• Korean Journal of Materials Research
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• v.29 no.11
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• pp.720-726
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• 2019

Recently, research on cost reduction and efficiency improvement of crystalline silicon(c-Si) photovoltaic(PV) module has been conducted. In order to reduce costs, the thickness of solar cell wafers is becoming thinner. If the thickness of the wafer is reduced, cracking of wafer may occur in high temperature processes during the c-Si PV module manufacturing process. To solve this problem, a low temperature process has been proposed. Conductive paste(CP) is used for low temperature processing; it contains Sn57.6Bi0.4Ag component and can be electrically combined with solar cells and ribbons at a melting point of $150^{\circ}C$. Use of CP in the PV module manufacturing process can minimize cracks of solar cells. When CP is applied to solar cells, the output varies with the amount of CP, and so the optimum amount of CP must be found. In this paper, in order to find the optimal CP application amount, we manufactured several c-Si PV modules with different CP amounts. The amount control of CP is fixed at air pressure (500 kPa) and nozzle diameter 22G(outer diameter 0.72Ø, inner 0.42Ø) of dispenser; only speed is controlled. The c-Si PV module output is measured to analyze the difference according to the amount of CP and analyzed by optical microscope and Alpha-step. As the result, the optimum amount of CP is 0.452 ~ 0.544 g on solar cells.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.4
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• pp.91-96
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• 2020

The 33-mode dielectric and piezoelectric properties of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 piezoelectric single crystals were measured under large electric field and compressive stress. The phase transition from the low temperature rhombohedral to the high temperature tetragonal structure was observed in the range of 110~140℃, and the Curie temperature changing to the cubic structure was about 165℃. The polarization change according to the compressive stress and electric field was measured. Relative dielectric constant was calculated from the slope of the polarization curve applied to the electric field, and the calculated relative dielectric constant increased as the applied stress increased, and the relative dielectric constant decreased as the applied electric field increased. The strain according to the compressive stress and electric field change was measured, the piezoelectric constant was calculated from the slope of the curve, and the phase transition according to the application of pressure was confirmed. In the case of practical application as an underwater or medical ultrasonic actuator, it is necessary to properly design the magnitude of the compressive stress applied to the device and the DC bias in order to maintain linear driving.

• Journal of Conservation Science
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• v.37 no.6
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• pp.821-830
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• 2021

The weapons excavated from the de-militarized zones (DMZ) of Korea are vulnerable to corrosion due to the immediate and drastic environmental change. Especially, the chloride ions (Cl^-) in iron weapons cause active corrosion and require removal. In this study, conservation treatment and de-salination was performed for the discovered weapons from excavation sites of soldiers killed in action during the Korean War. Furthermore, an attempt was made to prepare the most stable plan for conservation treatment through the comparative study of soaking weapons in distilled water without chemicals and in a solution of sodium (SSC) at different temperatures. In the preliminarily experiments, the comparison of the eluted Cl^- ions according to different conditions of de-salination showed that the highest number of ions were detected from the de-salination with SSC at a temperature of 100℃, and its duration was much smaller, i.e., 1~2 weeks. Accordingly, for the parts from the guns and rifles amongst other objects, a six-time de-salination was conducted in the SSC solution for 8 hours at 100℃ and subsequently, for 16 hours at room temperature during which the distilled water and SSC were exchanged every week. However, in the case of a loaded rifle, the de-salination was not conducted, considering the risk that the high temperature and pressure by impregnation in vacuum could cause an explosion

• Journal of Hydrogen and New Energy
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• v.25 no.5
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• pp.533-540
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• 2014

The remanufacturing industry for automotive parts is a major issue which affects the environment protection and CO2 reduction throughout the world. Beside this, remanufacturing technologies of worn-out diesel engines have been developing to make as close to new as possible. In this study, the characteristics of the engine-power output and exhaust emissions of remanufactured diesel engine by hydrogen enrichment are evaluated by measuring the engine and vehicle test. Moreover, with worn-out diesel engine and first generation common-rail engine, we compared by testing their characteristics, resulting in the restoration of engine-power output more than 93%, as well as marvelously reduces the THC and NOx emission. At a guess, high pressure injection of diesel increases fuel atomization characteristics with excellence combustion efficiency, resulting in reduction of THC emission. Also, rapid cooling of EGR decreases combustion temperature, resulting in reduction of NOx emission. Consequently, these remanufacturing for diesel engine enables worn-out diesel engine to have restoration to the original state. Simultaneously achieved 2 goals called that CO2 emission reduction and protection of environment by remanufacturing engine.

• Applied Chemistry for Engineering
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• v.16 no.5
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• pp.609-613
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• 2005

Daidzein and genistein were extracted from Korean soybean by supercritical $CO_2$ and sub/supercritical water. The extracted sample was analyzed by reversed-phase high performance liquid chromatography (RP-HPLC). The retention time, retention factor, column efficiency, column selectivity and resolution of aglycons were compared with the change in the temperature and pressure of supercritical fluid and ethanol concentration. The characteristics of extraction of daidzein and genistein were more affected by ethanol concentration using supercritical $CO_2$. The most desirable extraction yield was obtained by supercritical $H_2O$ with $400^{\circ}C$ and 250 bar. Generally, the extraction yield of aglycons increased over 10 times using supercritical $CO_2$ than sub/supercritical $H_2O$.

