• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2009년도 춘계학술대회 논문집
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• pp.177-181
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• 2009

Compositional gradient CrNx coatings were fabricated using arc ion plating in Ar/$N_2$ gaseous mixture by gradually increasing $N_2$ flux rate from 0 to 120 SCCM. The effect of negative substrate bias on the film microstructure and mechanical properties were systematically investigated with XRD, GDOES, and SEM. The results show that substrate bias has an important influence on film growth and microstructure of gradient CrNx coatings. The coatings mainly crystallized in the mixture of hexagonal $Cr_{2}N$ and fcc CrN phases. By increasing substrate bias, film microstructure evolved from an apparent columnar structure to an equiaxed one. With increasing substrate bias, deposition rate first increased, and then decreased. The maximum of deposition rate was 15 nm/min obtained at a bias of -50V.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.240-241
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• 2007

In general, high temperature superconducting coated conductors have intermediary buffers layer consisting of seed, diffusion barrier and cap layers. Simplification of the oxide materials buffer architecture in the fabrication of high temperature superconducting coated conductors is required because the deposition of multi-layers buffer architecture leads to a longer manufacturing time and a higher cost process of coated conductors. Thus, single buffer layer deposition seems to be important for practical coated conductor manufacturing process. In this study, a single gradient layered buffer deposition process of YZO for low cost coated conductors has been tried using DC reactive sputtering technique. About several thick YZO gradient single buffer layers deposited by DC co-sputtering process were found to act as a diffusion layer.

• 한국초전도ㆍ저온공학회논문지
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• 제25권4호
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• pp.24-27
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• 2023

Until now, many research activities have been conducted to commercialize high-temperature superconducting (HTS) wires for electric applications. Most of all researchers have focused on enhancing the piece length, critical current density, mechanical strength, and throughput of HTS wires. Recently, HTS magnet for generating high magnetic field shows degraded performance due to the deformation of HTS wire by high electro-magnetic force. The deformation can be derived from widthwise thickness non-uniformity of HTS wire mainly caused by wet processes such as electro-polishing of metal substrate and electro-plating of copper. Gradient sputtering process is designed to improve the thickness uniformity of HTS wire along the width direction. Copper stabilizing layer is deposited on HTS wire covered with specially designed mask. In order to evaluate the thickness uniformity of HTS wire after gradient sputtering process, the thickness distribution across the width is measured by using the optical microscope. The results show that the gradient deposition process is an effective method for improving the thickness uniformity of HTS wire.

• 한국결정성장학회지
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• 제12권2호
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• pp.101-109
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• 2002

Hot-wall CVD법으로 SiC/C 경사기능재료를 증착시키는 공정을 열역학적으로 해석하였다. Si-C-H-Cl계에 대한 열역학적 계산을 통해 공정변수(증착온도, 반응기 압력 원료 기체의 C/[Si+C]비와 H/[Si+C]비)가 증착층의 조성과 증착 수율에 미치는 영향을 조사하였고, 이를 통해 SiC/C 경사기능재료 증착에 있어서의 CVD 상평형도와 최적 공정 조건의 범위를 예측할 수 있었다.

• 한국세라믹학회지
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• 제32권6호
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• pp.685-696
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• 1995

The most important techniques in the synthesis of SiC/C function gradient material (FGM) are to control the SiC/C ratio and to obtain the moderate deposition rate. For these, various gas systems and flow rates were attempted and evaluated. It turned out that the CH4＋SiCl4＋H2 system was suitable for the deposition of SiC-rich layers, the C3H8＋SiCl4＋Ar system for the deposition of carbon-rich layers, and the C3H8＋SiCl4＋H2＋Ar system was good to deposit the layers between them.

• Carbon letters
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• 제25권
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• pp.25-32
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• 2018

In this study, a thermal-gradient chemical vapor infiltration (TG-CVI) process was numerically studied in order to enhance the deposition uniformity within the preform. The computational fluid dynamics technique was used to solve the governing equations for heat transfer and gas flow during the TG-CVI process for two- and three-dimensional (2-D and 3-D) models. The temperature profiles in the 2-D and 3-D models showed good agreement with each other and with the experimental results. The densification process was investigated in a 2-D axisymmetric model. Computation results showed the distribution of the SiC deposition rate within the preform. The results also showed that using two-zone heater gave better deposition uniformity.

