• Journal of the Korean Ceramic Society
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• v.28 no.6
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• pp.478-482
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• 1991

Numerous researchers have observed the bubble formation from C/C composite at high temperature (1300$^{\circ}C$∼1700$^{\circ}C$). According to thermodynamic calculation, the bubble can be formed at the temperatures above 1500$^{\circ}C$ in the case of SiC coated C/C composite. However, the bubble below 1500$^{\circ}C$ could not be explained. Therfore, in an effort to explain the low temperature bubble formation, the effects of inhibitors such as B, Al, Zr and Si were thermodynamically investigated along with hydrogen and water vapor impurities resolved in C/C composite and SiC coating layer.

• Journal of Welding and Joining
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• v.31 no.3
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• pp.66-75
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• 2013

In this study, the effect of coating thickness($20{\mu}m$ and $30{\mu}m$) on microstructure and tensile properties in Yb:YAG disk laser welds of Al-Si-coated boron steel (1.2mmt) was investigated. In the case of as welds, the quantity of ferrite was found to be higher in base metal than that in HAZ (Heat Affected Zone) and fusion zone, indicating, fracture occurrs in base metal, and the fracture position is unrelated to the coating thickness. Furthermore, yield strength, tensile strength of base metal and welded specimens showed similar behavior whereas elongation was decreased. On the other hand, base metal and HAZ showed existence of martensite after heat treatment, the fusion zone indicated the presence of full ferrite or austenite and ferrite during heat treatment ($900^{\circ}C$, 5min), After water cooling, austenite was transformed to martensite, and the quantity of ferrite in fusion zone was higher as compared with in base metal, resulting in sharply decrease of yield strength, tensile strength and elongation, which leads to fracture occured at fusion zone. In particular, results showed that because the concentration of Al was higher in 30um coating layer specimen than that of 20um coating specimen, after heat treatment, producing a higher quantity of ferrite was higher after heat treatment in the fusion zone; howevers, it leads to a lower tensile property.

• Journal of the Korean Applied Science and Technology
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• v.41 no.1
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• pp.46-57
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• 2024

In this study, the various process conditions for high-power DC Magnetron Sputtering (DCMS) on the surface roughness of carbon thin films were investigated. The optimal conditions for Si/C coating were 40min for deposition time, which does not deviate from normal plasma, to obtain the maximum deposition rate, and the conditions for the best surface roughness were -16volt bias voltage and 400watt DC power with 1.3x10-3torr chamber pressure. Under these optimal conditions, an excellent carbon thin film with a surface roughness of 1.62nm and a thickness of 724nm was obtained. As a result of XPS analysis, it was confirmed that the GLC structure (sp² bonding) was more dominant than the DLC structure (sp³ bonding) in the thin film structure of the carbon composite layer formed by DC sputtering. Except in infrequent cases of relatively plasma instability, the lower bias voltage and applied power induces smaller surface roughness value due to the cooling effect and particle densification. For the optimal conditions for Graphite/C composite layer coating, a roughness of 36.3 nm and a thickness of 711 nm was obtained under the same conditions of the optimal process conditions for Si/C coating. This layer showed a immensely low roughness value compared to the roughness of bare graphite of 242 nm which verifies that carbon coating using DC sputtering is highly effective in modifying the surface of graphite molds for glass forming.

• Journal of the Korean Society of Safety
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• v.12 no.4
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• pp.79-85
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• 1997

In order to improve the surface characteristics of polymethylmethacrylate(PMMA), oxide thin film coatings were applied using the sol-gel dip-coating technique. The $Si(OC_2H_5)_4$, tetra-ethyl-ortho-silicate(TEOS) was used as a starting material for $SiO_2$ coating. The hardness of the alkoxy-derived oxide-coated PMMA was increased from 190 MPa for non-coated PMMA with increasing film thickness. By optimizing the heating conditions and the hydrolysis conditions, a maximum apparent hardness obtained In the present study was achieved 310 MPa using the withdrawal velocity of 5cm/min and heat treatment at $90^{\circ}C$ for 5 hours, which is about 1.6 times larger than that of uncoated PMMA.

• Journal of the Korean Ceramic Society
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• v.34 no.1
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• pp.37-44
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• 1997

Barium ferrite thin films on the thermal oxidized Si substrate were prepared by using sol-gel method (dip coating) from the sol of composition ratio of 5.25, designated by mole ratio 2Fe/Ba. The gelation process was largely divided into 4 step, and the sol prepared by reaction for 90 minutes at 8$0^{\circ}C$ was the suit-able for coating. Needle shaped particles formed on the coating layer were placed parallel to substrate and the inclination was increased with film thickness. The easy-direction of magnetization of needle shaped par-ticles was long-axis direction.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.169.2-169.2
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• 2013

