• Title/Summary/Keyword: Nano-diamond

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Convective heat transfer characteristics of diamond nanofluid produced by matrix synthetic method (매트릭스합성 분산법에 의해 제조된 다이아몬드 나노유체의 대류열전달 특성)

  • Son, Kwun;Lee, Jung-Seok;Park, Tae-Hee;Park, Kweon-Ha
    • Journal of Advanced Marine Engineering and Technology
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    • v.37 no.1
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    • pp.9-15
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    • 2013
  • The effective use and management of energy resources has been issued to solve the global warming problem and petrolium price increase. To improve the energy efficiency of a heat exchanger, a new countermeasure is required and the heat transfer research of nano-fluids as a new working fluid is needed. This study was carried out with increasing the Reynolds number and the vol% of nano-fluids in the inlet temperature of $25^{\circ}C$ and $50^{\circ}C$. As the result, the higher the entrance temperature is, the higher the convective heat transfer coefficient is.

Hydrophobicity and Nanotribological Properties of Silicon Channels coated by Diamond-like Carbon Films

  • Pham, Duc Cuong;Na, Kyung-Hwan;Pham, Van Hung;Yoon, Eui-Sung
    • KSTLE International Journal
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    • v.10 no.1_2
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    • pp.1-5
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    • 2009
  • This paper reports an investigation on nanotribological properties of silicon nanochannels coated by a diamond-like carbon (DLC) film. The nanochannels were fabricated on Si (100) wafers by using photolithography and reactive ion etching (RIE) techniques. The channeled surfaces (Si channels) were then further modified by coating thin DLC film. Water contact angle of the modified and unmodified Si surfaces was examined by an anglemeter using the sessile-drop method. Nanotribological properties, namely friction and adhesion forces, of the Si channels coated with DLC (DLC-coated Si channels) were investigated in comparison with those of the flat Si, DLC-coated flat Si (flat DLC), and Si channels, using an atomic force microscope (AFM). Results showed that the DLC-coated Si channels greatly increased hydrophobicity of silicon surfaces. The DLC coating and Si channels themselves individually reduced adhesion and friction forces of the flat Si. Further, the DLC-coated Si channels exhibited the lowest values of these forces, owing to the combined effect of reduced contact area through the channeling and low surface energy of the DLC. This combined modification could prove a promising method for tribological applications at small scales.

Characteristic of Nitrogen doped Diamond-Like Carbon film on the Silicon substrates (실리콘 기판에 증착된 질소도핑 DLC 박막의 특성)

  • Nguyen, Van Cao;Kim, Tae Hyeon;Kim, Hye Sung;Shin, Dong Chul;Kim, Tae Gyu
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.12 no.2
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    • pp.34-40
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    • 2013
  • Various depositional conditions, such as substrate, pressure, deposition time, temperature of substrate, power and gas composition, have mainly been studied to attain DLC films using RF sputtering system up to the current. In this study, the $N_2/Ar/CH_4$ gas mixture factored on characteristics of DLC deposited film such as structure, hardness, electrical property were investigated. The concentration of the $N_2$ gas in the sputtering gas may be a significant effect on the growth rate of the doped films, because nitrogen ions react not only with the carbon atoms on the target but also with $C_xH_y$ ions in the plasma on the substrate surface. It was seen from this experimental that the resistance of deposited film is decreased, and the relative intensity ratio of D to G peak is increased as nitrogen content of film deposition is increased.

Nano-surface Machining Technology of Tungsten Carbide Blade for MLCC Cutting Process (MLCC 절단용 초경합금 칼날의 나노표면 가공 기술)

  • Kang, Byung-Ook;Shin, Gun-hwi;Kwak, Tae-Soo
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.18 no.11
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    • pp.41-46
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    • 2019
  • The purpose of this study is to examine and propose a high quality blade manufacturing method by applying ELID grinding technology to machining the tungsten carbide blade edge for MLCC sheet cutting. In this study, experiments are performed according to the abrasive type of grinding wheel, grinding method and grinding direction using the non-stop continuous dressing ELID grinding technology. By comparing and analyzing the chipping phenomena and surface roughness of both the blade grinding surface and the processed surface, a method for machining the tungsten carbide blade for cutting MLCC sheet is proposed. From the analysis of the surface roughness and chipping phenomena, it is confirmed that the use of diamond abrasive is advantageous for the blade machining. In addition, it succeeds in the machining of $6{\mu}m$ fine blade without any chipping, by using the grinding wheel #4000 with the diamond abrasive.

Tuning the Interference Color with PECVD Prepared DLC Thickness (PECVD를 이용한 DLC 두께 제어에 따른 간섭색 구현)

  • Park, Saebom;Kim, Kwangbae;Kim, Hojun;Kim, Chihwan;Choi, Hyun Woo;Song, Ohsung
    • Korean Journal of Materials Research
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    • v.31 no.7
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    • pp.403-408
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    • 2021
  • Various surface colors are predicted and implemented using the interference color generated by controlling the thickness of nano-level diamond like carbon (DLC) thin film. Samples having thicknesses of up to 385 nm and various interference colors are prepared using a single crystal silicon (100) substrate with changing processing times at low temperature by plasma-enhanced chemical vapor deposition. The thickness, surface roughness, color, phases, and anti-scratch performance under each condition are analyzed using a scanning electron microscope, colorimeter, micro-Raman device, and scratch tester. Coating with the same uniformity as the surface roughness of the substrate is possible over the entire experimental thickness range, and more than five different colors are implemented at this time. The color matched with the color predicted by the model, assuming only the reflection mode of the thin film. All the DLC thin films show constant D/G peak fraction without significant change, and have anti-scratch values of about 19 N. The results indicate the possibility that nano-level DLC thin films with various interference colors can be applied to exterior materials of actual mobile devices.

A study on stress-strain relation measurement for micro scale UV-curable polymer structure (UV-경화 폴리머 마이크로 구조물의 응력-변형률 관계 측정에 관한 연구)

  • Jeong S.J.;Kim J.H.;Lee H.J.;Park S.H.;Yang D.Y.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.10a
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    • pp.492-497
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    • 2005
  • In this study, we propose an advanced nanoindentaion test, Nano Pillar Compression Test (NPCT) to measure a stress-strain relation for micro scale polymer structures. Firstly, FEM analysis is performed to research behavior of micro polymer pillars in several specimen aspect ratios and different friction conditions between specimen and tip. Based on the FEM results, micro scale UV-curable polymer pillars are fabricated on a substrate by Nano Stereo Lithography (NSL). To measure their mechanical properties, uniaxial compression test is performed using nanoindentation apparatus with flat-ended diamond tip. In addition, the dependency of compression properties on loading condition and specimen size are discussed.

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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.