• Journal of the Korean Chemical Society
• /
• v.13 no.4
• /
• pp.289-296
• /
• 1969

The rate constants for the addition reaction of ethylmercaptan to ethylcinnamate has been measured by iodometry and for the proposed reaction mechanism a rate equation which can be applied over wide pH range was derived. From this rate equation, one may conclude that the reaction is started by addition of ethylmercaptan molecule below pH 3. However, above pH 7, this addition reaction is proceeded by the ethylmercaptide ion. At pH 3-7, the complex addition reaction mechanism can also be revealed by this rate equation.

• Journal of the Korean Ceramic Society
• /
• v.27 no.3
• /
• pp.401-411
• /
• 1990

Deposition of diamond films on Si(100) from the mixtures of methane and hydrogen were investigated using hot W filament CVD method. The nucleation density could be increased thousandfold by surface treatment with SiC powder. Upon oxygen addition to the mixture, crystal facets became developed more clearly by selectively removing non-diamond carbons, but the film growth rate generally decreased. However, at a very high methane content(e.g. 10%), a small amount of oxygen addition has resulted in an increase in the film deposition rate presumably by promotion of methane decomposition. When the gas pressure was varied, the growth rate exhibited a maxiumum at around 20torr and the film crystallinity steadily improved with the pressure increase. The observed variation of the growth rate by oxygen addition was discussed in terms of its role in the pyrolysis and the subsequent gas phase reactions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.21 no.4
• /
• pp.305-310
• /
• 2008

Deep trench etching of silicon was investigated as a function of RF source power, DC bias voltage, $C_4F_8$ gas flow rate, and $O_2$ gas addition. On increasing the RF source power from 300 W to 700 W, the etch rate was increased from $3.52{\mu}m/min$ to $7.07{\mu}m/min$. The addition of $O_2$ gas improved the etch rate and the selectivity. The highest etch rate is achieved at the $O_2$ gas addition of 12 %, The selectivity to PR was 65.75 with $O_2$ gas addition of 24 %. At DC bias voltage of -40 V and $C_4F_8$ gas flow rate of 30 seem, We were able to achieve etch rate as high as $5.25{\mu}m/min$ with good etch profile.

• Journal of Korea Foundry Society
• /
• v.17 no.6
• /
• pp.608-614
• /
• 1997

The effect of mold preheating temperature on the microstructure such as grain size, eutectic silicon morphology was investigated for the Al-7wt%Si-0.3wt%Mg alloy. Microstructural variations have been characterized as a function of Sr addition and cooling rate during solidification. Microstructures were correlated with cooling rate, local solidification time and eutectic nucleation temperature, etc. In this study, Sr addition caused increase of local solidification time, undercooling and reduction of eutectic plateau temperature. In logarithmic scale, local solidification time was in inverse proportion to cooling rate. Eutectic nucleation temperature was in inverse proportion to cooling rate of logarithmic scale. Increasing the cooling rate refined dendrite arm spacing and eutectic silicon. Dendrite arm spacing was logarithmically in inverse proportion to cooling rate. Without modifier addition, eutectic silicon was modified at cooling rate of $7^{\circ}C/s$ or higher.

• Korean Journal of Veterinary Research
• /
• v.9 no.2
• /
• pp.19-25
• /
• 1969

The effects of some chemicals for the germinative stimulation of Clostridium chauvoei spore studied. The results obtained were as follows: 1. Cooked meat medium (CMM) was superior to Liver-liver bouillon (LLB) for cultivation of the organisms. 2. Heating the organisms at $70^{\circ}C$ for 30 minutes prior to cultivation in CMM stimulated the germination rate. 3. The addition of 0.5mM L-alanine to CMM was found to be most effective for the rapid germination of the spores. 4. The addition of 0.2 mM D-alanine to CMM inhibited the germination of the spores even if the spores were heat treated. 5. The addition of 0.1mM manganese retarded the germination time, but the final germination rate was greater with 0.1mM manganese than with 0.5mM L-alanine. 6. The addition of both 0.5mM L-alanine and 0.1mM manganese stimulated the germination rate to 100 per cent. 7. The germination rate was greater with the addition of germination stimulants than without any stimulants. The germination rate was approximately 6 per cent greater with prior heat treatment than without heat treatment. 8. The optimum time for the harvest of vegetative forms of the organisms was 15 hours after cultivation in the media which contain suitable germination stimulants.

