• 대한금속재료학회지
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• 제49권1호
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• pp.40-45
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• 2011

Using the spark plasma sintering process (SPS process), the WC-6wt.%Co hard materials were densified using an ultra fine WC-Co powder. The WC-Co was almost completely dense with a relative density of up to 100% after the simultaneous application of a pressure of 60 MPa and the DC pulse current for 3 min without any significant change in the grain size. The average grain size of WC that was produced through this experiment was about $0.2{\sim}0.8{\mu}m$. The hardness and fracture toughness were about $1816kg/mm^2$ and $15.1MPa{\cdot}m^{1/2}$, respectively, for 60 MPa at $1200^{\circ}C$.

• Journal of Ceramic Processing Research
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• 제13권spc2호
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• pp.189-192
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• 2012

Manufacturing process for silicate glass phosphors containing Eu2+ activator and their photoluminescence property have been studied. We adopted powder sintering process instead of traditional glass melting process for making glass phosphor. At first, phosphor powders were synthesized at 1200 ℃ for 2-3 hours under a reducing atmosphere with 10% H2-90% N2 gas mixture. The reduced powders were compacted into discs and then the discs weresintered at 1400 ~ 1500 ℃ for 1 hr under a reducing atmosphere of 5H2-95% N2. The enhancement of PL intensity by Al2O3 addition, XPS binding energy shift of Si 2p and O 1s, sintering shrinkage, and crystallization were characterized.

• 한국세라믹학회지
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• 제53권3호
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• pp.288-294
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• 2016

The densification process during liquid-phase sintering was simulated by Monte Carlo simulation. The Potts model, which had been applied to coarsening during liquid-phase sintering, was modified to include vapor particles. The results of two- and threedimensional simulations showed a temporal decrease in porosity, in other words, densification, and an increase in the average size of pores. The results also showed growth of solid grains and the effect of wetting angle on microstructure.

• 한국결정성장학회지
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• 제21권1호
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• pp.34-40
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• 2011

무기성 폐기물인 준설토를 원료로 인공골재를 제조함에 있어, 직화소성법을 이용하여 소성온도(1100 및 $1200^{\circ}C$)와 시간(10~60 min)을 변수로 하여 인공골재의 부피비중, 흡수율 그리고 미세구조를 제어하였다. 또한 직화소성과 기존에 발표된 승온소성의 방법 차이에 따른 인공골재의 물성을 비교 분석하였다. 직화소성 시, 소성온도가 $1100^{\circ}C$에서 $1200^{\circ}C$로 증가하면, 껍질의 두께가 증가함과 동시에 블랙 코어 부분의 기공크기가 증가하면서 골재의 부피비중이 1.0 이하를 나타내었다. 또한 같은 소성온도에서 소성시간이 증가할수록 블랙코어의 단면적이 감소하고, 껍질의 두께가 증가하면서 흡수율이 감소하였다. 부피비중 1.0 이하의 인공골재는 직화소성이나 승온소성으로 제조된 경우 모두 블랙 코어부분의 미세구조가 서로 비슷한 경향을 나타내었다. 반면, 껍질(shell)의 미세구조는 승온소성된 경우에 더 치밀한 구조를 나타냈으며, 따라서 직화소성된 골재의 흡수율이 상대적으로 높았다. 이로서 직화소성법은 세라믹 담체 또는 흡착제등에 적용될 인공골재 제조에 적합한 방법임을 알 수 있었다.

• 한국분말재료학회지
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• 제8권1호
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• pp.61-69
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• 2001

Spark-Plasma Sintering(SPS) is one of the new sintering methods which takes advantages both inconventional pressure sintering and electric current sintering. It is known that SPS is very effective for the densification of hard-to-sinter materials like refractory metals, intermetallic compounds, glass and ceramics without grain growth. However, a clear explanation for sintering mechanism and an experimental evidence for the formation of weak plasma during SPS are not given yet. In this study, fundamental study on sintering behavior and mechanism of SPS was investiged. For this study, various spherical Fe powders were prepared such as as-received, as-reduced, and as-oxidized and then sintered by SPS facility. In order to confirm the surface cleaning effect during SPS neck region and fracture surface of sintered body was observed and analyzed by SEM/EPMA. Densification behavior was analyzed from the data of deflection along the pressure axis. Some specimens were additionally produced by Hot Pressing and the results were compared with those of SPS.

