결정 성장 방법에서 황산 농도가 황산 칼슘 결정 형태 및 법랑질과 복합 레진의 결합 강도에 미치는 영향

은희춘,구기갑,임호남 대한치과기재학회 1999 대한치과재료학회지 Vol.26 No.1

The calcium sulfate dihydrate(gypsum) crystal morphology on enamel surface treated by sulfuric acid aqueous solution (from 0.1M to 1.0M) was observed by scanning electron microscope. The shear bond strength between enamel and composite resin was measured by universal testing machine. From the experimental results, the conclusions of this study were; (1) The shear bond strength between enamel and composite resin was maximum at 0.1M sulfuric acid. The shear bond strength was decreased to 0.3M, hardly bonded from 0.4M to 0.6M, and increased from 0.7M as increasing sulfuric acid concentration. (2) The crystals was disordered as increasing sulfuric acid concentration. (3) The crystals formed by sulfuric acid aqueous solution were not firmly bonded on enamel surface because only crystal nuclei were attached on enamel, so fracture was occurred between enamel and crystal interface.

CO_2와 Methanol로부터 Dimethyl Carbonate의 직접 합성시 복합산화물(Ce_0.8Ti_0.2O_2)과 이에 담지된 금속/산화물 촉매의 효과

이용상,고재천,김광주,구기갑 한국공업화학회 2003 응용화학 Vol.7 No.1

Dimethyl carbonatc was used as a reagent which introduces the carbonyl and methyl group into chemical compound. In thi work, mixed oxide catalysts were prepared from cerium(Ⅲ) nitrate hexahydrate and titanium dioxide. Also, noble and transition metals were incorporated wiht the ixed oxide catalyst. After the calcination of corresponding catalysts under 5% H2 gas, the mixed oxide catalysts were empioyed in the synthesis of dimethyl carbonate. Prior to the calcination, mixed oxide cctalyst shows the high activity for the reaction. But, after the treatment, the activity of catalyst was greatly reduced. From the expertmental results, the oxidation state of noble metal incorporated with mixed oxide catalysts have an offect on the oxidation reaction of methanol in the synthesis of dimdthyl carbonate.

노말브틸아크릴레이트/메틸메타아크릴레이트계 유화중합에 관한 계면활성제의 영향

고기영,김철웅,김광주,구기갑 한국공업화학회 2002 응용화학 Vol.6 No.2

Polymer latexes for polymer cement were prepared by introducing small amount offunctional monomers(acrylic acid and acrylic amide) during the semicontinuousemulsion polymerization of methylmetacrylate(MMA) and n-butyl acrylate(n-BA). Thepolymerization was investigated by following the variation of the amount and type, of surfactants on particle size, polymer content at different times of the polymerization process. The results showed that both particle size and polymer content can be controlled by the amout and types of surfactants. LE and NE types out of nonionic surfactants used were good surfactants due to the formation of stable polymer latex without coagulants. Especially, a hydrophilic chain length(n) of these nonionic surgactants had a signigicant effect on the final particle size and polymer content.

상분리법을 통하여 제조된 새로운 개념의 지지형 액막의 기체투과특성

최평호,김범식,이정민,김철웅,구기갑,이상학 한국공업화학회 2004 공업화학 Vol.15 No.1

새로운 지지형 액막(SLM)을 용매 증발에 따른 1차, 2차 상분리법으로 3성분 고분자 용액으로부터 제조하였다. 액막재로 이온액인 BMIBF_(4) (BMI+ =1-(1-butyl)-3-methylimidazolium, BF_(4)=tetra-fluoro boratr)와 매트릭스 고분자로 polyvinylidenefluoride(PVDF)가 사용되었다. 이 고정화 액막의 O_(2), N_(2) 그리고 CO_(2) 기체 투과특성을 여러 조작 조건에서 조사하였다. SLM은 가혹한 조건에서 조작하였음에도 불구하고 오랜 시간동안 높은 CO_(2) 투과도 및 선택성을 유지하였다. 투과거동을 나타내는 인자인 투과도, 확산도, 그리고 용해도를 연속 측정 장치를 통하여 구함으로써 특성을 관찰하였다. SLM은 다른 기체에 비하여 CO_(2)에 대해서 높은 투과도와 선택도를 갖고 있었다. 특히, 막내 CO_(2)의 용해도는 다른 기체들에 비하여 매우 높은 반면 확산도는 큰 차이를 보이지 않았다. 또한 막내 이온액의 조성은 CO_(2) 용해도에 영향을 관찰할 수 있었다. 막내 이온액의 조성이 증가함에 따라서 CO_(2) 의 투과도 및 선택도가 극격히 증가하였다. 이는 SLM를 통한 기체 투과에 있어서 용해도가 주인자로 큰 영향을 끼침으로써 막내 이온액 조성 증가 SLM의 투과에 큰 영향을 미침을 확인하였다. The new supported liquid membranes (SLMs) were fabricated from ternary polymer solution contained ionic liquid in which primary and secondary phase separations were induced by the solvent by the solvent evaporaton. The used ionic liquid and polymer matrix were BMBF_(4) (BMI+=-(1-butyl)-3-methylimidazolium, BF_(4)-tetra-fluoro boratel and polyvinylidene fluoride (PVDF). Gas permeation properties of the SLM to O_(2), N_(2) and CO_(2) were studied at various operating conditions. Although the SLM were operated under severe operating condition, it maintained high CO_(2) permeability and selectivity for quite long time. The solubility coefficient of CO_(2) in the membrace was very high in comparison with those of other gases; whereas there was no big difference in the diffusivity between CO and other gases. Moreover, in the permeation of pure gases, it is observed that the ionic liquid content in the membrane affected the solubility of CO_(2) in the memhranc. With increasing ionic liquid content in the membrane, the permeability and selectivity of CO_(2) increase significantly. There fore, in the permeation of gases through SLM, the overall permeation performances weir affected mainly by solubility coefficient. This observation can be discussed in terms of the influence of solubility coefficient with ionic liquid content in the membrane.

