• Korean Journal of Materials Research
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• v.12 no.3
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• pp.190-194
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• 2002

InN/GaN multi-layers were grown by metalorganic chemical vapor deposition(MOCVD) in order to get the appropriate structure for an high power blue-green light emitting diode(LED), and effects of growth conditions (growth temperature, pressure, and $trimethylindium(TMIn)-NH_3-N_2\; flow\; rare)$ on the integrated photoluminescence (PL) intensity and PL peak energy in InN/GaN multi-layers were investigated. The optimized growth conditions with the highest integrated PL intensity for InN/GaN multi-layers were obtained: the growth temperature at $780^{\circ}C$, the growth pressure at 325 Torr, the TMIn flow rate with 150 $m\ell$/min, the $NH_3$flow rate with 3.2 ι/min, and $N_2$ flow rate with 2 ι/min.

• Korean Journal of Materials Research
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• v.24 no.2
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• pp.81-86
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• 2014

The nitrogen solubility and nitride capacity of $CaO-SiO_2-Al_2O_3-MgO-CaF_2$ slag systems were measured by using gas-liquid equilibration at 1773K. The nitrogen solubility of this slag system decreased with increasing CO partial pressure, with the linear relationship between nitrogen contents and oxygen partial pressure being -3/4. This system was expected to show two types of nitride solution behavior. First, the nitrogen solubility decreased to a minimum value and then increased with the increase of CaO contents. These mechanisms were explained by considering that nitrogen can dissolve into slags as "free nitride" at high basicities and as "incorporated nitride" within the network at low basicities. Also, the basicity of slag and nitride capacity were explained by using optical basicity. The nitrogen contents exhibited temperature dependence, showing an increase in nitrogen contents with increasing temperature.

• Journal of Powder Materials
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• v.25 no.1
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• pp.48-53
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• 2018

One-dimensional rutile $TiO_2$ is an important inorganic compound with applicability in sensors, solar cells, and Li-based batteries. However, conventional synthesis methods for $TiO_2$ nanowires are complicated and entail risks of environmental contamination. In this work, we report the growth of $TiO_2$ nanowires on a Ti alloy powder (Ti-6wt%Al-4wt%V, Ti64) using simple thermal oxidation under a limited supply of $O_2$. The optimum condition for $TiO_2$ nanowire synthesis is studied for variables including temperature, time, and pressure. $TiO_2$ nanowires of ${\sim}5{\mu}m$ in length and 100 nm in thickness are richly synthesized under the optimum condition with single-crystalline rutile phases. The formation of $TiO_2$ nanowires is greatly influenced by synthesis temperature and pressure. The synthesized $TiO_2$ nanowires are characterized using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HR-TEM).

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.6
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• pp.543-547
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• 2008

In the paper, we develop the ultrasonic bonding technique for LCD driver chips having small size and high pin-density. In general, the mounting technology for LCD driver ICs is a thermo-compression method utilizing the ACF (An-isotropic Conductive Film). The major drawback of the conventional approach is the long process time. It will be shown that the conventional ACF method based on thermo-compression can be remarkably enhanced by employing the ultrasonic bonding technique in terms of bonding time. The proposed approach is to apply the ultrasonic energy together with the thermo-compression methodology for the ACF bonding process. To this end, we design a bonding head that enables pre-heating, pressure and ultrasonic excitation. Through the bonding experiments mainly with LCD driver ICs, we present the procedures to select the best combination of process parameters with analysis. We investigate the effects of bonding pressure, bonding time, pre-heating temperature before bonding, and the power level of ultrasonic energy. The addition of ultrasonic excitation to the thermo-compression method reduces the pre-heating temperature and the bonding process time while keeping the quality bonding between the LCD pad and the driver IC. The proposed concept will be verified and demonstrated with experimental results.

• Journal of Drive and Control
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• v.15 no.2
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• pp.32-37
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• 2018

The power plants use turbine output control devices to supply or shut off steam to high pressure and low-pressure steam turbines connected to generators. This turbine output control device is driven by a hydraulic servo actuator. The gas flows into the hydraulic servo actuator during periodic inspection or normal operation, and the resulting adiabatic compression of the gas raises the internal temperature of the actuator to $500^{\circ}C$. This temperature increase causes the seals to burn and show wear and tear, resulting in failure. In this study, an air vent valve was installed to allow gas inside the hydraulic servo actuator to flow large quantities of air at the beginning of the operation and after the periodic inspection. Gas was passed through for only minute flow during normal operation of the power plant. By applying the air vent valve, it improves the reliability of the hydraulic servo actuator by discharge the gas appropriately to improve the life of the seal.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.372-375
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• 1999

