• Journal of the Korean Ceramic Society
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• v.36 no.9
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• pp.954-964
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• 1999

The effect of fabrication variables and microstructures on the compressive strength of open cell alumina zirconia and silicon nitride ceramics fabricated by polymeric sponge method was investigated. Bulk density and compressive strength of open cell ceramics were mainly affected by coating characteristics of ceramic slurry on polymeric sponge that controlled a shape thickness and defect of the struts. Sintering temperature was optimized for enhancement of strut strength and compressive strength of open cell ceramics. Relative density and compressive strength behaviors were relatively well matched with the predicted values. Open cell ceramics of lower relative density below 0.1 prepared by first relatively well matched with the predicted values. Open cell ceramics of lower relative density below 0.1 prepared by first coating of ceramic slurry had thin triangular prismatic struts that were often broken or longitudinally cracked. With an application of second coating of slurry shape of struts was transformed into thickner cylindrical one and defects in struts were healed but the relative density increased over 0.2 Open cell zirconia had both the highest bulk density and compressive strength and alumina had the lowest compressive strength while silicon nitrides showed relatively high compressive strength and the lowest density. Based upon the analysis open cell silicon nitride was expected to be one of potential structural ceramics with light weight.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.37 no.2 s.110
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• pp.38-46
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• 2005

Experimental work was carried out in order to produce a novel grade of ink-jet paper that has both high print-out quality and price competitiveness. Usually, silica and PVOH has been used for ink-jet paper to design the coating layer that has a hydrophilic and micro-porous structure. However, poor rheological characteristics and low productivity of the silica-PVOH system make the price of the ink-jet paper high. The main focus of this study was replacing the conventional silica (coating pigment) PVOH (binder) coating system with the new PCC (coating pigment) cationic starch (binder) coating system, and optimizing thecoating technology associated with PPC-cationic starch system. In this study, ink-jet print quality of PCC-coated papers was compared with that of silica-coated paper. Two types of PCC were used: conventional type and colloid type. It turned out that PCC C, a conventional coating pigment, has not given a desirable result: it showed high dot reproduction, but it gave low optical density. In spite of low dot reproduction, the qualities of PCC A were comparable or superior to those of silica in optical density, color reproduction, and the uniformity of printing surface. It was also shown that the problems that are happened when the dosage level of cationic starch was too low were varied with ink-type used in each printer. However, in the case of low binder level, the produced image was widely spread resulting fromtoo low optical density of images, or from the lack of bonding ability to set ink into coating surface.

• Journal of the Korean institute of surface engineering
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• v.30 no.5
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• pp.347-354
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• 1997

Composite plating is a method of co-depositing fine particles of metallic, non-metallic compound or polymers in the plated layer to improve material properties such as were-resistance, lubrication, or corrosion resistance. Graded Ni-Sic composite coating were produced in this research. Prior to produce Graded Ni-SiC composite coatings, effects of particle size, particle content, pH of electrolyte, temperature, current density, stirring rate on the amount of SiC deposited in the Ni layer were investigated. By manipulating current density and plating time properties of these coating were evaluated by micro-indentation hardness test.

• Journal of the Korean institute of surface engineering
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• v.50 no.5
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• pp.366-372
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• 2017

Plasma electrolytic oxidation(PEO) has attracted attention as a surface treatment which has high wear resistance and corrosion resistance. PEO is generally considered as cost-effective, environmentally friendly and superior in terms of coating performance. Most of studies about the PEO processes have been applied to light metals such as Al and Mg. Because the strength of Al and Mg is weaker than that of steel, there is a limit to the application. In this study, PEO process was used to form oxide coatings on Hot dipped aluminized(HDA) steel and the characteristics of the coating film according to the PEO current density were studied. The morphology was observed by SEM and component was analyzed by using EDS. The corrosion behaviors of PEO coating films were estimated by exposing salt spray test at 5 wt.% NaCl solution and measuring polarization curves in deaerated 3 wt.% NaCl solution. With the increase of PEO process current density, the pore size of the coating surface and the thickness of coating increased. It was confirmed that no Fe component was present on the coating surface. PEO coating films obviously showed good corrosion resistance compared with HDA. It is considered that the PEO coating acts as a barrier to protect the base material from external factors causing corrosion.

• Computers and Concrete
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• v.21 no.2
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• pp.181-187
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• 2018

In order to solve the life prediction problem of damaged coating steel bar in magnesium cement concrete, this study tries to establish the marginal distribution function by using the corrosion current density as a single degradation factor. Representing the degree of steel corrosion, the corrosion current density were tested in electrochemical workstation. Then based on the Copula function, the joint distribution function of the damaged coating was established. Therefore, it is indicated that the corrosion current density of the bare steel and coated steel bar can be used as the boundary element to establish the marginal distribution function. By using the Frank-Copula function of Copula Archimedean function family, the joint distribution function of the damaged coating steel bar was successfully established. Finally, the life of the damaged coating steel bar has been lost in 7320d. As a new method for the corrosion of steel bar under the multi-dimensional factors, the two-dimensional Copula function has certain practical significance by putting forward some new ideas.

