• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.1
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• pp.8-14
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• 2014

In this study, we investigated synthesis and characteristics of gallium oxide ($Ga_2O_3$) powders prepared by precipitation method. $Ga_2O_3$ powders were synthesized using $Ga(NO_3)_3$ as a starting material and $NH_4OH$ as a precipitant. The oxidation temperature of $Ga(OH)_3$ and phase transition temperature of $Ga_2O_3$ was revealed using TG-DSC analysis. The crystal structural change of $Ga_2O_3$ powders was investigated by XRD analysis. The morphologies and size distributions of $Ga_2O_3$ particles were analyzed using SEM.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.793-794
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• 2010

Fischer-Tropsch(F-T) reaction, in which syngas($H_2+CO$) is transformed into liquid fuels, has attracted much attention recently due to the limited reservoir of petroleum. The formed F-T wax can be converted into various liquid fuels, such as gasoline, diesel, jet fuel, lubricants, etc., through the hydrocracking reaction. To carry out the hydrocracking reaction, the bifunctional catalyst is required, in which hydrogenation/dehydrogenation occurs over metal and cracking proceeds over solid acid sites. In this contribution, we review the reported hydrocracking catalysts and summarize some process variables (feed compositions, reaction temperature and reaction pressure) for each catalyst.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.1
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• pp.88-97
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• 1996

The metallization is the key to determining cell costs, cell performance, and system reliability. Screen printing technology suffers from several limitations affecting mainly the front grid. The buried contact solar cell (BCSC) was specifically desinged to be compatible with low cost, mass production techniques and avoid the conventional metallization problem. By using electroless plating technique, we performed this metallization inexpensively and reliably. This paper presents the details of the optimization procedure of metallization schemes on laser grooved cell surfaces. Commercially available Ni, Cu and Ag plating solutions were applied for the cell metallization. The application of those solutions on the buried contact front metallization has resulted in an cell efficiency of 18.8%. The cell parameters are an open circuit voltage of 651 mV, short circuit current density of 37.1 mA/$\textrm{cm}^2$, and fill factor of 77.8 %. The efficiency of over 18 % was achieved in the above 90% of the batch.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.5
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• pp.193-198
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• 2015

In the study, electroless Ni-plating on flexible ethylene-propylene-diene-monomer (EPDM) rubber sheets for the application of an insert block for shielding electromagnetic interference of multi cable transit (MCT) systems was investigated. Ni crystallinity and adhesion have been found to vary with processing parameters such as pH and temperature of the plating bath. It was shown that Ni-films having the high crystallinity and optimum electric conductivity were obtained on EPDM rubber sheets under pH 7 and 8 at $60{\sim}70^{\circ}C$. The conductive Ni-plated EPDM rubber prepared at pH 7 at $70^{\circ}C$ showed the enhanced adhesion and electric conductivity, and the high electromagnetic interference shielding effect in the 400 MHz~1 GHz range.

• Korean Journal of Materials Research
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• v.5 no.6
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• pp.706-714
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• 1995

Silicon oxide thin films were deposited by remote plasma chemical vapor deposition (RPCYD). The effect of the operating variables, such as plasma power, deposition temperature and partial pressure of reactant on the material Properties of the silicon oxide film was investigated. By XPS, it was found out that the film was suboxide (O/Si<2) and small amount of nitrogen due to the plasma excitation was accumulated at the Si/SiO$_2$interface. The amount of dangling bonds at the Si/SiO$_2$interfaces were measured by ESR and the concentration of hydrogen bond was obtained by SIMS and FT-IR. The bond angle distribution(d$\theta$/$\theta$) was shown to be similiar to thermal oxide above 20$0^{\circ}C$ but the etch rate was higher than that of the thermal oxides due to the structural difference and the stress between silicon substrate and silicon oxide film.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.1
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• pp.9-14
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• 1999

One of the IIDSt difficult problems in a tri-band fluorescent lamp manufacture is to search a desired color by an adequate mixing of tri-color phosphors. When a light spectrum of a phosphor is slightly changw or distorted due to process variable or when another spectrum such as from Ar, Kr or a iDosphor of calcium halo-phosphate as a first layer exist, it is even rrnre difficult to search a desired color. In this work, a rapid awuaching rrethod to a desired light color was studied. 1bree single-color fluorescent lamps and three-color-mixed fluorescent lamps with different mixing ratios were prepared and the spectra of these lamps were measured, from which the rrercury and the argon spectra were eliminatffl to obtain the rrndifiw color coordinates. From this rrndifiw color coordinate, h.lIlHl ratios of green and blue to red were correlatffl with their weight ratios. This correlation was awliw to the industrial line for single and double layer coating and proven to be valuable as a desired color matching procWure in tri-color fluorescent lamp manufacture.acture.

