• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1078-1079
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• 2006

The paper presents the possibilities of obtaining new composite materials based on sintered porous ceramics with particles and fibre of $Al_2O_3$ infiltrated by aluminum alloy. The EN AC - AlSi12 alloy features the matrix material, whereas the RF50AX-301 preform, of Saffil Automotive, was used as the reinforcement. Examinations of ceramics preforms permeability were made. Metallographic examination of composite materials made on light microscope and in scanning electron microscope show that aluminum alloys fill micropores in the matrix. New composite materials show twice higher value of hardness in comparison with matrix. Results indicate that it is possible to infiltrate porous ceramic with liquid aluminum alloy to obtain new composite materials were advantageous properties of each component are connected.

• 한국주조공학회지
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• 제19권6호
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• pp.493-500
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• 1999

Squeeze casting was used for fabricating a light metal base composite having high strength and wearresistance. Reactive sintering was used to prepare the preform of Squeeze casting. To utilize Fe-Al intermetallic compounds and SiC particle as a reinforcement, there needs to prepare Fe-Al mixed powder at 50, 60, 70at.%Al, and add SiC powder to the above mixture at 4, 7, 16, 24wt.%. The prepared mixture with SiC was reactive sintered in a tube furnace at $660^{\circ}C$ to get a porous hybrid preform of intermetallic compound and SiC. The preform prepared above was placed in a metal mold, preheated at $660^{\circ}C$ AC4C matrix was injected into the mold with the temperature of the melt at $610^{\circ}C$ After these processes, 66MPa was applied to the mold for 5 minute to finish the whole procedure. The maximum reaction temperature was increased with the increased Al amount, but decreased with the increased SiC amount. The density of the preform was decreased with SiC amount increase in the compacts due to swelling of the preform. An optical microscope was applied to observe the micro structure and the dispersion of the reinforcements. To analyze phases, We utilized XRD, EDS. Hardness test were chosen to get the information of mechanical properties. There were no significant changes in micro structure between the composite and preform. However, it was shown that uniform dispersion of the reinforcers and complete infiltration of the melt into the preform were achieved through the procedure of the squeeze casting. It was observed that the hardness of the composite is decreased with increased SiC amount, resulting from the volumetric expansion of the preform.

• 한국토양비료학회지
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• 제42권Spc호
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• pp.40-44
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• 2009

이 연구는 Rock-dust로 채워진 농업 용지(Technosol)의 환경에서 물이 보이는 침투성과 삼투성의 특정을 파악하고자 수행되었다. 이 실험은 A와 B 두 장소에서 이루어졌으며 피실험지의 토양층은 각각 4가지 층으로 분류되었다. 모든 토양층의 토성은 미사질 양토로 분석되었으며 장소 A의 가장 낮은 층에서만은 양질사토였다. 두 토양에서, 각 토양층에 대한 용적밀도는 $1.49g{\cdot}cm^{-3}$을 대체로 상회하였으며, 이는 통상적인 medium textured mineral soil의 $1.25g{\cdot}cm^{-3}$을 크게 웃도는 값이다. 경운 직후 측정된 장소 A의 표토는 이보다 낮았다. 두 토양 표면에서의 $P_2O_5$의 집적은 각각 1962 (A), 1613 (B)$mg{\cdot}kg^{-1}$이었다. 이러한 집적은 3.2~6.5번에 걸쳐서 $300{\sim}500mg{\cdot}kg^{-1}$만큼 작물 생장에 알맞은 규모로 이루어졌다. 두 토양 표변에서의 Infiltration rate는 3.54 (A), 2.85 (B)$cm{\cdot}hr^{-1}$이었으나 각 토양층에 대한 percolation rate는 0.3 이하 (A), 0.003 이하 (B)$cm{\cdot}hr^{-1}$였다. 이러한 결과들은 표토가 동의 작용을 받은 반면 심토는 암분의 농업용지 형성 과정에서 생겨난 구조적인 문제인 바위 부스러기의 응집과 농업기계에 대한 다짐현상으로 인한 것임을 의미한다고 여겨진다.

