• Nuclear Engineering and Technology
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• 제43권2호
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• pp.159-166
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• 2011

Si-rich-layer-coated U-7 wt%Mo plates were prepared in order to evaluate the diffusion barrier performance of the Si-rich layer in U-Mo vs. Al interdiffusion. Pure Si powder was used for coating the U-Mo plates by annealing at $900^{\circ}C$ for 1 h under vacuum of approximately 1 Pa. Si-rich layers containing more than 60 at% of Si were formed on U-7 wt%Mo plates. Diffusion couple tests were conducted in a muffle furnace at $560-600^{\circ}C$ under vacuum using Si-rich-layer-coated U-Mo plates and pure Al plates. Diffusion couple tests using uncoated U-Mo plates and Al-(0, 2 or 5 wt%)Si plates were also conducted for comparison. Si-rich-layer coatings were more effective in suppressing the interaction during diffusion couple tests between coated U-Mo plate and Al, when compared with U-Mo vs. Al-Si diffusion couples, since only small amounts of Al in the coating could be found after the diffusion couple tests. Si-rich-layer-coated U-7wt%Mo particles were also prepared using the same technique for U-7 wt%Mo plates to observe the microsturctures of the coated particles.

• 한국표면공학회지
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• 제20권2호
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• pp.49-59
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• 1987

The properties of $Cr_2O_3-Al_2O_3-SiO_2$ composite oxide coatings on steel surface were investigated. The results obtained were as follows: The microhardness of oxide coating layer increased with increasing heat-treatment temperature and $Cr_2O_3$ content in coating layer. The hardness showed the highest value (850Hv) treated at 700$^{\circ}C$ for $SiO_2:Al_2O_3:Cr_2O_3$=1:1:4. Increasing heat-treatment temperature, corrosion current density became lower and coating layer became denser. The corrosion current density showed the lowest value $(6.5{\times}10^{-5}\;Acm^2)$ treated at 750$^{\circ}C\;for\;SiO_2:Al_2O_3:Cr_2O_3$=1:1:3. These results were explained by protective layer which was formed during heat-treatment. The bonding between matrix and coating layer is expected to be made mechanically and chemically by the inter diffusion of Ni and Fe. The composite oxide coating was formed by softening of the binder with increasing heat-treatment temperature. The strengthening of coating layer is to be resulted from the dispersion of major oxide particles.

• 한국분말재료학회지
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• 제24권5호
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• pp.370-376
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• 2017

In this study we manufacture a Ni-Cr-B-Si +WC/12Co composite coating layer on a Cu base material using a laser cladding (LC) process, and investigate the microstructural and mechanical properties of the LC coating and Ni electroplating layers (reference material). The initial powder used for the LC coating layer is a powder feedstock with an average particle size of $125{\mu}m$. To identify the microstructural and mechanical properties, OM, SEM, XRD, room and high temperature hardness, and wear tests are implemented. Microstructural observation of the initial powder and LC coating layer confirm the layer is composed mainly of ${\gamma}-Ni$ phases and WC and $Cr_{23}C_6$ carbides. The measured hardness of the LC coating and Ni electroplating layers are 653 and 154 Hv, respectively. The hardness measurement from room up to high temperatures of $700^{\circ}C$ result in a hardness decrease as the temperature increases, but the hardness of the LC coating layer is higher for all temperature conditions. Room temperature wear results show that the wear loss of the LC coating layer is 1/12 of the wear level of the Ni electroplating layer. The measured bond strength is also greater in the LC coating than the Ni electroplating.

• 한국분말재료학회지
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• 제21권6호
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• pp.434-440
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• 2014

Silicon carbide(SiC) layer is particularly important tri-isotropic (TRISO) coating layers because it acts as a miniature pressure vessel and a diffusion barrier to gaseous and metallic fission products in the TRISO coated particle. The high temperature deposition of SiC layer normally performed at $1500-1650^{\circ}C$ has a negative effect on the property of IPyC layer by increasing its anisotropy. To investigate the feasibility of lower temperature SiC deposition, the influence of deposition temperature on the property of SiC layer are examined in this study. While the SiC layer coated at $1500^{\circ}C$ obtains nearly stoichiometric composition, the composition of the SiC layer coated at $1300-1400^{\circ}C$ shows discrepancy from stoichiometric ratio(1:1). $3-7{\mu}m$ grain size of SiC layer coated at $1500^{\circ}C$ is decreased to sub-micrometer (< $1{\mu}m$) $-2{\mu}m$ grain size when coated at $1400^{\circ}C$, and further decreased to nano grain size when coated at $1300-1350^{\circ}C$. Moreover, the high density of SiC layer (${\geq}3.19g/cm^3$) which is easily obtained at $1500^{\circ}C$ coating is difficult to achieve at lower temperature owing to nano size pores. the density is remarkably decreased with decreasing SiC deposition temperature.

