• 자원리싸이클링
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• 제2권2호
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• pp.27-38
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• 1993

본 연구에서는 제철소에서 발생하는 전로 dust를 사용하여 심강법(분급)에 의한 철산화물을 분리하여 고순도의 철분말을 회수하였으며, 아래와 같은 결론을 얻었다. 가. 전로 dust의 물성 1) 재항의 1제강, 2제강 C/F(Clarifier) dust, 광장의 E/C(Evaporation coolar), dust, 중국강철공사(C.S.C) OM(Clarifier underflow) dust 금철분이 63~72%로 높고, Metal Fe 가 21~50% 함유되어 있으며, 기타 산화물로는 CaO, MgO, Al$_{2}O_{3}$, SiO$_{2}$ 등이 있다. 2) 재항의 1제강, 2제강 C/F dust, 광양의 E/C, E/P dust, 중국강철공사(C.S.C), OM(clarifier underflow) dust 입자의 형상은 청입이 주로 구형으로 응고된 모양이었으며, 일반적으로는 출립의 외각부는 magnetite, hematite 등으로 산화가 진해되어 있다. 3) 전로 dust 들에 대한 X-ray 회절분석결과, 재항의 1제강, 2제강, C/F dust, 광양의 E/C, E/P dust는 ${\alpha}$-Fe, FeO(wusute)가 중성분으로 존재하며 그 밖에 FE$_{3}O_{4}$9magnetite), Fe$_{2}O_{3}$ CaO가 소량으로 존재하고 있었으며, 중국강철공사(C.S.D) OM(underflow) dust는 ${\alpha}$-Fe, ${\alpha}Fe_{2}O_{3}$, graphite가 주성분으로 존재하며, 그 밖에 $Fe_{3}O_{4}$, Fe$_{2}O_{3}$, ZnO이 소량으로 존재하고 있었다. 4) 순수한 순철분말과 전로 dust를 구성하고 있는 순철은 마광에 따른 입자의 분쇄보다는 마광시 구형의 입자가 소성변형으로 인해 flake형상으로 변하여 체질입도분석시 입도의 증가를 초래하였으며, 반면 철산화물은 마광에 따른 입자의 미세화가 발생함을 볼 수 있었다. 나. 철분구 외수 실험 1) 광양의 dust를 40분간 마광하여 심강(분급)실험을 행했을 때 Fe 99.17% 품위 철분말을 37.8% 회수할 수 있었다. 2) 재항의 C/F dust를 40분간 마광하여 심강(분급)실험을 행했을 때 Fe 98.38% 품위의 철분말을 44.42% 회수할 수 있었다. 3) 70 gauss 자석을 사용하여 자력선별을 행했을 때 +65-200 mesh 사이에서 Fe 품위 98% 이상의 철분말을 회수 할 수 있으나 회수율(14%)이 낮다.

• 한국분말재료학회지
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• 제25권4호
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• pp.327-330
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• 2018

This study is conducted as a preliminary research to verify the feasibility of Ti-based Oxide dispersion strengthened (ODS) alloy. Pure-Ti powder is mixed with $Y_2O_3$ powder and subsequently, mechanically alloyed at $-150^{\circ}C$. The Ti-based ODS powder is hot-isostatically pressed and subsequently hot-rolled for recrystallization. The microstructure consists of elongated grains and Y excess fine particles. The oxide particle size is larger than that of the typical Fe-based ODS steel. Tensile test shows that the tensile ductility is approximately 25%, while the strength is significantly higher than that of pure Ti. The high-temperature hardness of the Ti-ODS alloy is also significantly higher than that of pure Ti at all temperatures, while being lower than that of Ti-6Al-4V. The dimple structure is well developed, and no evidence of cleavage fracture surface is observed in the fracture surface of the tensile specimen.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.306-308
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• 2007

