• International Journal of Precision Engineering and Manufacturing
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• 제9권3호
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• pp.18-21
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• 2008

The study deals with the effects of parameters in the synthesis of carbon nanotubes in liquid nitrogen to find the most appropriate conditions such as electrical voltage and time that give carbon nanotubes with large volume and less proportion of impurity, which is a non-nanotubed carbon. The experiment employed the method of arc-discharge between graphite cathode and anode which are immersed in liquid nitrogen. The electrical DC current of 60A and 70A were applied with the time period ranging from 10 seconds to 25 seconds. It was found that the electrical current of 60A and 13 seconds arc-discharge time allowed the largest volume of carbon nanotubes generation. The longer time leads to more impurities around the carbon nanotubes. By the filtration of CNTs-suspended solution using 0.2 micrometers porous paper filter and the characterization using TEM, the carbon nanotubes synthesized in the study were approximately 25 layers multi-walled nanotubes with the average diameter of 18.2 nanometers.

• Tribology and Lubricants
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• 제38권3호
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• pp.101-108
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• 2022

The structure and properties of tetrahedral amorphous carbon (ta-C) coatings depend on the main process parameters and bending angles of the magnetic field filter used in the filtered cathodic vacuum arc (FCVA). During the process, it is possible to effectively control the plasma flux of carbon ions incident on the substrate by controlling the arc discharge current, thereby influencing the mechanical properties of the coating film. Furthermore, we can control the size and amount of large particles mixed during carbon film formation while conforming with the bending angle of the mechanical filter mounted on the FCVA; therefore, it also influences the mechanical properties. In this study, we consider tribological characteristics for filtered bending angles of 45° and 90° as a function of arc discharge currents of 60 and 100 A, respectively. Experiment results indicate that the frictional behavior of the ta-C coating film is independent of the bending angle of the filter. However, its sliding wear behavior significantly changes according to the bending angle of the FCVA filter, unlike the effect of the discharge current. Further, upon changing the bending angle from 45° to 90°, abrasive wear gets accelerated, thereby changing the size and mixing amount of macro particles inside the coating film.

• 한방안이비인후피부과학회지
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• 제24권1호
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• pp.181-191
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• 2011

Backgrounds : Pompholyx is a distinctive reaction pattern presenting as symmetric vesicular hand and foot dermatitis. Other than acute symptoms like itching and vesicles, chronic changes with scaling, fissure and pain may follow. As patients are treated by steroid for a long period, it tends to present side effects after quitting steroid treatment. Objectives : This study was carried out to investigate the effect of carbon arc lamp therapy and oriental medical therapy that venesection therapy, ointments and herbal medicine on chronic plantar pompholyx including steroids side effects. Methods : We treated one case of chronic plantar pompholyx which had continued about 10 years, including steroids side effects with venesection therapy, carbon arc lamp therapy, ointments and herbal medicine. To evaluate the results of this treatment, we categorized symptoms into six items which are vesicles, itching, fissures, pain, erosions and scales. Results : Except mild itching, vesicles and scales in a small area, all the symptoms were subsided. Conclusions : It is considered that various kinds of oriental medical therapy including carbon arc lamp therapy could replace steroid therapy which has many side effects.

• 한국표면공학회지
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• 제54권2호
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• pp.53-61
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• 2021

The properties of tetrahedral amorphous Carbon (ta-C) film can be determined by multiple parameters and comprehensive effects of those parameters during a deposition process with filtered cathodic vacuum arc (FCVA). In this study, Taguchi method was adopted to design the optimized FCVA deposition process of ta-C for improving deposition efficiency and mechanical properties of the deposited ta-C thin film. The influence and contribution of variables, such as arc current, substrate bias voltage, frequency, and duty cycle, on the properties of ta-C were investigated in terms of deposition efficiency and mechanical properties. It was revealed that the deposition rate was linearly increased following the increasing arc current (around 10 nm/min @ 60 A and 17 nm/min @ 100A). The hardness and I_D/I_G showed a correlation with substrate bias voltage (over 30 GPa @ 50 V and under 30 GPa @ 250 V). The scratch tests were conducted to specify the effect of each parameter on the resistance to plastic deformation of films. The analysis on variances showed that the arc current and substrate bias voltage were the most effective controlling parameters influencing properties of ta-C films. The optimized parameters were extracted for the target applications in various industrial fields.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.157-157
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• 2011

Graphene has generated significant interest in the recent years as a functional material for electronics, sensing, and energy applications due to its unique electrical, optical, and mechanical properties. Much of the considerable interest in graphene stems from results obtained for samples mechanically exfoliated from graphite. Practical applications, however, require reliable and well-controlled methods for fabrication of large area graphene films. Recently high quality graphene layers were fabricated using chemical vapor deposition (CVD) on nickel and copper with methane as the source of the carbon atoms. Here, we report a simple and efficient method to synthesize graphene layers using solid carbon source. Few-layer graphene films are grown using filtered vacuum arc source (FVAS) technique by evaporation of carbon atom on Ni catalytic metal and subsequent annealing of the samples at 800$^{\circ}$C. In our system, carbon atoms diffuse into the Ni metal layer at elevated temperatures followed by their segregation as graphene on the free surface during the cooling down step as the solubility of carbon in the metal decrease. For a given annealing condition and cooling rate, the number of graphene layers is easily controlled by changing the thickness of the initially evaporated amorphous carbon film. Based on the Raman analysis, the quality of graphene is comparable to other synthesis methods found in the literature, such as CVD and chemical methods.