This paper presents an arc(hot-gas flow field) analysis method in GCB. This method includes the Lorentz's force due to magnetic field, turbulent viscous effect and radiation heat transfer which are indispensable to the analysis of hot-gas flow. To verify the applicability of the Proposed method, steady state hot-Eas flow analysis within a simplified interrupter has been carried out. Inlet boundary pressure values were assumed to be 9.0atm and 12.0atm. For each inlet boundary condition, three cases of hot-gas flow field analyses were performed according to the values of arc currents which were assumed to be D.C 0.6kA. 1.0kA and 2.0kA. The results revealed that the arc radius at nozzle throat has been concentrated by increasing the pressure of nozzle upstream and that the maximum temperature of arc core has been decreased along to nozzle exit and the high temperature lesion come to be wide in nozzle downstream. From these results, it is confirmed that the proposed method will be applicable to predict the large current interruption capability of GCB.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.2
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• pp.1-6
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• 2008

In recent years, developments in the semiconductor and electronic industries have brought a rapid increase in the use of large size silicon wafer. For further improvement of the ultra precision surface and flatness of Si wafer necessary to high density ULSI, it is known that polishing is very important. However, most of these investigation was experiment less than 300mm diameter. Polishing is one of the important methods in manufacturing of Si wafers and in thinning of completed device wafers. This study reports the machining variables that has major influence on the characteristic of wafer polishing. It was adapted to polishing pressure, machining speed, and the slurry mix ratio, the optimum condition is selected by ultra precision wafer polishing using load cell and infrared temperature sensor. The optimum machining condition is selected a result data that use a pressure and table speed data. By using optimum condition, it achieves a ultra precision mirror like surface.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.05a
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• pp.169-172
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• 2002

This study demonstrated the feasibility of using tape-casting followed by sintering as a low-cost alternative for coating glass-ceramic or glass film on a metal substrate. The process has been successfully used to fabricate a glass-on-stainless steel and a glass-ceramic-on-molybdenum electrostatic chuck(ESC) with the insulating layer thickness about $150{\mu}{\textrm}{m}$. Electrical resistivity data of the coaling were obtained between room temperature and 55$0^{\circ}C$; although the resistivity values dropped rapidly with increasing temperature in both coatings, the glass-ceramic still retained a high value of $10^{10}$ ohm-cm at $500^{\circ}C$. Clamping pressure measurements were done using a mechanical apparatus equipped with a load-cell at temperatures up to $350^{\circ}C$ and applied voltages up to 600V; the clamping behavior of all ESCs generally followed the voltage-squared curve as predicted by theory. Based on these results, we believe that we have a viable technology for manufacturing ESCs for use in reactive-ion etch systems.

• Korean Journal of Materials Research
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• v.16 no.6
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• pp.341-345
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• 2006

[ $Ni_2Si$ ] mixed powders were mechanically alloyed by a ball mill and then processed by hot isostatic pressing (HIP) and spark plasma sintering (SPS). In the powder that was mechanically alloyed for 15minutes(MA 15 min), only Ni and Si were observed but in the powder that was mechanically alloyed for 30minutes(MA 30 min), $Ni_2Si$, Ni and Si were mixed together. Some of the MA 15 min powder and MA 30 min powder were processed by HIP under pressure of 150MPa at the temperature of $1000^{\circ}C$ for two hours and some of them were processed by SPS under pressure of 60 MPa at the temperature of $1000^{\circ}C$ for 60 seconds. Both methods completely compounded the powders to $Ni_2Si$. The maximum density of sintered lumps by HIP method was 99.5% and the maximum density of the sintered lump by SPS method was 99.3%. with the hardness of HRc 66 with the hardness of HRc 63. Therefore, the SPS method that can sinter in short time at low cost is considered to be more economical that the HIP method that requires complicated sintering conditions and high cost and the sintering can produce target materials in desired sizes and shapes to be used for thin film.

• Membrane and Water Treatment
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• v.5 no.3
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• pp.207-219
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• 2014

Fouling is one of the critical factors associated with the application of membrane technology in treating palm oil mill effluent (POME), due to the presence of high concentration of solid organic matter, oil, and grease. In order to overcome this, chemical cleaning is needed to enhance the effectiveness of membranes for filtration. The potential use of sodium hydroxide (NaOH), sodium chloride (NaCl), hydrochloric acid (HCl), ethylenediaminetetraacetic acid (EDTA), and ultrapure water (UPW) as cleaning agents have been investigated in this study. It was found that sodium hydroxide is the most powerful cleaning agent, the optimum conditions that apply are as follows: 3% for the concentration of NaOH, $45^{\circ}C$ for temperature solution, 5 bar operating pressure, and solution pH 11.64. Overall, flux recovery reached 99.5%. SEM images demonstrated that the membrane surface after cleaning demonstrated similar performance to fresh membranes. This is indicative of the fact that NaOH solution is capable of removing almost all of the foulants from PES membranes.