• Journal of Powder Materials
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• v.22 no.6
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• pp.391-395
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• 2015

We report on the successful fabrication of ZnO nanorod (NR)/polystyrene (PS) nanosphere hybrid nanostructure by combining drop coating and hydrothermal methods. Especially, by adopting an atomic layer deposition method for seed layer formation, very uniform ZnO NR structure is grown on the complicated PS surfaces. By using zinc nitrate hexahydrate $[Zn(NO_3)_2{\cdot}6H_2O]$ and hexamine $[(CH_2)_6N_4]$ as sources for Zn and O in hydrothermal process, hexagonal shaped single crystal ZnO NRs are synthesized without dissolution of PS in hydrothermal solution. X-ray diffraction results show that the ZnO NRs are grown along c-axis with single crystalline structure and there is no trace of impurities or unintentionally formed intermetallic compounds. Photoluminescence spectrum measured at room temperature for the ZnO NRs on flat Si and PS show typical two emission bands, which are corresponding to the band-edge and deep level emissions in ZnO crystal. Based on these structural and optical investigations, we confirm that the ZnO NRs can be grown well even on the complicated PS surface morphology to form the chestnut-shaped hybrid nanostructures for the energy generation and storage applications.

• Applied Chemistry for Engineering
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• v.17 no.6
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• pp.648-652
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• 2006

Demand for $MnO_{2}$ has been increased with interest for its various applications in the fields of battery, catalyst, and capacitor. In this study, $MnO_{2}$ hollow microspheres were synthesized by sacrificial core method. $MnO_{2}$ nano particles were produced by the hydrolysis and condensation of manganese acetate. The stable $MnO_{2}$ hollow microspheres can very well be synthesized with mixing 0.2% of water, 0.65 mM of manganese acetate, and 0.02 mM catalyst at a room temperature.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.155-158
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• 2007

Printed organic thin-film transistor(OTFT) to use as a switching device for an organic light emitting diode(OLED) were fabricated in the microcontact printing and direct printing processes at room temperature. The gate electrodes($5{\mu}m$, $10{\mu}m$, and $20{\mu}m$) of OTFT was fabricated using microcontact printing process, and source/drain electrodes ($W/L=500{\mu}m/5{\mu}m$, $500{\mu}m/10{\mu}m$, and $500{\mu}m/20{\mu}m$) was fabricated using direct printing process with hard poly(dimethylsiloxane)(h-PDMS) stamp. Printed OTFT with dielectric layer was formed using special coating system and organic semiconductor layer was ink-jet printing process. Microcontact printing and direct printing processes using h-PDMS stamp made it possible to fabricate printed OTFT with channel lengths down to $5{\mu}m$, and reduced the process by 20 steps compared with photolithography. As results of measuring he transfer characteristics and output characteristics of OTFT fabricated with the printing process, the field effect characteristic was verified.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.2
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• pp.117-122
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• 2010

BCY($Ba(Ce_{0.9}Y_{0.1})O_{3-\delta}$) oxide, shows high protonic conductivity at high temperatures, and are referred to as hydrogen separation membrane. For high efficiency of hydrogen separation ($H_2$ flux and selectivity) and low fabrication cost, ultimate thin and dense BCY-Ni layer have to be coated on a porous substrate such as $ZrO_2$. Aerosol depostion (AD) process is a novel technique to grow ceramic film with high density and nano-crystal structure at room-temperature, and would be applied to the fabrication process of AD integration ceramic layer effectively. XRD and SEM measurements were conducted in order to analyze the characteristics of BCY-Ni membrane fabricated by AD process.

• Journal of Energy Engineering
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• v.25 no.2
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• pp.65-78
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• 2016

Initial studies of the photocatalyst has been developed from the field relating to the conversion and storage of solar energy. Recently, the study of the various organic decomposition compound and the water purification and waste water treatment by ultraviolet irradiation in the presence of light or a photocatalyst are being actively investigated. In addition, the oxidized material-carbon nanotubes, graphene-nanocomposites have been studied. Such a complex is suitable as a material constituting the solar cells and photolysis nanoelectronics, including the flexible element due to thermal and chemical stability.

• Korean Journal of Materials Research
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• v.31 no.10
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• pp.546-551
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• 2021

To improve ferroelectric properties of PZT, many studies have attempted to fabricate dense PZT films. The AD process has an advantage for forming dense ceramic films at room temperature without any additional heat treatment in low vacuum. Thick films coated by AD have a higher dielectric breakdown strength due to their higher density than those coated using conventional methods. To improve the breakdown strength, glass (SiO₂-Al₂O₃-Y₂O₃, SAY) is mixed with PZT powder at various volume ratios (PZT-xSAY, x = 0, 5, 10 vol%) and coating films are produced on silicon wafers by AD method. Depending on the ratio of PZT to glass, dielectric breakdown strength and energy storage efficiency characteristics change. Mechanical impact in the AD process makes the SAY glass more viscous and fills the film densely. Compared to pure PZT film, PZT-SAY film shows an 87.5 % increase in breakdown strength and a 35.3 % increase in energy storage efficiency.

