• Journal of the Korean Solar Energy Society
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• v.33 no.2
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• pp.11-17
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• 2013

Silicon nitride($SiN_x:H$) deposited by radio frequency plasma enhanced chemical vapor deposition(RF-PECVD) is commonly used for anti-reflection coating and passivation in crystalline silicon solar cell fabrication. In this paper, characteristics of the deposited silicon nitride was studied with change of working pressure, deposition temperature, gas ratio of $NH_3$ and $SiH_4$, and RF power during deposition. The deposition rate, refractive index and effective lifetime were analyzed. The (100) p-type silicon wafers with one-side polished, $660-690{\mu}m$, and resistivity $1-10{\Omega}{\cdot}cm$ were used. As a result, when the working pressure increased, the deposition rate of SiNx was increased while the effective life time for the $SiN_x$-deposited wafer was decreased. The result regarding deposition temperature, gas ratio and RF power changes would be explained in detail below. In this paper, the optimized condition in silicon nitride deposition for silicon solar cell was obtained as 1.0 Torr for the working pressure, $400^{\circ}C$ for deposition temperature, 500 W for RF power and 0.88 for $NH_3/SiH_4$ gas ratio. The silicon nitride layer deposited in this condition showed the effective life time of > $1400{\mu}s$ and the surface recombination rate of 25 cm/s. The crystalline silicon solar cell fabricated with this SiNx coating showed 18.1% conversion efficiency.

• Journal of Ocean Engineering and Technology
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• v.27 no.2
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• pp.33-38
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• 2013

In the past, a very popular method for reducing the corrosion on zinc involved the use of chemical conversion layer coatings based on $Cr^{+6}$. However, there is an important problem with using chromium salts as a result of restrictive environmental protection legislation. This study investigated the optimum condition for galvanized steel using an organic/inorganic solution with a Ti composition. In the case of a fixed heat treatment time, the corrosion resistance values of LR-0727(1) and LR-0727(2) were improved as the heat treatment temperature increased, and the optimum minimum temperature decreased with the heat treatment time. At the optimum heat treatment condition of two coating solutions, the heat treatment time of the LR-0727(1) solution was shorter than LR-0727(2) for the same heat treatment temperature. LR-0727(1) coated specimens did not show desquamation, and all of the specimens showed a good adhesive property. In contrast, in the case of the LR-0727(2) coated specimens, desquamation arose. Therefore, the adhesive property of LR-0727(1) was superior to that of LR-0727(2). The pencil hardness had a 3H average for all of the coating solutions and heat treatment conditions. In the case of a corrosion resistance test with boiling water, the coated specimens of LR-0727(1) were discolored, but LR-0727(2) was not. Finally, LR-0727(1) was more moisture proof than LR-0727(2).

• Transactions on Electrical and Electronic Materials
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• v.5 no.1
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• pp.1-6
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• 2004

Zinc sulfide is a semiconductor with wide band gap and high refractive index and hence promising material to be used as ARC on commercial silicon solar cells. Uniform deposition of zinc sulfide (ZnS) by using chemical bath deposition (CBD) method over a large area of silicon surface is an emerging field of research because ZnS film can be used as a low cost antireflection coating (ARC). The main problem of the CBD bath process is the huge amount of precipitation that occurs during heterogeneous reaction leading to hamper the rate of deposition as well as uniformity and chemical stoichiometry of deposited film. Molar concentration of thiorea plays an important role in varying the percentage of reflectance and refractive index of as-deposited CBD ZnS film. Desirable rate of film deposition (19.6 ${\AA}$ / min), film uniformity (Std. dev. < 1.8), high value of refractive index (2.35), low reflectance (0.655) have been achieved with proper optimization of ZnS bath. Decrease in refractive index of CBD ZnS film due to high temperature treatment in air ambiance has been pointed out in this paper. Solar cells of conversion efficiency 13.8 ％ have been successfully achieved with a large area (103 mm ${\times}$ 103 mm) mono-crystalline silicon wafers by using CBD ZnS antireflection coating in this modified approach.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.4
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• pp.405-412
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• 2012

In the past, a very popular way to reduce the corrosion rate of zinc was the use of chemical conversion layers based on $Cr^{+6}$. However, the use of chromium salts is now restricted because of environmental protection legislation. Previous research investigated the optimum corrosion resistance of galvanized steel treated with an organic/inorganic solution containing Si. The result showed that the optimum corrosion resistance occurred by heat treatment of $190^{\circ}C$ in 5 min. In this study, one organic and three hybrid organic/inorganic coating solutions were applied to cold-rolled (CR) carbon steel. The coatings were then evaluated for corrosion resistance under a salt spray test. The coating solutions examined in this study consisted of urethane-only, urethane-Si, urethane-Si-Ti, and urethane-Si-Ti-epoxy. The results of the 7 h salt spray test showed that the urethane-Si-Ti and urethane-Si-Ti-epoxy coating solutions had superior corrosion resistance on CR steel.

