• Title/Summary/Keyword: graphite coating

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Thermodynamic Comparison of Silicon Carbide CVD Process between CH3SiCl3-H2 and C3H8-SiCl4-H2 Systems (탄화규소 CVD 공정에서 CH3SiCl3-H2과 C3H8-SiCl4-H2계의 열역학적 비교)

  • Choi, Kyoon;Kim, Jun-Woo
    • Korean Journal of Metals and Materials
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    • v.50 no.8
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    • pp.569-573
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    • 2012
  • In order to understand the difference in SiC deposition between the $CH_3SiCl_3-H_2$ and $C_3H_8-SiCl_4-H_2$ systems, we calculate the phase stability among ${\beta}$-SiC, graphite and silicon. We constructed the phase-diagram of ${\beta}$-SiC over graphite and silicon via computational thermodynamic calculation considering pressure (P), temperature (T) and gas composition (C) as variables. Both P-T-C diagrams showed a very steep phase boundary between the SiC+C and SiC region perpendicular to the H/Si axis, and also showed an SiC+Si region with a H/Si value of up to 6700 in the $C_3H_8-SiCl_4-H_2$, and 5000 in the $CH_3SiCl_3-H_2$ system. This difference in phase boundaries is explained by the ratio of Cl to Si, which is 4 for the $C_3H_8-SiCl_4-H_2$ system and 3 for the $C_3H_8-SiCl_4-H_2$ system. Because the C/Si ratio is fixed at 1 in the $CH_3SiCl_3-H_2$ system while it can be variable in the $C_3H_8-SiCl_4-H_2$ system, the functionally graded material is applicable for better mechanical bonding during SiC coating on graphite substrate in the $C_3H_8-SiCl_4-H_2$ system.

Electrochemical Properties of Natural Graphite coated with PFO-based Pitch for Lithium-ion Battery Anode (리튬이차전지 음극용 석유계 피치로 코팅된 천연 흑연의 전기화학적 특성)

  • Kim, Geun Joong;Jo, Yoon Ji;Lee, Jong Dae
    • Korean Chemical Engineering Research
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    • v.57 no.5
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    • pp.672-678
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    • 2019
  • The electrochemical properties of pitch-coated natural graphite(NG) were investigated as an anode for lithium-ion batteries. The anode materials were prepared by heat-treatment of mixture of NG and petroleum pitch at $1000^{\circ}C$. The pitches with various softening points were used as carbon precursor. The physical properties of anode materials were analyzed by TGA, SEM, PSA and BET. As the softening point increased, the thickness of the coating layer increased and the specific surface area decreased. The electrochemical performances were investigated by initial charge/discharge efficiency, cycle stability, cyclic voltammetry, rate performance and electrochemical impedance spectroscopy. The carbon-coated NG using pitch with softening points of $250^{\circ}C$ showed an initial discharge capacity of 361 mAh/g and a coulombic efficiency of 92.6%. Also, the rate performance(5 C/0.2 C) was 1.6 times higher than that of NG, and it had a capacity retention (90%) after 50 cycles at 0.5 C.

Fabrication of SiOx Anode Active Materials Using Spherical Silica Powder and Shape Control Technology (구형 단분산 실리카 분말을 이용한 SiOx 음극활물질 제조 및 형상조절 기술)

  • Ju-Chan Kwon;Bok-Hyun Oh;Sang-Jin Lee
    • Korean Journal of Materials Research
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    • v.33 no.12
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    • pp.530-536
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    • 2023
  • The theoretical capacity of silicon-based anode materials is more than 10 times higher than the capacity of graphite, so silicon can be used as an alternative to graphite anode materials. However, silicon has a much higher contraction and expansion rate due to lithiation of the anode material during the charge and discharge processes, compared to graphite anode materials, resulting in the pulverization of silicon particles during repeated charge and discharge. To compensate for the above issues, there is a growing interest in SiOx materials with a silica or carbon coating to minimize the expansion of the silicon. In this study, spherical silica (SiO2) was synthesized using TEOS as a starting material for the fabrication of such SiOx through heating in a reduction atmosphere. SiOx powder was produced by adding PVA as a carbon source and inducing the reduction of silica by the carbothermal reduction method. The ratio of TEOS to distilled water, the stirring time, and the amount of PVA added were adjusted to induce size and morphology, resulting in uniform nanosized spherical silica particles. For the reduction of the spherical monodisperse silica particles, a nitrogen gas atmosphere mixed with 5 % hydrogen was applied, and oxygen atoms in the silica were selectively removed by the carbothermal reduction method. The produced SiOx powder was characterized by FE-SEM to examine the morphology and size changes of the particles, and XPS and FT-IR were used to examine the x value (O/Si ratio) of the synthesized SiOx.