본 연구에서는 gas를 이용한 PECVD 공법중 이온화 에너지가 높고 대면적 코팅이 용이한 Hybrid 코팅 장비에서 Linear Ion-Gun 이용하여 탄화수소 계열의 gas인 $C_2H_2$ 와 Si을 함유한 TMS (tetramethylsilane, $Si(CH_3)_4)$ gas를 이용하여 저마찰, 고경도 특성을 갖는 Si-DLC 코팅에 대한 연구를 수행하였다. Si-DLC 코팅에 앞서 전처리 공정으로 Linear Ion-Gun에 Ar gas를 주입하고 고전압의 DC 전원을 인가하여 제품 표면의 건식세정 및 표면 활성화를 진행 후, $C_2H_2$ 와 TMS gas를 Linear Ion-Gun에 주입하여 Si-DLC 코팅 공정을 진행하였다. Si-DLC 코팅시 $C_2H_2$ gas 주입량을 고정하고 TMS 가스 유량을 5~20sccm으로 조절하여 Si 함유량에 따른 Si-DLC 코팅막의 특성을 분석하였다. 이렇게 코팅된 Si-DLC의 박막 특성 분석으로 마찰계수 측정을 위해 ball-on-disk 타입의 tribometer를 사용하였으며, 박막 경도 측정은 Nano-indenter를 이용하여 분석을 진행하였다. 그 결과 Si을 포함하지 않는 DLC의 경우 마찰계수가 ~0.2를 가지는 반면, Si-DLC의 경우 Si 함유량이 약 1.5at%일 때, 마찰계수 ~0.04 저마찰의 우수한 특성을 지니며, 박막의 경도는 22[Gpa]로 고경도의 Si-DLC 코팅을 확인할 수 있었다.

• Journal of the Korean Ceramic Society
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• v.46 no.5
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• pp.534-539
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• 2009

Reaction Bonded Silicon Carbide(RBSC) has been used for engineering ceramics due to low-temperature fabrication and near-net shape products with excellent structural properties such as thermal shock resistance, corrosion resistance and mechanical strength. Recently, attempts have been made to develop hot gas filter with gradient pore structure by RBSC to overcome weakness of commercial clay-bonded SiC filter such as low fracture toughness and low reliability. In this study a fabrication process of porous RBSC with multi-layer pore structure with gradient pore size was developed. The support layer of the RBSC with multi-layer pore structure was fabricated by conventional Si infiltration process. The intermediate and filter layers consisted of phenolic resin and fine SiC powder were prepared by dip-coating of the support RBSC in slurry of SiC and phenol resin. The temperature of $1550^{\circ}C$ to make Si left in RBSC support layer infiltrate into dip-coated layer to produce SiC by reacting with pyro-carbon from phenol resin.

• Journal of the Korean Society for Heat Treatment
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• v.20 no.6
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• pp.299-305
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• 2007

The effect of spray deposition of oxide particles on oxidation behaviors of as-cast Mo-14.2Si-9.6B (at%) alloys at $1200^{\circ}C$ up to for 100 hrs has been investigated. Various oxide powders are utilized to make coatings by spray deposition, including $SiO_2,\;TiO_2,\;ZrO_2,\;HfO_2$ and $La_2O_3$. It is demonstrated that the oxidation resistance of the cast Mo-Si-B alloy can be significantly improved by coating with those oxide particles. The growth of the oxide layer is reduced for the oxide particle coated Mo-Si-B alloy. Especially, for the alloy with $ZrO_2$ coating, the thickness of oxide layer becomes only one fifth of that of uncoated alloys when exposed to in air for 100 hrs. The reduction of oxide scale growth of the cast Mo-Si-B alloy due to oxide particle coatings are discussed in terms of the change of viscosity of glassy oxide phases that form during oxidation at high temperature.

• Korean Journal of Materials Research
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• v.11 no.11
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• pp.965-971
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• 2001

The objective of this study is to investigate the characteristics - microstructure, hardness, adhesive strength and friction coefficient - of the coatings with aging - treatment after optimizing internal- plasma spraying parameters for Al-30wt%Si powder as a basic research to manufacture the cylinder block bore for Al engine composed of Al-30wt%Si alloy on Al alloy, The optimum internal-plasma spraying parameters of Al-30wt%Si alloy are summarized as follows: voltage: 37.5V, current: 160A, working distance: 25mm, gun traverse speed: 4.5mm/s, rotating speed: 518m/min. The primary Si particles grew aggressively with increasing heat-treating temperature. The hardness of the as-sprayed coating was about Hv=275 but this value was abruptly decreased with increasing heat-treating temperature. And average friction coefficient of the coating was below 0.08 after heat treatment for 48h at $175^{\circ}C$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.7
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• pp.481-485
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• 2003

Amorphous silicon (a-Si:H) based TFT process has been studied at the maximum temperature of 15$0^{\circ}C$ with 25${\mu}{\textrm}{m}$ thick flexible and adhesive tape type polyimide foil substrate, which has benefit on handling a rugged, flexible plastic substrate trough sticking simply it to glass. This paper summarize the process procedure of the TFT on the plastic substrate and shows its electrical characteristics in comparison with glass substrate using primarily the ON/OFF current ratio and the field effect mobility as the quality criterion. The a-SiN:H coating layer played an important role in decreasing surface roughness of plastic substrate, so leakage current of TFT was decreased and mobility was increased. The results show that high quality a-Si:H TFTs can be fabricated on the plastic substrates through coating a rough plastic surface with a-SiN:H.