• Title/Summary/Keyword: Al-graphite composite

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Corrosion Behavior of the parts of Carbon Steel Bolted GECM(Graphite Epoxy Composite Material)/Al plates (탄소강 볼트 체결된 GECM(Graphite Epoxy Composite Material)/Al 판재의 구성 부재의 부식 거동)

  • Kim, Youngsik;Park, Sujin;Yoo, Youngran
    • Corrosion Science and Technology
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    • v.11 no.6
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    • pp.232-241
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    • 2012
  • This work focused on corrosion of carbon steel bolted GECM/Al parts in tap water and NaCl solutions. In tap water and NaCl solutions, open circuit potential of GECM and its potentials in a series of carbon steel bolt>Ti>Al became active. Regardless of test materials, open circuit potentials in tap water were noble, and increasing NaCl concentration, its potentials became active. Immersion test of single specimen showed that no corrosion occur in Ti and GECM. In tap water, carbon steel bolt didn't show red corrosion product and in chloride solutions, corrosion rate in 1% NaCl solution was greater than its rate in 3.5% NaCl solution and red corrosion product in 1% NaCl solution was earlier observed than that in 3.5% NaCl solution. It seems that this behavior would be related to zinc-coatings on the surface of carbon stee l bolt. On the other hand, aluminium was corroded in tap water and chloride solutions. Corrosion of aluminium in tap water was due to the presence of chloride ion in tap water by sterilizing process.

Aluminum Effect as Additive Material in Expanded Graphite/Sand Composite for High Thermal Conductivity

  • Areerob, Yonrapach;Nguyen, Dinh Cung Tien;Dowla, Biswas Md Rokon;Ali, Asghar;Oh, Won-Chun
    • Korean Journal of Materials Research
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    • v.27 no.8
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    • pp.422-430
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    • 2017
  • Al/expanded graphite was successfully synthesized through a facile method including ultrasonic and heat treatment. In the well-designed three dimensional structure, expanded graphite(EG) works as a conductive matrix to support coated Al particles. The effects of the fabrication parameters on the microstructures and thermal conductivities of these composites were investigated. As a result, it was found that composites with graphite volume fraction of 17.4-69.4 % sintered at $600^{\circ}C$/45MPa exhibit in-plane thermal conductivities of 380-940 W/mK, over 90 % of the predictions by rule of mixture. According to the non-destructive analysis results, the synergistic enhancement was caused by the formation of efficient thermally conductive pathways due to the hybrid of the differently sized EG. The structure integrates the advantages of expanded graphite as a conductive support, preserving the electrode activity and integrity and improving the electrochemical performance.

High temperature and damping properties of squeeze cast Mg hybrid Metal Matrix Composites. (하이브리드 Mg 복합재료의 진동 감쇠능 및 고온 특성평가)

  • 장재호;김봉룡;최일동;조경목;박익민
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2002.10a
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    • pp.143-146
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    • 2002
  • Mg alloy is the lightest material of structural materials and is noticed for lightweight automotive parts because of excellent castability, superior ductility and damping capacity than Al alloy. But Mg Alloy is poor corrosion resistance and high temperature creep properties. In this study, Mg Matrix Composites were fabricated by squeeze casting method to improve high temperature creep properties and damping capacity. Hybrid Mg composites reinforced with Alborex, graphite particle, and SiCp was improved creep properties and damping capacity compared with Mg alloy. Compared to the length ($9\mu\textrm{m}, 27\mu\textrm{m}, 45\mu\textrm{m} etc.$), Hybrid Mg composites reinforced with SiCp, one of the most superior of the length and Alborex were more superior than those reinforced with graphite particle and Alborex in mechanical properties, creep characteristics, and damping capacity, etc.

