• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.8 no.2
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• pp.48-54
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• 2012

To analyze the cooling performance of fin-tube evaporator in the refrigerator truck using R744 according to frost growth, the analytical model of evaporator was developed under frost and non-frost conditions. The performance of fin-tube evaporator was investigated with frost thickness and indoor temperature. Besides, the performance of evaporator under frost condition was compared to that under non-frost condition. As a result, area of air passage and system performance were decreased as the frost thickness increased. The cooling capacity was reduced by 10%, 20%, 30% when the frost thickness was 0.7 mm, 1.1 mm, and 1.6 mm respectively. At these conditions, the block ratio was 31%, 48%, and 71%. In addition, the outlet quality of refrigerant was not over 1 when the frost thickness was 1.6 mm in spite of high indoor air temperature.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.10 no.2
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• pp.1-6
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• 2014

As Korea's economy is entering a period of gradual growth, rate of growth on the construction market is becoming slow like that in developed countries. Remodeling construction market will be gradually expanded due to change in the social environment and diversification of individual demand. This study aims to promote the status of building equipment field with corresponding strategies based on the current situation that the importance of building equipment field is emphasized. Although it is desirable that building equipment construction companies lead remodeling construction, the building equipment part of general construction companies take the important role may be a advisable way, because the technology of building equipment construction companies is a little insufficient. Though building equipment field has become more important, the number of credits and professor of the field is still small than other fields of architectural engineering. More practical curriculums are necessary to meet the expectation of companies. Mechanical part of building equipment construction does not have independent law otherwise the other parts of building equipment construction. Establishing the independent law is urgent to promote the remodeling construction technology.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.202.1-202.1
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• 2013

ZnO nanostructure was fabricated on a Si substrate using two-step growth. The seed layer was grown on the Si substrate by a sol-gel spin-coating. In the first step, ZnO nanorods were grown by a hydrothermal method at $140^{\circ}C$ for 5 min. In the second step, a ZnO thin film was grown on the ZnO nanorods by spin-coating. After growth, these films were annealed at $800^{\circ}C$ for 10 min. Electrical and optical properties of ZnO nanostructures have modified by plasma-assisted molecular beam epitaxy (PA-MBE) regrowth. The carrier concentration and resistivity increased by PA-MBE regrowth. In the photoluminescence, the full width at half maximum and intensity were decreased and increased, respectively, by PA-MBE regrowth.

• Journal of the Semiconductor & Display Technology
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• v.9 no.2
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• pp.49-54
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• 2010

We have successfully synthesized $CeO_2$ nanopowders by means of the hydrothermal method, in a low temperature range of $100-200^{\circ}C$. In order to investigate the structure and morphology of the nanopowders, scanning electron microscopy and X-ray diffraction have been employed. In addition, for exploring the optical properties, Raman spectroscopy, Fourier transform infrared spectroscopy, and photoluminescence spectroscopy have been used. In the optimized condition, with the pH, velocity, and time of 4.5, 600 rpm, and 60 h, the $CeO_2$ nanopowders with a diameter ranging from 50 to 150 nm have been synthesized. The nanopowders exhibited the visible emission mainly in the blue region. With comparing the reaction time, it is revealed that the extinction of functional groups at 60 h contributed to the growth and homogenization of the $CeO_2$ powders. Since the overgrowth and agglomeration of nanopowders were found, we suggest that the cracking/growth process is more favorable mechanism than the dissolution/precipitation process.

• Journal of Powder Materials
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• v.22 no.4
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• pp.229-233
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• 2015

Porous metallic glass compact (PMGC) are developed by electro-discharge sintering (EDS) process of gas atomized $Zr_{41.2}Ti_{13.8}Cu_{12.5}Ni_{10}Be_{22.5}$ metallic glass powder under of 0.2 kJ generated by a $450{\mu}F$ capacitor being charged to 0.94 kV. Functional iron-oxides are formed and growth on the surface of PMGCs via hydrothermal synthesis. It is carried out at $150^{\circ}C$ for 48hr with distilled water of 100 mL containing Fe ions of 0.18 g/L. Consequently, two types of iron oxides with different morphology which are disc-shaped $Fe_2O_3$ and needle-shaped $Fe_3O_4$ are successfully formed on the surface of the PMGCs. This finding suggests that PMGC witih hydrothermal technique can be attractive for the practical technology as a new area of structural and functional materials. And they provide a promising road map for using the metallic glasses as a potential functional application.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2613-2618
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• 2012

