• 한국응용과학기술학회지
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• 제27권2호
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• pp.216-221
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• 2010

Polyvinyl acetate (PVAc) prepared by emulsion polymerization has broad applications for additive such as paint binder, adhesive for wood and paper due to its low glass transition temperature which help to plasticize substrate resins. Since emulsion polymerization has a disadvantage that surfactant and ionic initiator degrade properties of the product polymer, poly (vinyl acetate-eo-ethyl acrylate) (VAc-EA) was synthesized using potassium persulfate as catalyst and polyvinylalcohol (PVA) as protective colloid to prevent the degradation. The copolymer latex product was internally plasticized and has enhanced adhesion, water resistance during VAc-EA emulsion polymerization. No coagulation and complete conversion occur with the reactant mixture of 10 mmol/L potassium persulfate, 10 mmol/L poly ( vinyl alcohol) (PVA 17). As the concentrations of PVA increase, the viscosity becomes increase.

• 한국식품과학회지
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• 제27권1호
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• pp.41-46
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• 1995

Changes of fatty acid composition and reaction rate were investigated according to reaction condition during partial hydrogenation reaction of soybean oil until its iodine value decreased from 134 to 110. The reaction conditions were varied in the range of from $170^{\circ}C$ to $210^{\circ}C$ of temperature, from 1.3 atm to 4.2 atm of pressure and from 0.005% to 0.1% of nickel concentration as catalyst. Lecithin was added in soybean oil to investigate the change of reaction rate. The result of addition of lecithin showed that reaction rate decreased to from 2 to 6 times in comparison with non-additive system.

• Bulletin of the Korean Chemical Society
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• 제34권11호
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• pp.3410-3414
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• 2013

Atom-economical esterification is of great importance in green chemistry. In this work, we demonstrated the catalyst and additive free esterification of alcohols by their reaction with 2-acyl-4,5-dichloropyridazin-3(2H)-ones without solvent at $100^{\circ}C$. Aliphatic and aromatic alcohols were converted into the corresponding esters in good to excellent yields. It is noteworthy that the reaction is solvent-free, atom-economic, easy-workup, and rapid and that the process is inexpensive.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 춘계학술발표회 논문집
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• pp.218-219
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• 2012

Carbon coils could be synthesized using $C_2H_2/H_2$ as source gases and $SF_6$ as an incorporated additive gas under thermal chemical vapor deposition system. Prior to the carbon coils deposition reaction, two kinds of samples having different combination of Ni catalyst and substrate were employed, namely a commercially-made $Al_2O_3$ ceramic boat with Ni powders and a commercially-made $Al_2O_3$ substrate with Ni layer. By using a commercially-made $Al_2O_3$ ceramic boat, the production yield of carbon coils could be enhanced as much as 10 times higher than that of $Al_2O_3$ substrate. Furthermore, the dominant formation of the microsized carbon coils could be obtained by using $Al_2O_3$ ceramic boat.

• 공업화학
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• 제26권4호
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• pp.394-399
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• 2015

본 연구에서는 Cu 촉매가 도입된 활성탄소섬유를 제조하여 고효율 $SO_2$ 흡착재를 제조하였다. 라이오셀 섬유를 내염화 및 탄화공정을 통해 탄소섬유를 얻었으며, $SO_2$ 흡착능을 향상시키기 위해 KOH 활성화를 사용하여 높은 비표면적 및 균일한 미세기공구조를 부여하였다. 활성탄소섬유에 Cu 촉매를 도입하기 위하여 $Cu(NO_3)_2{\cdot}3H_2O$ 수용액을 사용하였으며, 공정 시 i) 탄소섬유 내 산소 관능기의 분해반응을 촉진하고, ii) 산화구리 및 질산염의 분해로 oxygen radical이 생성되어 탄소섬유의 활성화 반응을 촉진시켰다. 이로 인해 활성탄소섬유의 미세공과 중기공 형성효과 및 탄소섬유 표면에 고르게 분산된 Cu 촉매를 확인하였다. Cu 촉매 도입 후, 활성탄소섬유에 비해 비표면적 및 미세공의 비율이 약 10% 이상 증가되었고, $SO_2$ 흡착능이 149% 이상 향상된 결과를 얻을 수 있었다. Cu 촉매도입공정 시, 전이금속 촉매효과에 의하여 발달된 미세공, 중기공 및 비표면적에 의한 물리적 흡착과 도입된 Cu 촉매에 의한 $SO_2$ 가스의 화학적 흡착반응의 시너지 효과에 기인하여 $SO_2$ 흡착능이 향상된 것으로 사료된다.

• 폴리머
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• 제36권1호
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• pp.98-103
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• 2012

구리 계열의 $Cu(NO_2)_2{\cdot}3H_2O$와 CuCl을 중합촉매로 사용하고 다양한 용매, 리간드와 염기의 함량을 변화시켜 poly(2,6-dimethyl-1,4-phenylene ether)(PPE) 중합반응을 고찰하였다. 이 가운데 CuCl/1-methylimidazole/ammonium hydroxide 시스템에서 가장 높은 중합 수율을 나타내었다. 한편, 몇 가지 다른 유기용매와 메탄올의 혼합용매 시스템에서 용매의 성분비율을 변화시켜 용매의 조성이 중합반응에 미치는 영향을 조사하였으며 2,4,6-trimethylphenol (TMP)를 사용하여 TMP 함량에 따른 분자량 조절 효과를 조사하였다. 클로로포름/메탄올 9/1(v/v) 혼합용매를 사용했을 때 가장 높은 중합 수율과 높은 분자량을 갖는 중합체($\overline{M_n}$ : 55 K; $\overline{M_w}$ : 92 K; PDI: 1.7)를 얻었다. 구리 일가 촉매인 CuCl 과 CuI를 사용하여 서로다른 짝이온, 즉 $Ci^-$와 $I^-$ 이온이 중합결과에 미치는 영향을 조사하였다. 촉매의 활성 비교를 위하여 산소 흡수량(oxygen-uptake)을 측정하였으며, 중합반응의 부산물인 5,5'-tetramethyl-4,4'-diphenoquinone (DPQ)의 함량을 자외선 분광기(ultraviolet spectroscopy)를 통하여 분석하였다.