• 한국표면공학회지
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• 제48권5호
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• pp.218-226
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• 2015

The goal of this study is to investigate a metal cladding that contains SiC composites as a protective layer and analysis the characteristics of the specimens on high temperature oxidation To make SiC composites, the current process needs a high temperature (about $1100^{\circ}C$) for the infiltration of fixing materials such as SiC. To improve this situation, we need a low temperature process. In this study, we developed a low temperature process for making SiC composites on the metal layer, and we have made two kinds: cladding with protective SiC composites made by polycarbosilane(PCS), and a PCS filling method using supercritical carbon dioxide. A corrosion test at $1200^{\circ}C$ in a mixed steam and Ar atmosphere was performed on these specimens. The result show that the cladding with protective SiC composites have excellent oxidation suprression rates. This study can be said to have developed new metal cladding with enhanced durability by using SiC composite as protective films of metal cladding instead of simple coating film.

• 한국세라믹학회지
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• 제36권8호
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• pp.805-812
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• 1999

• 한국세라믹학회지
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• 제52권4호
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• pp.284-289
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• 2015

This study examined carbon layer coating on silicon carbide (SiC) fibers by utilizing solid-state and wet chemistry routes to confer toughness to the fiber-reinforced ceramic matrix composites, as an alternative to the conventional pyrolytic carbon (PyC) interphase layer. Electrophoretic deposition (EPD) of carbon black nanoparticles using both AC and DC current sources, and the vacuum infiltration of phenolic resin followed by pyrolysis were tested. Because of the use of a liquid phase, the vacuum infiltration resulted in more uniform and denser carbon coating than the EPD routes with solid carbon black particles. Thereafter, vacuum infiltration with controlled variation in phenolic resin concentration, as well as the iterations of infiltration steps, was improvised to produce a homogeneous carbon coating having a thickness of several hundred nanometers on the SiC fiber. Conclusively, it was demonstrated that the carbon coating on the SiC fiber could be achieved using a simpler method than the conventional chemical vapor deposition technique.

• Carbon letters
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• 제8권2호
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• pp.91-94
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• 2007

The application of Carbon and graphite based materials in unprotected environment is limited to a temperature of $450^{\circ}C$ or so because of their susceptibility to oxidation at this temperature and higher. To over come these obstacles a low cost chemical vapour reaction process (CVR) was developed to give crystalline and high purity SiC coating on graphite and isotropic C/C composite. CVR is most effective carbothermal reduction method for conversation of a few micron of carbon layer to SiC. In the CVR method, a sic conversation layer is formed by reaction between carbon and gaseous reagent silicon monoxide at high temperature. Characterization of SiC coating was carried out using SEM. The other properties studied were hardness density and conversion efficiency.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 추계학술대회 논문집
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• pp.117-118
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• 2012

• 한국세라믹학회지
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• 제36권5호
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• pp.513-520
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• 1999

Alumina-coated SiC whiskers wee prepared by the calcination (1150$^{\circ}C$, 1h, Ar) of the alumina hydrate layer which was precipitated homogeneously on whisker surface from a solution of Al2(SO4)3 and urea as a precipitant. In addition carbon coated SiC whiskers were prepared by the pyrolysis (1000$^{\circ}C$, 4h Ar) of phenolic resin coated whisker. The effects of coating conditions on the thickness and morphology of the coated layers were examined by SEM and TEM. It was found that Al2O3-coating layers become thinner and more uniform with decreasing the Al2(SO4)3 concentration. Thin (0.075-0.1$\mu\textrm{m}$) and uniformly alumina-coating layers were obtained at the Al2(SO4)3 concentration 0.010mol/l. On the other han carbon-coating layers were uniform but very thin (5-16 nm) in thickness. For thicker carbon-coating layers ethanol as a disperse medium was found to be more efficient compared tousing acetone.