• Polymer(Korea)
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• v.27 no.5
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• pp.421-428
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• 2003

The kinetics of photoinitiated polymerization of reactive oligomer methacrylates and oligomer methacrylate/SBS blends have been studied to characterize the diffusion-controlled reaction using Fourier Transform Infrared Spectroscopy-Attenuated Total Reflectance (ATR-FTIR). The polymerization rates of reactive oligomer methacrylates and oligomer methacrylate/SBS blends were autocatalytic in nature at the initial stage and then a retardation of the reaction conversion occurred gradually as the polymer matrix became vitrified, and finally the reaction became diffusion controlled. Photopolymerization behavior of methacrylate/SBS blends was well predicted using the diffusion-controlled reaction model. N-Vinyl-2-pyrrolidinone (NVP) as a reactive solvent was used to incorporate SBS into methacrylate to form semi-IPN via photopolymerization. Due to the high reactivity of NVP, polymerization rate increased with the increase of NVP content. As the content of NVP-SBS in the blends increased up to 10 phr, the reaction conversion maintained almost constant. But above 20 phr of NVP-SBS in the blends, the reaction conversion gradually decreased since the increase of viscosity affected on the photopolymerization rate. The semi-IPN films of methacrylate/SBS blends were transparent at room temperature as well as at increased temperature and were able to be applied to surface coating.

• Journal of the Korean Ceramic Society
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• v.38 no.9
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• pp.846-852
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• 2001

A two-dimensional Monte Carlo simulation has been used to investigate the effect of the reaction temperature on the formation of the silicon carbide conversion layer near the surface of graphite substrate The carbothermal reduction of silica is the reaction mechanism of silicon carbide formation on graphite substrate by chemical vapor reaction methods. The chemical composition of silicon carbide conversion layer gradually changes from carbon to silicon carbide because gaseous reactants diffuse through micropores within graphite substrate and react with carbon at the surface of inner pores. The simulation was carried out under the condition of reaction temperature at 1900K, 2000K, 2100K and 2200K for 500MCS. It was found from the results of simulation that the thickness of silicon carbide conversion layer increases with reaction temperature.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.12
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• pp.189-194
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• 2014

In this study, from a new x-ray detector that combines a columnar CsI:Na scintillation layer with a photosensitive mercuric iodide layer was investigated. In this structure, X-rays are converted into visible light on a thick CsI:Na layer, which is then converted to electric charges in a thin $HgI_2$ bottom layer. The thin coplanar mercuric iodide films as a photosensitive converter requiring only a few tens of volts of bias, associated with a thick columnar coating of phosphor layer, were simulated and designed. The results of this research suggest that the new coplanar x-ray detector with a hybrid-type structure can resolve the following problems: high voltage from the a-Se, and low conversion efficiency from the indirect conversion method. The results of this research suggest that the new CsI:Na/$HgI_2$ x-ray detector with a double-layer type structure can resolve the following problems: high voltage from the direct conversion method, and low conversion efficiency from the indirect conversion method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.11
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• pp.740-745
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• 2014

ZnO nanowires were grown by hydrothermal synthesis process and piezoelectric poly vinylidene fluoride (PVDF) was then coated on top of the ZnO-nanowires by spray-coating technique. The composite layer of ZnO-nanowires/PVDF was applied to an energy harvesting device based on piezoelectric-conversion mechanism. A defined mechanical force was given to the nanogenerator device to evaluate their electric power generation characteristics, where output current density and voltage were examined. Electric power generation property of the ZnO-nanowires/PVDF based nanogenerator device was compared to that of the nanogenerator device with ZnO-nanowires as single active layer. Effect of the ZnO-nanowires on improvement of power generation was discussed to examine its feasibility for the nanogenerator device.

• International Journal of Automotive Technology
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• v.1 no.2
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• pp.89-94
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• 2000

As a promising catalyst reducing cold start emissions of automobiles, a photocatalyst systems has been studied. Since the photocatalyst is only activated by UV wavelength light, it needs no heat energy like a conventional TWC, therefore no light-off time. However, as a cold temperature catalyst to treat cold start emissions of a vehicle, previous studies on characteristic of photocatalyst have room for improvement in terms of performance and durability investigated from the viewpoints of performance and durability improvement. Eleven different coating samples were prepared with the combination of six kinds of additives and two kinds of photocatalyst materials. Then these samples were aged with a hydrothermal aging process. The performance of these samples was measured on a model gas apparatus with simulated exhaust gases. The durability was also analyzed with X-ray diffraction meter.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.37-44
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• 2007

A nickel foam, one of metal foams was seleced as a catalyst support instead of conventional ceramic materials. $Al_2O_3$ was coated on the surface of nickel foam to increase the surface area. $Al_2O_3$ coating process was based on sol-gel process. SEM image was obtained and $Al_2O_3$ coverage was confirmed. Combustion experiments were carried out using SUS combustor and $H_2$/air mixture. Temperatures were measured with different equivalence ratios and $H_2$ flow rates. $H_2$ conversion rates were calculated by the analysis of product gas using gas chromatography. Catalytic combustion of $H_2$ was complete and stable with Pt/$Al_2O_3$ coated nickel foam and influences of water vapor were confirmed during the beginning of combustion.