• 한국재료학회지
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• 제22권6호
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• pp.316-320
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• 2012

$Co_3O_4$, $Al_2O_3$ and $Co_3O_4$/$Al_2O_3$ mesoporous powders were prepared by a sol-gel method with starting matierals of aluminum isopropoxide and cobalt (II) nitrate. A P123 template is employed as an active organic additive for improving the specific surface area of the mixed oxide by forming surfactant micelles. A transition metal cobalt oxide supported on alumina with and without P123 was tested to find the most active and selective conditions as a heterogeneous catalyst in the reaction of styrene epoxidation. A bBlock copolymer-P123 template was added to the staring materials to control physical and chemical properties. The properties of $Co_3O_4$/$Al_2O_3$ powder with and without P123 were characterized using an X-ray diffractometer (XRD), a Field-Emission Scanning Electron Microscope (FE-SEM), a Bruner-Emmertt-Teller (BET) surface analyzer, and $^{27}Al$ MAS NMR spectroscopy. Powders with and without P123 were compared in catalytic tests. The catalytic activity and selectivity were monitored by GC/MS, $^1H$, and $^{13}C$-NMR spectroscopy. The performance for the reaction of epoxidation of styrene was observed to be in the following order: [$Co_3O_4$/$Al_2O_3$ with P123-1173 K > $Co_3O_4$/$Al_2O_3$ with P123-973 K > $Co_3O_4$-973 K>$Co_3O_4$/$Al_2O_3$-973 K > $Co_3O_4$/$Al_2O_3$ with P123-1473 K > $Al_2O_3$-973 K]. The existence of ${\gamma}$-alumina and the nature of the surface morphology are related to catalytic activity.

• Restorative Dentistry and Endodontics
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• 제17권1호
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• pp.36-54
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• 1992

The purpose of this study was to compare the shear bond strengths to ground dentin surfaces of four dentinal bonding agents in 193 teeth. Various dentin surfaces treated with four dentin bonding agents were attached with two restorative composite resins. The effectiveness of the bonding were tested by the monitoring the shear bond strength. The shear bond strengths were measured after 2 hours and 24 hours after surface conditioning with four dentin bonding agents. Effects of EDTA, the additive illumination, and sealer treatments without primer on bond strength to dentin surfaces were assessed. In addition the effects of the thickness of specimens ranging from 0.65 mm to 1.95 mm and the ratio of catalyst and base paste on the bond strength of chemical cure composite resin were estimated. The shear bond strength was determined by testing specimens in the Instron universal testing machine (Model No. 1122) at a crosshead speed of 1.0 mm/min. Following condusions were drawn: 1. The highest mean shear bond strengths of chemical cure composite resin to dentin conditioning with dentin bonding agents aged 2 hours were obtained, and then that was decreased with time followed by EDTA treatment. 2. In light cure composite resin, the shear bond strength was increased following dentin conditioning with bonding agents with time, irradiation time and EDTA treatment except in SB group. 3. The thicker the composite resin specimen was, the less the shear bond strength in chemical cure composite resin was. 4. In light cure composite resin, there was a little change in shear bond strength following dentin conditioning with bonding agents. 5. In chemical cure composite resin, the shear bond strength was the highest in the ratio of 1/1 of catalyst and base part. 6. Without a dentin primer, shear bond strength to dentin conditioned only with UB sealer was the highest among four sealers in light cure composite resin.

• 공학논문집
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• 제2권1호
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• pp.139-145
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• 1997

촉매연소용 촉매담체인 $\gamma$-$Al_2O_3$의 열안정화에 미치는 Ba의 첨가 효과에 대하여 연구하였다. Ba의 첨가는 $Ba(No_3)_3$.$6H_2O$를 $\gamma$-$Al_2O_3$ 분말에 wet impergnation시키는 방법으로 행하였다. Ba는 $\gamma$-$Al_2O_3$의 소결을 억제함으로써 $\gamma$-$Al_2O_3$의 열안정화에 효과적인 첨가제임을 확인하였으며 최적의 첨가량은 전체 열처리 조건에서 5 mol%임을 알 수 있었다. 이러한 Ba첨가에 의한 열안정화 효과는 이온반경이 큰 $Ba^{2+}$이온이 $\Al^{3+}$이온의 자리에 치환하여 $\Al^{3+}$이온의 표면 확산을 억제하는 효과에서 기인하는 것으로 사료된다.

• 한국결정성장학회지
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• 제23권6호
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• pp.296-301
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• 2013

Carbon coils could be synthesized using $C_2H_2/H_2$ as source gases and $SF_6$ as an incorporated additive gas under the thermal chemical vapor deposition system. A 304-type stainless steel was used as a substrate with nickel powders as the catalyst. The surface of the substrate was pretreated using a sand paper or a mechanical drill to enhance the production yield of the carbon coils. The characteristics of the deposited carbon nanomaterials on the substrates were investigated according to the surface state on the stainless steel substrate. The protrusion induced by the grooves on the substrate surface could enhance the formation of the carbon nanomaterials having the coils geometries. The cause for the enhancement of the carbon coils formation by the grooves was suggested and discussed with the surface energies for the interaction between as-growing carbon elements. Finally, we could obtain the massive production yield of the carbon coils by the surface pretreatment using SiC sand papers on the several tens grooved stainless steel substrate.