• Korean Journal of Materials Research
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• v.15 no.10
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• pp.626-631
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• 2005

GaN-related compound semiconductors were grown on the corrugated interface substrate using a metalorganic chemical vapor deposition system to increase the optical power of white LEDs. The patterning of substrate for enhancing the extraction efficiency was processed using an inductively coupled plasma reactive ion etching system and the surface morphology of the etched sapphire wafer and that of the non-etched surface were investigated using an atomic force microscope. The structural and optical properties of GaN grown on the corrugated interface substrate were characterized by a high-resolution x-ray diffraction, transmission electron microscopy, atomic force microscope and photoluminescence. The roughness of the etched sapphire wafer was higher than that of the non-etched one. The surface of III-nitride films grown on the hemispherically patterned wafer showed the nano-sized pin-holes that were not grown partially. In this case, the leakage current of the LED chip at the reverse bias was abruptly increased. The reason is that the hemispherically patterned region doesn't have (0001) plane that is favor for GaN growth. The lateral growth of the GaN layer grown on (0001) plane located in between the patterns was enhanced by raising the growth temperature ana lowering the reactor pressure resulting in the smooth surface over the patterned region. The crystal quality of GaN on the patterned substrate was also similar with that of GaN on the conventional substrate and no defect was detected in the interface. The optical power of the LED on the patterned substrate was $14\%$ higher than that on the conventional substrate due to the increased extraction efficiency.

• Journal of Energy Engineering
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• v.25 no.1
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• pp.171-176
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• 2016

Sour gas is natural gas or any other gas containing significant amounts of hydrogen sulfide ($H_2S$). Natural gas is usually considered sour gas if there are more than 5.7 milligrams of $H_2S$ per cubic meter of natural gas, which is equivalent to approximately 4 ppm by volume under standard temperature and pressure We have surveyed on the treatment and removal technology of sour gas, sour gas include a lot of hydrogen sulfide($H_2S$), Carbon dioxide($CO_2$), utane($C_4H_{10}$) and mercaptan($C_nH_{4n-1}SH$) etc. We need high technology for development for these kinds of raw gases and we should specially take care of treating and removal of theses raw gases. Therefor we are going to describe about these kinds of raw gases and about methods how to treat these kinds of gases.

• Journal of the Korean Ceramic Society
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• v.51 no.5
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• pp.435-441
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• 2014

Silicon carbide-based ceramics and their composites have been studied for application to fusion and advanced fission energy systems. For fission reactors, $SiC_f$/SiC composites can be applied to core structural materials. Multilayered SiC composite fuel cladding, owing to its superior high temperature strength and low hydrogen generation under severe accident conditions, is a candidate for the replacement of zirconium alloy cladding. The SiC composite cladding has to retain its mechanical properties and original structure under the inner pressure caused by fission products; as such it can be applied as a cladding in fission reactor. A hoop strength test using an expandable polyurethane plug was designed in order to evaluate the mechanical properties of the fuel cladding. In this paper, a hoop strength test of the multilayered SiC composite tube for nuclear fuel cladding was simulated using FEA. The stress caused by the plug was distributed nonuniformly because of the friction coefficient difference between the inner surface of the tube and the plug. Hoop stress and shear stress at the tube was evaluated and the relationship between the concentrated stress at the inner layer of the tube and the fracture behavior of the tube was investigated.

• Journal of Hydrogen and New Energy
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• v.5 no.2
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• pp.99-109
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• 1994

To develop high capacity hydrogen storage alloys for secondary Ni/MH batteries, electrochemical charge/discharge characteristics of $Zr_{1-x}Ti_xMn_{1-y}V_yNi_{1-z}M_z$ (M=Al,Co,Fe) alloys were investigated, in which $0.2{\leq}x{\leq}0.6$, $0.2{\leq}y{\leq}0.8$, $0.2{\leq}z{\leq}0.4$. With increasing Ti content(x) and/or decreasing V content(y), lattice constants and maximum theoretical capacities of the alloys were decreased and equilibrium pressure of hydrogen absorption were increased. Electrochemical discharge capacities were increased with increasing Ti content(x). Especially, the alloys of x= 0.4~0.6 showed better charge/discharge efficiencies than those of x<0.4. Discharge capacities of $Zr_{0.4}Ti_{0.6}Mn_{0.4}V_{0.6}Ni_{0.8}Fe_{0.2}$, $Zr_{0.4}Ti_{0.6}Mn_{0.4}V_{0.6}Ni_{0.8}Al_{0.2}$ and $Zr_{0.5}Ti_{0.5}Mn_{0.4}V_{0.6}Ni_{0.6}Co_{0.4}$ were 385, 328 and 333mAh/g, respectively. These alloys were fully activated within five charge/discharge cycles and had a good charge and discharge rate capabilities and temperature characteristics.

• IEIE Transactions on Smart Processing and Computing
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• v.3 no.5
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• pp.331-337
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• 2014

Ge is becoming an increasingly popular semiconductor material with high Si compatibility for on-chip optical interconnect technology. For a better manifestation of the meritorious material properties of Ge, its surface treatment should be performed satisfactorily before the electronic and photonic components are fabricated. Ex-situ rapid thermal annealing (RTA) processes with different gases were carried out to examine the effects of the annealing gases on the thin-film quality of Ge grown epitaxially on Si substrates. The Ge-on-Si samples were prepared in different structures using the same equipment, reduced-pressure chemical vapor deposition (RPCVD), and the samples annealed in $N_2$, forming gas (FG), and $O_2$ were compared with the unannealed (deposited and only cleaned) samples to confirm the improvements in Ge quality. To evaluate the thin-film quality, room-temperature photoluminescence (PL) measurements were performed. Among the compared samples, the $O_2$-annealed samples showed the strongest PL signals, regardless of the sample structures, which shows that ex-situ RTA in the $O_2$ environment would be an effective technique for the surface treatment of Ge in fabricating Ge devices for optical computing systems.