• 대한기계학회논문집
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• 제18권10호
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• pp.2585-2596
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• 1994

Many particle filled materials like Poweder/Binder mixtures for poweder injection moldings, have complicated rheological behaviors such as an yield stress and slip phenomena. In the present study, numerical simulation programs via a finite element method and a finite difference method were developed for the quasi-three-dimensional flows and the two-dimensional flow models, respectively, with the slip phenomena taken into account in terms of a slip velocity. In order to qualitatively understand the slip effects, typical numerical results such as vector plots, pressure contours in the cross-channel plane, and isovelocity controus for the down-channel direction were discussed with respect to various slip coefficients. Slip velocities along the boudary surfaces were also investigated to find the effects of the slip coefficient and processing conditions on the overall flow behavior. Based on extensive numerical calculations varying the slip coefficients, pressure gradient, aspect ratio, and power law index, the screw characteristics of the extrusion process were studied in particular with comparisons between the slip model and non-slip model.

• 소성∙가공
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• 제15권7호
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• pp.518-523
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• 2006

Wet wire drawing of brass coated steel wire, used for tire reinforcement, is realized with Tungsten Carbide(WC) dies sintered with a cobalt(Co) binder. Dies wear represents an important limitation to the production process and cost savings. Several parameters, such as Co content, WC grain size of tungsten carbide, sintering conditions, and so on, affect on the wear of the drawing die. In this study, the effect of the diamond abrasive particle size on the life of the WC centered dies of the wet wire drawing was investigated. Wet wire drawing experiments were carried out on a wet wire drawing machine. From the experiments, the dies life, dies fracture, wire surface roughness, and wire breaks were investigated. From the results, it was found that the wear of the WC dies increased with the increase in the diamond abrasive particle size.

• 한국분말재료학회지
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• 제24권5호
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• pp.364-369
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• 2017

Ceramic powder, such as MgO, is added as a binder to prepare the green compacts of molten salts of an electrolyte for a thermal battery. Despite the addition of a binder, when the thickness of the electrolyte decreases to improve the battery performance, the problem with the unintentional short circuit between the anode and cathode still remains. To improve the current powder molding method, a new type of electrolyte separator with porous MgO preforms is prepared and characteristics of the thermal battery are evaluated. A Spherical PMMA polymer powder is added as a pore-forming agent in the MgO powder, and an organic binder is used to prepare slurry appropriate for tape casting. A porous MgO preform with $300{\mu}m$ thickness is prepared through a binder burnout and sintering process. The particle size of the starting MgO powder has an effect, not on the porosity of the porous MgO preform, but on the battery characteristics. The porosity of the porous MgO preforms is controlled from 60 to 75% using a pore-forming agent. The batteries prepared using various porosities of preforms show a performance equal to or higher than that of the pellet-shaped battery prepared by the conventional powder molding method.

• 한국잠사곤충학회지
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• 제43권1호
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• pp.41-48
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• 2001

The purification, dissolution and powdering of stained waste silk obtained from weaving and dyeing process were studied for the surface modification of textile fabric and plastic materials. The whiteness of stained waste silk could be improved through degumming and bleaching with sodium hydrosulfite. The water-soluble fibroin solution can be obtained by dissoving the degummed waste silk in a boiling solution of 50% calcium chloride for 60 minutes. The salts and heavy metals contained in fibroin solution were removed by electric dialysis, wool fiber filtration and gel filtration chromatography. The fibroin powder was prepared by using a fine grinder after the alkali treatment for weakening the silk fiber. The fine fibroin powder of particle size around 30 ㎛ was obtained with a ultra fine-mill, while it was finer below 10 ㎛ with a ball-mill. The dissolved or powdered silk was applied to the surface of fabric with addition of the binder (a urethane resin). The moisture content of polyester and nylon fabrics treated with the silk solution was improved due to hygroscopic property of silk. The fine fibroin powder mixed with the binder ws coated on the surface of synthetic film by use of the air pressed sprayer. It was revealed that the hygroscopicity as well as the softness of fibroin powder coated film was much improved. Therefore, it is thought that the fine silk fibroin powder is applicable as an coating agent for the surface modification of plastic and synthetic leather.

• 한국분말재료학회지
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• 제5권3호
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• pp.199-209
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• 1998

A new low melting inorganic binder, monoclinic $HBO_2$, has been developed for Selective Laser Sintering (SLS) of alumina powder by dehydration process of boron oxide powder in a vacuum oven at $120^{\circ}C$. It led to better green SLS parts and higher bend strength far green and fired parts compared to other inorganic binders such as aluminum and ammmonium phosphate. This appeared to be due to its low viscosity and better wettability of the alumina particle surface. A low density single phase ceramic, aluminum borate ($Al_{18}B_4O_{33}$), and multiphase ceramic composites, $A_{12}O_3-A_{14}B_2O_9$, were successfully developed by laser processing of alumina-monoclinic $HBO_2$ powder blends followed by post-thermal processing; both $Al_{18}B_4O_{33}$ and $A_{14}B_2O_9$ have whisker-like grains. The physical and mechanical properties of these SLS-processed ceramic parts were correlated to the materials and processing parameters. Further densification of the $A_{12}O_3-A_{14}B_2O_9$ ceramic composites was carried out by infiltration of colloidal silica, and chromic acid into these porous SLS parts followed by heat-treatment at high temperature ($1600^{\circ}C$). The densities obtained after infiltration and subsequent firing were between 75 and 80% of the theoretical densities. The bend strengths are between 15 and 33 MPa.

