• Current Photovoltaic Research
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• v.2 no.1
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• pp.14-17
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• 2014

In this paper, indium reduced materials for transparent conductive electrodes (TCE) were fabricated and their physical properties were evaluated. Two of materials, indium-zinc-tin oxide (IZTO) and aluminum (Al) were selected as TCE materials. In case of IZTO nanoparticles, composition ratios of In, Zn and Sn is 8:1:1 were synthesized. Size of the synthesized IZTO nanoparticles were less than 10 nm, and specific surface areas were about $90m^2/g$ indicating particle sizes are very fine. Also, the IZTO nanoparticles were well crystallized with (222) preferred orientation despite it was synthesized at the lowered temperature of $300^{\circ}C$. Composition ratios of In, Zn and Sn were very uniform in accordance with those as designed. Meanwhile, Al was deposited onto glass by sputtering in a vacuum chamber for mesh architecture. The Al was well deposited onto the glass, and no pore was observed from the Al surface. The sheet resistance of Al on glass was about $0.3{\Omega}/{\square}$ with small deviation of $0.025{\Omega}/{\square}$, and adhesion was good on the glass substrate since no pelt-off part of Al was observed by tape test. If the Al mesh is combined with ink coated layer which is consistent of IZTO nanoparticles, it is expected that the good and reliable metal mesh architecture for TCE will be formed.

• Composites Research
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• v.31 no.3
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• pp.83-87
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• 2018

An object in the Low Earth Orbit (LEO) is affected by many environmental conditions unlike earth's surface such as, Atomic oxygen (AO), Ultraviolet Radiation (UV), thermal cycling, High Vacuum and Micrometeoroids and Orbital Debris (MMOD) impacts. The effect of all these parameters have to be carefully considered when designing a space structure, as it could be very critical for a space mission. Polybenzimidazole (PBI) is a high performance thermoplastic polymer that could be a suitable material for space missions because of its excellent resistance to these environmental factors. A thin coating of PBI polymer on the carbon epoxy composite laminate (referred as CFRP) was found to improve the energy absorption capability of the laminate in event of a hypervelocity impact. However, the overall efficiency of the shield also depends on other factors like placement and orientation of the laminates, standoff distances and the number of shielding layers. This paper studies the effectiveness of using a PBI coating on the front bumper in a multi-shock shield design for enhanced hypervelocity impact resistance. A thin PBI coating of 43 micron was observed to improve the shielding efficiency of the CFRP laminate by 22.06% when exposed to LEO environment conditions in a simulation chamber. To study the effectiveness of PBI coating in a hypervelocity impact situation, experiments were conducted on the CFRP and the PBI coated CFRP laminates with projectile velocities between 2.2 to 3.2 km/s. It was observed that the mass loss of the CFRP laminates decreased 7% when coated by a thin layer of PBI. However, the study of mass loss and damage area on a witness plate showed CFRP case to have better shielding efficiency than PBI coated CFRP laminate case. Therefore, it is recommended that PBI coating on the front bumper is not so effective in improving the overall hypervelocity impact resistance of the space structure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05d
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• pp.61-64
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• 2003

This paper presents Bi thin films have been fabricated by atomic layer-by-layer deposition and co-deposition at an IBS method. The growth rates of the films was set in the region from 0.17 to 0.27 nm/min. Mg(100) was used as a substrate. In order to appreciate stable existing region of Bi 2212 phase with temperature and ozone pressure, the substrate temperature was varied between 655 and $820^{\circ}C$ and the highly condensed ozone gas pressure$(PO_3)$ in vacuum chamber was varied between $2.0{\times}10^{-6}$ and $2.3{\times}10^{-5}$ Torr. Bi 2212 phase appeared in the temperature range of 750 and $795^{\circ}C$ and single phase of Bi 2201 existed in the lower region than $785^{\circ}C$. Whereas, $O_3$ dependance on structural formation was scarcely observed regardless of the pressure variation. And high quality of c-axis oriented Bi 2212 thin film with $T_c$(onset) of about 90 K and $T_c$(zero) of about 45 K is obtained. Only a small amount of CuO in some films was observed as impurity, and no impurity phase such as $CaCuO_2$ was observed in all of the obtained films.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.4
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• pp.868-878
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• 1998

