• 한국자기학회지
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• 제19권1호
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• pp.12-16
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• 2009

Z-Type 바리움 페라이트($Ba_{3}Co_{0.8}Zn_{1.2}Fe_{24}O_{41}$)를 공침법으로 제조하고 결정구조와 자기적 성질을 조사하였다. $Ba_{3+{\delta}}Co_{0.8}Zn_{1.2}Fe_{24}O_{41}$(${\delta}$ = 3, 5, 7, 13 wt%)와 $Ba_{3}Co_{0.8}Zn_{1.2}Fe_{{24}+{\delta}}O_{41}$(${\delta}$ = 5, 7, 10 wt%)의 조성을 가진 분말의 ${\delta}$ 값에 따른 자기적 성질의 변화를 조사하였다. 제조된 모든 바리움 페라이트에는 Z-type으로 상전이 하지 않은 M-type이 상당량 잔류하고 있었다. 포화자화는 Ba와 Fe의 과잉 첨가량 ${\delta}$가 각각 7 wt%와 5 wt% 일 때 최대로 나타났고 보자력은 조사된 모든 분말에서 다소 높게 나타났다. 높은 보자력은 M-type이 잔류하기 때문이다. 과잉의 Ba와 Fe 첨가에 따른 결정구조의 변화는 없었다. Z-type 바리움 페라이트의 연자성 특성을 향상시키기 위해서는 M-type이 Z-type 형성온도에서 상전이가 일어나도록 해야 함을 알았다.

• 한국식품과학회지
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• 제15권2호
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• pp.202-204
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• 1983

이산화탄소 측정기 및 제어기를 사용하여 글루탐산 발효공정의 자동화 방법을 개발하였다. 이는 발효배기가스 중의 이산화탄소와 균체의 성장 간에 직선관계가 있고 따라서 적절한 균체농도에서 페니실린 투여를 자동화할 수 있었다. 페니실린 투여 후 균체성장 및 글루탐산 생성의 고농도당에 대한 저해작용을 감소시켜 주기 위한 방법으로서 회분식 추가당 첨가공정을 자동화할 수 있었으며, 그 결과로서 회분식 발효에 비하여 생산성과 수율이 향상되었다.

• Current Photovoltaic Research
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• 제7권1호
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• pp.21-27
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• 2019

Lifetime of Si photovoltaics modules are about 25 years and a large amount of waste modules are expected to be discharged in the near future. Therefore, the extraction and collection of valuable metals out of discharged Si modules will be one of the important technologies. In this study, we demonstrated that supercritical $CO_2$ extraction method can be effectively used to remove Cu, one of the abundant elements in the module, as well as its oxide form, $Cu_2O$. Especially, we proved that the addition of hexane as co-solvent is effective for the removal of both materials. The optimal ratio of $CO_2$ and hexane was 4:1 at a fixed temperature and pressure of $250^{\circ}C$ and 250 bar, respectively. In addition, it was proven that the removal of $Cu_2O$ was preceded via reduction of $Cu_2O$ to Cu.

• 한국재료학회지
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• 제15권6호
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• pp.375-381
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• 2005

High temperature oxidation behavior of thermal barrier coating (TBC) system (IN738 substrate + NiCoCrAlY or NiAl bond coat with or without Pt + yttria stabilized zirconia) prepared by air plasma spray (APS) process has been studied in order to understand the effect of Pt addition to bond coat on the stability of TBC system. Specimens were oxidized in thermal cycling and isothermal oxidation test at $1100^{\circ}C$. The Pt addition in TBC system with NiCoCrAlY bond coat showed a longer life time compared to that without addition of Pt. Pt addition to TBC system is believed to help the formation of more stable thermally grown oxide, $Al_2O_3$, at the TBC/bond coat interface, leading to a longer lifetime of TBC system.

• 한국축산식품학회지
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• 제37권1호
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• pp.29-37
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• 2017

Defatted bovine liver (DBL) is a potential source of protein and minerals. Supercritical carbon dioxide ($SC-CO_2$) and a traditional organic solvent method were used to remove lipid from bovine liver, and the quality characteristics of a control bovine liver (CBL), bovine liver defatted by $SC-CO_2$ ($DBLSC-CO_2$) at different pressures, and bovine liver defatted by organic solvent (DBL-OS) were compared. The $DBLSC-CO_2$ samples had significantly higher (p<0.05) protein, amino acid, carbohydrate, and fiber contents than CBL and DBL-OS. There was a higher yield of lipid from CBL when using $SC-CO_2$ than the organic solvent method. SDS-PAGE analysis demonstrated that the CBL and $DBLSC-CO_2$ had protein bands of a similar intensity and area, whereas DBL-OS appeared extremely poor bands or no bands due to the degradation of proteins, particularly in the 50 to 75 kDa and 20 to 25 kDa molecular weight ranges. In addition, $DBLSC-CO_2$ was shown to have superior functional properties in terms of total soluble content, water and oil absorption, and foaming and emulsification properties. Therefore, $SC-CO_2$ treatment offers a nutritionally and environmentally friendly approach for the removal of lipid from high protein food sources. In addition, $SC-CO_2$ may be a better substitute of traditional organic solvent extraction for producing more stable and high quality foods with high-protein, fat-free, and low calorie contents.

