• 제목/요약/키워드: Graphite particles

검색결과 145건 처리시간 0.022초

Ag 및 탄소 나노윤활유의 제조 및 윤활특성 평가 (Tribological Behavior of Lubricating Oil-Based Nanofluids Containing Ag and Carbon Nanoparticles)

  • 최철;정미희;최영민;오제명
    • 한국재료학회지
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    • 제18권11호
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    • pp.610-616
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    • 2008
  • Oil-based nanofluids were prepared by dispersing Ag, graphite and carbon black nanoparticles in lubricating oil. Agglomerated nanoparticles were dispersed evenly with a high-speed bead mill and/or ultrasonic homogenizer, and the surfaces of the nanoparticles were modified simultaneously with several dispersants. Their tribological behaviors were evaluated with a pin-on-disk, disk-on-disk and four-ball EP and wear tester. It is obvious that the optimal combination of nanoparticles, surfactants and surface modification process is very important for the dispersity of nanofluids, and it eventually affects the tribological properties as a controlling factor. Results indicate that a relatively larger size and higher concentration of nanoparticles lead to better load-carrying capacity. In contrast, the use of a smaller size and lower concentration of particles is recommended for reducing the friction coefficient of lubricating oil. Moreover, nanofluids with mixed nanoparticles of Ag and graphite are more suitable for the improvement of load-carrying capacity and antiwear properties.

Thermal Emissivity of Nuclear Graphite as a Function of its Oxidation Degree (3): Structural Study using Scanning Electron Microscope and X-Ray Diffraction

  • Seo, Seung-Kuk;Roh, Jae-Seung;Kim, Suk-Hwan;Chi, Se-Hwan;Kim, Eung-Seon
    • Carbon letters
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    • 제12권1호
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    • pp.8-15
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    • 2011
  • We study the relationships between the thermal emissivity of nuclear graphites (IG-110, PCEA, IG-430 and NBG-18) and their surface structural change by oxidation using scanning electron microscope and X-ray diffraction (XRD). The nonoxidized (0% weight loss) specimen had the surface covered with glassy materials and the 5% and 10% oxidized specimens, however, showed high roughness of the surface without glassy materials. During oxidation the binder materials were oxidized first and then graphitic filler particles were subsequently oxidized. The 002 interlayer spacings of the non-oxidized and the oxidized specimens were about $3.38{\sim}3.39{\AA}$. There was a slight change in crystallite size after oxidation compared to the nonoxidized specimens. It was difficult to find a relationship between the thermal emissivity and the structural parameters obtained from the XRD analysis.

탄소재료의 적용 방법에 따른 파티클 보드의 연소 특성 (Evaluation of Fire Characteristics for Particle-board with Exfoliated Graphite Nanoplatelets Added)

  • 서현정;조정민;황욱;이민철
    • 한국연소학회지
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    • 제22권4호
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    • pp.1-8
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    • 2017
  • This study was conducted to evaluate the fire retardant performance of exfoliated graphite nanoplatelets (xGnP) applied for particleboard. This work measured heat release rate(HRR), total heat release(THR) and smoke production rate(SPR) of xGnP added particleboard, using cone calorimeter to assess its fire characteristics according to the KS F ISO 5660-1 standard code. Heat release rates of all specimens treated by xGnP were less than the $200kW/m^2$ for a total experiment period of five minutes. Heat release rates of the specimens coated with xGnP were lower than those of the specimens made by mixing wood particles with xGnP directly. Meanwhile, the total heat release rates of xGnP coated specimen maintained quite lower level than the uncoated so the xGnP coating were effective in improving the fire retardant performance of particleboard. However, the smoke emission peaking problem at the initial combustion period, which was caused by adding base coating materials, should be resolved for further satisfaction as a fire retardant materials.

