• 한국재료학회지
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• 제2권5호
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• pp.360-365
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• 1992

Ga 첨가효과 및 Sputter 제조조건이 전기적 특성에 미치는 영향을 고찰하기 위해 ZnO분말과 G$a_2O_3$분말을 소결하여 타겟트를 제조하여 Sputter법으로 유리기판에 Ga-doped ZnO 다결정박막을 제조하였다. RF 전력밀도, 아르곤 개스압력 및 Ga 함유량등을 최적화한 후 제조한 투명한 Ga-doped ZnO 박막의 비저항은 1$0^{-3}$ohm-cm이며, undoped 및 Ga-doped ZnO 박막의 전자농도는 각 $10^{18}$, $10^{21}$/c$m^2$이였다. 공기와 질소분위기에서 열처리를 행하였을 때 Ga-doped ZnO 박막의 비저항은 $10^{2}$ order 증가하였다. 가시광영역의 투과율은 80% 이상이였으며, Ga 함유량이 증가하면 optical band gap도 넓어졌다.

• 한국재료학회지
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• 제20권3호
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• pp.125-131
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• 2010

In this study, Ti powders were fabricated from Ti scrap by the Hydrogenation-Dehydrogenation (HDH) method. The Ti powders were prepared from the spark plasma sintering (SPS) and their microstructure was investigated. Hydrogenation reactions of Ti scrap occurred at near $450^{\circ}C$ with a sudden increase in the reaction temperature and the decreasing pressure of hydrogen gas during the hydrogenation process in the furnace. The dehydrogenation process was also carried out at $750^{\circ}C$ for 2 hrs in a vacuum of $10^{-4}$ torr. After the HDH process, deoxidation treatment was carried out with the Ca (purity: 99.5%) at $700^{\circ}C$ for 2 hrs in the vacuum system. It was found that the oxidation content of Ti powder that was deoxidized with Ca showed noticeably lower values, compared to the content obtained by the HDH process. In order to fabricate the Ti compacts, Ti powder was sintered under an applied uniaxial punch pressure of 40 MPa in the range of $900-1200^{\circ}C$ for 5 min under a vacuum of $10^{-4}$ torr. The relative density of the compact was 99.5% at $1100^{\circ}C$ and the tensile strength decreased with increasing sintering temperature. After sintering, all of the Ti compacts showed brittle fracture behavior, which occurred in an elastic range with short plastic yielding up to a peak stress. Ti improved the corrosion resistance of the Ti compacts, and the Pd powders were mixed with the HDH Ti powders.

• 자원리싸이클링
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• 제17권1호
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• pp.66-72
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• 2008

폐알칼리망간전지로부터 침출과 공침반응을 이용하여 Mn-Zn ferrite 분말을 제조하기 위한 기초실험을 수행하였다. 100g/L 광액 농도 3.0M $H_2SO_4$, $60^{\circ}C$ 및 교반속도 200 rpm의 조건에서 과산화수소 30ml를 첨가하여 얻어진 아연과 망간의 침출율은 각각 97.9%, 93.9% 이상이었으며, 침출용액을 가지고 반응시간, 반응온도, $O_2$ 가스량을 조절하며 공침반응을 진행하였다. 공침반응 결과 pH 12, $80^{\circ}C$, $O_2$ 1.3L/min, 교반속도 400 rpm의 조건에서 Mn-Zn ferrite를 저온 합성할 수 있었다. 합성된 Mn-Zn ferrite분말은 $0.143{\mu}m$의 구형 ferrite로서 80 emu/g의 포화자화값을 가지고 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.145-145
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• 2010