A Study on the Improvement of the Oxidation-Resistance of the Graphite Substrate by Forming of SiC Film on its Surface (탄화규소막의 형성에 의한 흑연소지의 내산화성 향상에 관한 연구)

  • Cho, Sung-Jun;Lee, Jong-Min;Kim, In-Ki;Jang, Jeen-Suck
    • The Journal of Natural Sciences
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    • v.8 no.2
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    • pp.137-146
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    • 1996
  • To increase the oxidation-resistance of graphite substrate, we have tried to form SiC film on its surface by Sol-Gel method. TEOS(Tetraethyl orthosilicate) and phenol resin have been used as silicon(Si) and carbon(C) sources, respectively. In order to know the effect of the TEOS Sol concentration on the forming of SiC film, we have taken 5 different $H_2O$/TEOS mol ratios of 2, 4, 6, 8 and 10. And the coating states of SiC on the graphite substrate have been analyzed with X-ray diffractometer and scanning electron microscope (SEM), and we have obtained about 5${\mu}m$, 12${\mu}m$, 7${\mu}m$, 7${\mu}m$ and 2 ${\mu}m$ as the thickness of SiC coating layers, respectively. For also knowing the oxidation resistance the SiC coated graphites at $1600^{\circ}C$ were heated again at $1000^{\circ}C$ under air atmosphere for 1 hr, and as a result we have received the weight losses of 26.17%, 20.97%, 17.28%, 21.73% and 28.13%, respectively.

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Diamond Like Carbon Coating on WC Core Pin for Injection Molding of Zirconia Optical Ferrule (지르코니아 광페룰 사출성형용 WC 코아 핀의 Diamond Like Carbon 코팅)

  • Park, Hyun-Woo;Jeong, Se-Hoon;Kim, Hyun-Young;Lee, Kwang-Min
    • Korean Journal of Materials Research
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    • v.20 no.11
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    • pp.570-574
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    • 2010
  • A diamond-like carbon (DLC) film deposited on a WC disk was investigated to improve disk wear resistance for injection molding of zirconia optical ferrule. The deposition of DLC films was performed using the filtered vacuum arc ion plating (FV-AIP) system with a graphite target. The coating processing was controlled with different deposition times and the other conditions for coating, such as input power, working pressure, substrate temperature, gas flow, and bias voltage, were fixed. The coating layers of DLC were characterized using FE-SEM, AFM, and Raman spectrometry; the mechanical properties were investigated with a scratch tester and a nano-indenter. The friction coefficient of the DLC coated on the WC was obtained using a pin-on-disk, according to the ASTM G163-99. The thickness of DLC films coated for 20 min. and 60 min. was about 750 nm and 300 nm, respectively. The surface roughness of DLC films coated for 60 min. was 5.9 nm. The Raman spectrum revealed that the G peak of DLC film was composed of $sp^3$ amorphous carbon bonds. The critical load (Lc) of DLC film obtained with the scratch tester was 14.6 N. The hardness and elastic modulus of DLC measured with the nano-indenter were 36.9 GPa and 585.5 GPa, respectively. The friction coefficient of DLC coated on WC decreased from 0.2 to 0.01. The wear property of DLC coated on WC was enhanced by a factor of 20.

Evaluation of Electromagnetic Pulse Shielding Effectiveness and Bonding Performance of Inorganic Paint based on Carbon Material (탄소재료 기반 무기계 도료의 전자파 차폐성능 및 부착성능 평가)

  • Jang, Kyong-Pil;Kim, Sang-Hee
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.22 no.1
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    • pp.801-807
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    • 2021
  • In various industrial fields and infrastructure based on electronic components, such as communication equipment, transportation, computer networks, and military equipment, the need for electromagnetic pulse shielding has increased. Two methods for applying electromagnetic pulse shielding are effective. The first is construction using shielding materials, such as shielding concrete, shielding doors, and shielding windows. The other is coating shielding paints on non-shielding structures. Electromagnetic pulse shielding paints are made using conductive materials, such as carbon nanotubes, graphite, carbon black, and carbon fiber. In this paint, electromagnetic pulse shielding performance is added to the commonly used water-based paint. In this study, the shielding effectiveness and bonding performance of paints using conductive graphite and carbon black as shielding materials were evaluated to develop electromagnetic pulse shielding inorganic paints. The shielding effectiveness and bonding performance were evaluated by applying six mixtures composed of different kinds and amounts of shielding material. The mixture of conductive graphite and carbon black at a weight ratio of 1:0.2 was the most effective in shielding as 33.6 dB. Furthermore, the mixture produced using conductive graphite only showed the highest bonding performance of 1.06 MPa.

Fabrication and Characterization of Carbon-Coated Cu Nanopowders by Pulsed Wire Evaporation Method (전기선폭발법에 의해 카본 코팅된 Cu 나노분말의 제조 및 특성 연구)

  • Lee, H.M.;Park, J.H.;Hong, S.M.;Uhm, Y.R.;Rhee, C.K.
    • Journal of Powder Materials
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    • v.16 no.4
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    • pp.243-248
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    • 2009
  • Carbon-coated Cu nanopowders with core/shell structure have been successfully fabricated by pulsed wire evaporation (PWE) method, in which a mixed gas of Ar/$CH_4$ (10 vol.%) was used as an ambient gas. The characterization of the samples was carried out using x-ray diffraction (XRD), scanning electron microscope (SEM), and high resolution transmission electron microscope (HRTEM). It was found that the nanoparticles show a spherical morphology with the size ranging of 10-40 nm and are covered with graphite layers of 2-4 nm. When oxygen-passivated Cu nanopowders were annealed under flowing argon gas (600 and 800$^{\circ}C$), the crystallinity of $Cu_2O$ phase and the particle size gradually increased. On the other hand, carbon-coated Cu nanopowders remained similar to as-prepared case with no additional oxide or carbide phases even after the annealing, indicating that the metal nanoparticles are well protected by the carbon-coating layers.

