• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.195.1-195.1
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• 2013

Cu는 금속 박막재료로서 높은 전기전도성을 지니고 있을 뿐만 아니라 Ag, Al, Pt 등 보다 비용이 저렴하여, 높은 전기전도성을 필요로 하는 박막 재료로써 폭넓게 사용되고 있다. 그러나, 낮은 기계적 특성을 지니고 있어서 interconnect와 같은 작은 단면적의 배선재료로 사용될 경우, 높은 전류밀도에 따른 electromigration 현상에 의하여 hillock 또는 void의 형성 등 박막재료의 변형이 생기게 되어서 전자소자의 수명이 단축된다는 단점이 있다. TiN은 금속재료 못지않은 높은 전기 전도성을 지니고 있을 뿐만 아니라, 금속재료에 비하여 높은 기계적 특성과 녹는점을 지니고 있어 다양한 분야로 사용되고 있다. 본 연구에서는 Cu와 TiN composite 박막을 soda-lime glass위에 증착하여 낮은 비저항 뿐만 아니라 Cu와 비교하여 기계적 특성이 향상된 박막을 제작하고자 하였다. Cu와 TiN composite 박막 증착을 위하여 DC reactive magnetron co-sputtering 장비를 사용하였으며, Cu와 Ti 타겟 power, Ar:N2 유량비(Flow rate)을 변화시켜 Cu와 Ti의 조성비 및 TiN의 결정성을 조절하였고, 이를 통하여 박막의 TiN 조성에 따른 낮은 비저항 값과 순수한 Cu 박막과 비교하여 높은 기계적 특성을 지닌 Cu-TiN 박막을 증착하였다. Cu-TiN composite 박막의 구조 및 조성은 SEM (Scanning Electron Microscope), EDS (Energy Dispersive Spectrometer), XPS (X-ray Photoelectron Spectroscopy)장비를 사용하여 분석하였으며, 전기전도도는 4-point probe를 사용하여 측정하였고, Knoop hardness 측정방법을 사용하여 박막의 기계적 특성을 측정하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.255-255
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• 2013

최근 그래핀 연구와 더불어 2차원 구조의 나노소재에 대한 관심이 급증하면서 육각형의 질화붕소(hexagonal boron nitride; h-BN) 박막(nanosheet)이나 붕소 탄화질화물(boron caronitride; BCN) 박막과 같은 2차원 구조체에 대한 연구가 활발히 진행되고 있다. 그 중 BCN은 반금속(semimetal)인 흑연(graphite)과 절연체인 h-BN이 결합된 박막으로 원소의 구성 비율에 따라 전기적 특성을 제어할 수 있다는 장점이 있다. 따라서 다양한 나노소자로의 응용을 위한 연구가 활발히 진행되고 있다. 본 연구에서는 폴리스틸렌(polystyrene, PS)과 보레인 암모니아(borane ammonia)를 고체 소스로 이용하여 열화학 기상증착법을 이용하여 BCN 박막를 SiO2 기판 위에 직접 합성하였다. SEM과 AFM 관측을 통해 합성된 BCN 박막을 확인하였으며, RMS roughness가 0.5~2.6 nm로 매우 낮은 것을 확인하였다. 합성과정에서 PS의 양을 조절하여 BCN 박막의 탄소의 밀도를 성공적으로 제어하였으며, 이에 따라 전기적인 특성이 제어되는 양상을 확인하였다. 또한 합성온도 변화에 따른 BCN 박막의 전기적인 특성이 제어되는 양상을 확인하였다. 추가적으로 같은 방법을 이용하여 BCN 박막을 Ni 위에서 합성하여 SiO2 기판위에 전사 하였다. 합성된 BCN 박막의 구조적 특징과 화학적 조성 및 결합 상태를 투과전자현미경(transmission electron microscopy), X-선 광전자 분광법(X-ray photoelectron spectroscopy)을 통해 조사하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.116.2-116.2
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• 2013

