titanium (TEMAT) has been investigated in Ar and $H_2$ gas atmospheres at gas temperatures of 100-400 ${^{\circ}C}$ by using Fourier Transform infrared spectroscopy (FTIR) as a fundamental study for the chemical vapor deposition (CVD) of titanium nitride (TiN) thin film. The activation energy for the decomposition of TEMAT was estimated to be 10.92 kcal/mol and the reaction order was determined to be the first order. The decomposition behavior of TEMAT was affected by ambient gases. TEMAT was decomposed into the intermediate forms of imine (C=N) compounds in Ar and $H_2$ atmosphere, but additional nitrile (RC$\equiv$N) compound was observed only in $H_2$ atmosphere. The decomposition rate of TEMAT under $H_2$ atmosphere was slower than that in Ar atmosphere, which resulted in the extension of the regime of the surface reaction control in the CVD TiN process.

• Journal of the Korean Vacuum Society
• /
• v.9 no.4
• /
• pp.394-399
• /
• 2000

The effects of the type and thickness of underlayer on the crystallographic texture and the sheet resistance of aluminum thin film were studied. Ti and Ti/TiN were examined as the underlayer of aluminum. Ti and TiN were prepared by ionized physical vapor deposition (I-PVD) metalorganic chemical vapor deposition (MOCVD), respectively. The texture and the sheet resistance of metal thin film stacks were investigated at various thicknesses of Ti or TiN, and the sheet resistance was measured after annealing at $400^{\circ}C$ in an nitrogen ambient. For I-PVD Ti underlayer, the excellent texture of aluminum <111> was obtained even at top of 5 nm of Ti. However, the sheet resistance of the metal stack was greatly increased after annealing due to the interdiffusion and reaction of Al and Ti. MOCVD TiN between Ti and Al could suppress the Al-Ti reaction without severe degradation of aluminum <111> texture. Excellent texture of aluminum was obtained for the MOCVD TiN thinner than 4 nm.

• Journal of the Korean Ceramic Society
• /
• v.44 no.8
• /
• pp.445-450
• /
• 2007

A conversion layer of SiC was fabricated on the graphite substrate by a chemical vapor reaction method in order to enhance the oxidation resistance of graphite. The effect of boron carbide containing powder bed on the morphology of SiC conversion layer was investigated during the chemical vapor reaction of graphite with the reactive silicon-source at $1650^{\circ}C\;and\;1700^{\circ}C$ for 1 h. The presence of boron species enhanced the conversion of graphite into SiC, and altered the morphology of the conversion layer significantly as well. A continuous and thick SiC conversion layer was formed only when the boron source was used with the other silicon compounds. The boron is deemed to increase the diffusion of SiOx in SiC/C system.

• The Korean Journal of Ceramics
• /
• v.4 no.3
• /
• pp.235-239
• /
• 1998

Ultrafine $SnO_2$ powder was prepared by the diffusion mixing gas-phase reaction of $SnCl_4$(g) and water vapor. The effects of reaction variables, such as the chloride partial pressure, the reaction temperature, and the residence time is the reactor, on the powder size were examined systematically. Calculated concentration and distribution of chemical species, using the Burke-Schumann diffusion mixing model, were compared with the experimetal results. The effects of the reaction variables on the powder size were also discussed qualitatively.