In this paper, we report that the effects of hydrogen doping on the electrical and optical properties of typical transparent conducting oxide films such as ZnO and $SnO_2$ prepared by magnetron sputtering. Recently, density functional theory (DFT) calculations have shown strong evidence that hydrogen acts as a source of n-type conductivity in ZnO. In this work, the beneficial effect of hydrogen incorporation on Ga-doped ZnO thin films was demonstrated. It was found that hydrogen doping results a noticeable improvement of the conductivity mainly due to the increases in carrier concentration. Extent of the improvement was found to be quite dependent on the deposition temperature. A low resistivity of $4.0{\times}10^{-4}\;{\Omega}{\cdot}cm$ was obtained for the film grown at $160^{\circ}C$ with $H_2$ 10% in sputtering gas. However, the beneficial effect of hydrogen doping was not observed for the films deposited at $270^{\circ}C$. Variations of the electrical transport properties upon vacuum annealing showed that the difference is attributed to the thermal stability of interstitial hydrogen atoms in the films. Theoretical calculations also suggested that hydrogen forms a shallow-donor state in $SnO_2$, even though no experimental determination has yet been performed. We prepared undoped $SnO_2$ thin films by RF magnetron sputtering under various hydrogen contents in sputtering ambient and then exposed them to H-plasma. Our results clearly showed that the hydrogen incorporation in $SnO_2$ leads to the increase in carrier concentration. Our experimental observation supports the fact that hydrogen acting as a shallow donor seems to be a general feature of the TCOs.

• 대한금속재료학회지
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• 제48권7호
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• pp.625-629
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• 2010

This study investigates the effects of porosity on the thermal stability and the thermal shock resistance of a porous nozzle used for blowing an inert gas. The samples of $Al_2O_3-SiO_2-ZrO_2$ system, which had the apparent porosity of 16~30% and bulk density of $2.6{\sim}3.2g/cm^3$, were prepared by adding different graphite contents (5, 10, 20 wt%) as a pore-forming agent. The thermal shock test was conducted at ${\Delta}T=500$, 1000, and $1400^{\circ}C$ also and the thermal stability was also carried out at 1550, 1600, and $1650^{\circ}C$ for 5 hrs. The specimen contained 10 wt% graphite had uniform pore size distribution, whereas the specimen with 20 wt% graphite showed non-uniform pore size distribution. As a result of thermal shock test, the specimen containing 10 wt% graphite appears to have higher mechanical strength than the other specimens (5, 20 wt% graphite). Both the 5 wt% and 20 wt% graphite specimens developed a non-uniform pore size distribution and cracks that were generated by intensive thermal stress.

• Nuclear Engineering and Technology
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• 제14권2호
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• pp.78-85
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• 1982

정상상태의 플라즈마의 이론적 해석을 통해서 플라즈마의 회전과 동위원소 분리기로서의 적합성을 분석하였다. 이 장치는 두개의 동심원통형 전극과 이들 사이의 원통형 공동으로 구성되었으며, 축 방향으로 외부자장이 걸려 있다. 두 전극사이에 생성되는 전류밀도는 전기방전의 형태로 동위원소 혼합물로부터 플라즈마를 생성하고, 자장과 교차되어 발생하는 Lorentz힘에 의해서 플라즈마를 회전시킨다. 자기 유체역학 방정식을 바탕으로 이 계를 설명하는 두개의 연립편미분방정식을 얻었고, 네 경계조건을 사용하여 Fourier-Bessel로 표현된 이차원적 전류밀도와 속도분포의 해를 얻었다. 실제로 가능한 조건하에서 플라즈마 회전속도는 $10^4$m/sec 정도에 달하고, Hartmann수가 커짐에 따라 플라즈마회전 속도도 커진다. 이 같은 고속의 회전속도를 감안해 볼때 플라즈마 원심분리기는 기계적으로 회전되는 가스원심분리기보다 훨씬 높은 효율을 가지게 될 것이다.

• Nuclear Engineering and Technology
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• 제53권8호
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• pp.2616-2628
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• 2021

The results of effective irradiation swelling in a wide range of burnup levels are numerically obtained for an inert matrix fuel, which are verified with DART model. The fission gas swelling of fuel particles is calculated with a mechanistic model, which depends on the external hydrostatic pressure. Additionally, irradiation and thermal creep effects are included in the inert matrix. The effects of matrix creep strains, external hydrostatic pressure and temperature on the effective irradiation swelling are investigated. The research results indicate that (1) the above effects are coupled with each other; (2) the matrix creep effects at high temperatures should be involved; and (3) ranged from 0 to 300 MPa, a remarkable dependence of external hydrostatic pressure can be found. Furthermore, an explicit multi-variable mathematic model is established for the effective irradiation swelling, as a function of particle volume fraction, temperature, external hydrostatic pressure and fuel particle fission density, which can well reproduce the finite element results. The mathematic model for the current volume fraction of fuel particles can help establish other effective performance models.