• 자원리싸이클링
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• 제7권4호
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• pp.35-42
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• 1998

오늘날 전자부품 산업에 실장기술은 크게 각광을 받고 있다. 페라이트 칩인덕터와 같이 전자부품의 소형화를 위해서는, 쉬트 적층법이나 스크린 인쇄법 등을 위하여 유기용매를 사용하는 세라믹 습식공정이 널리 사용되고 있다. 본연구에서는 물이 혼합된 용매계를 이용한 NiCuZn Ferrite(NCZF) 슬러리와 그린쉬트의 제조 및 평가에 관한 연구를 하였다. 볼밀링에 의하여 21 vol%의 NCZF 슬러리를 제조하였으며, polacrylic vinyl copolymer를 바인더로서 사용하였다. 용매로서는 isopropyl alcohol과 2-butoxy ethanol에 40∼80% 물을 혼합하여 사용하였다. 그 결과, NCZF 슬러리의 분산안정성은 입자의 정전기적 힘보다는 free polymer에 의해 나타났으며, 슬러리의 점성은 용매중의 물함량에 크게 의존하였다.

• 한국수소및신에너지학회논문집
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• 제17권2호
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• pp.141-148
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• 2006

This study was carried out to analyze the microstructure characteristics of electrolyte membrane through XRD, SEM and AC impedance measurement for using in high temperature steam electrolysis(HTE). It was investigated that thermal stability and electric characteristics by sintering condition using dry and wet process, and confirmed growth of particle and density change by sintering temperature. The sintering temperature and behavior had an effect on the relative density of the ceramic and the average grain size. The more amount of dispersant in organic compound increase, the more the density increased. But the binder was shown opposite phenomenon. It was analyzed that electrolyte resistance and electrical characteristics using AC impedance. The electrical properties of YSZ grain boundary changed with the sintering temperature.

• 한국응용과학기술학회지
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• 제10권1호
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• pp.49-55
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• 1993

Ground Calcium Carbonate, among paper coating pigments, will influence less dispersant demand, less binder demand, increase coating solids from 58% to 70%, which means high speed coating, less shrinkage during drying, less energy consumption, more uniform coverage of fibers. The quality point of view of Ground Calcium Carbonate, brightness, particle size, Particle size distribution, hardness, impurities content are important. More important factors of Ground Calcium Carbonate which influence the paper coating process are dispersion mechanisms and their effects. The study was made to investigate the effect of Ground Calcium Carbonate dispersion by sodium salt of polyacrylate dispersant composition and dispersion condition. Basic tests such as physical, optical and chemical were perfumed, and dispersion effects were investigated by different conditions. The results showed that the type of dispersant affected the dispersion effects, and the Ground Calcium Carbonate has critical dispersant demand.

• 한국식품과학회지
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• 제18권1호
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• pp.48-54
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• 1986

본 연구는 유동층 조립기로 조립시킨 보리 미숫가루 입자들의 인스탄트 성질에 영향을 주는 인자들을 조사하였다. 조립에 사용된 바인더는 맥아당, 포도당, 젤라틴의 수용액과 물 이었으며 조립입자의 인스탄트 효과는 입자의 습윤성, 침강성, 분산성 및 용해성을 측정하여 결정하였다. 바인더의 종류별로 조립된 시료의 인스탄트 성질의 개선에 대한 기여도는 낮은 바인더 수용액에서 5%젤라틴수용액>5%맥아당수용액>5%포도당수용액의 순으로 나타났으며 물은 가장 낮은 인스탄트효과를 보였다. 바인더 용액의 농도증가에 따른 조립입자의 인스탄트성질은 포도당, 맥아당과 같은 당류의 경우 증가되었으나 젤라틴의 경우에는 이와 반대경향을 나타내었다. 조립입자의 크기가 인스탄트성질에 미치는 영향은 현저하였으며 입자의 크기가 $0.1{\sim}0.3mm$일 때, 시료의 인스탄트효과가 가장 좋았다. 조립입자의 건조온도($60^{\circ}C,\;70^{\circ}C,\;80^{\circ}C$)는 입자의 인스탄트효과에 거의 영향을 미치지 않았다. 바인더용액을 사용하여 조립한 미숫가루입자의 흡습속도는 각각의 상대습도(42%, 67%, 92%)에서 5%젤라틴수용액>5%맥아당수용액>5%포도당수용액의 순으로 빠르게 나타났으며 이러한 결과는 바인더 종류가 인스탄트 성질에 미치는 효과와 동일한 순서로 일치함을 보여주었다.

• 한국추진공학회지
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• 제22권3호
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• pp.8-13
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• 2018

ZPP(Zirconium Potassium Perchlorate)는 산화제 potassium perchlorate, 금속원료 zirconium, 결합제 Viton 조성의 점화제이다. ZPP는 항공우주산업, 추진제 점화원, 자동화 산업에 사용되고 있다. 본 연구에서는 PMD(Pyrotechnic Mechanical Device)에 사용되는 ZPP의 제조공정 및 형상/열량/압력값과 같은 특성을 연구하였다. ZPP 제작 시, 원료들을 고속으로 교반하여 ZPP가 균일한 입자크기 및 형상으로 제작될 수 있도록 혼화공정을 설계하였다.