• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.1
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• pp.49-59
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• 2001

Functionally gradient materials(FGMs) generally consist of different material components, such as ceramics and metals. Continuous changes in their composition, microstructure, porositys, and so on result in gradients in the properties of FGMs. In this study AlN/Al-$Al_3$Ti FGM cubes were fabricated by the powder metallurgical process, and the characteristics of the FGMs were investigated. Powders of Mg and Ti mixed with Al in different ratios or the stack of the mixed powders having a stepwisely controlled compositional gradient from one plane to another were formed in a steel mold. The more the composition of Mg and sintering temperature are increased, the more the amount of AlN is formed. AlN and $Al_3$Ti distributed with continuously gradient composition were detected by XRD analysis and also revealed in optical microstructures, and microhardness tests.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.245-248
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• 2003

저온동시소성 세라믹으로 제작된 모듈을 고주파 대역에 적용할 경우 dimension의 오차는 모듈 특성의 오차를 유발시킨다. Constrained sintering 기술은 XY 방향의 수축을 억제시킴으로써 세라믹 소결체의 dimensional tolerance를 향상시키기 위하여 개발된 기술이다. LTCC의 소성온도에서는 수축하지 않는 비소성층을 LTCC 적층체의 위 아래에 함께 적층시킴으로써 XY 방향의 수축은 기계적으로 억제되며, 두께 방향으로만 수축이 일어난다. 본 연구에서는 LTCC 기판을 constrained sintering 방법으로 소성하고, 그 특성값을 일반적인 소성방법으로 제작하였을 때와 비교하였다. 알루미나 테잎의 제조조건 빛 적층조건을 변화시켜 이에 따른 면수축 제어 특성의 변화를 고찰하였다. 실험결과 알루미나 테잎의 고형분 용량과 부착층의 두께가 면수축 제어를 위하여 고려되어야할 주요 인자임을 확인할 수 있었다.

• Journal of Powder Materials
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• v.12 no.5 s.52
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• pp.345-350
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• 2005

In this study the nanostructured ${\alpha}-Al_{2}O_3$ ceramics have been fabricated by the combined application of magnetic pulsed compaction (MPC) and subsequent spark plasma sintering (SPS), and their density and hardness properties were investigated. The ${\alpha}-Al_{2}O_3$ prepared by the combined processes showed an increase by $8.4\%$ in density, approaching the value close to the true density, and an enhancement by $210\~400\;Hv$ in hardness, compared to those fabricated by MPC or static compaction method followed by sintering treatment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.3 no.2
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• pp.126-130
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• 2002

This paper presents the basic concept of new solid freeform fabrication system using rapid prototyping method. The system could fabricate an arbitrary ceramic form by laser cutting, transferring, stacking, and sintering of each slide. The system consists mainly of laser apparatus. X-Y table, a slide transferring system, and electric oven. The system could fabricate an object that has smooth surface with comparatively short period of time. The system is effective in terms of its direct fabrication capability without second mechanical process. The fabricated shape could directly be used as part of a whole assembly and therefore its method could be applied to various application areas.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.288-289
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• 2006

We studied the effect of sol-gel processing and sintering temperature on the microwave properties of $MgCo_2(VO_4)_2$ system(MCV) which is applicable to LTCC(low-temperature cofired ceramics). The MCV was synthesized by sol-gel process using solution that contains precursor molecules for Mg, Co, and V. SEM analysis shows that the average particle size is ${\sim}1{\mu}m$ and size distribution is very uniform compared to the one prepared by conventional solid-state reaction process. Highly dense samples were obtained at the sintering temperature range of $750^{\circ}C{\sim}930^{\circ}C$. The maximum $Q{\times}f_0$ value of 55,700GHz, dielectric constant(${\varepsilon}_r$) of 10.41 and temperature coefficient(${\tau}_f$) of $-85ppm/^{\circ}C$ was obtained at the sintering temperature of $930^{\circ}C$. The superior microwave properties of sol-gel processed MCV relative to conventional solid-state reaction processed one is remarkable especially at lower sintering temperatures such as $750^{\circ}C$ and $800^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.204-204
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• 2010