• Korean Chemical Engineering Research
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• 제57권2호
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• pp.172-176
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• 2019

저생 미생물 연료전지(BMFC)는 바다나 호수의 뻘 속에서 저생미생물이 유기물을 분해하면서 발생시키는 전기를 이용한 연료전지다. 본 연구에서는 BMFC 전극으로 카본 소재를 발수 처리한 고분자 전해질 연료전지(PEMFC)의 가스확산층(GDL)을 사용해서 성능이 높게 나오는 구동조건을 찾고자 하였다. 높은 저항 값을 갖는 외부저항을 사용했을 때 성능이 높았으며 바닷물에서 리드선의 부식에 의한 전극과 접촉저항 증가를 피해야 성능을 유지할 수 있었다. 기포 발생기를 사용해 최고출력밀도를 2배 이상 높일 수 있었고 최적 구동 온도는 $40^{\circ}C$였다.

• 한국분말재료학회지
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• 제26권4호
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• pp.282-289
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• 2019

Ti has received considerable attention for aerospace, vehicle, and semiconductor industry applications because of its acid-resistant nature, low density, and high mechanical strength. A common precursor used for preparing Ti materials is $TiCl_4$. To prepare high-purity $TiCl_4$, a process based on the removal of $VOCl_3$ has been widely applied. However, $VOCl_3$ removal by distillation and condensation is difficult because of the similar physical properties of $TiCl_4$ and $VOCl_3$. To circumvent this problem, in this study, we have developed a process for $VOCl_3$ removal using Cu powder and mineral oil as purifying agents. The effects of reaction time and temperature, and ratio of purifying agents on the $VOCl_3$ removal efficiency are investigated by chemical and structural measurements. Clear $TiCl_4$ is obtained after the removal of $VOCl_3$. Notably, complete removal of $VOCl_3$ is achieved with 2.0 wt% of mineral oil. Moreover, the refined $TiCl_4$ is used as a precursor for the synthesis of Ti powder. Ti powder is fabricated by a thermal reduction process at $1,100^{\circ}C$ using an $H_2-Ar$ gas mixture. The average size of the Ti powder particles is in the range of $1-3{\mu}m$.

• Journal of Nutrition and Health
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• 제52권4호
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• pp.323-331
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• 2019

Purpose: Glucocorticoids (GCs) are implicated in secondary osteoporosis, and the resulting fractures cause significant morbidity. Polyunsaturated fatty acids (PUFAs) play a vital role in bone metabolism. However, few trials have studied the impact of omega-3 PUFA-containing oils against GC-induced osteoporosis. Therefore, the present study was undertaken to determine whether supplementation with omega-3 PUFA-containing dietary oils such as fish oil, flaxseed oil or soybean oil can impede the development of GC-induced osteoporosis. Methods: The fatty acids (FAs) content of oils was determined using gas chromatography. Male rats were subdivided into 5 groups (8 rats each): normal control (balanced diet), prednisolone control (10 mg/kg prednisolone daily), soybean oil (prednisolone 10 mg/kg + soybean oil 7% w/w), flaxseed oil (prednisolone 10 mg/kg + flaxseed oil 7% w/w), and fish oil (from cod liver; prednisolone 10 mg/kg + fish oil 7% w/w). Results: The study data exhibited a significant depletion in bone mineral density (BMD) and femur mass in the prednisolone control compared to the normal control, accompanied with a marked decrease in the levels of plasma calcium and 1,25-$(OH)_2$-vitamin $D_3$, and elevated levels of C-terminal telopeptide (CTX), tumor necrosis factor-alpha (TNF-${\alpha}$) and malondialdehyde (MDA). Supplementation with fish oil, soybean oil or flaxseed oil helped to improve plasma calcium levels, and suppress oxidative stress and inflammatory markers. Additionally, bone resorption was suppressed as reflected by the decreased CTX levels. However, fish oil was more effective than the other two oils with a significant improvement in BMD and normal histological results compared to the normal control. Conclusion: This study demonstrated that supplementation with dietary oils containing omega-3 PUFAs such as fish oil, soybean oil or flaxseed oil can play a role in the prevention of bone loss and in the regulation of bone metabolism, especially fish oil which demonstrated a greater level of protection against GC-induced osteoporosis.