혼합용매법에 의한 Mullite 전미분체 생성기구에 관한 연구

황운연,이정운,박형상,김용렬,구기갑 한국화학공학회 2003 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.41 No.4

Si-와 Al-알콕시드의 반응속도 차이를 조절하기 위한 부분 가수분해법과 입자 형태를 제조하기 위한 혼합용매법을 이용하여 구형의 미세한 mullite 전미분체를 제조하였다. Mie 이론을 적용시켜 반응시간에 따른 반응용액의 탁도 및 입자 수밀도의 변화를 측정하여 혼합용매법에 의한 입자 생성기구에 대하여 고찰하였다. 알콕시드와 옥탄올 용액에 아세토니트릴을 첨가하면 알콕시드의 용해도가 낮아지고 따라서 알콕시드의 일부가 액적을 형성하며, 액적은 안정화제 (HPC)에 의하여 구형을 유지하게 된다. 그리고 가수분해 및 축합중합 반응에 의하여 액적의 입자 크기는 감소하며, 동시에 혼합용액에 용해되어 있던 알콕시의 가수 분해 및 축합중합 반응에 의하여 미세 입자가 생성된다. 액적형태로 생성된 큰 입자와 미세 입자의 응집에 의하여 최종 입자가 생성되었다. In this study, spherical fine pre-mullite particles were prepared by partial hydrolysis method to control the reaction rate difference of two alkoxides, and by mixed solvent method to control the particle shape. Based on the adaptation of Mie theory, the formation mechanism of pre-mullite particle in alkoxide-octanol-acetonitile system has been investigated by measuring of the turbidity of solution, the number density and the size of the particles during the reaction. As the acetonitrile was added in the alkoxide-octanol solution, the solubility of the alkoxide decreased. A part of alkoxide was segregated from solution in the form of droplets. whereas the rest of the alkoxide existed as dissolved state in octanol. The droplets are stabilized with stabilizer (HPC). In the next step. hydrolysis and condensation reactions of the alkoxide droplets decrease the size of droplets and, at the same time, fine particles are formed from the alkoxide dissolved in octanol. Subsequently, the final particles are produced by aggregation between the large particles through the droplet form and the fine particles.

전도도 측정에 의한 암모니아 수용액의 농도 예측 - NH3/H2O 계의 기액 상평형 기초 실험

구기갑(Kee Kahb Koo),은희춘(Hee Chun Eun),정시영(Si Young Jeong),김병주(Byong Joo Kim) 한국공업화학회 2002 공업화학 Vol.13 No.4

NH_3/H_2O계 흡수식 냉동기를 설계, 개발하고 유지, 보수하기 위해서는 각 운전 요소에서 암모니아의 농도 측정이 필수적이다. 현재 적정법 등에 의해 암모니아의 농도를 측정하고 있으나 고압의 유체를 추출하는 과정에서 시료의 기화 또는 응축이 발생하여 측정 오차가 발생할 가능성이 크다. 그러므로 정확한 측정을 위해서는 암모니아의 농도는 장치 내부에서 실시간으로 측정되어야 한다. 본 연구는 전도도를 이용한 인라인 농도 측정 방법 개발을 위한 예비 실험으로 전도도 측정을 위한 백금 전극 및 암모니아의 부식에 견딜 수 있는 용기를 제작하였다. 농도 25% 이하의 암모니아 수용액에 대해 전도도를 측정하였고 전도도와 농도 사이에 상관 관계가 있음을 확인하였다. 흡수식 냉동기의 작동 조건과 유사한 범위에서의 실험을 위해 암모니아 가스를 가압하여 주입하고 일정 온도, 압력에서 평형이 유지되는 장치를 제작하였고 기상과 액상의 조성 및 전도도를 동시에 측정하였다. 또한 기존의 실험 데이터에 Patek and Klomfar에 의해 제안된 NH_3/H_2O 계의 기액 상평형 상관식을 적용하여 정확도를 평가하였다. Concentration Measurements of ammonia are important for the design, development and maintenance of a NH_3/H_2O absorption refrigeration system. The titration method has been commonly used as a concentration measurement method. However, during the sampling, a significant experimental error can occur due to either evaporation or condensation of the sampled component. To obtain more accurate data, the concentration must be measured within the system. The present study was conducted as a preliminary study for development of an in-line concentration prediction method by conductivity measurements. A platinum electrode with measuring instruments resistant to corrosive ammonia were prepared. The conductivity of ammonia solution (<25%) was measured and it was confirmed that conductivity correlates the concentration. To extend the experimental range, similar to the working conditions of absorption refrigerator, an apparatus that can pressurize the ammonia gas and analyze the composition of vapor and liquid phases was built. In this apparatus the conductivity and composition are measured simultaneously. In the evaluation of the accuracy of correlation for the vapor/liquid equilibrium of NH_3/H_2O system, the method suggested by Patek and Klomfar was utilized.

