• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.5
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• pp.22-27
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• 2015

Processing of low toughness graphite material requires high-speed machine tools and DLC coating. In this study, results of investigation of the tool wear and machining properties of the DLC coating according to the thickness, and the machining time of the tool used for the machining of graphite electrodes, were as follows. 1. DLC coating thickness shows a larger wear amount of the tool center in accordance with thickness; the wear amount of the tool increases in proportion to the machining time. 2. The difference between the amount of wear depending on the processing time shows edge portions larger than the tool wear amount in the center. This amount of wear of the tool edge is formed since the rotating torque is in contact with the graphite material surface significantly more than the central portion. 3. The thicker the DLC coating, the more the coating tool eliminated of the coating area by the interface between the cemented carbide tool being coated with an increased friction of the graphite material and the DLC coating area.

• Corrosion Science and Technology
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• v.6 no.1
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• pp.18-23
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• 2007

DLC coatings have been deposited onto substrate of STS 316L and Ti alloy using r.f. PACVD (plasma-assisted chemical vapor deposition) with a mixture of $C_{6}H_{6}$ and $SiH_{4}$ as the process gases. Corrosion performance of DLC coatings was investigated by electrochemical techniques (potentiodynamic polarization test and electrochemical impedance spectroscopy) and surface analysis (scanning electron microscopy). The electrolyte used in this test was a 0.89% NaCl solution of pH 7.4 at temperature $37^{\circ}C$. The porosity and protective efficiency of DLC coatings were obtained using potentiodynamic polarization test. Moreover, the delamination area and volume fraction of water uptake of DLC coatings as a function of immersion time were calculated using electrochemical impedance spectroscopy. This study provides the reliable and quantitative data for assessment of the effect of substrate on corrosion performance of Si-DLC coatings. The results showed that Si-DLC coating on Ti alloy could improve corrosion resistance more than that on STS 316L in the simulated body fluid environment. This could be attributed to the formation of a dense and low-porosity coating, which impedes the penetration of water and ions.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.327-327
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• 2011

DLC 필름은 바이오 적합성, 특히 생체 적합성이 뛰어나기 때문에 바이오 코팅분야에서 널리 이용된다. 많은 연구 결과에 의하면 세포와 장기 등이 바이오 재료 표면에 적절히 접합할 수 있도록, 재료 표면을 산소나 질소를 이용하여 플라즈마 처리로 초친수성 표면으로 개질하고 있다. 하지만, 시간이 지남에 따라서 친수성 표면은 점차 재료의 표면 처리 전의 성질인 소수성을 회복하게 된다. D실제 생체에 적용하기 위해서 이러한 시효 효과에 대한 정확한 평가가 이루어져야 한다. 따라서 산소와 질소 플라즈마 처리 후의 친수성 성질이 소수성 성질로 변해가는 거동을 조사하는게 중요하다. 13.56 MHz의 plasma assisted chemical vapor deposition (PACVD) 법을 이용하여 DLC와 Si-DLC를 500 ${\mu}m$ 두께의 P-type 실리콘(100) 기판에 증착하였다. 박막 증착 과정에 사용한 기체는 벤젠과 희석된 silane이 사용되었다(SiH4/H2=10:90). 박막 증착은 -400 V의 바이어스 전압을 인가하였으며, 이때 증착 압력은 1.33Pa으로 일정하게 유지하여, 두께 $0.55{\pm}0.01{\mu}m$로 증착하였다. X-ray Photoelectron Spectroscopy (XPS) 법을 이용하여 실리콘 함량을 측정하였으며, 증착 된 Si-DLC의 실리콘 함량은 0~4.88 at. %였다. 이후에 질소와 산소 플라즈마를 이용하여 챔버 압력을 1.33 Pa로 유지하여, -400 V의 바이어스 전압을 인가하여 10분간 표면 처리를 하였다. 표면 처리된 DLC와 Si-DLC 표면 위에서의 물방울(water droplet)의 젖음각을 20일간 측정하였다. 플라즈마 표면 처리 된 모든 시편에서 초기 젖음각은 $10{\sim}20^{\circ}$의 친수성 성질을 보였지만, 점차 젖음각이 상승하여 산소 플라즈마 처리 된 Si-DLC를 제외하고는 5일이 지나면서 거의 소수성 표면으로 회복되었다. 산소 플라즈마 처리 된 Si-DLC의 경우, 젖음 각 측정 기간(20일) 동안 $15^{\circ}$ 미만의 친수성 성질을 유지하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.397-397
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• 2007

Diamondlike carbon (DLC) coatings were deposited on alumina ceramic seals using a plasma immersion ion deposition technique (PIID). Then they were subjected to tribological tests using a pin-on-disc tribometer under a high load (1.3 GPa) and under elevated temperatures up to 400C. Coefficients of friction (COFs) were recorded and compared with that of the untreated alumina while the wear tracks were analyzed using SEM with EDS to characterize the DLC films. To enhance the DLC adhesion to the substrate, various interlayers including Si and Cr were deposited using the PIID process or an ion beam assisted deposition (IBAD) method. It was observed that the DLC coating, if adhering well to the substrate, reduced the COFs significantly, from 0.4-0.8 for the uncoated alumina to about 0.05-0.1, within the tested temperature range. The adhesion was determined by the interlayer type and possibly by the application method. Cr interlayer did not perform as well as the Si interlayer. This could also be due to the fact that the Cr interlayer and the subsequent DLC coating had to be done in two different processing systems, while both the Si interlayer and the subsequent DLC film were deposited in one system without breaking the chamber. The coating failure mode was found to be delamination between the Cr and the alumina substrate. In contrast, the Si interlayer with proper DLC deposition procedures resulted in very good adhesion and hence excellent tribological performance. Further study may lead to future DLC applications of ceramic seals.

