• Korean Journal of Materials Research
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• v.25 no.11
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• pp.622-629
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• 2015

Cu circuits were successfully fabricated on flexible PET(polyethylene terephthalate) substrates using wettability difference and electroless plating without an etching process. The wettability of Cu plating solution on PET was controlled by oxygen plasma treatment and $SiO_x$-DLC(silicon oxide containing diamond like carbon) coating by HMDSO(hexamethyldisiloxane) plasma. With an increase of the height of the nanostructures on the PET surface with the oxygen plasma treatment time, the wettability difference between the hydrophilicity and hydrophobicity increased, which allowed the etchless formation of a Cu pattern with high peel strength by selective Cu plating. When the height of the nanostructure was more than 1400 nm (60 min oxygen plasma treatment), the reduction of the critical impalement pressure with the decreasing density of the nanostructure caused the precipitation of copper in the hydrophobic region.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.103.1-103.1
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• 2016

플라즈마 코팅은 진공 및 진공에서 발생된 플라즈마 대기압 플라즈마를 이용하여 기판에 코팅하는 기술을 의미하는 것으로 최근 다양한 코팅 소스 및 물질계가 개발되면서 그 응용을 넓혀가고 있다. 플라즈마 코팅은 물리증착 및 화학증착에서 주로 이용하고 있는데 플라즈마를 이용하는 대표적인 기술로 스퍼터링과 음극아크증착, 플라즈마 화학증착 등이 있다. 스퍼터링은 기존의 마그네트론 스퍼터링에 비해 이온화율이 대폭 향상된 HIPIMS(High Power Impulse Magnetron Sputtering) 기술이 개발되면서 경질피막 제조의 신기술로 자리 잡고 있고 음극아크증착의 경우는 다양한 Filtered 아크소스가 개발되면서 후막 고경도 DLC(Diamond-like Carbon) 등 기존의 방법으로 달성할 수 없었던 코팅층의 제조가 가능하게 되었다. 최근 수명 및 물성이 크게 향상된 소재들이 다양하게 개발되었는데 이들 소재는 가공이 잘 되지 않는 난삭재가 대부분이어서 기존의 가공 Tool이 한계를 드러내고 있다. 이에 따라 난삭재 가공용 새로운 Tool에 대한 수요가 크게 증가하고 있는데 이에 대응하는 유력한 방법 중의 하나가 플라즈마를 이용한 경질코팅이다. 이렇듯 플라즈마 코팅은 난삭재가공용 Tool을 비롯하여 기계나 자동차 부품의 고경도, 저마찰 코팅, 기능성 코팅 등 다양한 분야에 응용을 확대하고 있다. 본 논문에서는 플라즈마 코팅의 최신 기술개발 동향과 그 응용에 대해 고찰하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.1027-1032
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• 2012

Two types of very small multiplying gears and arrays have been developed for new dental hand-pieces, and the increased speed ratios, modules, number of teeth, gear diameters, and gear types were calculated based on the dynamics of the machinery. The contacting and bending strengths were evaluated for gear teeth with two design concepts using AGMA equations and finite element analyses, and the contacting stresses on teeth with and without DLC (diamond-like-carbon) coating layers were calculated. Fatigue and tension tests were performed to obtain an S-N curve, the Young's modulus, and the strength of the gear material, and these were utilized in the analyses. Slightly larger stresses were found for 2-axis-type gears than for other types of gears, and the S-N curves showed that a gear lifetime of 109 cycles was satisfied. The contacting stresses in gears coated with DLC were reduced by 30%. A new prototype model of a hand-piece with small gears was successfully fabricated and tested.

• Korean Journal of Materials Research
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• v.20 no.11
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• pp.559-569
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• 2010

The liquid-phase sintering method was used to prepare a glass lens forming core composed of SiC-$Al_2O_3-Y_2O_3$. Spark plasma sintering was used to obtain dense sintered bodies. The sintering characteristics of different SiC sources and compositions of additives were studied. Results revealed that, owing to its initial larger surface area, $\alpha$-SiC offers sinterability that is superior to that of $\beta$-SiC. A maximum density of $3.32\;g/cm^3$ (theoretical density [TD] of 99.7%) was obtained in $\alpha$-SiC-10 wt% ($6Al_2O_3-4Y_2O_3$) sintered at $1850^{\circ}C$ without high-energy ball milling. The maximum hardness and compression stress of the sintered body reached 2870 Hv and 1110 MPa, respectively. The optimum ultra-precision machining parameters were a grinding speed of 1243 m/min, work spindle rotation rate of 100 rpm, feed rate of 0.5 mm/min, and depth of cut of $0.2\;{\mu}m$. The surface roughnesses of the thus prepared final products were Ra = 4.3 nm and Rt = 55.3 nm for the aspheric lens forming core and Ra = 4.4 nm and Rt = 41.9 for the spherical lens forming core. These values were found to be sufficiently low, and the cores showed good compatibility between SiC and the diamond-like carbon (DLC) coating material. Thus, these glass lens forming cores have great potential for application in the lens industry.

• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.44-44
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• 1998

It was observed that the friction coefficient decreased with increasing Si concentration in the l ilms. Furthermore, the friction behavior became more s때ble even when very small amount of S Si of less than 0.5 at. % was incorporatA:회 By analyzing the composition of the debris f formed, we could show that the low and stabilized friction coefficient is in마nately relatA:었 w with the formation of the Si rich oxide debris. These result supports the mechanism that the h hydrated silica debris is the reason for low friction coefficient in humid environment. Second e evidence of the role of Si rich oxide debris could be found in the triOO-chemical reactions d during initial stage of triho-test. When the Si concen$\sigma$ation was less than 5 at.%, initial t transient period of high friction coefficient was commonly observed. Mter the transient period, m the friction coefficient becomes lower with increasing contact cycles. The initial $\sigma$ansient p peri여 becomes shorter and the starting and maximum friction coefficients in $\sigma$ansient 야,riod d decreased with increasing Si concentration. Composition of the debris on the wear scar s surface was analyzed by Auger spe따'Oscopy at v뼈ous stages in the initial transient period. W We observed that when the friction coefficient increased in earlier stage of the $\sigma$'ansient p period, iron and oxygen was observed in the debris. However, decrease in the 당iction c coefficient in the later stage of the transient period was associated with the formation of s silicon rich oxide debris. This result also supports the friction mechanism of Si-DLC films t that the formation of Si rich oxide debris results in low friction coefficient in ambient a atmosphere. atmosphere.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.3
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• pp.89-94
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• 2019

K1A1 tank commander's primary thermal sight is a device that enables tank commanders to detect, identify, aim and track the target by observing targets in all directions during day, night and in situations of smokescreen and fog through $360^{\circ}$ rotation independent from the gunner's primary thermal sight and stabilizing the line of sight even under the vibrations occurring when the tank is standstill and moving. The main function of this device is to detect and process visible and thermal images and deliver the final images to the tank commander. One of the core parts to that end is the observation window (daytime/thermal image window). This core part is mounted at the entrance of the optical path for observing the target and plays the role of making visible light during the daytime and infrared light during the night pass through the target and transmitting the resultant images to the internal optical system of the tank commander's primary thermal sight. Such core parts have been selected as depot maintenance items so that they are replaced by new parts instead of being recycled when they are subjected to maintenance in most cases. That is, the military budget is wasted because such parts are replaced by new parts despite that they can be recycled for maintenance. Therefore, this study proposed a mounting tool for polishing and coating observation windows (daytime and thermal image window) using planar polishing equipment and DLC (Diamond-Like Carbon) coating equipment. In addition, this study presented an amendment (proposal) of the Depot Maintenance Work Request (DMWR) already published to verify the performance of recycled products including the establishment of inspection standards for recycling processes.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.144.2-144.2
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• 2016

Diamond-like carbon (DLC) coatings have been widely applied to the mechanical components, cutting tools due to properties of high hardness and wear resistance. Among them, hydrogenated amorphous carbon (a-C:H) coatings are well-known for their low friction properties, stable production of thin and thick film, they were reported to be easily worn away under high temperature. Non-hydrogenated tetrahedral amorphous carbon (ta-C) is an ideal for industrial applicability due to good thermal stability from high $sp^3$-bonding fraction ranging from 70 to 80 %. However, the large compressive stress of ta-C coating limits to apply thick ta-C coating. In this study, the thick ta-C coating was deposited onto Inconel alloy disk by the FCVA technique. The thickness of the ta-C coating was about $3.5{\mu}m$. The tribological behaviors of ta-C coated disks sliding against $Si_3N_4$ balls were examined under elevated temperature divided into 23, 100, 200 and $300^{\circ}C$. The range of temperature was setting up until peel off observed. The experimental results showed that the friction coefficient was decreased from 0.14 to 0.05 with increasing temperature up to $200^{\circ}C$. At $300^{\circ}C$, the friction coefficient was dramatically increased over 5,000 cycles and then delaminated. These phenomenon was summarized two kinds of reasons: (1) Thermal degradation and (2) graphitization of ta-C coating. At first, the reason of thermal degradation was demonstrated by wear rate calculation. The wear rate of ta-C coatings showed an increasing trend with elevated temperature. For investigation of relationship between hardness and graphitization, thick ta-C coatings(2, 3 and $5{\mu}m$) were additionally deposited. As the thickness of ta-C coating was increased, hardness decreased from 58 to 49 GPa, which means that graphitization was accelerated. Therefore, now we are trying to increase $sp^3$ fraction of ta-C coating and control the coating parameters for thermal stability of thick ta-C at high temperatures.