• 한국세라믹학회지
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• 제18권3호
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• pp.147-151
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• 1981

On the calcium silicate hydrothermal reaction, the effect of NaOH and KOH Studied. Forincreasing the yield of fibers and to promote crystal growth, Rotary autoclae has been used. By addition NaOH solution, approximately 150${\mu}{\textrm}{m}$ of pectolite was grown. By addition KOH solution, approximately 30${\mu}{\textrm}{m}$ of 11$\AA$-Tobermorite was grown under the conditon of 21$0^{\circ}C$ 10 days reaction. These results indicate that 11$\AA$-Tobermorite was stabilized by KOH over a wide Temperature and composition range.

• 한국세라믹학회지
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• 제33권7호
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• pp.779-784
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• 1996

The spinel/cubic stabilized zirconia composites were fabricated via, The reaction sintering of monoclinic zirco-nia(baddeleyite) added with MgAl powder. During heating Mg and Al were oxidizedfirst and subsequently the oxides formed spinel (MgAl2O4) and finally remained MgO stabilized the zirconia, Because the oxides formed during the oxidation process would have very fine grain size (order of submicron) mainly due to the effects of attrition milling the reaction sintering was more effective in densification and improvement of strength and fracture toughness than conventional sintering with direct addition of MgO. The sintering behavior phase transformation during firing and mechanical properties of sintered body were investigated with emphasis on the relations between spinel formation due to MgAl addition and sintering and mechanical properties.

• Bulletin of the Korean Chemical Society
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• 제1권2호
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• pp.45-49
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• 1980

During the homolytic reactions of $CCl_4$ or $Cl_3CBr with ${\beta}-halo^1$-styrenes,$\beta$-haloradicals are key intermediates. They are to be stabilized via three pathways; $\beta$-cleavage, halogen transfer and telomerization. The three reaction paths are delicately controlled by the energetics of their formation and stabilization. When the formation of a $\beta$-haloradical is accompanied by considerable excess of energy from an exothermic reaction, $\beta$ -cleavage is often dominant over the halogen transfer. On the other hand, if the radical forms via a reversible reaction, two processes become competitive. $\beta$-Eliminated bromine atoms from ${\beta}$ -bromoradicals generate $Br_2$ via $Cl_3CBr + {\cdot}Br {\leftrightarrow} Br_2 + {CCl_3}{\cdot}{Br_2}$ may act as a better scavenger than Cl3CBr for the ${\beta}$-bromoradicals. Different reactivities of chlorine, bromine and trichloromethyl radicals towards olefinic pi-bond are clarified in terms of the beat content of the addition reactions.

• Bulletin of the Korean Chemical Society
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• 제10권6호
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• pp.500-503
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• 1989

Synthetic studies have been carried out for the addition or substitution of phosphorus nucleophiles to the cation $[(exo-6-R-{\eta}^ {5_-}2-MeO-C_6H_5)Mn(CO)_2NO]PF_6,$ 2. $PPh_3$ reacts with 2 to yield the CO displaced product and $MePPh_2$ attacks the dienyl ring of 2 to yield the phosphonium adduct or the metal to give the CO displaced depending upon the reaction temperatures. Nucleophilic addition of HPPh2 to the dienyl ring of 2 gives a neutral substituted product. $P(OMe)_3$ reacts with 2 to yield a mixture of ring adduct and CO displaced product at room temperature. $At - 20^{\circ}C,\;P(OMe)_3$ attacks the dienyl ring of 2 to give a posphonium adduct, which underwent Arbuzov reaction. This reaction affords a new route to the phosphonate complexes.

• Bulletin of the Korean Chemical Society
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• 제10권3호
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• pp.273-278
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• 1989

The gas-phase reactions of methyl formate with anions, $-NH_2,\;-OH,\;-CH_2CN$, are studied theoretically using the AM1 method. Stationary points are located by the reaction coordinate method, refined by the gradient norm minimization and characterized by the determination of Hessian matrix. Potential energy profiles and the stationary point structures are presented for all conceivable processes. Four reaction paths are found to be possible: formyl proton and methyl proton abstractions, carbonyl addition, and $S_N2$ process. For the most basic anion $-NH_2$ the proton abstraction path is favored, while in other case, $OH\;and\;-CH_2CN$, the carbonyl addition paths are favored. In all cases the $S_N2$ process is the most exothermic, but due to the relatively high activation barrier the process can be ruled out.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.264-264
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• 2012