• Journal of the Korean institute of surface engineering
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• v.26 no.2
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• pp.55-62
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• 1993

The effect of interlayer coating thickness of Ni and Ti on corrosion behavior was studied for TiN ion plat-ed steel plate. Interlayer coating was carried out in a single and bi-layer to a various thickness combination prior to final TiN coating. Corrosion behavior was evaluated by anodic polarization test in 1N H2SO4 as well as salt spray test. Ni interlayer coating was effectived in reducing corrosion current density of active region and Ti interlayer coating over Ni coating reduced the anodic corrosion current density by an order of 4 with increasing the thickness of Ti up to$ 3\mu\textrm{m}$. The improvement of corrosion resistance by Ni/Ti interlayer coating was attributed to the effective prevention of penetration of active corrosion agent resulting from the inherent corrosion resistance of Ni and Ti. Putting corrosion behavior was observed from salt spray test result for all specimens and corrosion resistance at salt atmosphere was enhanced with increasing Ni and Ti thickness, Cor-lay TiN coating was spalled out by the generation of corrosion products.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.3
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• pp.552-559
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• 2011

There is a method for offering continuous information by AF track circuits. Magnetic fields are formed by current through rails in the AF track circuit systems. So, the continuous information is received by the magnetic fields on a on-board antenna. Coating materials of spray on rails are researched to decrease defects such as head check, shelling, corrugation, squats and so on in Germany. Currently, a coating method of rail construction is proposed by using the ceramics in Korea. When deciding physical characteristic of the coating material of spray, researches are required about variation of flux density and resistivity by using the coating material of spray. In case that the flux density is much lower than existing value, the information for train control is not transmitted to the on-board antenna. In this paper, inductance on rails is calculated and a model is presented about variation of the magnetic field intensity and resistivity in the AF track circuit. Standard permeability of the coating material of spray is proposed. Also, standard resistivity of the coating material of spray is presented by analyzing short current.

• Journal of Welding and Joining
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• v.25 no.4
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• pp.42-48
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• 2007

An inert gas atomized NiTiZrSiSn bulk metallic glass feedstock was sprayed onto the copper plate using vacuum plasma spraying process. In order to change the in-flight particle energy, that is, thermal energy, the hydrogen gas flow rate in plasma gas mixture was increased at the constant flow rate of argon gas. Coating and single pass spraying bead were produced with the least feeding rate. Regardless of the plasma gas composition, fully melted through unmelted particle could be observed on the overlay coating. However, the frequency of the unmelted particle number density was increased with the decrease of the hydrogen gas flow rate. The amorphous phase fraction within coating was also affected by the number density of the unmelted particle.

• Journal of the Korean Ceramic Society
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• v.37 no.5
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• pp.497-504
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• 2000

In this study, mullite-zirconia comosite was fabricated by adding ZrOCl2.8H2O using of boehmite gel coating to Hadong kaolin (pink A grade) in order to enhance strength of the mullite specimens. The influence of ZrOCl2.8H2O content and fireing temperature on the crystall phase, microstructure, bulk density, strength of the specimens was investigated. Mullite-zirconia composite was produced in the process of coating zirconia to mullite powder synthesized thereafter and mixing simultaneously of starting materials with boehmite-zirconia gel. Maximum strength with in this study was 251 sintered at 1$600^{\circ}C$ for 2h. Bulk density and strength of the composite with zirconia coated mullite was higher than simultaneous on mixture of starting materials.

• Journal of the Korean institute of surface engineering
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• v.35 no.1
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• pp.53-63
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• 2002

Ni coating was carried out by pulse plating at room temperature. So, experimental conditions for Ni-coating were based on Watt's bath, and new additives(propionic acid) were introduced in the Watt's bath electrolyte as $H_3$$BO_3$ alternatives. By adding propionic acid, coating layer demonstrated a good adhesion and uniformity without special pre-treatment of the 316L stainless steel at room temperature. With a decrease of amount of propionic acid and applied average current density, cathode current efficiency increased. Also, edge effect was decreased with decreasing a peak current and increasing a pulse frequency in the same bath condition. It was found that the optimum condition for Ni coating was a current density of 10~20mA/$\textrm{cm}^2$ at below 500 mA peak current in the $5m\ell/\ell$ propionic acid solution.