• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
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• pp.9-13
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• 2012

In the iron ore sinter process, temperature distribution pattern in sintering bed is related with productivity and quality of sintered ore. Evenly heat distribution make the uniform quality of sintered ore but in normal operating condition, upper part of bed has lack of heat and scarce quality of sintered ore, thus yeild rate is decreased and productivity is diminished. Therefore, using the additional fuel for increasing quality and flue gas recirculation for increasing productivity are considered and effect of both processes are discussed.

• 한국분말재료학회지
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• 제22권4호
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• pp.283-288
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• 2015

Two sintering methods of a pressureless sintering and a spark-plasma sintering are tested to densify the Fe-TiC composite powders which are fabricated by high-energy ball-milling. A powder mixture of Fe and TiC is prepared in a planetary ball mill at a rotation speed of 500 rpm for 1h. Pressureless sintering is performed at 1100, 1200 and $1300^{\circ}C$ for 1-3 hours in a tube furnace under flowing argon gas atmosphere. Spark-plasma sintering is carried out under the following condition: sintering temperature of $1050^{\circ}C$, soaking time of 10 min, sintering pressure of 50 MPa, heating rate of $50^{\circ}C$, and in a vacuum of 0.1 Pa. The curves of shrinkage and its derivative (shrinkage rate) are obtained from the data stored automatically during sintering process. The densification behaviors are investigated from the observation of fracture surface and cross-section of the sintered compacts. The pressureless-sintered powder compacts show incomplete densification with a relative denstiy of 86.1% after sintering at $1300^{\circ}C$ for 3h. Spark-plasma sintering at $1050^{\circ}C$ for 10 min exhibits nearly complete densification of 98.6% relative density under the sintering pressure of 50 MPa.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.347-351
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• 2007

The influence of compaction pressure and sintering temperature on the hydraulic cylinder block fabricated by powder metallurgy is investigated in this study. The cylinder block is powder compacted under various compaction pressures and sintered under various sintering temperatures, and its density and dimensions are measured to reveal the relation of the process condition with the product quality. Moreover, finite element analyses of the density distributions are conducted under the same conditions with the experiments and the predicted results are compared with the measured ones.

• 한국분말재료학회지
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• 제24권3호
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• pp.223-228
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• 2017

Nanopowders provide better details for micro features and surface finish in powder injection molding processes. However, the small size of such powders induces processing challenges, such as low solid loading, high feedstock viscosity, difficulty in debinding, and distinctive sintering behavior. Therefore, the optimization of process conditions for nanopowder injection molding is essential, and it should be carefully performed. In this study, the powder injection molding process for Fe nanopowder has been optimized. The feedstock has been formulated using commercially available Fe nanopowder and a wax-based binder system. The optimal solid loading has been determined from the critical solid loading, measured by a torque rheometer. The homogeneously mixed feedstock is injected as a cylindrical green body, and solvent and thermal debinding conditions are determined by observing the weight change of the sample. The influence of the sintering temperature and holding time on the density has also been investigated. Thereafter, the Vickers hardness and grain size of the sintered samples have been measured to optimize the sintering conditions.

• 한국분말재료학회지
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• 제22권5호
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• pp.356-361
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• 2015

Fe-30 wt% TiC composite powders are fabricated by in situ reaction synthesis after planetary ball milling of (Fe, $TiH_2$, Carbon) powder mixture. Two sintering methods of a pressureless sintering and a spark-plasma sintering are tested to densify the Fe-30 wt% TiC composite powder compacts. Pressureless sintering is performed at 1100, 1200 and $1300^{\circ}C$ for 1-3 hours in a tube furnace under flowing argon gas atmosphere. Spark-plasma sintering is carried out under the following condition: sintering temperature of $1050^{\circ}C$, soaking time of 10 min, sintering pressure of 50 MPa, heating rate of $50^{\circ}C/min$, and in a vacuum of 0.1 Pa. The curves of shrinkage and its derivative (shrinkage rate) are obtained from the data stored automatically during sintering process. The densification behaviors are investigated from the observation of fracture surface and cross-section of the sintered compacts. The pressureless-sintered powder compacts are not densified even after sintering at $1300^{\circ}C$ for 3 h, which shows a relative denstiy of 66.9%. Spark-plasma sintering at $1050^{\circ}C$ for 10 min exhibits nearly full densification of 99.6% relative density under the sintering pressure of 50 MPa.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 추계학술대회 논문집 학회본부
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• pp.311-315
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• 1991

