• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.599-600
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• 2006

This paper described the state of art of porous metal materials, the typical manufacturing technologies and performances of sintered metal porous materials, with emphasis on the recent research achievements of CISRI in development of porous metal materials. High performance porous metal materials, such as metallic membrane, sub-micron asymmetric composite porous metal, large dimensional and structure complicated porous metal aeration cones and tube, metallic catalytic filter elements, lotus-type porous materials, etc, have been developed. Their applications in energy industry, petrochemical industry, clean coal process and other industrial fields were introduced and discussed.

• Current Photovoltaic Research
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• 제2권3호
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• pp.115-119
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• 2014

$Cu(In,Ga)Se_2$ (CIGS) thin films have been used as a light absorbing layer in high-efficiency solar cells. In order to improve the quality of the CIGS thin film, often selenization step is applied. Especially when the thin film was formed by non-vacuum powder process, selenization can help to induce grain growth of powder and densification of the thin film. However, selenization is not trivial. It requires either the use of toxic gas, $H_2Se$, or expensive equipment which raises the overall manufacturing cost. Herein, we would like to deliver a new, simple method for selenization. In this method, instead of using a costly two-zone furnace, use of a regular tube furnace is required and selenium is supplied by a mixture of selenium and ceramic powder such as alumina. By adjusting the ratio of selenium vs. alumina powder, selenium vaporization can be carefully controlled. Under the optimized condition, steady supply of selenium vapor was possible which was evidently shown by large grain growth of CIGS within a thin powder layer.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.273-276
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• 2003

High-temperature superconduction materials(Bi2223) possess electrical/electronic and magnetic properties. Because high-temperature superconduction materials is a ceramic powder, that can not be produced singlehandedly. So Ag sheathed Bi-2223 wire was produced by drawing process using powder-in-tube(PIT) method. This superconductor has many difficulties to produce. The main difficulty is that the mechanical properties of the ceramic powder are very different from those of the Ag sheath. Bi2223 high-temperature superconductivity have a single filament drawing process, and multi-filament drawing process. This study analysed multi-filament drawing process by FEM, a defects during multi-filament drawing was studied by FEM.

• 한국진공학회지
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• 제17권6호
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• pp.538-543
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• 2008

나노급 다이아몬드는 최근 폭발법이나 증착법에 의한 신공정으로 100 nm 이하의 분말형태의 제조가 가능하다. 나노급 다이아몬드의 소결을 이용하면 이상적인 연마기기의 제작이 가능하다. 이러한 나노급 다이아몬드의 소결 공정에서 생기는 비이상적인 나노결정의 결정립성장과 다이아몬드 결합장애를 방지하기 위해서 나노급 무기물을 균일하게 코팅하는 공정개발이 필요하다. 본 연구에서는 나노급 다이아몬드의 소결 특성을 향상시키기 위해서 ALD(atomic layer deposition)을 이용하여 진공에서 $20{\sim}30\;nm$ 두께의 ZnO 박막을 코팅해 보았다. 나노급 다이아몬드 분말 전면에 경제적으로 ZnO ALD를 위해서 기존의 기계적 진동효과 또는 전용 fluidized bed reactor를 대치하여 새로이 20 mm 석영튜브 안에 다이아몬드 분말을 넣고 다공성 유리필터로 막은 후 펄스와 퍼지 공정시의 압력에 의한 다이아몬드의 부유를 이용한 변형된 fluidized bed 공정을 채용하였다. 다공성 유리필터로 양쪽이 막힌 석영튜브 안에 전구체 DEZn (diethylzinc : $C_4H_{10}Zn$)와 반응기체 $H_2O$를 사용하여 ZnO 박막을 캐니스터 온도 $10^{\circ}C$에서 원자층증착하였다. 공정 순서 및 반응물질 주입 시간은 DEZn pulse-0.1초, DEZn purge-20초, $H_2O$ pulse-0.1초, $H_2O$ purge-40초와 같이 설정하였으며, 이 네 단계를 1 cycle로 정의하여 100 cycle 반복 실시하였다. 다이아몬드 분말과 ZnO 박막이 증착된 다이아몬드 분말의 미세구조를 확인하기 위하여 투과전자현미경 (transmission electron microscope)을 이용하였다. TEM 측정결과, ALD 증착 전 나노급 다이아몬드 분말의 직경이 약 $70{\sim}120\;nm$이었고 사면체, 육면체 등의 다양한 형태를 보임을 확인하였다. ZnO 박막이 ALD코팅된 다이아몬드 분말의 직경은 약 $90{\sim}150\;nm$이었고, 다이아몬드 분말과 ZnO의 명암차이에 의해 약 $20{\sim}30\;nm$ 두께의 균일한 ZnO 박막이 다각형 형태의 다이아몬드 파우더 표면에 성공적으로 증착되었음을 확인하였다.

