• 한국수소및신에너지학회논문집
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• 제25권2호
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• pp.151-160
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• 2014

CL-SPEEK/Cs-TPA/$CeO_2$ composite membrane was prepared for polymer electrolyte membrane water electrolysis (PEMWE). In order to improve the electrochemical, mechanical, durabilities and electrocatalytic characteristics, engineering plastic of polyether ether ketone (PEEK) as polymer matrix was sulfonated and the organic-inorganic blend composite membranes was prepared by loading cesium-substituted tungstophosphoric acid (Cs-TPA) by titration method with cross-linking agent contents of 0.01mL. Ceria ($CeO_2$) was used to scavenge free radicals which attack the membrane in the PEMWE circumstance and to increase the duration of the membrane. CL-SPEEK/$Cs_{(1)}$-TPA/CeriaIn conclusion, 1% membrane showed the optimum results such as 0.119 S/cm at $80^{\circ}C$ of proton conductivity and 62MPa of tensile strength.

• 대한치과보철학회지
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• 제34권4호
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• pp.657-664
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• 1996

The purpose of this study was to compare the dimensional stability, compression resistance, elastic recovery and surface hardness of elastomeric interocclusal recording materials. Five commonly used elastomeric interocclusal recording materials(Ramitec, Regisil, Blue-Mousse, Stat-Br, Coltoflax) were selected for this study. According to ADA specification No. 19, two types of specimen were fabricated. Cylinder type specimens were used to test compression resistance and elastic recovery and plate type specimens were used to evaluate dimensional stability and surface hardness. Paired t-test was applied to detect significance among the occlusal registration materials. The obtained results were as follows: 1. There were statistical difference in dimensional stability between the elastic interocclusal recording materials. The dimensional stability of silicone was higher than that of polyether tested(p<0.05). 2. Coltoflax was significantly less resistance to compression than the other elastic interocclusal recording materials(p<0.001). 3. The elastic recovery capacity of Blu-Mousse and Stat-Br is better than that of Coltoflax (p<0.01). 4. The surface hardness of Coltoflax was lower than that of Blu-Mousse and Stat-Br(p<0.05). 5. The percentage dimensional change of alll materials was acceptable according to the limid of 0.5% suggeted by ADA specificatin No. 19.

• 대한치과보철학회지
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• 제42권1호
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• pp.11-20
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• 2004

Problem : The several studies were reported to the effects of individual tooth tray with the parallel tooth, but not reported to the effect of individual tooth tray with severe undercut in impression making. Purpose : The purpose of this study is to examine the effect of individual tooth tray; 1) the accuracy of impression in terms of distance. 2) reproducibility of pocket. Material and methods : In this study, a metal model with 3 teeth including tooth prepared 30-degree undercut and gingival crevice of the depth 5mm, width 0.4mm was cast. Impressions of the metal model were taken in 5 times used 4 kinds of impression materials with individual tooth tray and another impression taking were made with conventional method without individual tooth, used same materials, procedure. The stone models were made. Distances between abutments were measured with a Micromeasurescoup-mm. Result : The following results were obtained ; 1. In the comparisonof inter-abutment distance between parallel tooth without individual tooth tray, 4elastomeric materials have not significant difference to the metal model(p>0.05). 2. In the comparisonof inter-abutment distance with undercut tooth without individual tooth tray, 4elastomeric materials have a significant difference to the metal model(p<0.05), especially polyether's dimensional change is large. 3. If individual tooth tray was used to take impression in abutment teeth with severe undercut, more stable results was achieved easily than conventional method. (p>0.05). 4. It is not true that the pressure of impression material with individual tooth tray increased to gingival sulcus. Conclusion : By the results, I knew the fact that individual tooth tray was useful impression method on the teeth with severe undercut for the dimensional stability. Also, I could not confirm the fact that individual tooth tray would increase the penetrating pressure into cervice.

• 구강회복응용과학지
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• 제30권1호
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• pp.23-27
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• 2014

목적: 요오드계 소독제의 고무인상체 안정성에 미치는 영향을 조사하고자 하였다. 연구 재료 및 방법: 폴리설파이드, 실리콘, 폴리이써 고무인상재를 이용하여 72개의 인상체를 채득하였다. 이를 요오드계 소독제인 iodophor 수용액에 각각 10분, 30분간 침적시키고 모형을 제작하여 대조군과 광학현미경을 이용하여 체적 안정성을 평가하였다. 결과: 모든 고무인상체는 0.5% 미만의 체적변화를 보였으나 30분 침적은 10분 침적에 비해 통계적으로 유의하게 변화량이 증가하였다(P < 0.05). 결론: 요오드계 소독제에 고무인상재를 침적시 10분정도의 시간경과가 고무인상재의 체적변화에 영향이 적었다.