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Manufacturing Functional Nano-Composites by Using Field-Aided Micro-Tailoring Manipulation (Field-Aided Micro-Tailoring에 의한 기능성 나노복합재 제조)

  • Cho, Hee-Keun;Rhee, Juhun;Sim, Eun-Sup
    • Composites Research
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    • v.25 no.6
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    • pp.178-185
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    • 2012
  • One of a unique technique in manipulating a multifunctional composite is demonstrated in this study. An electric field is applied to a liquid suspension in order to align the inclusions along with the direction electric field. This is called FAiMTa(Field Aided Micro Tailoring). It makes orthotropic polymer composites by arranging the micro and/or nano size particle inclusions in chain-line formation. Several kinds of particles such as $Al_2O_3$, graphite, CNT(Carbon Nano Tube), W(Tungsten) are tested to verify the effectiveness of the FAiMTa. The particles redistributed in an epoxy suspension and their coupons show that mechanical and thermal properties of orthotropic and random composites containing those particles depend on the trend of particles' alignment. The micro-images of the functional composite from FAiMTa have been captures and their physical properties demonstrate their wide-range and state-of-the-art application for advanced multifunctional composites.

The Effect of Electrochemical Performance and Safety by Surface Modification of Anode Materials for Lithium Secondary Battery (리튬 이차 전지를 위한 음극 활물질 표면의 코팅으로 인한 전기화학적 특성 및 안전성)

  • Heo, Yoon-Jeong;Ko, Sung-Tae
    • Journal of the Korean Electrochemical Society
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    • v.12 no.3
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    • pp.239-244
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    • 2009
  • This paper aims to report the effect of surface treatment on graphite and its effect on the improvement of $Al_2O_3$ and $nano-Li_4Ti_5O_{12}$. The structure and property of surface treatment on graphite were determined by scanning electron microscopy, transmission electron microscopy and electrochemical property and safety were determined by charge/discharge cycler, accelerating rate calorimeter. The composite with different metallic oxide exhibited the first efficiency of 82.5% and specific capacity of 350 mAh/g. Although the composite showed same efficiency and specific capacity at first cycle, surface treatment on graphite by $nano-Li_4Ti_5O_{12}$ exhibited a higher charge/discharge rate, cycle life and thermal stability.

The Effects of Dielectric Coatings on Electron Emission from Tungsten

  • Al-Qudah, Ala'a M.;Alnawasreh, Shady S.;Madanat, Mazen A.;Trzaska, Oliwia;Matykiewicz, Danuta;Alrawshdeh, Saad S.;Hagmann, Mark J.;Mousa, Marwan S.
    • Applied Microscopy
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    • v.47 no.1
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    • pp.36-42
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    • 2017
  • Field electron emission measurements were performed on dielectric-coated tungsten emitters, with apex radii in the nanometer and micrometer range, which were prepared by electrochemical etching in NaOH solution. Measurements were performed in a field electron microscopy (FEM) with a base pressure <$10^{-6}$ Pascal ($10^{-8}$ mbar). Four different types of dielectric were used, namely: (1) Clark Electromedical Instruments epoxylite resin, (2) Epidian 6 produced by Ciech Sarzyna S. A., (3) a Radionox solution of colloidal graphite; and (4) Molyslip 2001 E compound ($MoS_2$ and MoS). Current-voltage measurements and FEM images were used to investigate the characteristics of these composite emitters, and to assess how the different types of dielectric coating affect the suitability of the composite emitter as a potential electron source.

Effect of Area Ratio on Galvanic Corrosion Between Metallic Materials and GECM in 3.5% NaCl Solution (3.5% NaCl 수용액 중에서의 금속과 GECM의 갈바닉 부식에 미치는 면적비의 영향)