Cycling Behavior of Binder-Free Graphite-Lithium Intercalation Anode In AICI3-EMIC-LiCI-SOCI2 Room-Temperature Molten Salt

  • Koura, Nobuyuki;Minami, Takuto;Etoh, Keiko;Idemoto, Yasushi;Matsumoto, Futoshi
    • 전기화학회지
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    • 제5권4호
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    • pp.178-182
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    • 2002
  • The electrochemical behavior of binder-free carbon anode, comprising of only artificial and natural graphite (AG and NG) particles, for intercalation and deintercalation of lithium ion $(Li^+)$ in aluminum chloride (AICI_3)-I-ethyl­3-methylimidazolium chloride (EMIC)-lithium chloride (LiCl)-thionyl chloride $(SOCI_2)$ room-temperature molten salt (RTMS) was studied. Binder-free carbon electrodes were fabricated using electrophoretic deposition (EPD) method. The binder-free carbon anodes provided a relatively flat charge and discharge potentials $(0\;to\;0.2V\;vs.\;Li/Li^+)$ and current capabilities $(250-340mAh{\cdot}g^{-1})$ for the intercalation and deintercalation of $Li^+$. Stability of the binder-free carbon anodes for intercalation and deintercalation of 50 cycles was confirmed.

Effect of Carbon Matrix on Electrochemical Performance of Si/C Composites for Use in Anodes of Lithium Secondary Batteries

  • Lee, Eun Hee;Jeong, Bo Ock;Jeong, Seong Hun;Kim, Tae Jeong;Kim, Yong Shin;Jung, Yongju
    • Bulletin of the Korean Chemical Society
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    • 제34권5호
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    • pp.1435-1440
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    • 2013
  • To investigate the influence of the carbon matrix on the electrochemical performance of Si/C composites, four types of Si/C composites were prepared using graphite, petroleum coke, pitch and sucrose as carbon precursors. A ball mill was used to prepare Si/C blends from graphite and petroleum coke, whereas a dispersion technique was used to fabricate Si/C composites where Si was embedded in disordered carbon matrix derived from pitch or sucrose. The Si/pitch-based carbon composite showed superior Si utilization (96% in the first cycle) and excellent cycle retention (70% after 40 cycles), which was attributed to the effective encapsulation of Si and the buffering effect of the surrounding carbon matrix on the silicon particles.

양성자 교환막 연료전지용 탄소 복합재료 분리판 개발 (Development of Carbon Composite Bipolar Plates for PEMFC)

  • 임준우
    • Composites Research
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    • 제32권5호
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    • pp.222-228
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    • 2019
  • 양성자 교환막 연료전지 (PEMFC) 시스템은 환경 친화적인 전력 공급원으로 많은 잠재적 용도를 가지고 있다. 탄소섬유 복합재료 분리판은 산성환경에서 내부식성이 우수하며 높은 비강도와 비강성을 갖지만, 상대적으로 낮은 전기전도도로 인하여 PEMFC의 효율을 떨어뜨린다. 본 연구에서는 분리판의 전기 저항을 감소시키기 위하여 전기 전도성 입자(흑연 분말과 카본 블랙)를 탄소-에폭시 복합재료 프리프레그에 도포하였다. 전기 저항과 기계적 특성을 기존의 시험 방법을 사용하여 측정하였으며, 개발된 탄소 복합재료 분리판의 단위 셀 성능평가를 실시하여 기존의 분리판과 비교하였다.

플라즈마 에칭 처리된 PTFE 표면의 발수성 연구 (Study on Water Repellency of PTFE Surface Treated by Plasma Etching)

  • 강효민;김재형;이상혁;김기웅
    • 한국가시화정보학회지
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    • 제19권3호
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    • pp.123-129
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    • 2021
  • Many plants and animals in nature have superhydrophobic surfaces. This superhydrophobic surface has various properties such as self-cleaning, moisture collection, and anti-icing. In this study, the superhydrophobic properties of PTFE surface were treated by plasma etching. There were four important factors that changed the surface properties. Micro-sized protrusions were formed by plasma etching. The most influential parameter was RF Power. The contact angle of the pristine PTFE surface was about 113.8°. The maximum contact angle of the surface after plasma treatment with optimized parameters was about 168.1°. In this case, the sliding angle was quite small about 1°. These properties made it possible to remove droplets easily from the surface. To verify the self-cleaning effect of the surface, graphite was used to contaminate the surface and remove it with water droplets. Graphite particles were easily removed from the optimized surface compared to the pristine surface. As a result, a surface having water repellency and self-cleaning effects could be produced with optimized plasma etching parameters.