• Macromolecular Research
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• 제15권7호
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• pp.676-681
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• 2007

A process designed to synthesize rigid polyurethane foam (PUF) with insulative properties via the modulation of PUF cell size via the addition of clay and the application of ultrasound was assessed. The blowing agents utilized in this study include water, cyclopentane, and HFC-365mfc, all of which are known to be environmentally-friendly blowing agents. The rigid PUFs were prepared from polymeric 4,4'-diphenylmethane diisocyanate (PMDI) and polyether polyol with a density of $50kg/m^3$. In addition, rigid PUFs/clay nanocomposites were synthesized with clay modified by PMDI with and without the application of ultrasound. The PUF generated using water as a blowing agent evidenced the highest tensile strength. The tensile strength of the PUF/nanocomposites was higher than that of the neat PUF and the strength was even higher with the application of ultrasound. The cell size of the PUF/clay nanocomposites was less than that of the neat PUF, regardless of the type of blowing agent utilized. It appears that the higher tensile strength and lower cell size of the PUF/clay nanocomposites may be attributable to the uniform dispersion of the clay via ultrasonic agitation. The thermal conductivity of the PUF/clay nanocomposites generated with HCFC-141b evidenced the lowest value when PUF/clay nanocomposites were compared with other blowing agents, including HFC-365mfc, cyclopentane, and water. Ultrasound has also proven effective with regard to the reduction of the thermal conductivity of the PUF/clay nanocomposites with any of the blowing agents employed in this study. It has also been suggested that the uniformly dispersed clay particles in the PUF matrix function as diffusion barriers, which prevent the amelioration of the thermal insulation property.

• 한국결정학회:학술대회논문집
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• 한국결정학회 2002년도 정기총회 및 추계학술연구발표회
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• pp.19-19
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• 2002

Perovskite-type titanate dielectrics have attracted much attention in memory devices such as DRAMs or FeRAMs due to their high dielectric constants. However, low volatility of the Ba, Sr, Pb or Zr precursors with only thd ligands has limitations in obtaining high quality thin films by liquid source metal organic chemical vapor deposition (LS-MOCVD) processes. To improve the volatility of these precursors, many attempts have been made such as adding polyether ligands to satisfy the coordinative saturation. We report the synthesis of new precursors Ba(thd)₂(tmeea) and Sr(thd)₂(tmeea), where tmeea = tris[2-(2-methoxyethoxy)ethyl]amino, and LS-MOCVD of barium strontium titanate (BSTO) thin films using these precursors. Due to increased basicity of amines compared with ethers, it is expected that the nitrogen-donor ligand will make a strong bond to a metal than an analogous oxygen-donor ligand, consequently improving the volatility and thermal behavior of these precursors. Thin films of BSTO were grown on Pt(111)/SiO₂/Si(100) substrates by LS-MOCVD using a cocktail source consisting of the conventional Ti precursor Ti(thd)₂(O/sup i/Pr), and these new Ba and Sr precursors. As-grown films were characterized by XPS, SEM, XRD, XRF, and C-V and I-V measurements. BSTO films grown at 420℃ were stoichiometric barium strontium titanate with very smooth surface morphology and their dielectric constants were found to be as targe as 450. Dependence of the composition, microstructure and the electrical properties of the BSTO films on the growth temperature, annealing temperature, working pressure, and the composition of the cocktail source will be discussed.

• KEPCO Journal on Electric Power and Energy
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• 제2권2호
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• pp.187-192
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• 2016

이산화탄소의 화학적 전환기술은 온실가스 저감뿐만 아니라 탄소자원화를 통해 유한한 자원을 대체할 수 있는 기술이다. 다양한 화학반응에 의한 이산화탄소의 전환이 상용화되어 있지만, 대량의 이산화탄소를 자원화하기 위해서는 혁신적인 기술개발이 필요하며 전세계적으로 이에 대한 연구가 활발히 진행되고 있다. 이산화탄소를 직접 분자구조내에 삽입하는 기술 중 고분자 원료물질로 이용되고 있는 Dimethyl carbonate와 Polyol에 대한 제조기술 현황에 대해 소개하였다. RIST에서는 Dimethyl carbonate 제조기술로 urea methanolysis에 의한 촉매 및 공정을 개발하였으며, Polyol의 경우 고유 촉매개발 및 polyol 제품군에 대한 연구를 수행중에 있다. 이들은 분자내에 이산화탄소를 40%이상 포함할 수 있는 화학제품이므로 실용화 성공 시 온실가스 저감에 큰 기여를 할 수 있을 것으로 기대된다.