The formation and transition of 2212 and 2223 phase have been studied in BPSCCO system. The 2212 phase formed in early sintering state reacts on $Ca_2PbO_4,\;Ca_2CuO_3$ and CuO during sintering process and thus produces the 2223 phase. A long sintering period is need to fabricate the superconductor with large volume fraction of 2223 phase. Also, the thin plate-like grains composed of Bi, Sr, Ca and Cu contribute to 2223 phase formation. Though the sample has lower volume fraction of 2223 phase, the critical temperature is measured highly in case of the grain grown to plate-like shape. In this work, the critical temperature of the sample sintered for 264 hr in air was measured 108 K. Microstructure of the sample was varied with condition of heat treatment after sintering process and the sample annealed with $500^{\circ}C$ for 5 hr showed excellent charateristics of 2223 phase formation.

• 멤브레인
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• 제15권4호
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• pp.349-354
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• 2005

이트리아 안정화 지르코니아(yttria stabilized zirconia, YSZ)를 전해질로 선정하여 소결조건에 따른 열적 안정성과 전기적인 특성을 분석하였다. SEM사진으로 소결온도가 증가할수록 입자가 커지므로 상대적으로 기공은 줄어드는 것을 보였고 입자크기에 따른 영향을 확인하였다. 전기적 특성을 알아보고자 2단자법(2-probe method)으로 $800\~1000^{\circ}C$의 오도에서 교류 임피던스 측정을 통하여 전해질 내의 저항과 전기전도도 측정으로 입자 내부 저항 및 전기적 성능을 평가하였다. 소결온도가 $1400^{\circ}C$일 때 건식법과 습식법에서 밀도는 각각 6.13, 6.25 $g/cm^3$이며, 상대밀도는 각각 98, 99$\%$였다. 소결온도가 올라갈수록 저항은 낮아지고, 전도도는 커지는 것을 확인할 수 있으며, 건식 및 습식법으로 제작한 전해질의 전기전도도는 $10000^{\circ}C$에서 각각 $8.8\times10^{-2},\;11\times10^{-2}$ S/cm이었다.

• 한국분말재료학회지
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• 제21권6호
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• pp.407-414
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• 2014

The powder injection molding process having advantages in manufacturing three-dimensional precision parts essentially requires a debinding process before sintering to remove the binders used for preparing feedstock. In this study, powder injection molding of translucent alumina was performed, and carbon dioxide ($CO_2$) is used as a supercritical fluid that makes it possible to remove a large amount of binder, which is paraffin wax. The relationship between the optical property of translucent alumina and the debinding condition (temperature and pressure) of supercritical $CO_2$ was investigated. As temperature and pressure increased, extraction rate of the binder showed rising tendency and average grain size after sintering process was relatively fine. On the other hand, optical transmittance was reduced. As a result, the debinding condition at $50^{\circ}C$ and 20 MPa that represents the lowest extraction rate, $8.19{\times}10^{-3}m^2/sec$, corresponds to the largest grain size of $14.7{\mu}m$ and the highest optical transmittance of 45.2%.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.661-662
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• 2006

Development of recycling method at cemented carbide scraps was researched. Some properties of recycled cemented carbides were investigated. Recycled WC fine powder suffered the surface oxidation. Therefore it was necessary to be done by reduction treatment at 1073K-3.6ks under hydrogen atmosphere. When sintering condition at 1673K-3.6ks was treated under vacuum condition, it gained the deflective strength of about 90%, and gained hardness and sintering density about same value compared with commercial alloys. As a result, it was able to recycle only by 7 processes.

• 한국결정성장학회지
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• 제26권1호
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• pp.28-34
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• 2016

원적외선 방사세라믹은 인체의 피부 안쪽으로 깊숙이 적외선을 침투시켜 온열 및 치료환경을 주는 매력적인 재료로써, 열적 치료 장치, 온열 매트, 히터 등과 같은 분야에 많은 응용이 되고 있다. 본 연구에서는 소결 온도와 시간을 변화시킴으로써 높은 방사율을 가지는 원적외선 방사세라믹의 소결 조건을 최적화하고자 하였다. 원적외선 방사체의 상 분석은 XRD로, 그 파단면의 미세구조는 SEM을 이용하여 분석하였다. 원적외선 방사율의 측정은 FT-IR으로 행하여, 결과를 종합적으로 해석하여 소결체의 최적 공정 조건을 확립하였다.