  • Kim, Y.S.;Lim, H.K.;Sohn, Y.I.;Yoo, Y.R.;Chang, H.Y.
    • Corrosion Science and Technology
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    • v.9 no.1
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    • pp.39-47
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    • 2010
  • Galvanic coupling between GECM(graphite epoxy composite material) and metallic materials can facilitate corrosion of metals and alloys because GECM is noble and electrically conductive. Galvanic corrosion is affected by many factors including metallic materials, area ratio, surface condition, and corrosivity. This work aims to evaluate the effect of area ratio on galvanic corrosion between GECM and several metals. In the case of glavanic coupling of carbon steel and Al to GECM, corrosion rate increased with increasing area ratio. Corrosion rate of sensitized STS 316S stainless steel decreased a little at an area ratio 1:1 but increased at an area ratio 30:1. It is considered to be due to that area ratio affects galvanic corrosion more in less corrosion resistant alloys. However, in case of STS 316 and Ti, galvanic coupling reduces corrosion rate by the formation of passive film.

Influences of Anodizing and Thermal Oxidation on the Galvanic Corrosion between Aluminium and Titanium and GECM (GECM과 Al 및 Ti 간의 갈바닉 부식에 미치는 양극산화 및 열산화의 영향)

  • Kim, Young-Sik;Lim, Hyun-Kwon;Sohn, Young-Il;Yoo, Young-Ran;Chang, Hyun-Young
    • Korean Journal of Metals and Materials
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    • v.48 no.6
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    • pp.514-522
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    • 2010
  • Graphite epoxy composite material (GECM) shows high specific strength and its application in the aerospace industry is gradually increasing. However, its application would induce galvanic corrosion between GECM and metallic materials. This work focused on the effects of anodizing and thermal oxidation on galvanic corrosion in a 3.5% NaCl solution between GECM and aluminium and titanium. In the case of anodized aluminium, galvanic corrosion resistance to the GECM was greatly improved by the anodizing treatment regardless of area ratio. In the case of anodized titanium, the anodizing by a formation voltage of 50V increased corrosion resistance of titanium in galvanic tests. Thermal oxidation of titanium also improved corrosion resistance of Ti to GECM.

Evaluations of Si based ternary anode materials by using RF/DC magnetron sputtering for lithium ion batteries

  • Hwang, Chang-Muk;Park, Jong-Wan
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.08a
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    • pp.302-303
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    • 2010
  • Generally, the high energy lithium ion batteries depend intimately on the high capacity of electrode materials. For anode materials, the capacity of commercial graphite is unlike to increase much further due to its lower theoretical capacity of 372 mAhg-1. To improve upon graphite-based negative electrode materials for Li-ion rechargeable batteries, alternative anode materials with higher capacity are needed. Therefore, some metal anodes with high theoretic capacity, such as Si, Sn, Ge, Al, and Sb have been studied extensively. This work focuses on ternary Si-M1-M2 composite system, where M1 is Ge that alloys with Li, which has good cyclability and high specific capacity and M2 is Mo that does not alloy with Li. The Si shows the highest gravimetric capacity (up to 4000mAhg-1 for Li21Si5). Although Si is the most promising of the next generation anodes, it undergoes a large volume change during lithium insertion and extraction. It results in pulverization of the Si and loss of electrical contact between the Si and the current collector during the lithiation and delithiation. Thus, its capacity fades rapidly during cycling. Si thin film is more resistant to fracture than bulk Si because the film is firmly attached to the substrate. Thus, Si film could achieve good cycleability as well as high capacity. To improve the cycle performance of Si, Suzuki et al. prepared two components active (Si)-active(Sn, like Ge) elements film by vacuum deposition, where Sn particles dispersed homogeneously in the Si matrix. This film showed excellent rate capability than pure Si thin film. In this work, second element, Ge shows also high capacity (about 2500mAhg-1 for Li21Ge5) and has good cyclability although it undergoes a large volume change likewise Si. But only Ge does not use the anode due to its costs. Therefore, the electrode should be consisted of moderately Ge contents. Third element, Mo is an element that does not alloys with Li such as Co, Cr, Fe, Mn, Ni, V, Zr. In our previous research work, we have fabricated Si-Mo (active-inactive elements) composite negative electrodes by using RF/DC magnetron sputtering method. The electrodes showed excellent cycle characteristics. The Mo-silicide (inert matrix) dispersed homogeneously in the Si matrix and prevents the active material from aggregating. However, the thicker film than $3\;{\mu}m$ with high Mo contents showed poor cycling performance, which was attributed to the internal stress related to thickness. In order to deal with the large volume expansion of Si anode, great efforts were paid on material design. One of the effective ways is to find suitably three-elements (Si-Ge-Mo) contents. In this study, the Si based composites of 45~65 Si at.% and 23~43 Ge at.%, and 12~32 Mo at.% are evaluated the electrochemical characteristics and cycle performances as an anode. Results from six different compositions of Si-Ge-Mo are presented compared to only the Si and Ge negative electrodes.