• 한국진공학회지
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• 제22권2호
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• pp.66-78
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• 2013

80 kW RF 플라즈마 토치 시스템을 개발하기 위하여, 토치 시스템에 대한 온도, 유체 거동 분석 등의 보다 많은 정보의 추출을 위하여 3차원 시뮬레이션을 진행했다. 파우더 주입관 위치, 입력 전류 변화에 따른 플라즈마 생성 특성, 세라믹 원통관 길이에 따른 플라즈마 방전 특성, 및 공정가스 유량에 따른 플라즈마 온도특성 등을 시뮬레이션 했다. 시뮬레이션을 통해 설계 제작된 RF 열 플라즈마 토치의 경우, 최대 89.3 kW까지 파워 인가가 측정되었다. 개발된 80 kW급 RF 열 플라즈마 토치 시스템의 양산성 평가로 Si 나노분말을 제조하고 특성을 고찰하였다. Si 나노분말의 생산량이 평균 539 g/hr의 양산 수준과 71.6%의 높은 수율을 달성했으며, 제조된 나노 분말은 $D_{99}/D_{50}$가 1.98의 좋은 입경 균일 분포도를 나타내었다.

• 한국분말재료학회지
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• 제22권4호
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• pp.240-246
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• 2015

Anodic aluminum oxide (AAO) has been widely used for the development and fabrication of nano-powder with various morphologies such as particle, wire, rod, and tube. So far, many researchers have reported about shape control and fabrication of AAO films. However, they have reported on the shape control with different diameter and length of anodic aluminum oxide mainly. We present a combined mild-hard (or hard-mild) anodization to prepare shape-controlled AAO films. Two main parameters which are combination mild-hard (or hard-mild) anodization and run-time of voltage control are applied in this work. The voltages of mild and hard anodization are respectively 40 and 80 V. Anodization was conducted on the aluminum sheet in 0.3 mole oxalic acid at $4^{\circ}C$. AAO films with morphologies of varying interpore distance, branch-shaped pore, diameter-modulated pore and long funnel-shaped pore were fabricated. Those shapes will be able to apply to fabricate novel nano-materials with potential application which is especially a support to prevent volume expansion of inserted active materials, such as metal silicon or tin powder, in lithium ion battery. The silicon powder electrode using an AAO as a support shows outstanding cycle performance as 1003 mAh/g up to 200 cycles.

• 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.

• 한국재료학회지
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• 제17권11호
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• pp.587-592
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• 2007

Al-42wt%Nb powder was prepared by high-energy mechanical milling(HEMM). The particle size, phase transformation and microstructure of the as-milled powder were investigated by particle size distribution (PSD) analyzer, scanning electron microscopy (SEM), X-ray diffractometery (XRD), transmission electron microscopy (TEM)and differential thermal analysis (DTA). The milled powders were heated to a sintering temperature at 1000C with under vaccum with vaccum tube furnace. Microstructural examination of sintered Ti-42wt%Nb alloy using 4h-milled powder showed Ti-rich phases (${\alpha}$-Ti) which are fine and homogeneously distributed in the matrix (Nb-rich phase: ${\beta}$-Ti). The sintered Ti-42wt%Nb alloy with milled powder showed higher hardness. The microstructure of the as quenched specimens fabricated by sintering using mixed and milled powder almost are same, but the hardness of as quenched specimen fabricated by using mixed powder increased due to solution hardening of Nb in Ti matrix. The aging effect of these specimens on microstructural change and hardening is not prominent.

• 한국자동차공학회논문집
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• 제12권6호
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• pp.151-157
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• 2004

In this paper deals with behavior of the magnetic abrasive using sludge on polishing characteristics in a new internal finishing of seamless stainless steel tube applying magnetic abrasive polishing. The magnetic abrasive using sludge-abrasive grain WA and GC used to resin bond fabricated low temperature. And sludge of magnetic abrasive powder fabricated that sludge was crused into 200 mesh. The previous research have made an experiment in the static state the movement of magnetic abrasive grain is nevertheless in the dynamic state. In this paper, We could have investigated into the changes of the movement of magnetic abrasive grain. In reference to this result, we could have made the experiment which is set under the condition of the magnetic flux density, polishing velocity according to the form of magnetic brush.

• 한국세라믹학회지
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• 제33권4호
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• pp.471-477
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• 1996

During Bi(Pb)-Sr-Ca-Cu-O superconductor wire fabrication the effect of the initial packing density on the final characteristics of superconductor wire was systematically studied. To increase the powder packing density with uniform distribution of superconducting core a billet insertion method processed by CIP was applied instead of the commonly used vibration and ramming method of powder insertion into silver sheath. Compared with the vibration and ramming method the billent insertion technique processed by CIP cause the 30% incre-specimen with 130${\mu}{\textrm}{m}$(core thickness : 45 ${\mu}{\textrm}{m}$)and 5.24 mm width processed at 84$0^{\circ}C$for 200hrs. shows specimen with 130${\mu}{\textrm}{m}$ (core thickness ; 45${\mu}{\textrm}{m}$)and 5.24 mm width processed at 84$0^{\circ}C$ for 200 hrs. shows maximum 34A for Ic and 16, 700 A/cm2 for Ic measured at 77K and 0T. Also the sample rolled 3 times shows maximum 7, 2A for Ic and 11, 000 A/cm2 for 77K and 0T. Based on X-ray experimental results the formation of Bi-2223 and texture were significantly well developed at the interface between the superconducting core and silver sheath as compared with those of the interior area of superconducting core.