본 연구에서는 RF 마그네트론 스퍼터링법으로 RF파워의 변화에 따라 증착한 a-IGZO 박막의 n-형 반도체 활용 특성과 관련된 구조적, 광학적, 전기적 특성 변화를 연구하였다. 기판은 corning 1737 유리 기판을 사용하였고, 유기 클리닝 후 즉시 챔버 내부에 장착되었다. IGZO 타겟은 $In_2O_3$, $Ga_2O_3$, ZnO 분말을 각각 1:1:2mol% 조성비로 혼합하여 소결한 타겟을 사용하였다. 박막 증착 조건으로 초기 압력 $2.0{\times}10^{-6}\;Torr$, 증착압력 $2.0{\times}10^{-2}\;Torr$, 반응가스 Ar 50sccm, 증착온도는 실온으로 고정하였으며, 공정변수로 RF 파워를 25W, 50W, 75W, 100W로 변화시키며 시편을 제작하였다. AFM 분석결과 RF 파워가 증가함에 따라 거칠기가 증가하였으며, XRD 분석결과 Bragg's 법칙을 만족하는 피크가 나타나지 않는 비정질 구조임을 확인할 수 있었다. Hall측정 결과 100W에서 $10cm^2/V^{-1}s^{-1}$이상의 우수한 이동도 특성을 보였으며, 가시광선 투과 특성은 RF 파워가 50W일때 85% 이상으로 양호하였다. XPS 분석결과 RF 파워가 증가할수록 밴드갭이 감소하는 현상은 박막내 산소 이탈 증가현상에 의한 산소 공공의 밀도가 높아지는 것과 연관성이 있음을 확인하였다.

• Korean Journal of Materials Research
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• v.26 no.2
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• pp.95-99
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• 2016

In this study, 5 um sized $ZrSiO_4$ was ground to 1.9 um, 0.3 um, and 0.1 um sized powders by wet high energy milling process, and the sintering characteristics were observed. Pure $ZrSiO_4$ itself can-not be sintered to these levels of theoretical density, but it was possible to sinter $ZrSiO_4$ powder of nano-scale size of, -0.1 um to the theoretical density and to lower the sintering temperature for full density. Also, the decomposition of $ZrSiO_4$ with a size in the micron range resulted in the formation of monoclinic $ZrO_2$; however, in the nano sized range, the decomposition resulted in the tetragonal phase of $ZrO_2$. So, it was possible to improve the sintering characteristics of nano-sized $ZrSiO_4$ powders.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.7
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• pp.747-754
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• 2004

Thermo-fluid characteristics in coke oven, sintering machine and blast furnace in iron-making facility are key processes related to the quality and productivity of the pig iron. Solid material in the processes usually forms a bed in a gas flow. For simulation of the processes by mathematical model, the solid beds are idealized to be a continuum and a reacting solid flow in the gas flow. Governing equations in the form of partial differential equations for the solid material can be constructed based on this assumption. Iron ore sintering bed is simulated and limited amount of parametric study have been performed. The results have a good agreement with the experimental results or physical phenomena, which shows the validity and applicability of the model.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.210-213
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• 2006

나노입자를 이용하여 치밀한 $Cu(In,\;Ga)Se_2$ 태양전지용 광흡수층을 제조하기 위해 먼저, 콜로이달 방법으로 합성된 20nm이하의 CIGS 나노입자를 저가의 스프레이 법을 이용하여 CIGS 막을 제조하였다. 제조된 CIGS막을 two-zone RTP (rapid temperature Process) 방법으로 Se 분위기 안에서 열처리를 행하였다. 입자의 치밀화를 위해 기판의 온도, Se 증발온도와 수송가스의 유량을 조절하여 CIGS 입자성장을 행하였다. 그러나, Se의 증발온도가 높을수록 CIGS와 MO 박막 사이에서 $MoSe_2$ 층이 형성되었다. 형성된 $MoSe_2$층의 부피 팽창으로 인해 하부의 유리기판과 Mo층 사이에서 peeling off 현상이 발생했다. 이러한 Peeling off현상을 억제하면서 CIGS 나노입자 성장을 하기 위해, Se 공급을 빨리 할 수 있도록 Se의 증기압을 높였으며, 최적조건에서 급속 열처리 공정을 통해 CIGS 나노입자 성장과 치밀화를 위한 소결거동을 관찰하였다.

• Resources Recycling
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• v.4 no.1
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• pp.60-68
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• 1995

Iron-bearing dust which stems from steelworks were pelletized and bonded with portland cement in order to attempt to use for blast iurnace burdens. The characterist~cs of cold bonded dust pellet were investigated. It was found that the compression strength of cold bonded pellet contaning portland cement of 10 wt.% reached above 150kg/p by proper curing treatment. Direcl contad of carbon with iron oxides seems to greately enhance a reduction reaction and herewxth increased chances to lorn pores at high temperature environment. Tumbler strength, RDI, and swelling of cold bonded pellet were similiar to and/or better than those of iron ore sinter and fired pellet.