• 대한화학회지
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• 제38권7호
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• pp.509-515
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• 1994

고리(12C4, 15C5, 18C6, DT18C6, DA18C6) 및 비고리$(Q_2O_5)$ 폴리에테르와 11가지의 1차 및 2차 알킬암모늄 이온과의 상호작용을 NMR 적정과 전기전도도법으로 조사하였다. 모든 알킬암모늄 이온은 크라운 에테르 및 비고리 폴리에테르와 수소결합에 의해 비교적 안정한 1:1 착물을 형성하였다. 알킬암모늄 이온과 동공의 크기가 다른 동일계열 호스트와의 상호작용의 세기는 18C6 > 15C5 > 12C4 순이었으며, 알킬암모늄 이온에 대한 호스트 주개원자의 세기는 N > O > S 순이었다. 18C6는 2차 알킬암모늄 이온에 비해 1차 알킬 암모늄 이온과 더 강한 상호작용을 하는 반면, DA18C6는 2차 알킬암모늄 이온과 더 강한 상호작용을 하였다. 또한 25$^{\circ}C$ 메탄올에서 18C6와 알킬암모늄 이온과의 착물형성에 대한 안정도 상수를 전기전도도법에 의해 구하였다. 착물의 안정도는 주로 알킬암모늄의 차수(또는 수소결합 수), 알킬기의 길이, 알킬기의 구조에 의한 입체장애 등에 의해 크게 영향을 받았다.

• 접착 및 계면
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• 제17권1호
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• pp.21-28
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• 2016

본 연구에서는 불법 조업 어선 제압 및 장비 불용화를 위한 접착형 퇴치제 개발의 일환으로 발포형 생분해성 폴리우레탄 연구를 수행하였다. 발포형 폴리우레탄 접착제는 폴리에스터계 및 폴리에테르 폴리올을 포함하는 주재와 고분자형의 이소시아네이트로 이루어진 경화제를 혼합하여 반응이 완결되는 2액형으로, 단기간의 생분해성을 위해 주재에 starch와 dextrin 및 amylase 등을 첨가하여 4주간 약 34%의 생분해도를 OECD 301C법에 의해 얻을 수 있었다. 주재와 경화제의 온도에 따른 점도를 $0{\sim}50^{\circ}C$의 온도범위에서 측정하여 혼합 시 참고할 수 있도록 하였으며, 또한 신속한 발포 및 접착성능을 위해서 $0{\sim}50^{\circ}C$의 온도 범위에서 발포형 폴리우레탄 접착제의 반응 완결 속도(rising time)를 조절하여 1 min 내외로 제어하였다. 또한 면 직물에 대한 T-peel 시험을 수행한 결과 최대 20.78 N/cm, 평균 11.95 N/cm의 접착력을 얻을 수 있었다.

• 대한치과보철학회지
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• 제39권3호
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• pp.273-281
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• 2001

Digital subtraction radiography may be one of the most precise and noninvasive methods for assessing subtle density changes in peri-implant bone, providing additional diagnostic information on implant tissue integration in overall maintenance. The aims of this study were to evaluate density changes after first, second surgery of dental implant and to measure the amount of marginal bone loss 9 months after second surgery using digital subtraction radiography. Bone change around 30 screw-shaped implants in 16 patients were assessed on radiographs. 17 Branemark implants of 3.75mm in diameter(Nobel Biocare, Goteborg, Sweden), 2 Branemark implants of 5.0mm in diameter, 11 $Replace^{TM}$ implants of 4.3mm in diameter(Nobel Biocare, Goteborg, Sweden) were used. To standardize the projection geometry of serial radiographs of implants, customized bite block was fabricated using XCP film holder(Rinn Corporation, Elgin, IL.) with polyether impression material of Impregum(ESPE, Germany) and direct digital image was obtained. Qualitative and quantitative changes on radiographs were measured with Emago software(The Oral Diagnostic System, Amsterdam, Netherlands). The results were as follows: 1. The peri-implant bone density of 69.2% implants did not change and the peri-implant bone density of 30.8% implants decreased after 3 months following first surgery. 2. The crestal bone density of 53.9% implants decreased first 3 months after second surgery. The crestal bone density of 58.8% implants increased 9 months after second surgery. No density change was observed around the midportion of the implants after second surgery, 3. The amount of marginal bone loss between different kinds of implants showed no statistically significant differences (p>0.05). 4. More than 90% of total marginal bone loss recorded in a 9-month period occurred during the first 3 months.