• Nuclear Engineering and Technology
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• v.53 no.5
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• pp.1593-1601
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• 2021

Oxide dispersion strengthening (ODS) tungsten alloys are highly desirable in irradiation applications. However, how to improve the properties of ODS-tungsten alloys efficiently has been worth studying for a long time. Here we report a nanostructuring approach that achieves W-La₂O₃ alloy with a high level of flexural strength and Vickers hardness at room temperature, which have the maximum value of 581 MPa and 703 Hv, respectively. This method named solution combustion synthesis (SCS) can generate 30 nm coating structures W-La₂O₃ composite powders by using Keggin-type structural polyoxometalates as raw materials in a fast and low-cost process. The composite powder can be fabricated to W-La₂O₃ alloy with an optimal microstructure of submicrometric W grains coexisting with nanometric oxide particles in the grain interior, and a stability interface structure of grain boundaries (GBs) by forming transition zones. The method can be used to prepare new ODS alloys with excellent properties in the future.

• Applied Biological Chemistry
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• v.40 no.2
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• pp.117-122
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• 1997

The conditions of cold storage of Citrus unshiu Marc. var. miyagawa produced in Cheju were investigated. Compared to the citrus fruits stored at room temperature, the content of soluble solids, total sugar, vitamin C and specific gravity decreased slightly on the fruits stored at $4^{\circ}C$ and 87% relative humidity. Decay ratio and weight loss were below 10% on keeping freshness relatively till late of March during cold storage. Weight loss, decrease of firmness and soluble solids occured gradually during cold storage. Nevertheless seal-packaging with 0.02 mm LDPE film or wax-coating of citrus fruits were effective on weight loss and appearance, decay ratio increased for long-term storage. It was needed to control humidity in cold chamber for preventing from decay and weight loss. Edible part ratio was decreased gradually by respiration, and peel and tissue of fruits were softened slightly by 60 days of cold storage. Decay ratio and weight loss of full-ripened citrus fruits were little during the storage for 100 days, compared to the fruits harvested early. Appearance and taste of citrus fruits stored for 4 month were good relatively, but decay occured rapidly on seal-packaging fruits putting out of cold room for a few days. Because of the difficulty of long-term storage for early variety of Citrus unshiu, the conditions and periods of cold storage would be determined after considering the physicochemical properties of fruits.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.329-334
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• 2005

The rocket grade hydrogen peroxide has been widely used as a monopropellant in propulsion systems. Conventional decomposition of hydrogen peroxide, however, requires preheating before feeding into the reactor. In the present paper, we described an experimental study of a catalytic reactor bed that employs multiple catalysts to enhance the low temperature response in the vicinity of the reactor inlet. $K_2MnO_4$ is experimentally chose as the inlet catalyst from the candidates of silver, platinum, $La_{0.8}Sr_{0.2}CoO_3(LSC),\;and\;K_2MnO_4$. We developed new synthesis and coating method using modified alumina sol-gel method to strengthen the adhesion of $K_2MnO_4$ catalyst. from the vaporizer experiment with hydrogen peroxide at room temperature, satisfactory vaporizing performance was measured.

• Journal of the Korean Society of Tobacco Science
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• v.2 no.1
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• pp.61-67
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• 1980

The greenhouse hulk curing and drying system utilizing the direct solar energy was tested to see how much fuel could be saved for curing flue-cured tobacco at the Daegu Experiment Station, Korea Tobacco Research Institute (North latitute: 35$^{\circ}$49'), in 1979. The structure consists of transparent fiberglass exterior, polyurethan boards covered with galvanized iron as the heat absorbers and insulation boards, air duct in which the air is introduced to the furnace room of bulk curing barn, and gravel heat storage system. All exterior surface of heat absorbers, air duct, and gravels were coated with black paint. The air temperature and total radiation were 20.5 to 35.5$^{\circ}C$ and 1004.2 to 1436.2 cal/$\textrm{cm}^2$ during the 3 replicated curing tests, respectively. The greenhouse bulk curing and drying system was able to cut fuel consumption by 25 percent compared with the conventional bulk curing barn. The maximum temperatures for the top absorber and the inlet air of the system were 89$^{\circ}C$ and 64$^{\circ}C$, respectively, and the average temperature of inlet air was higher than that of conventional one by 18$^{\circ}C$.