Laser Assisted Surface Alloying of Cast Iron with Thermal Sprayed Titanium Coatings (티타늄 용사피막을 이용한 주철의 레이저 표면합금화)

  • Park, Heung-Il;Kim, Sung-Gyoo;Lee, Byung-Woo
    • Journal of Korea Foundry Society
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    • v.17 no.4
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    • pp.393-401
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    • 1997
  • Commercial flake graphite cast iron substrate was coated with titanium powder by low pressure plasma spraying and was irradiated with a $CO_2$ laser to produce the wear resistant composite layer. From the experimental results of this study, it was possible to composite TiC particles on the surface layer by direct reaction between carbon existed in the cast iron matrix and titanium with thermal sprayed coating by remelting and alloying them using laser irradiation. The cooling rate of laser remelted cast iron substrate without titanium coating was about $1{\times}10^4$ K/s to $1{\times}10^5$ K/s in the order under the condition used in this study. The microstructure of alloyed layer consisted of three zones, that is, TiC particule crystallized zone (MHV $400{\sim}500$), the mixed zone of TiC particule+ledebulite (MHV $650{\sim}900$) and the ledebulite zone (MHV $500{\sim}700$). TiC particules were crystallized as a typical dendritic morphology. The secondary TiC dendrite arms were grown to the polygonized shape and were necking. And then the separated arms became cubic crystal of TiC at the slowly solidified zone. But in the rapidly solidified zone of fusion boundry, the fine granular TiC particules were grouped like grape.

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Thermal Emission Effect of Electronic Parts Using Carbon Materials (탄소물질을 이용한 전자부품의 열 방출효과)

  • Eom, Woon-Yong;Roh, Jae-Seung;Seo, Seung-Kuk;Ahn, Jai-Sang;Kang, Dong-Su;Kim, Suk-Hwan
    • Korean Journal of Materials Research
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    • v.20 no.4
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    • pp.204-209
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    • 2010
  • Recent high efficiency electronic devices have been found to have heat emission problems. As for LEDs, an excessive increase in the device temperature causes a drop of the luminous efficiency and circuit lifetime. Therefore, heat release in the limited space of such electronic parts is very important. This is a study of the possibility of using a coating of carbon materials as a solution for the thermal emission problem of electronic devices. Powdered carbon materials, cokes, carbon blacks, amorphous graphite, and natural flakes were coated with an organic binder on an aluminum sheet and the subsequent thermal emissivity was measured with an FT-IR spectrometer and was found to be in the range of $5{\sim}20\;{\mu}m$ at $50^{\circ}C$. The emissivity of the carbon materials coated on the aluminum sheet was shown to be over 0.8 and varied according to carbon type. The maximum thermal emissivity on the carbon black coated-aluminum surface was shown to be 0.877. The emissivity of the anodized aluminum sheets that were used as heat releasing materials of the electronic parts was reported to be in the range of 0.7~0.8. Therefore, the use of a coating of carbon material can be a potential solution that facillitates heat dissipation for electronic parts.

A Study on the DLC Film Coating for Improving Loosening Torque of Dental Implant Screw (치과 임플란트 스크루 풀림토크 개선용 DLC 박막 코팅에 관한 연구)

  • Jeong, Woon-Jo;Cho, Jae-Cheol
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.67 no.10
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    • pp.1375-1381
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    • 2018
  • In this paper, we studied coatings of the DLC thin film for improving loosening torque of dental implant screw. We used a filtered arc ion plating process which can realize the most dense DLC layer by coating the DLC thin film on the surface of the dental abutment screw. It showed both hardness comparable to diamond and low friction coefficient similar to graphite, and to improve the loosening phenomenon by increasing the screw tightening force Cr/CrN, Ti/TiN or Ti/TiN/Cr/CrN buffer layers were deposited for 5 to 10 minutes to improve the adhesion of the DLC thin film to the surface of the Ti (Gr.5), and then the DLC thin film was coated for about 15 minutes. As a result, the Cr/CrN buffer layer exhibited the highest hardness of 29.7 GPa, the adhesion of 18.62N on average, and a very low coefficient of friction of less than 0.2 as a whole. And we measured loosening torque after one million times with masticatory movement simulator. As a result, the values of the coated screw loosening torque were clearly higher than those of the uncoated screw. From this, it was found that the DLC coating was effective methods improving the loosening torque. In addition, it was confirmed that the cytotoxicity test and cell adhesion test showed high biocompatibility.