• 한국분말재료학회지
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• 제23권5호
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• pp.384-390
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• 2016

Tri-isotropic (TRISO) coatings on zirconia surrogate beads are deposited using a fluidized-bed vapor deposition (FB-CVD) method. The silicon carbide layer is particularly important among the coated layers because it acts as a miniature pressure vessel and a diffusion barrier to gaseous and metallic fission products in the TRISO-coated particles. In this study, we obtain a nearly stoichiometric composition in the SiC layer coated at $1400^{\circ}C$, $1500^{\circ}C$, and $1400^{\circ}C$ with 20 vol.% methyltrichlorosilane (MTS), However, the composition of the SiC layer coated at $1300-1350^{\circ}C$ shows a difference from the stoichiometric ratio (1:1). The density decreases remarkably with decreasing SiC deposition temperature because of the nanosized pores. The high density of the SiC layer (${\geq}3.19g/cm^2$) easily obtained at $1500^{\circ}C$ and $1400^{\circ}C$ with 20 vol.% MTS did not change at an annealing temperature of $1900^{\circ}C$, simulating the reactor operating temperature. The evaluation of the mechanical properties is limited because of the inaccurate values of hardness and Young's modulus measured by the nano-indentation method.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2003년도 춘계종합학술대회
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• pp.366-369
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• 2003

High T$_{c}$ superconducting lines will be applied as key materials in the areas of power transmission line; magnetic levitation of vehicle; magnetic separation; magnetic energy storage and marine propulsion. A combination method of electrophoresis deposition and zone-melting for preparation of YBaCuO tape is proposed. The submicron particle powder of YBaCuO made by sol-gel method is used in the electrophoresis process. A 40~50${\mu}{\textrm}{m}$ thickness of YBaCuO film on Ag plate could be deposited in about three minutes. After deposition the film is rolled and heat treated in order to increase the density and the adhesion of the film to the Ag plate. Silver(Ag) and lead oxide(PbO) were added in the YBaCuO powder in order to reduce its melting point. The YBaCuO coating with controlled Ag and PbO contents was preliminarily zone-melted at about 945$^{\circ}C$.>.

• Journal of information and communication convergence engineering
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• 제1권2호
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• pp.63-66
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• 2003

High $T_c$ superconducting lines will be applied as key materials in the areas of power transmission line; magnetic levitation of vehicle; magnetic separation; magnetic energy storage and marine propulsion. A combination method of electrophoresis deposition and zone-melting for preparation of YBaCuO tape is proposed. The submicron particle powder of YBaCuO made by sol-gel method is used in the electrophoresis process. A 40∼50 ${\mu}\textrm{m}$ thickness of YBaCuO film on Ag plate could be deposited in about three minutes. After deposition the film is rolled and heat treated in order to increase the density and the adhesion of the film to the Ag plate. Silver(Ag) and lead oxide(PbO) were added in the YBaCuO powder in order to reduce its melting point. The YBaCuO coating with controlled Ag and PbO contents was preliminarily zone-melted at about $945^{\circ}C$.

• KEPCO Journal on Electric Power and Energy
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• 제7권1호
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• pp.129-135
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• 2021

Recently, additive manufacturing (AM) technology such as powder bed fusion (PBF) and directed energy deposition (DED) are actively attempted as consumers' needs for parts with complex shapes and expensive materials. In the present work, the effect of processing parameters on the mechanical properties of 316L stainless steel coupons fabricated by PBF and DED AM technology was investigated. Three major mechanical tests, including tension, impact, and fatigue, were performed on coupons extracted from the standard components at angles of 0, 45, 90 degrees for the build layers, and compared with those of investment casting and commercial wrought products. Austenitic 316L stainless steel additively manufactured have been well known to be generally stronger but highly vulnerable to impact and lack in elongation compared to casting and wrought materials. The process-induced pore density has been proved the most critical factor in determining the mechanical properties of AM-built metal parts. Therefore, it was strongly recommended to reduce those lack of fusion defects as much as possible by carefully control the energy density of the laser. For example, under the high energy density conditions, PBF-built parts showed 46% higher tensile strength but more than 75% lower impact strength than the wrought products. However, by optimizing the energy density of the laser of the metal AM system, it has been confirmed that it is possible to manufacture metal parts that can satisfy both strength and ductility, and thus it is expected to be actively applied in the field of electric power section soon.

• 한국분말재료학회지
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• 제29권4호
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• pp.314-319
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• 2022

The effect of the laser beam diameter on the microstructure and hardness of 17-4 PH stainless steel manufactured via the directed energy deposition process is investigated. The pore size and area fraction are much lower using a laser beam diameter of 1.0 mm compared with those observed using a laser beam diameter of 1.8 mm. Additionally, using a relatively larger beam diameter results in pores in the form of incomplete melting. Martensite and retained austenite are observed under both conditions. A smaller width of the weld track and overlapping area are observed in the sample fabricated with a 1.0 mm beam diameter. This difference appears to be mainly caused by the energy density based on the variation in the beam diameter. The sample prepared with a beam diameter of 1.0 mm had a higher hardness near the substrate than that prepared with a 1.8 mm beam diameter, which may be influenced by the degree of melt mixing between the 17-4 PH metal powder and carbon steel substrate.