• Korean Journal of Materials Research
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• v.7 no.1
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• pp.27-32
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• 1997

본 연구에서는 고밀도 플라즈마를 형성하는 planar magnetron RF 플라즈마 CVD를 이용하여 DLC(diamond-like carbon) 박막을 합성하였다. 이 방법을 이용하여 DLC 박막을 합성한다면 고밀도 플라즈마 때문에 종래의 플라즈마 CVD(RF-PECVD)법보다 증착속도가 더욱더 향상될 것이라는 것에 착안하였다. 이를 위해 magnetron에 의한 고밀도 플라즈마가 존재할 때도 역시 DLC박막형성에 미치는 RF 전력과 반응가스 압력이 중요한 반응변수인가에 대해 조사하였고, 일정한 자기장의 세기에서 RF전력과 DC self-bias 전압과의 관계를 조사하였다. 또한 RF전력변화에 따른 박막의 증착속도와 밀도를 측정하였다. 본 연구에 의해 얻어진 박막의 증착속도는 magnetron에 의한 이온화율이 매우 높아 기존의 RF-PECVD 법보다 매우 빠르며, DLC박막의 구조와 물질특성을 알아보기 위해 FTIR(fourier transform infrared)및 Raman 분광분석을 행한 결과 전형적인 양질의 고경질 다이아몬드상 탄소박막임을 알 수 있었다.

• Journal of Industrial Technology
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• v.32 no.A
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• pp.119-123
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• 2012

Diamond-like carbon(DLC) thin films with interlayer were deposited on silicon substrate using a reactive sputtering method. The thermal stability of the films was investigated by annealing the films for 1hr in air in the range of 100 to $500^{\circ}C$. The $I_D/I_G$ ratio increased with increasing temperature as related to the $sp^3-to-sp^2$transition. Accordingly, G-position shifting started from $150^{\circ}C$ in the DLC films and from $270^{\circ}C$ in the a-Si/DLC films. Moreover, in the case of the a-Si/DLC films the film still observed even after annealing at $500^{\circ}C$. The thermal stability of the reactive sputtered DLC films appeared to be improved by the a-Si interlayer.

• The Korean Journal of Ceramics
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• v.1 no.4
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• pp.185-190
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• 1995

Tribological behavior of the diamond-like carbon (DLC) films sliding on floppy disk has been investigated. Hydrogenated DLC films have been prepared by plasma enhanced chemical vapor deposition (PECVD) using methane and hydrogen mixture in different volume ratios on ferrite substrates. DLC films show lower friction coefficients (0.2~0.4) than those of the uncoated ferrite(0.4~0.5). DLC films containing more hydrogen exhibit higher wear resistance. To investigate the roughness effect on wear, the substrates were polished with SiC papers prior to deposition. Too fine or too rough DLC surfaces result in poor wear resistance. Wear resistance of annealed DLC films at higher temperature slightly increases with respect to as-deposited film.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.956-960
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• 2004

Effects of ion implantation and deposition on the tribological properties of DLC film as a function of implanted energies and process times were investigated. TiC ions were implanted and deposited on the Si-wafer substrates followed by DLC coating using ion beam deposition method. In order to study tribological properties such as friction coefficient and behavior of DLC film on the modified surface as a function of implanted energies and process times, we used a ball-on-disc type apparatus in the atmospheric environment. From results of wear test, as the implanted energy was increased, the friction coefficient was more stable below 0.1.

• Korean Journal of Materials Research
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• v.33 no.4
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• pp.124-129
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• 2023

This study assessed the influences of fluorine introduced into DLC films on the structural and mechanical properties of the sample. In addition, the effects of the fluorine incorporation on the compressive stress in DLC films were investigated. For this purpose, fluorinated diamond-like carbon (F-DLC) films were deposited on cobalt-chromium-molybdenum substrates using radio-frequency plasma-enhanced chemical vapor. The coatings were examined by Raman scattering (RS), Attenuated total reflectance Fourier transform infrared spectroscopic analysis (ATR-FTIR), and a combination of elastic recoil detection analysis and Rutherford backscattering (ERDA-RBS). Nano-indentation tests were performed to measure hardness. Also, the residual stress of the films was calculated by the Stony equation. The ATR-FTIR analysis revealed that F was present in the amorphous matrix mainly as C-F and C-F₂ groups. Based on Raman spectroscopy results, it was determined that F made the DLC films more graphitic. Additionally, it was shown that adding F into the DLC coating resulted in weaker mechanical properties and the F-DLC coating exhibited lower stress than DLC films. These effects were attributed to the replacement of strong C = C by feebler C-F bonds in the F-DLC films. F-doping decreased the hardness of the DLC from 11.5 to 8.8 GPa. In addition, with F addition, the compressive stress of the DLC sample decreased from 1 to 0.7 GPa.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.7
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• pp.618-623
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• 2006

Hydrogenated Diamond-like carbon (DLC) films were prepared by the radio frequency plasma enhanced chemical vapor deposition (RF PECVD) method on silicon substrates using methane $(CH_4)$ and hydrogen $(H_2)$ gas. The wear track on the DLC films was examined after the ball-on disk (BOD) measurement with a Raman mapping method. The BOD measurement of the DLC films was performed for 1 to 3 hours with a 1-hour step time. The sliding traces on the hydrogenated DLC film after the BOD measurement were also observed using an optical microscope. The surface roughness and cross-sectional images of the wear track were obtained using an atomic force microscope (AFM). The novel Raman mapping method effectively shows the graphitization of DLC films of $300{\mu}m\times300{\mu}m$ area according to the sliding time by G-peak positions (intensities) and $I_D/I_G$ ratios.