There are recently increasing needs for precision XYZ-stage in the fields of nanotechnology, specially in AFMs(Atomic Force Microscope) and STMs(Scanning Tunneling Microscope). Force measurements are made in the AFM by monitoring the deflection of a flexible element (usually a cantilever) in response to the interaction force between the probe tip and the sample and controlling the force neasyred constant topography can be obtained. The power of the STM is based on the strong distance dependence of the tunneling current in the vacuum chamber and the current is a feedback for the tip to trace the surface topography. Therefore, it is required for XYZ-stage to position samples with nanometer resolution, without any crosscouples and any parasitic motion and with fast response. Nanometer resolution is essential to investigate topography with reasonable shape. No crosscouples and parasitic motion is essential to investigate topography without any shape distortion. Fast response is essential to investigate topography without any undesirable interaction between the probe tip and sample surface ; sample scratch. To satisfy these requirements, this paper presents a novel XYZ-stage concept, it is actuated by PZT and has a monolithic flexible body that is made symmetric as possible to guide the motion of the moving body linearly. PZT actuators have a very fast response and infinite resolution. Due to the monolithic structure, this XYZ-stage has no crosscouples and by symmetry it has no parasitic motion. Analytical modeling of this XYZ-stage and its verification by FEM modeling are performed and optimal design that is to maximize 1st natural frequencies of the stage is also presented and with that design values stage is manufactured.

• Journal of the Korean Society for Nondestructive Testing
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• v.13 no.2
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• pp.20-30
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• 1993

Electric Speckle Pattern Interferometry (ESPI) using a CW-laser, a video system and an image processor was applied to the thermal coefficient measurements on free thermal expansions at high temperatures : ESPI provides the distribution of in-plane displacement resolved in a preselected direction. ESPI retains the merits of little or no surface preparation, no contact with the surface and the real-time presentation of interference fringes. Appling ESPI at high temperatures, several problem which caused the reduction of fringe visibility were encountered. The problem on the turbulence in the hot air surrounding high temperature objects will be solved by using a vacuum chamber. The background radiations from the objects were suppressed considerably by an interference filter. The problem on the oxidation of the object surface could't be solved. The interference fringe, whose spacings were calculated by FFT to avoid human error, were observable up to $800^{\circ}C$. The results measured by ESPI were nearly equal to the data which have already been published, up to about $800^{\circ}C$.

• Journal of the Korean Society of Combustion
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• v.7 no.4
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• pp.36-44
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• 2002

Carbon molecules with closed-cage structures are called fullerenes $(C_{60},\;C_{70})$, whose applications include super-conductors, sensors, catalysts, optical and electronic device, polymer composites, and biological and medical materials. The synthesis of fullerenes has been recently studied with low-pressure benzene/argon/oxygen flames. The formation of fullerene is known as molecular weight growth processes of PAHs (polycyclic aromatic hydrocarbon). This study presents results of PAHs and fullerene measurements performed in a low-pressure benzene/argon/oxygen normal co-flow laminar diffusion flame. Through the central tube of the burner, benzene vapors carried by argon are injected. The benzene vapors are made in a temperature-controlled bubbler. The burner is located in a chamber, equipped with a sampling system for direct collection of condensable species from the flame, and exhausted to a vacuum pump. Samples of the condensable are analyzed by HPLC (High Performance Liquid Chromatography) to determine the yields of PAHs and fullerene. Also, we computed mole fraction of fullerene and PAHs in a nearly sooting low pressure premixed, one-dimensional benzene/argon/oxygen flame (equivalence ratio ${\Phi}=2.4$, pressure=5.33kPa). The object of computation was to investigate the formation mechanism of fullerenes and PAHs. The computations were performed with CHEMKIN/PREMIX. As a result of this study, fullerenes were synthesized in a low pressure (20torr) $C_6H_6/Ar/O_2$ flames and the highest concentration of fullerene was detected just above the visible surface of a flame.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.2
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• pp.101-105
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• 2010

