• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.440-441
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• 2006

Several titanate powders ($Al_2TiO_5,\;SrTiO_3$, etc.) were synthesized by an ethylene glycol solution route. Titanium isopropoxide and nitrate salts were dissolved in stoichiometric proportions in liquid-type ethylene glycol without any precipitation. The parent precursor sols were dried to porous gels, and then the gels were calcined and crystallized. All synthesized titanate powders had stable crystallization behavior at low temperature and high specific surface area after a simple ball-milling process. A three-component PZT $(Pb(Zr_{0.52}{\cdot}Ti_{0.48})O_3)$ powder was also synthesized successfully by the ethylene glycol method. In this study, the characteristics of the multi-component titanate powders by the ethylene glycol method are examined.

• 한국분말재료학회지
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• 제10권4호
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• pp.249-254
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• 2003

WC-6wt%Co hard metal powders were sintered by a 2.45 GHz multimode microwave applicator in Ar atmosphere. Microwave sintering of WC-6wt%Co powder lowered the sintering temperature and shortened the processing time in less than two hours than by a conventional method. Microstructures of the sintered specimen were studied with scanning electron microscope (SEM) and no abnormal grain growth was observed. Mechanical properties were similar to the values of the specimens sintered by a conventional method. Specimen sintered at 135$0^{\circ}C$ for 30 minutes ,hewed 99%, 20.5 GPa and 8.1 MPa$\sqrt{m}$ of theoretical density, hardness and fracture strength, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.555-558
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• 2004

In this paper, the variable producing conditions of YBCO superconducting powder by use of sol-gel method was investigated. YBCO superconducting powder which was prepared by sol-gel method was shown the characteristic gel formation, particle size and its properties under variable preparation conditions, such as pH, drying and processing time, and powder heat treatment, etc.

• 소성∙가공
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• 제12권5호
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• pp.457-464
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• 2003

In the powder compact melting technique, proper precursor fabrication is very important because density distribution after foaming and foamability are determined during precursor fabrication process. The fabrication of the precursor has to be performed very carefully because any residual porosity or other defects will lead to poor results in further processing. In order to evaluate the effect of the compaction parameters on the kinetics of the foaming process, a series of experiments were performed. In this study, aluminium foams with a closed cell structure were fabricated by using both the powder compact method and the induction heating process. A proper induction coil was designed to obtain a uniform temperature distribution over the entire cross sectional area of precursor. To establish the foamable precursor fabrication conditions, effects of process parameters such as the titanium hydride content (0.3∼1.5 wt.%), pressing pressure of the foamable precursor (50∼150kN) on the pore morphology were investigated.

• 한국정밀공학회지
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• 제15권7호
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• pp.85-90
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• 1998

The business of manufacturing is increasingly becoming time-compressing, precise and long-life oriented, owing to various needs from the consumers and harsh global competition. With the emergence of the layer laminate manufacturing method, it is possible to produce prototypes directly from 3D CAD and additive process, the production time and cost have shortened dramatically. However there are some problems like surface-step, dimensional deviation and warp. A newly developed powder casting is suitable for rapid-manufacturing metallic tools. Powder casting can serve as a promising rapid tooling method because of high density characteristics and low dimensional shrinkage below 0.1％ during sintering and infiltration. By this process, we have realized significant time savings bypassing the wait for prototype tooling and cost savings eliminating the expense of conventional prototype tooling process.

• Applied Microscopy
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• 제32권4호
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• pp.311-317
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• 2002

입자 크기에 따라 상전이 경로가 달라지며 매우 큰 응집체로 존재하는 gibbsite 분말과 같은 재료의 정량적인 전이 구조 분석의 전제로서 입자 크기가 선택적인 TEM 시편의 준비가 절실히 요구된다. 입자 크기 선택성을 실현한 TEM 시편 준비의 방법론을 확립하기 위한 방안으로서 본 실험이 전개되었다. 약 1 wt%의 gibbsite 원료 분말을 에탄올 용매에 혼합 한 뒤, ball-milling에 의해 조분쇄 처리를 하고 증류수에 1 : 19의 비로 희석된 분산 조제, Darvan C, 0.25 vol%의 첨가와 함께 ultrasonic 처리를 하여 gibbsite suspension을 만들었다. 제조된 gibbsite suspension의 누적 농도 변화 관찰에 의한 침강 시간의 조정 후 정적 침강 분리에 의해 nm 크기별로 분리된 TEM 시편을 만들 수가 있었다. 시편의 전체적인 양상은 SEM으로 관찰하였고 개개 입자들의 morphology 는 TEM으로 분석하였다. 또한, 공정 과정 중의 상변화 가능성을 검토하기 위해 XRD 분석을 실시하였다.