비이온 계면활성제를 사용한 토양으로부터 오일의 제거에 관한 연구

이기서(Kee-Suh Lee   &),김영호(Young-Ho Kim),김철웅(Chul-Ung Kim   ),이정민(Jung-Min Lee   ),구기갑  (Kee-Kahb Koo) 한국청정기술학회 2000 청정기술 Vol.6 No.1

나노크기의 ZSM -5 결정의 제조 및 섬유로의 응용

설용건,구기갑,정경택,현진호,김두성 한국공업화학회 1998 응용화학 Vol.2 No.1

Zeolite fiber was manufactured from the nanosized ZSM-5 crystals. In this process, it was found that the size of zeolite particles ($lt;200nm) play critical role in the fiber formation. To obtain nanosized zeolite crystals, ZSM-5 zeolite was crystallized at the temperature of 100℃ and atmospheric pressure. The size of zeolite was observed to be dependent on Si/Al ratio. Si/Al ratio of 33 was found to be optimum for the synthesis of 200nm sized zeolites. The formation of zeolite fiber was also affected by interaction between particles and solvent, and high adhesion energy of nano-sized zeolite particles. ZSM-5 zeolite fiber does not scatter much light and shows transparency because the size of zeolite particles is below the wavelength of visible light (400-700nm).

Molecular Approach to the Effect of Interfacial Energy on Growth Habit of ε-HNIW

Shim, Hong-Min,Koo, Kee-Kahb American Chemical Society 2016 Crystal Growth & Design Vol.16 No.11

<P>The present work describes how consideration of the onset of supersaturation for 2D nucleation, sigma(2D), is very important for prediction of the growth habit of epsilon-hexanitrohexaazaisowurtzitane (epsilon-HNIW) when the edge energy decreases extremely in solution. From ethyl acetate, the spiral growth model without considering sigma(2D) was shown to accurately predict the polyhedral morphology of e-HNIW, where the {110}, {101}, {11 (1) over bar}, {002}, and {10 (1) over bar} faces are mainly constructed. However, that model was found to be inappropriate for predicting the bipyramidal morphology of epsilon-HNIW from methanol because the {101} face was anticipated to dominate, but a bipyramid shape is possible only if the {101} face grows faster and finally disappears. The present simulation results show that the edge energy of the {101} face is considerably reduced from methanol by forming a hydrogen bond. This gives rise to a decrease in the sigma(2D) compared with the growth of epsilon-HNIW from ethyl acetate, which means that the {101} face has a relatively high probability to grow faster by 2D nucleation. As a consequence, a parameter of sigma(2D) enables us to exclude the morphologically unimportant faces among flat-faces by determining which face tends to grow faster by 2D nucleation.</P>

Shadow Mask GRS 공정에서의 반응수율 향상을 위한 기술개발

윤문규(Munkyu Yoon),구기갑(Kee-Kahb Koo),이문용(Moonyong Lee) 한국청정기술학회 2007 청정기술 Vol.13 No.3

급속한 성장에 따른 디스플레이 산업에서의 생산량 증가는 원료 사용의 증가와 배출액의 증가를 야기하고 있으며 이에 따른 폐액 처리양이 증가되어 환경적, 경제적 문제점을 안고 있다. 본 연구에서는 브라운관 소재인 shadow mask의 식각공정 시 사용한 식각용액의 피로도를 감수시키기 위하여 산화반응을 이용하여 신액 사용량과 구액 배출량을 최소화해주는 GRS(Green Recycling System)공정의 수율을 향상시키기 위해 실험실 및 현장적용 실험을 통하여 공정의 최적화를 하기위한 방법을 연구하였다. 공정변수들과 GRS 공정의 수율과의 관계를 규명하였으며 GRS 반응기의 내부구조 개선으로 인해 약 10%의 수율증가를 확인하였으며 공정의 수율 향상과 최적화에 큰 도움이 되었다. In the present study, we developed a methodology to minimize a waste solution produced in the etching process. The condition for the optimization of the GRS process was studied on the basis of laboratory experiment and field test as well as pilot test. Through the study, we analyse the relation of the main process variables and the yield of the GRS process. The application of the new operation condition and the reactor internal modification results in 10% yield improvement in the GRS process and accordingly decreases a wasted solution.