We fabricated FEDs(Filed emission devices) based on ZnO nanowires. The ZnO nanowires were synthesized on Au thin films by hydrothermal method at the temperature of 90[$^{\circ}C$] on hot plate. In order to form tips of the ZnO nanowire, SDS(Sodium Dodecyl Sulfate) was mixed in O.05-0.3[wt%] solution as capping material. After 2 hour growth, we obtained nanowires of chain form The high-purity nanowires showed sharp tip geometry with a wurtzite structure. The field emission properties of the ZnO nanowires were investigated in high vacuum chamber. The turn-on field for the ZnO nanowires was found to be about 4.1[V/${\mu}m$] at a current density of 0.1[${\mu}A/cm^2$].

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.615-618
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• 2003

This paper presents Bi thin films have been fabricated by atomic layer-by-layer deposition and co-deposition at an IBS method. The growth rates of the films was set in the region from 0.17 to 0.27 nm/min. MgO(l00) was used as a substrate. In order to appreciate stable existing region of Bi 2212 phase with temperature and ozone pressure, the substrate temperature was varied between 655 and 820 $^{\circ}C$ and the highly condensed ozone gas pressure(PO$_3$) in vacuum chamber was varied between 2.0$\times$10$^{-6}$ and 2.3$\times$10$^{-5}$ Torr. Bi 2212 phase appeared in the temperature range of 750 and 795$^{\circ}C$ and single phase of Bi 2201 existed in the lower region than 785 $^{\circ}C$. Whereas, PO$_3$ dependance on structural formation was scarcely observed regardless of the pressure variation. And high quality of c-axis oriented Bi 2212 thin film with T$_{c}$(onset) of about 90 K and T$_{c}$(zero) of about 45 K is obtained. Only a small amount of CuO in some films was observed as impurity, and no impurity phase such as CaCuO$_2$ was observed in all of the obtained films.lms.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.2
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• pp.162-165
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• 2011

In this paper, $CuInSe_2$ thin film was prepared by use of the co-evaporation method with the variation of the substrate temperature in the range of $100^{\circ}C$ to $400^{\circ}C$. The film was annealed at $300^{\circ}C$ for an hour in a vacuum chamber at $3{\times}10-4$ Pa. After annealing, the thin film prepared at the substrate temperatures of $100^{\circ}C$ and $200^{\circ}C$ was observed. The XRD (x-ray diffraction) pattern of sample prepared at $100^{\circ}C$ showed the single phase formation of $CuInSe_2$. However, at $200^{\circ}C$, there was no apparent difference in the XRD pattern except a variation in the intensity of the peak. As the annealing treatment of substrate improved the crystal structure of the film, it affected to the increase of an electron mobility, resulted in an increase in conductivity and a decrease in resistance. As a results, when the substrate temperature was at $200^{\circ}C$ and $300^{\circ}C$, the sheet resistance was 1.534 $\Omega/\Box$ and 1.554 $\Omega/\Box$, respectively, and the resistivity was $1.76{\times}10-6\;{\Omega}{\cdot}cm$ and $1.7210-6\;{\Omega}{\cdot}cm$, respectively. From the absorption spectrum measurements, there was no variation between the before and after annealing conductions. And it means that the annealing step does not affect the thickness of the thin film.

• Journal of Sensor Science and Technology
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• v.7 no.5
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• pp.372-376
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• 1998

We developed a pulsed laser deposition(PLD) apparatus for depositing various thin films. In this study, the formation of $NbS_2$ thin film was performed in the vacuum chamber by PLD method. $Al_2O_3$(012) and Si(111) were used as the substrates. In order to investigate the growth conditions of a high crystalline $NbS_2$ thin film, the S/Nb composition ratio was varied from 2.0 to 5.25 and the substrate temperature was varied from the room temperature to $600^{\circ}C$. From the result of X-ray diffraction studies of the prepared $NbS_2$ thin films, it was reported that the $NbS_2$, thin film showed a good crystallinity at substrate temperature $600^{\circ}C$ and with S/Nb composition ratio 4.0 on $Al_2O_3$(012) but did not on Si(111). The films exhibited c-axis orientation.