• 한국표면공학회지
• /
• 제50권5호
• /
• pp.352-359
• /
• 2017

The growth of nanocrystalline diamond films on a p-type poly silicon substrate was studied using microwave plasma chemical vapor deposition method. A 6 mm thick poly silicon plate was mirror polished and scratched in an ultrasonic bath containing slurries made of 30 cc ethanol and 1 gram of diamond powders having different sizes between 5 and 200 nm. Upon diamond deposition, the specimen scratched in a slurry with the smallest size of diamond powder exhibited the highest diamond particle density and, in turn, fastest diamond film growth rate. Diamond deposition was carried out applying different DC bias voltages (0, -50, -100, -150, -200 V) to the substrate. In the early stage of diamond deposition up to 2 h, the effect of voltage bias was not prominent probably because the diamond nucleation was retarded by ion bombardment onto the substrate. After 4 h of deposition, the film growth rate increased with the modest bias of -100 V and -150 V. With a bigger bias condition(-200 V), the growth rate decreased possibly due to the excessive ion bombardment on the substrate. The film grown under -150V bias exhibited the lowest contact angle and the highest surface roughness, which implied the most hydrophilic surface among the prepared samples. The film growth rate increased with the apparent activation energy of 21.04 kJ/mol as the deposition temperature increased in the range of $300{\sim}600^{\circ}C$.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1990년도 추계학술대회 논문집 학회본부
• /
• pp.101-105
• /
• 1990

A DC thermal plasma system has been designed and constructed to obtain diamond films from a mixture of CH4 and H2. The effects of the deposition conditions such as substrate temperature ($850^{\circ}C-1050^{\circ}C$), gas mixing ratio (0.5-1.5% CH4 in H2), chamber pressure (50 - 200 Torr), axial magnetic field (0 - 900 Gauss) on the diamond film properties such as morphology, purity of the film and deposition rate, etc. have been examined with the aids of Scanning Electron Microscopy, X-Ray Diffraction and Raman Spectroscopy. Under optimum conditions, high quality diamond films can be obtained with high deposition rate (>$1{\mu}m/min$). Both of the growth rate and' particle size increased with the substrate temperature but the morphology changed from the faceted to unshaped when the temperature deviates its proper range. Furthermore, higher growth rates of $1.5{\mu}m/min$ can be obtained by applying an axial magnetic field to plasma torch. The observed values of interplanar spacings of diamond were in a good agreement with the values reported in ASTM data and all deposits have the diamond peak of $1332.5\;cm^{-1}$ in the Raman Spectra.

• 한국항해항만학회:학술대회논문집
• /
• 한국항해항만학회 2000년도 추계학술대회논문집
• /
• pp.116-119
• /
• 2000

The advantage of plasma-sprayed coating is their good resistance against thermal shock due to the porous state of the coated layer with a consequently low Youngs modulus. However, the existence of many pores with a bimodal distribution and a laminar structure in the coating reduces coating strength and oxidation protection of the base metals. In order to counteract these problems, there have been many efforts to obtain dense coatings by spraying under low pressure or vacuum and by controlling particle size and morphology of the spraying materials. The aim of the present study is to survey the effects of the HIP treatment between 1100 and 130$0^{\circ}C$ on plasma-sprayed oxide coating of A1$_2$O$_3$, A1$_2$O$_3$-SiO$_2$on the metal substrate (type C18N10T stainless steel). These effects were characterized by phase identification, Vickers hardness measurement, and tensile test before and after HIPing. These results show that high-pressure treatment has an advantage for improving adhesive strength and Vickers hardness of plasma-sprayed coatings.

• 신재생에너지
• /
• 제3권1호
• /
• pp.60-67
• /
• 2007

Catalyst coated membrane [CCM] type and catalyst coated substrate [CCS] type of membrane electrode assembly [MEA] were manufactured and evaluated their performance. Degradation test were conducted to find the difference of long term stability in two types of MEA and the factor for performance degradation problem occurred. Performance degradation test of single cell in two different types of MEA were carried out when current density was $200mA/cm^{2}$. The degradation test had proceeded for 230 hours and performance degradation was checked by I-V curve and impedance measurement at regular intervals. Also, MEA before/after operation and changes of catalyst layer were characterized by SEM, TEM, and XRD. Maximum power density of CCM type was higher than that of CCS type. Meanwhile, an increase of particle size of catalyst and an increase of impedance resistance after long term operation were observed. In the case of using CCM type MEA, the performance was deteriorated 38% of initial performance. In the case of using CCS type MEA, the performance was deteriorated 43% of initial performance. In consideration of difference of initial performance, performance of CCM type is higher than that of CCS type but both types had similar problems during degradation test.

• 한국세라믹학회지
• /
• 제55권2호
• /
• pp.178-184
• /
• 2018

In the present study, $TiB_2-Co$ composite coatings were thermally sprayed onto the surface of a 304 stainless steel substrate using an atmospheric plasma spray (APS). The phase analysis of the powders and plasma-sprayed coatings was performed using X-ray diffractometry analysis. The microstructures of the coatings were studied by a scanning electron microscope (SEM). The average particle size and flowability of the feedstocks were also measured. Both $TiB_2-32Co$ and $TiB_2-45Co$ (wt.%) coatings possessed typical dense lamellar structures and high-quality adhesion to the substrate. The oxidation behaviors of the coatings were studied at $900^{\circ}C$ in an atmospheric environment. In addition, the cross-sectional images of the oxidized coatings were analyzed by SEM. A thin and well-adhered layer was formed on the surface of both $TiB_2-Co$ coatings, confirming satisfactory high-temperature oxidation resistance. The kinetic curves corresponding to the isothermal oxidation of the coatings illustrated a short transient stage from rapid to slow oxidation during the early portion of the oxidation experiment.