• Bulletin of the Korean Chemical Society
• /
• v.20 no.6
• /
• pp.712-714
• /
• 1999

The rate constants for the nucleophilic addition of potassium cyanide to α,N-diphenylnitrone and its derivatives (p-OCH3, p-CH3, p-Cl, and p-NO2) were determined by ultraviolet spectrophotometer at 25℃, and the rate equations which can be applied over a wide pH range were obtained. On the basis of pH-rate profile, adduct analysis, general base catalysis and substituent effect, a plausible mechanism of this addition reaction was proposed: At high pH, the cyanide ion to carbon-nitrogen double bond was rate controlling, however, in acidic media, the reaction proceeded by the addition of hydrogen cyanide molecule to carbon-nitrogen double bond after protonation at oxygen of a,N-diphenylnitrone. In the range of neutral pH, these two reactions occured competitively.

• Journal of the Korean Applied Science and Technology
• /
• v.14 no.1
• /
• pp.27-32
• /
• 1997

Furfurylidene acetophenone derivatives were synthesis, it was measured that nucleophilic addition made use of UV at a wide pH 1.0${\sim}$13.0 range in 30% dioxane-$H_2O$ solution, 25$^{\circ}C$. On the basis of general base catalysis, substitutent effect, confirmation of nucleophilic addition products, it was measured the reaction rate of furfurylidene acetophenone derivatives for the pH change. It may be concluded that a part was unrelated to pH and another part was in proportion to concentration of hydroxide ion: Above pH 10.0. sulfide anion adds to the double bond (Michael type addition), a part having no concern with pH, addition reaction to double bond is initiated by addition of neutral thiourea molecule. From the result of measurement the reaction rate, nucleophilic addition of furfurylidene acetophenone derivatives confirmed to the irreversible first order. Through measurement the substituent effect. It found that reaction rate was accelerated by electron attracting group. On the basis of these findings, nucleophilic addition of thiourea for the furfurylidene acetophenone derivative was proposed a fitting mechanisms.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.04b
• /
• pp.112-116
• /
• 2000

This paper presents anisotropic ethcing characteristics of single-crystal silicon in tetramethylammonium hydroxide(TMAH):isopropyl alcohol(IPA) solutions containing pyrazine. With the addition of IPA to TMAH solutions, etching characteristics are exhibited that indicate an improvement in flatness on the etching front and a reduction in undercutting, but the etch rate on (100) silicon is decreased. The (100) silicon etch rate is improved by the addition of pyrazine. An etch rate on (100) silicon of $0.8\;{\mu}m/min$, which is faster by 13 % than a 20 wt.% solution of pure TMAH, is obtained using 20 wt.% TMAH:0.5 g/100 ml pyrazine solutions, but the etch rate on (100) silicon is decreased if more pyrazine is added. With the addition of pyrazine to a 25 wt.% TMAH solution, variations in flatness on the etching front were not observed and the undercutting ratio was reduced by 30 ~ 50 %.

• Journal of the Korean Ceramic Society
• /
• v.37 no.1
• /
• pp.82-89
• /
• 2000

In lithium silicate photosensitive glass-ceramics, the relationship between lithography time and crystallization, and the effect of addition of mineral acid in etching rate and pattern shape were investigated. Irradiation times for micropatterning were less than 5 minutes in which Ce3+ ions in glass were changed rapidly to Ce4+ with ultra violet light. Overexposure to ultra brought about blot of pattern by diffiraction of light. Addition of mineral acid to HF enhanced etching rate as compared with HF solution only. The addition of H2SO4 especially increased the etching rate by 70%. But the mixed solution also increased the etching rate of the noncrystallized portion of the glass and this resulted in heavy etching. Etching with ultrasonic wave showed higher etching rate than that with the static or fluid method.

• Proceedings of the IEEK Conference
• /
• 2000.06b
• /
• pp.298-301
• /
• 2000

We investigated the etch rate of SiO$_2$ in E-ICP, ICP system and the addition gas (O$_2$H$_2$) effect on SiO$_2$ etch characteristics. In all conditions, E-ICP shows higher etch rate than ICP. Small amount of O$_2$ addition increase F atom and O$\^$*/ concentration. at optimized condition (30％ O$_2$ in CF$_4$, 70Hz) E-ICP system shows highest etch rate (about 6000${\AA}$). H$_2$addition in CF$_4$ Plasma make abrupt decrease Si etch rate and moderate decrease SiO$_2$ etch rate.