최근 그래핀, hexagonal boron nitride (h-BN) 및 $MoS_2$ (molybdenum disulfide)와 같은 2차원 결정 물질들은 무어의 법칙 (Moore's Law)를 뛰어넘어 계속적인 소자의 소형화를 가능케 하고 또한 대면적, 저비용 소자 개발을 가능케 하는 우수한 특성을 가진 차세대 반도체 트랜지스터 소재로 각광받고 있다. $MoS_2$는 bulk 상태일 때는 1.2 eV의 indirect 밴드갭을 가지지만 단층형태일 때는 1.8 eV의 direct 밴드갭을 가지며 dielectric screening 기법 등을 통해 mobility를 향상시킬 수 있는 것으로 연구된 바 있다. 본 연구에서는 화학기상증착(chemical vapor deposition, CVD)법을 이용하여 $MoS_2$박막을 형성하기 위한 기초연구인 Mo전구체의 특성 평가 및 적합한 공정조건 개발 연구를 수행하였다. 사용한 전구체는 $Mo(CO)^6$ (Molybdenum hexacarbonyl)이고, 온도 및 압력, 반응기체($H_2S$, Hydrogen sulfide) 유량 등의 공정 조건 변화에 따른 거동을 Fourier transform infrared spectroscopy (FT-IR) 시스템을 사용하여 측정하였다. 또한 $Mo(CO)^6$의 분자구조를 상용 프로그램인 Gaussian으로 시뮬레이션 하여 실제 FT-IR 측정 결과값과 비교 분석하였다. 화학기상증착법을 이용한 $MoS_2$ 증착조건 최적화를 위하여 다양한 온도, 유량, 압력, 및 기판 종류에 대하여 증착 실험을 수행하였으며, 증착된 샘플은 scanning electron microscope (SEM), Raman spectroscopy를 이용하여 분석하였다.

• Journal of the Korean Society for Heat Treatment
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• v.19 no.2
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• pp.90-95
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• 2006

Nitriding or carburizing of carbon steels results in good mechanical properties such as high surface hardness and wear resistance but it has no affection on the corrosion resistance. Corrosion properties of nitriding and carburizing steels could be deteriorated. So, recently, there have been great demand for oxi-nitriding to enhance both mechanical properties and corrosion resistance. In this study, the corrosion resistance of carbon steel, S35C, and free cutting steel, SUM222, are prepared by vacuum nitriding and vacuum post-oxidation were compared with those treated by nitriding. After vacuum post-oxidation, $5{\mu}m$ oxide layer was formed on the nitride layer with $20{\sim}30{\mu}m$ depth. Potentio-dynamic polarization curve in corrosion test showed that the corrosion potential after post oxidation was increased from 200 mV to 800 mV in S35C and from 600 mV to 1200 mV in SUM222. SEM analyses showed that pores was increased and surface roughness became rougher with post oxidation. However, the formation of $Fe_3O_4$ resulted in the enhanced corrosion resistance of steels.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.2
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• pp.137-148
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• 1995

The nitridation kinetics of titanium powder were studied by isothermal and non-isothermal (dynamic) methods in high purity nitrogen under I atm pressure. For the comparison with nitridation, the oxidation kinetics of titanium powder were also studied in dry oxygen at I atm pressure. An automatic recording electrobalance was used to measure the weight gain as a function of time and temperature. For the reaction with nitrogen, the nitride was formed at over $700^{\circ}C$. The reaction with nitrogen followed the parabolic rate law, and the activation energy was calculated to be 31 kcal/mol in the isothermal method (above $900^{\circ}C$). The non-stoichiometric TiNx has been synthesized by the nitridation at a proper temperature and time, followed by the homogenizing treatment above $1100^{\circ}C$. In comparison with the stoichiometric $TiN_{1.0}$ and the non-stoichiometric TiNx ($TiN_{0.5}$ and $TiN_{0.65}$), the hot oxidation characteristics of the former is superior to that of the latter. However, both non-stoichiometric nitrides make little difference in the hot oxidation characteristics.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.3
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• pp.649-657
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• 2008

This paper describes the optimized output performances such as output power and the third order intermodulation in GaN high power transistor packages which consist of chip die, chip capacitors, and wire bonding. The optimized output power according to wire bonding techniques, and third order intermodulation performances according to wire bonding and bias conditions are discussed. In addition, it is shown through the nonlinear simulation that how the output performances are sensitive to the inductance values which are realized by wire bonding for matching network in the limited package area.