• 한국대기환경학회지
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• 제16권6호
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• pp.585-594
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• 2000

Through an application of Micrometerorological methods, we conducted measurements of Hg fluxes from Nan-Ji-Do which is well known as one of the major local areal sources in Seoul metropolitan area during Match/April of 2000. In the course of our study, we determined the concentration gradients of total gaseous Hg(between 20 and 2000 cm heights) and combined these data with Micrometerorological components to derive is fluxes. It turned out that emission from and dry deposition to soil surfaces occurred at the ratio of 72:27 from a total of 271 hourly measurements. The validity of measured concentration gradients( or resulting fluxes) was evaluated in terms of percent gradient. Accordingly, about more than 95% of gradient data derived were statistically significant. The mean fluxes of Hg across soil-air interface, when computed using the concentrations gradients and relevant parameters, were found at 253(during emission) and -846ng/$m^2$/h(during dry deposition) The occurrences of abnormalously high exchange rates appear to be the combined effects of enormously high gradient values and high transfer coefficients. While the emissions of Hg occurred constantly during the whole study periods, the occurrences of dry deposition events were observed most intensively during very limited time periods(3/29 and 4/3). The results of our study cleary indicated that the studied area is a strong local areal source, while exhibiting great potential as a major sink simultaneously.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1997년도 Proceedings of the 12th KACG Technical Meeting and the 4th Korea-Japan EMGS (Electronic Materials Growth Symposium)
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• pp.7-11
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• 1997

SiC/C functionally gradient material (FGMs) were formed on graphite substrates by hot-wall chemical vapor deposition (CVD) technique using the SiCl$_4$-C$_3$H8-H$_2$ chemistry. Thermochemical equilibrium calculations were carried out to investigate the deposition process. The effect of process variables on the deposition yield and the SiC/C ratio in deposited layers was studied in detail. Calculated results showed a reasonable agreement with the experiment in a qualitative sense. SiC/C FGMs with excellent mechanical and thermal properties could be successfully formed on graphite substrates by carefully controlling the compositions in the deposited layers.

• 한국결정성장학회지
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• 제30권1호
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• pp.7-11
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• 2020

TiZrN 코팅의 도핑 공정에서 탄소 페이스트 증착 방식에 따른 탄소의 용해성 변화를 격자왜곡(lattice distortion)과 원자농도(atomic concentration)를 통해 비교 및 고찰하였다. 딥코팅, 스핀코팅과 스크린프린팅 방식을 이용하여 탄소 페이스트를 도포한 후, 레이저를 조사하여 탄소 구배층(carbon gradient layer)을 형성시켰다. 모든 구배층은 탄소가 도핑되는 구조였으며, 두께 및 탄소 도핑량은 페이스트 도포 방식에 의존하였다. 결정 구조 분석 결과, 딥코팅에 의해 코팅층을 도핑할 때 보다 스핀코팅과 스크린프린팅에 의해 코팅층을 도핑하였을 때, 더 큰 격자 팽창이 일어남을 확인할 수 있었다. 또한 XPS depth profile을 통해 딥코팅에 의한 탄소 구배층 두께는 약 30 nm, 스핀코팅과 스크린프린팅의 경우 대략 100 nm로 더 깊은 구배층이 형성됨을 확인하였다. 침탄 전 코팅의 경도는 약 30 GPa였으며, 침탄 후에는 딥코팅 시편의 평균 경도가 약 31 GPa였고 스핀코팅과 스크린프린팅의 평균 경도는 대략 37 GPa로 증가한 것으로 보아 탄소 도핑을 통한 격자팽창 및 구배층의 영향을 확인하였다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1994년도 춘계 학술발표 강연 및 논문 개요집
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• pp.124-124
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• 1994