• 한국재료학회지
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• 제22권11호
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• pp.598-603
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• 2012

MgO based cement for the low-temperature calcination of magnesite required less energy and emitted less $CO_2$ than the manufacturing of Portland cements. Furthermore, adding reactive MgO to Portland-pozzolan cement can improve their performance and also increase their capacity to absorb atmospheric $CO_2$. In this study, the basic research for magnesia cement using $MgCO_3$ and magnesium silicate ore (serpentine) as starting materials was carried out. In order to increase the hydration activity, $MgCO_3$ and serpentinite were fired at a temperature higher than $600^{\circ}C$. In the case of $MgCO_3$ as starting material, hydration activity was highest at $700^{\circ}C$ firing temperature; this $MgCO_3$ was completely transformed to MgO after firing. After the hydration reaction with water, MgO was totally transformed to $Mg(OH)_2$ as hydration product. In the case of using only $MgCO_3$, compressive strength was 35 $kgf/cm^2$ after 28 days. The addition of silica fume and $Mg(OH)_2$ led to an enhancements of the compressive strength to 55 $kgf/cm^2$ and 50 $kgf/cm^2$, respectively. Serpentine led to an up to 20% increase in the compressive strength; however, addition of this material beyond 20% led to a decrease of the compressive strength. When we added $MgCl_2$, the compressive strength tends to increase.

• 청정기술
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• 제24권1호
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• pp.35-40
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• 2018

$N_2O$ 촉매 분해 반응을 위한 $Co_3O_4$ 촉매는 공침법을 이용하여 제조하였으며, 조촉매로서 Ce 및 Zr의 양을 (Ce 또는 Zr)/Co = 0.05의 몰비로 고정하여 제조하였다. 또한 K가 촉매에 미치는 영향을 조사하기 위해 1 wt%의 $K_2CO_3$를 함침하여 촉매를 제조하였다. 제조된 촉매의 특성은 BET, SEM, XRD, $H_2-TPR$, XPS를 통해 분석하였다. $Co_3O_4$ 촉매는 스피넬 결정상을 나타냈으며, 조촉매의 첨가는 입자 크기와 결정 크기를 감소시켜 비표면적을 증가시키는 것으로 나타났다. K의 도핑은 촉매 활성 물질인 Co의 활성 종인 $Co^{2+}$의 농도를 증가시켜 촉매 활성을 향상시키는 것으로 확인되었다. $N_2O$ 분해 반응 테스트는 $GHSV=45,000h^{-1}$, $250{\sim}375^{\circ}C$에서 수행되었으며 $Co_3O_4$ 촉매에 조촉매를 첨가하였을 때도 반응성이 증가하였지만, K를 함침하면 활성이 더욱 크게 증가하는 것으로 나타났다. K의 도핑이 활성 종인 $Co^{2+}$의 농도를 증가시키며, 환원온도를 낮춰 주어 활성에 큰 영향을 주는 것으로 확인하였다.

• Journal of Electrochemical Science and Technology
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• 제2권2호
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• pp.97-102
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• 2011

Different amounts of excess lithium in the range of x = 0~0.3 were added to $Li_{1+x}[Mn_{0.720}Ni_{0.175}Co_{0.105}]O_2$ cathode materials synthesized using the co-precipitation method to investigate its microstructure and electrochemical properties. Pure layered structure without impurities was confirmed in the XRD pattern analysis and increasing peak intensity of $Li_2MnO_3$ was observed along with the addition of over 0.2 mol Li. The initial discharge capacity of the stoichiometric composition was determined to be 246 mAh/g, while the discharge capacity of the addition of 0.1 mol Li was obtained to be 241 mAh/g, which was not significantly different from that of the stoichiometric composition. However, the discharge capacities decreased dramatically after the addition of 0.2 and 0.3 mol Li to 162 mAh/g and 146 mAh/g, respectively. In the rate capability test, the active $Li_{1+x}[Mn_{0.720}Ni_{0.175}Co_{0.105}]O_2$ cathode material of the stoichiometric composition showed a dramatic decrease in its discharge capacity with increasing C-rate, as evidenced by the result that the discharge capacity at 5C was 13% compared with 0.1C. On the other hand, the discharge capacity of compositions containing excess lithium was improved at higher current rates. The cycling test showed that the composition containing an excess of 0.1 mol Li had the most outstanding capacity retention.

• 한국주조공학회지
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• 제6권4호
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• pp.269-276
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• 1986

The effects of Se, $CaCO_3$ and CaO addition on the first stage graphization of malleable iron were evaluated. The results obtained in this work were as follows. 1. Many gas bubbles were found in the white cast iron under Se, $CaCO_3$ addition. 2. Nodular graphite were formed by annealing of the white cast iron with remained gas bubbles. 3. When specimens were annealed, bubbles provided the nucleation sites that were needed in graphite precipitation, so the nucleation rate of graphite was increased. 4. The remained gas bubbles and defects were more effective for the graphitization than metallic compounds.

• 한국군사과학기술학회지
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• 제6권2호
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• pp.9-19
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• 2003

Nitrogen oxide gases which were produced by spontaneous reaction of nitrocellulose(NC) in the single base propellant accelerate the decomposition of propellant, and result in the reduction of shelf life. The amount of nitrogen oxide was reduced by the addition of 0.3wt% $CaCO_3$ to conventional stabilizer(DPA) and down of the solvent leaching temperature from $64^{\circ}C$ to $56^{\circ}C$, which extended the shelf life of the single base propellant as much as twice compare with commercial propellant. The perforation diameter increase of propellant from 0.64mm to 0.77mm could compensate for the drop of burning rate which was caused the addition of $CaCO_3$.