• 한국분말재료학회지
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• 제19권6호
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• pp.435-441
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• 2012

A new manufacturing process of Fe-Cr-Al powder porous metal was attempted. First, ultra-fine fecralloy powders were produced by using the submerged electric wire explosion process. Evenly distributed colloid (0.05~0.5% powders) was dispersed on PU (Polyurethane) foam through the electrospray process. And then degreasing and sintering processes were conduced. In order to examine the effect of sintering temperature in process, pre-samples were sintered for two hours at temperatures of $1350^{\circ}C$, $1400^{\circ}C$, $1450^{\circ}C$, and $1500^{\circ}C$, respectively, in $H_2$ atmospheres. A 24-hour TGA (thermo gravimetric analysis) test was conducted at $1000^{\circ}C$ in a 79% $N_2$+21% $O_2$ to investigate the high temperature oxidation behavior of powder porous metal. The results of the high temperature oxidation tests showed that oxidation resistance increased with increasing sintering temperature (2.57% oxidation weight gain at $1500^{\circ}C$ sintered specimen). The high temperature oxidation mechanism of newly manufactured Fe-Cr-Al powder porous metal was also discussed.

• 한국데이타베이스학회:학술대회논문집
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• 한국데이타베이스학회 1999년도 춘계공동학술대회: 지식경영과 지식공학
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• pp.261-270
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• 1999

Sintering transforms powdered ore into lumped ore so that the latter can be used in a blast furnace. The powdered ore combined with coke and other materials is loaded into a container and moved along by a pallet while the ignited coke bums. The speed by which the pallet moves determines how much sintering takes place. Since the process is complicated and lacks an accurate mathematical model, human operators manually control the speed by monitoring various factors in the plant. In this paper, we propose a neural network-based pallet speed controller which copies human operator knowledge. Actual process data were collected from a sintering plant fer eight months and preprocessed to remove noisy and inconsistent data. A multilayer perceptron was trained using a back-propagation learning algorithm. In on-line testing at the sinter plant, the proposed model reliably controlled pallet speed during normal operation without the help of human operators. Moreover, the duality and productivity was as good as with human operators.

• 한국지능정보시스템학회:학술대회논문집
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• 한국지능정보시스템학회 1999년도 춘계공동학술대회-지식경영과 지식공학
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• pp.261-270
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• 1999

Sintering transforms powdered ore into lumped ore so that the latter can be used in a blast furnace. The powdered or combined with coke and other materials is loaded into a container and moved along by a pallet while the ignited coke burns. The speed by which the pallet moves determines how much sintering takes place. Since the process is complicated and lacks an accurate mathematical model, human operators manually control the speed by monitoring various factors in the plant. In this paper, we propose a neural network-based pallet speed controller which copies human operator knowledge. Actual process data were collected from a sintering plant for eight months and preprocessed to remove noisy and inconsistent data. A multilayer perceptron was trained using a back-propagation learning algorithm. In on-line testing at the sinter plant, the proposed model reliably controlled pallet speed during normal operation without the help of human operators. Moreover, the quality and productivity was as good as with human operators.

• 한국분말재료학회지
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• 제12권4호
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• pp.261-265
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• 2005

In order to fabricate complex-shaped polycrystalline ceramics by sintering, organic binders are usually pre-mixed with ceramic powders to enhance the formability during the shape forming process. These organic binders, however, must be eliminated before sintering so as to eliminate the possibilities of poor densification and unusual grain growth during sintering. The present work studies the effect of binder addition on grain growth behavior during sintering of $92(70Pb(Mg_{1/3}Nb_{2/3})O_3-30PbTiO_3))$-8PbO(mol%) piezoelectric ceramics. The microstructures of the sintered samples were examined for various heating profiles and debinding schedules of the binder removal process. Addition of Polyvinyl butyral(PVB) binder promoted abnormal grain growth especially in incompletely debinded regions. Residual carbon appears to change the grain shape from comer-rounded to faceted and enhance abnormal grain growth.

• 한국분말재료학회지
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• 제20권1호
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• pp.1-6
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• 2013

The key concept of nanopowder agglomerate sintering (NAS) is to enhance material transport by controlling the powder interface volume of nanopowder agglomerates. Using this concept, we developed a new approach to full density processing for the fabrication of pure iron nanomaterial using Fe nanopowder agglomerates from oxide powders. Full density processing of pure iron nanopowders was introduced in which the powder interface volume is manipulated in order to control the densification process and its corresponding microstructures. The full density sintering behavior of Fe nanopowders optimally size-controlled by wet-milling treatment was discussed in terms of densification process and microstructures.