• Journal of Powder Materials
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• v.12 no.2 s.49
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• pp.136-145
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• 2005

Graphite-Ni composite powders were synthesized by mechanical alloying(MA) and spray drying(SD). Fabricated powders as well as commercial graphite-Ni powders were thermally sprayed on mild steel substrates using high velocity oxygen fuel (HVOF) thermal spray process and flame thermal spray process. The effects of several process parameters on related properties in thermally sprayed coatings have been investigated and correlated with microstructures in this study. The results indicated that the desired properties can be obtained when commercial powders were applied using HVOF process, while coating properties in case of MA powder application were inferior to those in HVOF process in so far. However, it is suggested that property enhancement can be obtained if the fraction of hexagonal graphite phase can be increased in mechanically alloyed powders.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.459-459
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• 2007

VHF ICP (Very High Frequency Inductively Coupled Plasma) 반응기에서 반응기 압력, 수증기 유량, 플라즈마 출력, 반응기온도 등의 공정변수에 따른 수증기 분해특성과 수소생성거동을 실험하였다. 플라즈마 분해 특성은 OES(Optical Emission Spectroscopy)를 사용하여 분석하였으며, QMS(Quadrapole Mass Spectroscopy)를 이용하여 배기가스 성분을 분석하여, 수증기 분해거동 및 수소생성 효율을 조사하였다. 본 연구실에서 설계한 초고주파 유도결합 플라즈마는 고밀도 플라즈마 생성과 낮은 압력에서도 안정된 플라즈마 발생 특징을 나타내었다. 플라즈마 출력의 증가에 따른 수증기의 분해와 수소생성 거동은 개시영역, 선형증가영역, 포화영역의 세 영역으로 구분되는 특징을 나타내었다. 유량 및 압력의 증가에 따라 포화에 필요한 플라즈마의 출력이 증가되는 경향을 나타내었다. 본 실험의 온도범위에서는 온도 증가에 따른 수증기 분해 및 수소생성 증가효과는 플라즈마 출력의 영향에 비하여 매우 미미한 정도로 플라즈마의 높은 에너지 전달효과를 확인할 수 있었다. 따라서, 낮은 반응기 온도에서도, 유량 및 압력에 따른 포화 플라즈마조건을 설정할 경우, 높은 에너지 효율의 수소 제조가 가능함을 알 수 있었으며, 물분해 플라즈마를 이용한 저온 산화물 박막증착에의 적용도 기대된다.

• Korean Journal of Materials Research
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• v.4 no.7
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• pp.783-791
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• 1994

Piezoelectric ZnO thin films were deposited on 7059 glass substrate by rf magnetron sputtering. The effects of deposition parameter, such as rf power, gas pressure and $O_{2}$/Ar gas ratio, on the crystallinity and electrical properties of the deposited ZnO thin films were studied. It was found that the deposition rate was higher than the previously reported values. ZnO films were suitable for SAW filter since a standard deviation of XRD (002) peak rocking curve was less than $6^{\circ}$. ZnO thin films, which were deposited at $O_{2}$/Ar ratio larger than 25%, showed high resistance. SAW filter was fabricated using ZnO film, of which thickness was 0.25 of the wavelength of the propatating surface acoustic wave. The measured frequency response was consistent with the calculated one. The SAW filter had center frequency 39.08 MHz, phase velocity 2501 m/sec and insertion loss 29 dB.

• Polymer(Korea)
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• v.36 no.1
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• pp.34-40
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• 2012

The foaming of poly(butylene succinate) (PBS) using supercritical $CO_2(scCO_2)$ was studied. In order to improve the melt strength, PBS was modified using the reactive compounding technique. Rapid decompression of $scCO_2$-saturated PBS at a temperature above the depressed $T_m$ yielded expanded microcellular foams. The resulting foam structure could be controlled by manipulating process conditions. Experiments varying the foaming temperature while holding other variables constant showed that higher temperatures produced larger cells and reduced cell densities. Higher saturated pressures led to higher nucleation densities and smaller cell sizes. Decreasing the rate of depressurization permitted a longer period of cell growth and therefore larger cells were obtained.