• Korean Journal of Materials Research
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• v.23 no.7
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• pp.392-398
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• 2013

A two-pass differential speed rolling(DSR) was applied to a deoxidized low-phosphorous copper alloy sheet in order to form a homogeneous microstructure. Copper alloy with a thickness of 3 mm was rolled to 75 % reduction by two-pass rolling at $150^{\circ}C$ without lubrication at a differential speed ratio of 2.0:1. In order to introduce uniform shear strain into the copper alloy sheet, the second rolling was performed after turning the sample by $180^{\circ}$ on the transverse direction axis. Conventional rolling(CR), in which the rotating speeds of the upper roll and lower roll are identical to each other, was also performed by two-pass rolling under a total rolling reduction of 75 %, for comparison. The shear strain introduced by the conventional rolling showed positive values at positions of the upper roll side and negative values at positions of the lower roll side. However, samples processed by the DSR showed zero or positive values at all positions. {100}//ND texture was primarily developed near the surface and center of thickness for the CR, while {110}//ND texture was primarily developed for the DSR. The difference in misorientation distribution of grain boundary between the upper roll side surface and center regions was very small in the CR, while it was large in the DSR. The grain size was smallest in the upper roll side region for both the CR and the DSR. The hardness showed homogeneous distribution in the thickness direction in both CR and DSR. The average hardness was larger in CR than in DSR.

• Journal of Environmental Science International
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• v.14 no.8
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• pp.801-810
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• 2005

The phosphor and ITO(Indium Tin Oxide) films for video phone tube (VPT) were simply prepared by the screen printing and thermal transfer methods. The increasing order of thermal firing of acrylic binder for phosphor and ITO was M6003 < M6664 < A/A 1919 < M500l < M670 1 and all mass of binders were perfectly decomposed at lower temperature than $400^{\circ}C.$ After thermal firing of phosphor paste, the residual of binder on the surface of phosphor could not be found by SEM. Aerosil as thickner provides the thixotropy property for phosphor paste but decrease the brightness of phosphor screen as residual after thermal firing. Since the thixotropy of M5001 binder without aerosil was shown and the storage modulus of phosphor paste by increasing the angular frequency was not nearly changed and the decrease of the storage modulus of phosphor paste by increasing the strain was remarkably shown. It was possible to prepare the phosphor paste which was predominant in the plate separation and the reproduction of pattern after the screen printing. Since the addition of dispersing agent to improve the printing process decreases the electrical conductivity and light transmission of ITa film, it could be found to be necessary the development of binder for phosphor paste that decreases the amount of dispersing agent possibly and does not use the aerosil as additive.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.11
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• pp.739-745
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• 2008

This paper presents the measurement of ground thermal conductivity and the characteristics of ground thermal diffusion by a ground heat exchanger(GHE). A borehole is installed to a depth of 175 m with a diameter of 150 mm. To analyze the thermal diffusion property of the GHE, thermocouples are installed under the ground near the GHE. The outdoor temperature, the ground temperature, and the water temperature of the GHE are monitored for evaluating the characteristics of ground thermal diffusion. The ground thermal conductivity is evaluated by the in-situ thermal response tester and the line source model. It is found to be 3.08 W/$m^{\circ}C$ in this study. The ground temperature is greatly dependent on the outdoor temperature from the ground surface to 2.5 m in depth and is stable below 10 m in depth. The surface temperature of the GHE varies as a function of the temperature of circulating water. But the ground temperature at 1.5 m far from the GHE is not changed in accordance with the temperature of circulating water.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.1 no.1
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• pp.37-42
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• 2000

Copper thin films have been prepared by a metal organic chemical vapor deposition (MOCVD) technology on polyimide and TiN substrates. The Cu-MOCVD technology has advantages of the high deposition rate and the good step coverage compared with the conventional physical vapor deposition (PVD) technology in several industrial applications. The Cu films have been deposited with varying the experimental conditions of substrate temperatures and copper source vapor pressures. The films were annealed in a vacuum condition after the deposition, and the annealing effect on the electrical properties of the films was measured. The crystallinity and the microstructures of the films were observed by scanning electron microscopy (SEM), and the electrical resistivity was measured by 4-point probe. In the case of the Cu deposition on TiN substrate, the best electrical property of the films was measured for the samples prepared at 18$0^{\circ}C$. Very high deposition rate of the Cu film up to 250 nm/min was obtained on the polyimide substrate when the mixture of liquid and vapour precursor was used.