• 대한한방내과학회지
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• 제29권2호
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• pp.456-468
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• 2008

Objective : The purpose of this study was to investigate the effects of Gamisagunja-tang(GS) on the airway hyper-reactivity (AHR), cytokine production and T cell activation during the ovalbumin (OVA)-induced allergic asthma in mice. Materials and Methods : BALB/c mice were sensitized and challenged with 100 mg of OVA and 1 mg of aluminum potassium sulfate intraperitoneally on days 1 and 7. On day 14, mice were challenged on 3 consecutive days with 5% OVA. AHR and bronchoalveolar fluid (BALF), total inflammatory cell count and the production of cytokines were measured. Results : GS significantly suppressed the infiltration of inflammatory cells in the lung tissue and AHR. GS significantly down regulated the production of IL-4, IL-5 and increases of $INF-{\gamma}$ in BALF. GS reduced the population of eosinophils from lung and spleen in OVA-induced allergic asthma. GS reduced the population of $CD4^{+}$ $CD69^{+}$ $CD25^{-}$ T cells in OVA-induced allergic asthma Conclusion : These results suggest that GS may inhibit the production of IL-4, IL-5 and infiltration of eosinophils and be beneficial oriental medicine for allergic asthma.

• 한국토양비료학회지
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• 제17권1호
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• pp.18-23
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• 1984

화동미사질식양토(華東微砂質埴壤土)의 침투속도(浸透速度)에 대한 공간변이성(空間變異性)이 지질통계학적(地質統計學的) 개념(槪念)인 지역변수이론(地域變數理論)으로 기술(記述)하였고, 구조분석(構造分析)에서 얻어진 정보(情報)를 이용(利用)하여 최양선형불편추정치(最量線型不偏推定値)(BLUE)인 Kriging값을 계산(計算)하였는 바 그 결과(結果)는 다음과 같다. 1. 최소(最少)의 분산(分散)으로 Kriging같이 추정(推定)되었다. 2. 설정(設定)된 선형(線型)의 평균(平均) Variogram은 Kriging값을 추정(推定)하는 데 적합(適合)하다고 판단(判斷)되었다. 3. 표본추출지점(標本抽出地點)에서의 Kriging값과 실관측치(實觀測値)의 상관(相關)은 고도(高度)의 유의성(有意性)을 나타내었다.

• Carbon letters
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• 제11권4호
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• pp.293-297
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• 2010

To investigate new potential application of a clay material for C/C composites, illite added C/C composites were prepared with various illite contents. The improvement of filler effect by illite size reduction was also investigated using wet ballmilling by evaluating illite/phenolic resin infiltration using bulk density and porosity measurements, chemical structural changes of the composites using XRD, and thermal oxidation stability in air of the composites using TGA. The size reduction of illite resulted in narrower particle size distribution and improved illite infiltration into carbon preform. And the resultant C/C composites prepared with illite had even more improved thermal oxidation stability in air, showing more increased IDTs up to $100^{\circ}C$, compared to those of the C/C composites with pristine illite, due to the SiC formation through carbothermal reduction between illite and carbon materials. The illite induced delay in oxidation of the illite-C/C composites was also observed and the delayed oxidation behavior was attributed to the layered structure of illite, which improved illite/phenol resin infiltration. Therefore, the potential use of illite as filler to improve oxidation stability of C/C composite can be promising. And the size reduction of illite can improve its effect on the desired properties of illite-C/C composites even more.

• 한국주조공학회지
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• 제13권5호
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• pp.441-449
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• 1993

SiC particulate reinforced magnesium matrix composites were fabricated by melt stirring method. The effet of several factors on mechanical properties and the efficiency of melt stirring method from the viewpoint of these properties were investigated. The tensile strength increased and the elongation decreased with decrease of the particle size or the increase of the paticulate volume fraction for pure magnesium matrix and Mg-5%Zn alloy matrix composites. A longer stirring time improved the tensile strength of these composites. The tensile strength of Mg-5%Ca alloy matrix composites which shows no uniform paticulate distribution was a little lower than that of matrix alloy. Rapid solidification rate is preferred for the improved tensile strength of these composites. The pure magnesium matrix and Mg-5%Zn alloy matrix composites have tensile strength of about 400MPa. This value agrees with the tensile strength of some magnesium matrix composites fabricated by liquid infiltration method or powder metallurgy method at the same volume fraction of reinforcements of whisker or particle. Therefore, the melt stirring method which has the advantages of simple process is considered to be efficient in fabricating magnesium matrix composites.