• 한국식품과학회지
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• 제36권1호
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• pp.25-31
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• 2004

Characteristics of good-quality red pepper powder produced using $N_{2}$-circulated low-temperature drying method were compared with those made through conventional sun and hot-air drying methods. Kimchi and kochujang were prepared with different types of red pepper powder, and their physicochemical and sensory properties were compared. Results revealed Hunter L (lightness), a (redness), and b (yellowness) values of $N_{2}$-circulated low temperature-dried red pepper were highest. Absorbance of crude capsanthin in hot air-dried red pepper powder ($0.584{\pm}0.001$) was significantly lower than sun-dried ($0.848{\pm}0.001$) and $N_{2}$-circulated low temperature-dried products ($0.832{\pm}0.002$. Use of $N_{2}$-circulated low-temperature drying method resulted in the highest amounts at reducing sugar and total vitamin C. Capsaicin content of $N_{2}$-circulated low temperature-dried products were higher than hot air-dried ones. The aL values of kochujaug made with sun-and low temperature-dried red peppers were higher than that of kochujang made with hot-dried red peppers. Physicochemical and sensory evaluation results showed red pepper powders made using $N_{2}$-circulated low-temperature drying method have the best quality among all samples tested.

• 한국식품영양학회지
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• 제32권5호
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• pp.571-579
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• 2019

For the purpose of promoting the consumption of rice powder, 5 cultivars were applied differently to establish the optimal manufacturing conditions and measured Hunter color values, hardness and expansion rate of Yakgwa for the optimal conditions. Looking into the optimal manufacturing conditions of Yakgwa, the commercial flour-facilitating Yakgwa is shown to have a great shape when the mold is made with a thick paste for C-2 manufacturing method, Hangaru 100 mesh for H100-2 manufacturing method, Hangaru 200 mesh for H200-2 manufacturing method, Shingil 100 mesh for S100-2 manufacturing method, and Shingil 200 mesh for S200-1 manufacturing method. It also showed a trend of chewy taste after frying without cracks. Hunter color values (L) and red chromaticity and value b of yellow chromaticity indicated a lower value for the commercial flour and Hangaru 200 mesh in its entirety. The hardness of Yakgwa is within the range of 1,981.41~3,756.45 g and the degree of hardness is shown differently for each rice powder exclusive cultivars. Rice flour developed as rice powder 5 cultivars, and as a result of measuring chromaticity, hardness and expansion rate of Yakgwa for the quality characteristics, the item of hangaru 200 mesh had outstanding quality characteristics for Yakgwa.

• E2M - 전기 전자와 첨단 소재
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• 제8권2호
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• pp.158-164
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• 1995

Solid solutions Sr$_{2}$(Ta$_{1-x}$ Nb$_{x}$)$_{2}$O$_{7}$, (x=0.0-1.0), composed of strontium tantalate(Tc=-107.deg. C) and strontium-niobate(Tc=1342.deg. C) were prepared by the conventional mixed oxide method and the flux method(molten salt synthesis method). Phase relation, sintering temperature, grain-orientation and dielectric properties for sintered ceramic samples were investigated with different compositions. Both Curie temperature and dielectric constant at Curie temperature were increased, and sintering behavior and the degree of grain-orientation were improved with the increase of Nb content. The single phase Sr$_{2}$(Ta/sib 1-x/Nb$_{x}$)$_{2}$O$_{7}$ powder was synthesized by using the flux method at lower temperatures, and sintering temperature was also reduced by using the flux method-derived powder than using the mixed oxide-derived powder. Sintering characteristics and dielectric properties of the specimens prepared by the flux method were better than those derived through the conventional mixed oxide method.thod.hod.

• 한국식생활문화학회지
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• 제20권1호
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• pp.103-112
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• 2005

The objective of this study was to clarify the effect of addition of green tea powder(0%, 2%, 4%, 6%, 8%) to Yackwa on quality and preservation. Addition of 4% green tea powder turned out to give positive effect on expansion. In test of physical characters, addition of green tea powder had a tendency to lower hardness, cohesiveness, springness and gumminess but to enhance brittleness. Considering the rancidity of oil within Yackwa, addition of green tea powder tended to show lower acid value and peroxide value than non-added treatment but its difference was slight. At the sensory test, surface color, bitterness and green tea flavor were strong but sweet and savory taste weak when green team powder was added(p<0.05). Overall quality appeared to have improved to 5.55 points which is compared to non-addition when the powder was added 4%(p<0.05). In conclusion, 4% addition of green tea powder would be the usefull method to enhance preference and quality of Yackwa.