Hydrothermal route have been used in different conditions for preparation of $Ni(OH)_2$ nanostructures. The NiO nanoparticles were obtained by calcining the $Ni(OH)_2$ precursor at $450^{\circ}C$ for 2 h. The effect of sodium dodecyl sulfonate (SDS) as surfactant on the morphology and size of $Ni(OH)_2$ nanoparticles were discussed in detail. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscopy were used to characterize the products. The growth mechanism of the as-synthesized nanostructures was also discussed in detail based on the experimental results. Coming up, the NiO nanoparticle modified carbon paste electrode was applied to the determination of captopril in aqueous solution.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.11
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• pp.1835-1839
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• 2016

In this study, ZnO nanorods were grown by a hydrothermal method. $SiO_2/Si$ wafers and glass were used as substrates. ~20 nm-thick ZnO thin films were rf magnetron sputtered for seed layers. The precursor was prepared by mixing zinc nitrate hexahydrate and hexamethylenetetramine (hexamine) in DI water. The concentration of zinc nitrate hexahydrate was fixed at 0.05 mol, and that of hexamine was varied between 0 mol to 0.1 mol. The reactor containing substrates and precursor was put in an oven maintained at $90^{\circ}C$ for 1 h. X-ray diffraction was carried out to analyze the crystallinity of ZnO nanorods, and a field emission scanning electron microscope was employed to observe the morphology of nanorods. Transmittance and absorbance were measured by a UV-Vis spectrophotometer. Photoluminescence measurements were conducted using 266 nm light.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.386-386
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• 2011

sol-gel 및 hydrothermal growth method를 이용한 zinc oxide nanorod는 제작 시 고가의 장비가 필요치 않기에 저비용 대면적 박막을 제작하는데 적합하지만 rod들의 array 및 density 조절에서 어려움을 가지고 있다. 본 연구에서는 이러한 nanorod array 형상 조절을 위하여 zinc oxide seed layer 형성 과정 중 precursor solution에 이종 나노 입자를 첨가하였다. 첨가한 seed precursor solution을 spin coating한 이후에 후처리 하여 hydrothermal method를 이용해 성장시켰다. 합성한 rod들을 optic과 FE-SEM으로 측정해 rod들의 density 변화를 확인할 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.640-640
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• 2013

본 연구에서는 유리 기판과 Si 기판에 Ag-doped ZnO 나노로드를 수열합성법을 이용하여 성장하였다. ZnO는 UV 영역에서 exciton 발광을 하며, 가시광선에서도 발광을 하는 것으로 알려져 있다. 그리고 Ag 금속은 입자형태로 ZnO 박막에 도포되었을 때 UV영역의 발광 세기를 강화시킨다는 사실이 알려져 있다. 이러한 내용을 바탕으로 ZnO 나노로드 합성 용액에 Ag powder의 양을 변화시켜 첨가하고, 유리와 Si기판을 넣고 80도에서 30분간 성장하였다. XRD, XPS를 통해 구조적 특성 변화를 보았고 SEM을 통해 나노로드의 형태를 확인하였다. 또한 PL, 투과도 측정을 통해 Ag 도핑에 따른 광학적 특성 변화를 확인하였다. SEM 측정으로 샘플의 단면을 확인한 결과 Ag 도핑 농도에 따른 차이가 거의 없음을 알았다. ZnO 나노로드가 성장된 유리 기판은 본래의 유리기판보다 투과도가 높았으며, Ag를 많이 첨가할수록 투과도가 낮아졌다.

• Journal of the Korean Ceramic Society
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• v.18 no.3
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• pp.147-151
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• 1981

On the calcium silicate hydrothermal reaction, the effect of NaOH and KOH Studied. Forincreasing the yield of fibers and to promote crystal growth, Rotary autoclae has been used. By addition NaOH solution, approximately 150${\mu}{\textrm}{m}$ of pectolite was grown. By addition KOH solution, approximately 30${\mu}{\textrm}{m}$ of 11$\AA$-Tobermorite was grown under the conditon of 21$0^{\circ}C$ 10 days reaction. These results indicate that 11$\AA$-Tobermorite was stabilized by KOH over a wide Temperature and composition range.