• Composites Research
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• 제36권3호
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• pp.180-185
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• 2023

본 논문에서는 스프레딩된 SiC 섬유를 적용해 SiC_f/SiC를 제조하였을 경우, 섬유의 분산도가 복합소재의 내부구조 및 기계적 강도에 어떠한 영향을 주는지를 연구하였다. Spread SiC 섬유를 적용한 시편의 섬유 체적비는 non-spread 시편 대비 9%p 감소하였으며, 수지 슬러리가 섬유 사이로 더 원활히 함침되어 기지내 기공도 거의 발견되지 않았다. 각 시편의 섬유 분산도를 비교하기 위해, 복합소재 내 섬유간 이격거리를 수치화하고 평가하는 방법을 제안하였다. 그 결과 spread 시편의 섬유간 중심거리는 non-spread 시편 대비 2.23 ㎛ 증가하였으며, 섬유 표면 사이 거리는 42.6%로 대폭 증가하였다. 3점 굽힘시험을 통해 spread 시편의 굽힘강도가 non-spread 시편 대비 49.3% 가량 높으며, 시험 데이터의 편차도 더 균일함을 확인하였다. 따라서 복합소재 기지내 SiC 섬유의 분산도 향상이 SiC_f/SiC의 균일한 기지상 치밀화와 기계적 강도 증가에 매우 큰 영향을 미친다는 점을 알 수 있다.

• 한국세라믹학회지
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• 제45권9호
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• pp.561-566
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• 2008

Carbon fiber fabric-silicon carbide composites were fabricated by liquid silicon infiltration (LSI) process. The porous two-dimensional carbon fiber fabric performs were prepared by 13 plies of 2D-plain-weave fabric in a three laminating method, [0/90], [${\pm}45$], [$0/90/{\pm}45$] lay-up, respectively. Before laminating, a thin pyrolytic carbon (PyC) layer deposited on the surface of 2D-plain weave fabric sheets as interfacial layer with $C_3H_8$ and $N_2$ gas at $900^{\circ}C$. A densification of the preforms for $C_f-Si-SiC$ matrix composite was achieved according to the LSI process at $1650^{\circ}C$ for 30 min. in vacuum atmosphere. The bending strength of the each composite were measured and the microstructural consideration was performed by a FE-SEM.

• 한국결정성장학회지
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• 제6권1호
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• pp.73-87
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• 1996

새로 개발된 분말침투 및 연속 다중함침법에 의해 제조된 세라믹 섬유 복합체의 기 계적 물성을 3점 곡강도 빛 인장 시험을 통하여 평가하였다. 정확한 물성 측정을 위하여 strain g gauge 빛 acoustic emission 측정 장비가 사용되였다. 실험 시편은 $Al_20_3$직포$Al_20_3$와 SiC직포/SiC를 기본 재료로 하고 있으며, 일방향으로 배열왼 SiC 섬유(Textron SCS - 6)/SiC 복합체를 비교 목적으로 제작 시험하였다. 이론 밀도의 약 73%인 SiC 직포/SiC 복합체의 최대곡강도는 300 MPa이고, 기지내 균열이 처음 발생하는 응력은 77 MPa였다. 인장강도는 곡강도의 1/3 정 도의 낮은 값을 나타내였고, 인장 시험중의 첫번째 기지 균열 응력 또한 곡강도 시험에서 얻은 값보다는 상당히 낮은 값을 보여주였다. 곡강도 물성에 비교하여 상대적으로 낮은 인장물성은 WeibuH 통계 처리 방법에 의하여 응력을 받고 있는 부피의 차로 정량적으로 해석하였다. 해석 결과, 직포가 충으로 배열된 복합체의 최대 인장강도는 응력을 받는 섬유의 길이에 의존하며, 기지내 균열이 생기는 첫번째 응력은 응력을 받는 부피에 의해 결정됨을 보여주었다. SiC 휘스 커를 기지에 보장함으로써 복합체의 기지파괴 strain을 향상시키는 이유로, 첫번째 기지 균일 응력이 증가됨을 확인하였다.