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Thermal conductivity of acrylic composite films containing graphite and carbon nanotube (흑연과 탄소나노튜브를 함유한 아크릴 복합체 박막의 열전도도)

  • Kim, Jun-Yeong;Gang, Chan-Hyeong
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2016.11a
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    • pp.185-185
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    • 2016
  • 아크릴계 수지(resin)에 인조 흑연과 탄소나노튜브(carbon nanotube)를 1:1 비율로 혼합한 충전제(filler)와 용제(solvent) 및 기타 첨가제(additives)를 혼합하여 방열도료를 제조하여 수직방향 열전도도를 상온에서 평가하였다. 충전제의 함량을 1, 2, 5 중량 %로 변화시키며 원료들을 준비하여 교반기로 혼합한 뒤 3단 롤 밀(three roll mill)로 분산공정을 진행하여 3 종류의 도료를 제조하였다. 제조한 도료를 가로 11 mm, 세로 11 mm, 두께 0.4 mm의 Al 5052 알루미늄 기판에 스프레이 코팅 방식으로 도포한 후 $150^{\circ}C$에서 30분 동안 열경화 건조 과정을 거쳐 샘플을 제작하였다. 측정 시료의 형상은 대략적으로 Fig. 1과 같다. 열전도도는 식 $k={\alpha}{\cdot}C_p{\cdot}{\rho}$를 사용해서 계산된다. 여기서 k는 열전도도($W/m{\cdot}K$), ${\alpha}$는 열확산계수($mm^2/s$), $C_p$는 비열($J/kg{\cdot}K$), ${\rho}$는 밀도($g/cm^3$)를 나타낸다. 열확산계수는 독일 NETZSCH 사의 Laser Flash Analysis 장비(모델명 LFA 457)를 사용하여 측정하였는데, 기판 뒤쪽에서 레이저를 조사하고 도료층 전면에서 적외선 온도센서를 통해 시간에 따른 온도 상승곡선을 구한 후, 두 물체의 계면에서의 접촉 열저항(contact thermal resistance)을 감안하여 장비에 내장되어 있는 소프트웨어로 열확산계수가 계산된다. 비열은 같은 회사의 DSC(Differential Scanning Calorimetry) 200 F3 장비를 사용해 측정했으며, 밀도는 부피와 질량을 측정한 값을 이용하여 계산하였다. 도료를 도포하지 않은 bare Al plate에 대해서는 쉽게 열확산계수, 비열, 밀도를 측정하여 열전도도를 구할 수 있다. 도료가 코팅된 샘플에 대해서는 도료층을 일부 떼어내 비열을 측정하고, 밀도를 구한 후, 도료층의 열전도도가 2-layer 법으로 장비 내장 소프트웨어로 계산된다, 이때 Al 기판의 열확산계수, 비열, 밀도는 미리 측정한 bare Al plate의 값을 적용하였다. 실험 결과를 Table 1에 정리하였다. 흑연과 탄소나노튜브를 혼합한 충전제를 함유한 아크릴 복합체 박막에서 측정된 열전도도는 보통 고분자 재료의 열전도도 값의 상한 영역에 육박하는 값이며, 충전제 함량이 증가할수록 열전도도가 증가하는 경향을 보이고 있다.

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