공정변수에 따른 microwave plasma CVD 다이아몬드/Ti 박막 증착 양상 조사 (Parametric study of diamond/Ti thin film deposition in microwave plasma CVD)

  • 조현;김진곤
    • 한국결정성장학회지
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    • 제15권1호
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    • pp.10-15
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    • 2005
  • Microwave plasma CVD 다이아몬드/Ti 박막 성장 시 CH₄/H₂ 가스의 유량비율, chuck bias, microwave power 등이 다이아몬드 박막의 구조적 특성과 입자밀도에 미치는 영향에 대하여 조사하였다. 2∼3 CH₄ Vol.% 조건일 때 sp³-결합성의 탄소 neutral 들이 우선적으로 형성되고 sp²-결합성의 탄소 neutral 들이 선택적으로 제거됨에 따라 양질의 다이아몬드 박막을 얻을 수 있었으며, 다이아몬드 입자 증착 기구를 해석하였다. Ti 기판에 걸어준 negative chuck bias가 증가함에 따라 다이아몬드 핵생성이 증진되어 다이아몬드 입자 밀도가 증가하였고, 임계 전압은 약 -50V 임을 확인하였다. 또한, microwave power가 증가함에 따라 미세결정질(micro-crystalline) graphite 층 생성이 제어되고 다이아몬드 층이 형성됨을 확인하였다.

옥천계(沃川系) 흑색(黑色)슬레이트내(內) 부존(賦存)하는 저품질(低品質) 우라늄광석(鑛石)에 대(對)한 광물학적(鑛物學的) 연구(硏究) (Mineralogy of Low-Grade Uranium Ores in the Black Slate of the Ogcheon Group, Korea)

  • 이동진
    • 자원환경지질
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    • 제19권2호
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    • pp.133-146
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    • 1986
  • Primary uraninite and secondary uranium minerals such as torbernite, metatorbernite, tyuyamunite, metatyuyamunite, autunite and metaautunite have been identified from various types of uranium ores. Uranium minerals occur as accessory minerals in both the primary and secondary ores. Low·grade uranium ores consist of various kinds of primary and secondary minerals. Major constituent minerals of primary uranium ores are graphite. quartz. Ba-feldspar and sericite/muscovite, and accessories are calcite, chlorite, fluorapatite, barite, diopside, sphene, rutile, biotite, laumontite, heulandite, pyrite, sphalerite and chalcopyrite, and secondary minerals consist of kaolinite, gypsum and goethite. Uraninite grains occur as microscopic very fine-grained anhedral to euhedral disseminated particles in the graphitic matrix, showing well·stratified or zonal distribution of uranium on auto-radiographs of low-grade uranium ores. Some uraninite grains are closely associated with very fine-grained pyrite aggregates, showing an elliptical form parallel to the schistosity. Some uraninite grains include extremely fine-grained pyrite particle. Sphalerite and pyrite are often associated with uraninite in graphite-fluorapatite nodule. The size of uraninite is $2{\mu}m$ to $20{\mu}m$ in diameter. Low-grade uranium ores are classified into 5 types on the basis of geometrical pattern of mineralization. They are massive, banded, nodular, quartz or sulfide veinlet-rich and cavity filling types. Well-developed alternation of uranium-rich and uranium-poor layers, concentric distribution of uranium in graphite-fluorapatite nodule and geopetal fabrics due to the load cast of the nodule suggest that the uranium was originally deposited syngenetically. Uraninite crystals might have been formed from organo-uranium complex during diagenesis and recrystallized by metamorphism. Secondary uranium minerals such as torbernite, tyuyamunite and autunite have been formed by supergene leaching of primary ores and subsequent crystallization in cavities.

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

  • 허윤정;고성태
    • 전기화학회지
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    • 제12권3호
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    • pp.239-244
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    • 2009
  • 리튬 이차 전지의 전기화학적 특성 및 안전성 향상을 위한 음극 활물질 표면 처리 재료로 $Al_2O_3$$nano-Li_4Ti_5O_{12}$등이 사용된다. 표면 처리된 음극 활물질의 형상과 특성을 관찰하기 위해 주사전자현미경(Scanning electron microscopy, SEM), 투과전자현미경(Transmission electron microscopy, TEM)으로 관찰하였으며, 전기화학적 특성 및 안전성 평가를 위해 충방전기 및 가속 율열량계(Accelerating Rate Calorimeter, ARC)를 사용하였다. 각각의 금속 산화물에 따른 초기 효율 및 초기 용량은 82.5%와 350mAh/g로 동일하지만, 충방전 율속에 따른 특성 및 수명, 그리고 열적 안전성은 $nano-Li_4Ti_5O_{12}$로 음극 활물질을 표면 처리 한 활물질이 더 우수하였다.