• Tribology and Lubricants
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• v.24 no.4
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• pp.190-195
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• 2008

Many researchers have tried to improve the tribological characteristics of lubricant by adding various nano particles in the base lubricant. But the reliability evaluation of the lubricants are rarely performed in its real operation condition. In this study, the physical property and the tribological characteristics of the graphite nano lubricant were evaluated and compared with raw lubricant after thermal degrading. In order to evaluate the tirbological characteristics, the disk-on-disk tribotester was adopted to measure the friction coefficient of the graphite nano lubricants. Also the temperature variations of friction surfaces were measured by the thermocouple installed on the fixed plate in the test chamber of the tribotester. The kinematic viscosity was measured using a capillary viscometer on the temperatures of 40, 60 and $80^{\circ}C$. The results showed that the graphite nano lubricant had lower friction coefficient and less wear on the friction surfaces than raw lubricant. After thermally degrading, the friction coefficients of graphite nano lubricant increased, but the friction coefficients after thermal degradation were still maintained lower than those of raw lubricant.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06a
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• pp.5-18
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• 1996

The solid state cesium ion source os alumino-silicate based zeolite which contains cerium. The material is an ionic conductor. Cesiums are stably stored in the material and one can extract the cesiums by applying electric field across the electrolyte. Cesium ion bombardment has the unique property of producing high negative ion yield. This ion source is used as the primary source for the production of a negative ion without any gas discharge or the need for a carrier gas. The deposition of materials as an ionic species in the energy range of 1.0 to 300eV is recently recognized as a very promising new thin film technique. This energetic non-thermal equilibrium deposition process produces films by “Kinetic Bonding / Energetic Condensation" mechansim not governed by the common place thermo-mechanical reaction. Under these highly non-equilibrium conditions meta-stable materials are realized and the negative ion is considered to be an optimum paeticle or tool for the purpose. This process differs fundamentally from the conventional ion beam assisted deposition (IBAD) technique such that the ion beam energy transfer to the deposition process is directly coupled the process. Since cesium ion beam sputter deposition process is forming materials with high kinetic energy of metal ion beams, the process provider following unique advantages:(1) to synthesize non thermal-equilibrium materials, (2) to form materials at lower processing temperature than used for conventional chemical of physical vapor deposition, (3) to deposit very uniform, dense, and good adhesive films (4) to make higher doposition rate, (5) to control the ion flux and ion energy independently. Solid state cesium ion beam sputter deposition system has been developed. This source is capable of producing variety of metal ion beams such as C, Si, W, Ta, Mo, Al, Au, Ag, Cr etc. Using this deposition system, several researches have been performed. (1) To produce superior quality amorphous diamond films (2) to produce carbon nitirde hard coatings(Carbon nitride is a new material whose hardness is comparable to the diamond and also has a very high thermal stability.) (3) to produce cesiated amorphous diamond thin film coated Si surface exhibiting negative electron affinity characteristics. In this presentation, the principles of solid state cesium ion beam sputter deposition and several applications of negative metal ion source will be introduced.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.178-181
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• 2003