As an environment-friendly alternative energy resource, ethanol may be used to obtain hydrogen, a clean energy source. Thus, studies on catalytic reactions involving ethanol have been studied to understand the underlying principles in the reaction mechanism using various oxide-supported catalysts. Among them, Au-based catalysts have shown a superior activity in producing hydrogen gas. In the present study, Au/$TiO_2$ catalysts were prepared by deposition-precipitation method to understand their catalytic activities toward ethanol and acetaldehyde with increasing gold loading, especially at the very low Au loading regime. A commercially available $TiO_2$ (Degussa P-25) was employed and the Au loading was varied to 0, 0.1, 0.5, and 1.0 wt% respectively. The catalysts showed characteristic x-ray diffraction (XRD) features at $2{\theta}=78.5^{\circ}$ that could be assigned to the presence of gold nanoparticles. Its reactivity measurements were performed under a constant flow of ethanol and acetaldehyde at a flow rate of ${\sim}0.6{\mu}mol/sec$ and the substrate temperature was slowly raised at a rate of 0.2 K/sec. We observed that the overall reactivity of the catalysts increased with increasing Au loading along with selectivity favoring dehydrogenation to product hydrogen gas. In addition, we disclosed various reaction channels involving competitive reaction paths such as dehydrogenation, dehydration, and condensation. In addition, subsequent reactions of acetaldehyde obtained from dehydrogenation of ethanol, were found to occur and produce butene, crotonaldehyde, furan, and benzene. Based on the results, we proposed overall reaction pathways of such reaction channels.

• 대한화학회지
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• 제7권3호
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• pp.216-224
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• 1963

有機含鹽素 에스테르, 알콜, 및 산과 金屬亞鉛 및 錫을 dimethyl formanmide 溶媒存在下에서 反應시킨 結果 有機金屬 콤프렉스를 좋은 收率로 生成하였다. 같은 反應을 混合紫外線照射下에서 進行시킨 結果 高溫 以外에서는 콤프렉스의 生成이 크지못하였다. D.M.F.에 依한 金屬 콤프렉스의 溶解效果는 토루엘이나 사이크로헥산보다 훨씬 컸었다. 鹽素를 含有한 酸에서는 酸의 金屬鹽의 金屬 콤프렉스가 生成됨을 觀察하였다. 카보닐 precursor와의 反應에 있어서는 少量의 雙合物과 함께 附加物을 生成하였으나 收率이 높지 못하였다(산 30∼40%, 에스테르 73%, 알콜 14.6%). 그러나 이 方法은 從來法에 比하여 簡便한 것임을 알았다. 硏究結果를 溶媒效果에 關聯시켜 論議하였으며 實驗方式을 報告하였다.

• 한국환경과학회지
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• 제4권1호
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• pp.91-103
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• 1995

The reaction rate, equilibrium, and flow injection analysis methods were fundamentally evaluated for the determination of aqueous ammonia. The selected indophenol blue method was based on the formation of indophenol blue in which ammonium ion reacted with hypochlorite and phenol in alkaline solution. In the optimized reaction condition, the reaction followed 1st order reaction kinetics and the final product was stable. The absorbance measurements before and after the equilibrium were utilized for the reaction rate and equilibrium methods. The reaction rate methods, based on the relative analytical signals for the possibility of eliminating interferents, were shown to have good linear calibration curves but the detection limit and the calibration sensitivity were poorer than those in the equilibrium method. The detection limits were 32-49 pub and 24 pub for the reaction rate and equilibrium methods, respectively In the flow injection analysis, the absorbance was measured before the equilibrium reached and thus resulted in 30% reduction of calibration sensitivity. However, the detection limit was 11 ppb, indicating that the peak-to-peak noise for the blank was remarkably improved. Compared to the manual methods, the optimized experimental condition in a closed reaction system reduced the blank absorbance and the inclusion of ammonia from the atmosphere was prevented. In addition, highly reproducible mixing of sample and reagents and analytical data extracted from continuous recording showed excellent reproducibility.

• Bulletin of the Korean Chemical Society
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• 제10권2호
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• pp.129-132
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• 1989

Reactions of thebaine with phenylsulfonylpropadiene in various solvents were investigated. It was found that Diels-Alder reaction adduct was obtained in nonpolar solvent, while addition reaction adduct was obtained in polar solvent. Transformations of these two products were also carried out.

• 통합자연과학논문집
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• 제2권3호
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• pp.219-223
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• 2009

Easy and simple synthesis of CdSe nanocrystals was achieved through sol-gel process. CdSe nanocrystals were synthesized from the reaction of cadmium oxide and selenium in the prescence of trioctylphosphine oxide, tributylphosphine, octadecene, octadecylamine, and stearic acid. The effect of reaction temperature for the determination of size of CdSe nanocrystals was investigated after the addition of selenium. The reaction temperature for the growth of CdSe nanocrystals was increased by every $20^{\circ}C$ from 170 to 190, 210, 230, 250, 270, and $290^{\circ}C$. When the reaction temperature was higher, the absorption wavelength in the absorption spectrum was increased which indicated that the size of CdSe nanocrystals was increased. The emission wavelength in the photoluminescence spectrum was increased from 438 to 489, 542, 591, 643, 692, and 745 nm, as the size of CdSe nanocrystals was increased. The control of the reaction temperature illustrated that the color tuning of emission wavelength were successfully obtained.