• Journal of Advanced Navigation Technology
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• v.17 no.5
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• pp.574-580
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• 2013

In this paper, The process of thin-film coating technology was applied to improve adhesion of the hardness thin film and nitride layer. This thin-film coating technology have formed composite thin-film to gain hardness and toughness used in press mold. The thin-film coating manufacturing technology increased vacuum present in the vacuum chamber and improved the throw ratio of the gun power using physical vapor deposition coating technology. Ti alloys target improved performance and surface material through the development of a composite film coating technology for various precision machining parts.

• Journal of Powder Materials
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• v.26 no.5
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• pp.415-420
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• 2019

SiAlON ceramics are used as ceramic cutting tools for heat-resistant super alloys (HRSAs) due to their excellent fracture toughness and thermal properties. They are manufactured from nitride and oxide raw materials. Mixtures of nitrides and oxides are densified via liquid phase sintering by using gas pressure sintering. Rare earth oxides, when used as sintering additives, affect the color and mechanical properties of SiAlON. Moreover, these sintering additives influence the cutting performance. In this study, we have prepared $Yb_{m/3}Si_{12-(m+n)}Al_{m+n}O_nN_{16-n}$ (m = 0.5; n = 0.5, 1.0) ceramics and manufactured SiAlON ceramics, which resulted in different colors. In addition, the characteristics of the sintered SiAlON ceramics such as fracture toughness and microstructure have been investigated and results of the cutting test have been analyzed.

• Steel and Composite Structures
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• v.33 no.1
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• pp.93-109
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• 2019

In the present study, vibration analysis of double bonded micro sandwich cylindrical shells with saturated porous core and carbon/boron nitride nanotubes (CNT/BNNT) reinforced composite face sheets under multi-physical loadings based on Cooper-Naghdi theory is investigated. The material properties of the micro structure are assumed to be temperature dependent, and each of the micro-tubes is placed on the Pasternak elastic foundations, and mechanical, moisture, thermal, electrical, and magnetic forces are effective on the structural behavior. The distributions of porous materials in three distributions such as non-linear non-symmetric, nonlinear-symmetric, and uniform are considered. The relationship including electro-magneto-hydro-thermo-mechanical loadings based on modified couple stress theory is obtained and moreover the governing equations of motion using the energy method and the Hamilton's principle are derived. Also, Navier's type solution is also used to solve the governing equations of motion. The effects of various parameters such as material length scale parameter, temperature change, various distributions of nanotube, volume fraction of nanotubes, porosity and Skempton coefficients, and geometric parameters on the natural frequency of double bonded micro sandwich cylindrical shells are investigated. Increasing the porosity and the Skempton coefficients of the core in micro sandwich cylindrical shell lead to increase the natural frequency of the structure. Cylindrical shells and porous materials in the industry of filters and separators, heat exchangers and coolers are widely used and are generally accepted today.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.10
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• pp.1-8
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• 2021

Cylinder liners used in diesel engines of combat equipment are prone to cavitation due to wet cooling. The damage caused by erosion and corrosion due to cavitation has a fatal effect on the performance and lifespan of a diesel engine. Therefore, a study was conducted to improve the durability of cylinder liners. Two surface treatment techniques were proposed: nitriding and chrome plating. It was observed that the amount of erosion on the surface of nitride-treated cylinder liners was high because the surface-treated part eroded due to its weak impact resistance against the bubble explosion generated by cavitation. In contrast, the chrome-plated cylinder liner had a lower amount of erosion among the specimens subjected to the accelerated test. These results verified that the resistance of chrome-plated liners against cavitation is high. Therefore, it can withstand the impact of bubble explosion. If the chrome plating thickness is set with reference to the KS standard, an exceptional durability of abrasion, wear resistance, and corrosion resistance can be obtained. If the thickness is set between 120~250㎛, it is expected that the durability of the cylinder liner can be improved. Although a recovery method for corroded cylinder liners is suggested, the proposed method has an inherent risk of crack generation. Therefore, further research is required to solve this problem.