In this work, we etched PZT films with various additive gases ($O_2$ and Ar) in $Cl_2/CF_4$ plasmas, while mixing ratio was fixed at 8/2. After the etching, the plasma induced damages are characterized in terms of hysteresis curves, leakage current, retention properties, and switching polarization. When the electrical properties of PZT etched in $O_2$ or Ar added $Cl_2/CF_4$ were compared, the value of remanent polarization in $O_2$ added $Cl_2/CF_4$ plasma is higher than that in Ar. added plasma. The maximum etch rate of the PZT thin films was 145 nm/min for 30% Ar added $Cl_2/CF_4$ gas having mixing ratio of 8/2 and 110 nm/min for 10% $O_2$ added to that same gas mixture. In order to recover the ferroelectic properties of the PZT thin films after etching, we annealed the etched PZT thin films at $550^{\circ}C$ in an $O_2$ atmosphere for 10 min. From the hysteresis curves, leakage current, retention property and switching polarization, the reduction of the etching damage and the recovery via the annealing was turned out to be more effective when $O_2$ was added to $Cl_2/CF_4$ than Ar. X-ray diffraction (XRD) showed that the structural damage was lower when $O_2$ was added to $Cl_2/CF_4$. And the improvement in the ferroelectric properties of the annealed samples was consistent with the increased intensities of the (100) and the (200) PZT peaks.

• The Research Journal of the Costume Culture
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• v.19 no.3
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• pp.612-621
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• 2011

The process of making or cultivating indigo dyes is very cumbersome and complex. The dye extraction and dyeing methods using general plant dye, moth repellent dye, fast acting natural dye, and other dyes are very different. This research investigates the extraction of indigo dye and liquid dye extraction of polygonum(indigo) plants using calcium oxide water. While extracting indigo dye the concentration of purified indigo dye may be controlled by adjusting the pH level. Due to the various uses of dyes the adjustment of surface color must be considered. In regard to the change according to different concentrations of reducing agents, it was found that cotton fabrics and ramie fabrics show the highest color difference at 0.4% and 0.3% respectively. As the reduction temperature increases, the color difference increases as well. The maximum color difference was found to appear at $90^{\circ}C$. Cotton fabrics and ramie fabrics showed 70.55 and 67.01 respectively. The color difference increases as the concentration of dyes increases, but at a concentration of 300%, cotton fabrics was found to show 6.22PB in H value using the Munsell color system, containing purple and blue color. The pH of the polygonum dyes extracted through this experiment were adjusted by adding calcium oxide to the experimental water, without directly adding calcium oxide to the liquid polygonum extract. In a refine state, it was mixed with polygonum extract to extract a more refine and highly concentrated indigo dye. When lye and reducing agents are added to extracted indigo dye and sealed for long-term storage, it can be effective and easily used for dyeing.

• Journal of the Korea Concrete Institute
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• v.17 no.1 s.85
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• pp.43-49
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• 2005

In the concrete structures, the magnitude and distribution of the temperature due to the heat of hydration are related to the thermal properties of each component composed of the concrete, the initial temperature, the type of formwork, and the ambient temperature of exposed surfaces. Even though the reinforcing steel bar has completely different thermal properties, it has been excluded. In the thermal analysis on the concrete structures. In this study, finite element analysis was performed on the concrete structures including the reinforcing steel in order to investigate their effect on temperature and stress distribution due to the heat of hydration. As the steel ratio increased, the maximum temperature and the internal-external temperature difference decreased by 32.5% and 10%, respectively. It is clear that the inclusion of reinforcing steel bars on the heat of hydration analysis is indispensable to obtain realistic solutions for the prediction of the maximum temperature and stresses

• Korean Journal of Materials Research
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• v.11 no.10
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• pp.851-858
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• 2001

One of the important phase of black titanium oxide is $Ti_4O_7$ which has the excellent properties such as the greatest electrical conductivity among the titanium oxides, chemical resistance against acidic and alkalic conditions and electro-wave absorption etc., so it has been considered as a promising material to be used widely all over the parts of industries. In this study, $Ti_4O_7$ phase was successfully synthesized by the reaction of TiO$_2$/ Mg system. With the change of the mole of TiO$_2$to Mg, the most excellent blackness was appeared in the 3.5 mole which was the smaller amount than the stoichiometric 4.0 mole. In addition, we found that the blackness decreased as the mole ratio of reactent increased. With decreasing particle size of magnesium, blackness of titanium oxide increased. The reaction property was changed with the compaction pressure, and optimum pressure was found to be 10 MPa. At 55$0^{\circ}C$ of reduction temperature, the blackness increased as the reaction time increased. The blackness of synthesized black titanium oxide was 14 to 18, and the average particle size was 0.2 $\mu\textrm{m}$.