• 한국전기전자재료학회논문지
• /
• 제30권12호
• /
• pp.812-816
• /
• 2017

$Fe_3O_4$ was prepared on the $TiO_2-coated$ natural mica substrate. The natural mica has an average particle size of $22{\mu}m$. The substrate was coated on $TiO_2$ thin films using hydrothermal synthesis at pH 1.5-2.5 at $75^{\circ}C$. The Fe precursor solution was prepared by mixing $FeSO_4$ (for $Fe^{2+}$ ion) and $FeCl_3$ (for $Fe^{3+}$ ions) with different molar ratios such as 1/2, 1/1, 2/1, 3/0, and $Fe_3O_4$ only. X-ray diffraction analysis shows that the crystal structure depends on the $FeCl_3-to-FeSO_4$ molar ratio. $Fe_3O_4$ crystal phase could be obtained at higher $FeSO_4$ contents.

• 한국세라믹학회지
• /
• 제31권4호
• /
• pp.427-435
• /
• 1994

Cu-metallized low firing temperature substrates were synthesized by cofiring green sheet of cordierite-based glass with Cu. By Sol-Gel method, Cu powder was coated with borosilicate gel which should act as a glass frit in Cu paste during cofiring. Theoretical weight ratios of Glass/Cu were controlled to be 2.5, 5, 10 and 15% by varying alkoxide concentrations. Average particle size of coated Cu was 0.629~0.674 ${\mu}{\textrm}{m}$ in comparison to that of as-received Cu(0.596 ${\mu}{\textrm}{m}$), which increased with alkoxide concentration but did not increase above certain concentration. The weight ratios of coated layer were 2.11~5.37%. The properties of Cu-metallized low firing temperature substrate, cofired at 90$0^{\circ}C$ for 1h under H2/N2 atmosphere, were as follows; sheet resistance was 13~43 m{{{{ OMEGA }}/$\square$, adhesion strength was 1.0~2.1 kgf/$\textrm{mm}^2$. From the observations of SEM photographs, the gel coated on Cu performed excellently as a glass frit.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2000년도 추계학술대회 논문집
• /
• pp.116-119
• /
• 2000

The advantage of plasma-sprayed coating is their good resistance against thermal shock due to the porous state of the coated layer with a consequently low Youngs modules. However, the existence of many pores with a bimodal distribution and a laminar structure in the coating reduces coating strength and oxidation protection of the base metals. In order to counteract these problems, there have been many efforts to obtain dense coatings by spraying under low pressure or vacuum and by controlling particle size and morphology of the spraying materials. The aim of the present study is to survey the effects of the HIP treatment between 1100 and 130$0^{\circ}C$ on plasma-sprayed oxide coating of A1$_2$O$_3$, A1$_2$O$_3$-SiO$_2$ on the metal substrate (type C18N10T stainless steel). These effects were characterized by phase identification, Vickers hardness measurement, and tensile test before and after HIPing, These results show that high-pressure treatment has an advantage for improving adhesive strength and Vickers hardness of plasma- sprayed coatings.

• 한국결정성장학회지
• /
• 제9권1호
• /
• pp.23-28
• /
• 1999

Au 미립자가 분산된 $TiO_{2}$ 박막을 졸겔담금법과 열처리공정으로 실리카 유리기판위에 제조하였다. $TiO_{2}$ 박막제조는 titanium tetraisopropoxide-EtOH-HCl-$H_{2}O$-hydrogen tetrachloroaurat (III) tetrahydrate계를 이용하였다. 고농도로 Au 화합물을 함유하면서 투명한 코팅용액을 형성하는 조건을 검토하였다. Au 금속미립자의 크기를 조절하기 위하여 광환원공정을 채택하였다. UV 조사에 따른 Au 입자의 변화와 $TiO_{2}$ 매트릭스의 상전이과정을 XRD, SEM, TEM and UV-visible spectrophotometer로 관찰하였다. 분산제로서 CPCl (Cetylpyridinium chloride monohydrate)의 효과를 평가하였다.

• 한국세라믹학회지
• /
• 제44권10호
• /
• pp.580-584
• /
• 2007

The ZrC layer instead of SiC layer is a critical and essential layer in TRISO coated fuel particles since it is a protective layer against diffusion of fission products and provides mechanical strength for the fuel particle. In this study, we carried out computational simulation before actual experiment. With these simulation results, Zirconium carbide (ZrC) films were chemically vapor deposited on $ZrO_2$ substrate using zirconium tetrachloride $(ZrCl_4),\;CH_4$ as a source and $H_2$ dilution gas, respectively. The change of input gas ratio was correlated with growth rate and morphology of deposited ZrC films. The growth rate of ZrC films increased as the input gas ratio decreased. The microstructure of ZrC films was changed with input gas ratio; small granular type grain structure was exhibited at the low input gas ratio. Angular type structure of increased grain size was observed at the high input gas ratio.