• 한국기계가공학회지
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• 제20권8호
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• pp.42-51
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• 2021

Investigations of process parameters are essential when fabricating high-quality parts using additive manufacturing. This study investigates the change in the mechanical characteristics of a SUS316L specimen fabricated using selective laser melting based on the energy density and bead overlap ratio. The SUS316L powder particles were spherical and 35 ㎛ in size. Single-bead and hexahedral shape deposition experiments were performed sequentially. A single bead experiment was performed to obtain the bead overlap ratios for different laser parameters utilizing laser power and scan speed as experimental parameters. A hexahedral shape deposition experiment was also performed to observe the difference in mechanical properties, such as the internal porosity, surface roughness, and hardness, based on the energy density and bead overlap ratio of the three-dimensional printed part. Laser power, scan speed, overlap ratio, and layer thickness were chosen as parameters for the hexahedral shape deposition experiment. Accordingly, the energy density applied for three-dimensional printing, and the experimental parameters were calculated, and the energy density and bead overlap ratio for fabricating parts with good properties have been suggested.

• 한국재료학회지
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• 제8권9호
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• pp.783-790
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• 1998

용융점 및 물리.화학적 특성이 $\textrm{UO}_{2}$와 비슷한 yttria-stabilized-zirconia ($\textrm{ZrO}_{2}$-$\textrm{Y}_{2}\textrm{O}_{3}$)분말을 유도플라즈마(induction plasma)로 용융 침적시켜 원자력발전용 핵연료펠렛 제조공정에 응용하고자 하였다. 분말의 용융정도는 플라즈마동력 및 분말의 크기에 영향을 받는 것으로 나타났으며, 쉬스가스 조성, 분말분사관 위치, 입자크기 및 분사거리 등을 최적화 하여 Ar/$\textrm{H}_{2}$유량120/20$\ell$/min, 플리즈마 동력 80KW, 분사관의위치 8cm , 챔버압력 200Torr, 분사거리 18cm에서 이론밀도의 97.91%, 침적속도 20mm/min의 최적조건을 도출하였다. 침적시험에서 도출된 최적조건으로 펠렛몰더에서 제조한 펠렛은 96.5%의 밀도를 나타내었으며, 균일도 및 외곤도 우수하여 신기술에 의한 핵연료의 제조가능성을 확인하였다. 고밀도 침적에 영향을 미치는 각 변수들의 영향과 이들 변수들의 상호영향은 ANOVA(Analysis of Variance)을 이용하여 분석하였다.

• 한국전기전자재료학회논문지
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• 제14권8호
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• pp.679-687
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• 2001

It is known that amorphous BaTiO$_3$ thin films have good insulating properties[1][2]. In this investigation, amorphous BaTiO$_3$ thin films were deposited by rf magnetron sputtering on thick BaTiO$_3$ films of AC powder EL devices which were fabricated by screen-printing. The electrical and optical properties of the EL devices were then investigated. Adding amorphous BaTiO$_3$ thin film, it showed that leakage current density was decreased. Especially, leakage current density was decreased more with he sample of 0.5-hour deposition than the sample of 4-hours deposition. This result led to the improvement of luminous efficiency by 11%. It could be concluded that proper amorphous BaTiO$_3$ thin film deposition improved the surface property of dielectric layer.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.115-118
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• 2001

High-temperature superconductor films of YBa$_2$Cu$_3$$O_{7-x}$ were fabricated by electrophoretic deposition (EPD) from alcohol-based suspension. Maximum stability is observed for the suspension containing iso-alcohol as the dispersion medium. However, for the formation of a dense and adherent coating of YBCO on a silver substrate by EPD, the best results were obtained in mix PrOH and BuOH suspension. The superconducting critical current density (J$_{c}$) was 1200 A/cm$^2$ for a films deposited in 30% iso-PrOH and 70 % iso-BuOH suspension.ion.

• 한국세라믹학회지
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• 제31권6호
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• pp.643-650
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• 1994

Highly [100]-oriented MgO thin films were deposited on Si(100) single crystal substrates by reactive RF magnetron sputtering. The effects of substrate temperature, gas pressure, RF input powder, and gas composition on the characteristics of MgO thin films were studied. The higher substrate temperature and the lower operating pressure were, the better crystallinity of the deposited MgO thin films were. The influences of the RF input power and oxygen to argon ratio were very complex. The physical characteristics of the films changed dramatically with deposition conditions. Highly smooth and epitaxial MgO films were obtained at the deposition conditions as follows; subatrate temperature, $600^{\circ}C$; operating pressure, 10 mtorr; RF input power density, 2 W/$\textrm{cm}^2$; the percentage of oxygen, 10%.