• 공업화학
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• 제35권4호
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• pp.321-328
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• 2024

불화탄소 기반 리튬일차전지(Li/CF_X)의 활물질로 이용되는 불화탄소는 낮은 전도성에 기인한 열악한 율속 특성으로 방전 성능이 제한적이다. 따라서, 본 연구에서는 이를 극복하기 위하여 불화탄소에 열분해 연료유를 이용하여 탄소 코팅을 진행하였고, 전기화학적 성능을 고찰하였다. 탄소 코팅에 의하여 불화탄소 표면에 무정형 탄소층이 형성되었으며, 열처리 온도에 따른 불화탄소의 표면 물리화학적 특성을 면밀히 고찰하였다. 상용 불화탄소를 450 ℃에서 열처리한 ARC@C450 샘플은 sp² 탄소 결합의 함량이 62%로 가장 크게 증가하였으며, 반이온성 C-F 결합이 가장 많이 형성되었다. 또한, ARC@C450 샘플을 환원극 활물질로 이용한 일차전지는 가장 높은 5 C 율속(392 mAh/g)에서 안정적인 방전 특성을 보였으며, R_ct 값은 미처리 시료에 비하여 53% 감소하였다. 따라서, 본 연구에서는 불화탄소의 낮은 전도성을 극복하기 위한 방법으로 열분해 연료유 기반 탄소 코팅을 제안하며, 탄소 코팅된 불화탄소는 우수한 율속 성능을 나타냄으로 고출력 일차전지로의 응용 가능성을 제시한다.

• Journal of Welding and Joining
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• 제8권1호
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• pp.54-61
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• 1990

A pilot production is made to the high carbon Cr-Ti alloy rail steels with slight quantity of Cr & Ti added to the eutectoid carbon steel. As a part of weldability of these alloy steels, SH-CCT diagram for welding is first applied to the high carbon Cr-ti alloy rail steel with 0.1wt% Ti. The microstructure, which will be appeared at the HAZ of Enclosed-arc welding of this alloy rail seel, is a single phase of pearlite. As a result of this, it shows that the welding condition of Enclosed-arc welding applied to this alloy rail steel is a good condition.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 추계 학술논문 발표대회
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• pp.164-165
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• 2013

This study is on the performance evaluation of concrete being used the CaMg based low carbon cement(LCC) as a binder and the rapidly cooled electric arc furnace oxidizing slag(EAF slag) as a fine aggregate. When using the sand as a fine aggregate, compressive strength of the concrete using LCC, as a binder, was reduced 9% comparing with that of OPC concrete. However, when using the EAF slag as a fine aggregate, the compressive strength was increased by 9%. We found that combination LCC and EAF slag contribute to the strength properties of concrete.

• 한국진공학회지
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• 제12권1호
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• pp.25-34
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• 2003

탄소 원자 간의 interaction potential로서 Tersoff에 의해 제안된 반 경험적인 potential을 이용하여 고경질 탄소박막의 합성 거동을 전산 모사하였다. 고에너지의 탄소익사를 diamond (100) 표면에 충돌시켜 고밀도의 비정질 탄소박막을 만들 수 있었으며, 전산모사에 의해 합성된 탄소 박막의 물성과 Shin 등이 발표한 filtered cathodic arc 공정에 의해 합성된 탄소의 물성을 비교하였다. ta-C 합성 실험에서 관찰된 바와 같이 최적의 에너지 영역에서 다이아몬드에 가장 유사한 물성의 필름이 합성되었으며, 이때의 입사원자 에너지인 50 eV 는 실험적으로 최적의 필름이 얻어지는 조건에서의 탄소이온 에너지와 유사하였다. 전산모사에 의해 합성된 박막은 비정질이었으며, 다이아몬드 lattice에 해당하는 short range order를 가지긴 있었다. 그러나, 최적의 에너지 조건에서는 2.1 $\AA$의 거리의 준안정 site에 탄소들이 많이 존재하는 것을 알 수 있었는데, 이는 필름 표면의 국부적 급냉효과가 최대가 되는 조건과 일치하였다. 이러한 결과는 다이아몬드상 카본필름의 합성에 있어서, 고 에너지의 탄소인자가 충돌하면서 발생하는 국소적인 열에너지의 증가가 가장 빨리 제거되는 조건에서 최적의 물성을 가지는 경질탄소 필름이 형성되는 것을 보여주고 있다.

• Journal of Welding and Joining
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• 제35권1호
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• pp.16-25
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• 2017

Gas Metal Arc Welding is a widely used process in Industry due to its high productivity and potential to automation. The present study investigates the effects of the welding speed, arc voltage, welding current and shielding gas on the bead geometry for a low-carbon steel. The Response Surface Methodology (RSM) is used to choose an experimental design and perform test runs accordingly in order to produce mathematical models predicting the geometry, the hardness and the heat input of the bead as functions of the welding parameters. The direct and interaction effects of the four welding parameters are represented graphically and allow to determine an optimum set of welding parameters.