Poly(ethylene glycol) dimethyl ether (PEGDME)/fumed silica/ 1-methyl -3-propylimidazolium iodide (MPII)/$I_2$ mixtures were used as polymer electrolytes in solid state dye-sensitized solar cells (DSSCs). The contents of MPII were changed and the concentration of $I_2$ was fixed at 0.1 mole% with respect to the MPII. The maximum ionic conductivity was obtained at [EG]:[MPII]:[$I_2$]=10:1.5:0.15. It was supposed that the maximum of ionic conductivities would match with that of cell efficiencies, if the ionic conductivity is a rate determining step in the sol id state DSSCs. However, the maximum composition did not show the maximum solar cell performance, indicating the mismatch between ionic conductivity and cell performance. This suggests that the ionic conductivity may not be the rate controlling step in determining the cell efficiency in these experimental conditions, whereas other parameters such as the electron recombination might play an important role. Thus, we tried to modify the surface of the $TiO_2$ particles by coating a thin metal oxide such as $Al_2O_3$ or $Nb_2O_5$ layer to prevent electron recombination. As a result, the maximum of the cell efficiency was shifted to that of the ionic conductivity. The peak shifts were also attempted to be explained by the diffusion coefficient and the lifetime of electrons in the $TiO_2$ layer.

• 한국대기환경학회지
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• 제20권3호
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• pp.317-330
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• 2004

The Purpose of this study was to develop the P $M_{2.5}$ source Profiles, which are mass abundances (fraction of total mass) of a chemical species in P $M_{2.5}$ source emissions. The source categories studied were soil, road dust, gasoline and diesel vehicles, industrial source, municipal incinerator, coal-fired power plant, biomass burning, and marine. The chemicals analyzed were ions. elements. and carbons. From this study, soil source had the crustal components such as Si, hi, and Fe. In the case of road dust. Si, OC, Ca, Fe had large abundances. The abundant species were S $O_4$$^{2-}$, C $l^{[-10]}$ , N $H_4$$^{+}$, and EC in the gasoline vehicle and EC, OC, C $l^{[-10]}$ , and S $O_4$$^{2-}$ in the diesel vehicle. The main components were S $O_4$$^{2-}$, S N $H_4$$^{+}$, and EC in the industrial source using bunker C oil as fuel, C $l^{[-10]}$ , N $H_4$$^{+}$, Fe, and OC in the municipal incinerator source, and Si, Al, S $O_4$$^{2-}$, and OC in the coal -fired power plant source. In the case of biomass burning, OC, EC, and C $l^{[-10]}$ were mainly emitted. The main components in marine were C $l^{[-10]}$ , N $a^{+}$, and S $O_4$$^{2-}$.EX> 2-/.

• 한국항공우주학회지
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• 제31권2호
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• pp.72-79
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• 2003

고체 추진제의 소화를 위한 연소실 압력 강하시 금속입자들에 의한 복사열전달에 동적소화에 미치는 영향을 알아보았다. AP:Binder의 화학반응으로 발생하는 전도열 플럭스를 구하기 위해 화염모델을 사용하였으며, 금속입자들에 복사열 플럭스를 구하기 위해 연소흐름 모델을 사용하였다. 연소실은 크기가 무한대인 경우와 노즐에 의해 제한된 형태 두 가지를 선택하여 계산을 수행하였다. 계산에 사용된 추진제 조성을 AP:Al:CTPB=76:10:14이며 최종압력 이후, 총 열 플럭스 중 복사열 플럭스가 차지하는 비중은 5~6%정도로 나타났다. 연소실 크기가 무한대인 경우, 복사열전달을 고려한 경우의 임계 압력강하율이 복하열을 고려하지 않은 경우보다 45% 크게 나타났다. 이는 복사열전달이 동적소화에 큰 영향을 미치는 것을 보여주는 것이다.

• 한국물환경학회지
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• 제30권3호
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• pp.261-268
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• 2014

Four clays (both natural and commercial types) mainly used in Korea were tested for removal efficiency of Microcystis spp. and ecotoxicity on Daphnia magna and Vibrio fischeri. Four clays (clay A~D) were composed of 91.9~100% of sand (0.02~0.2 mm in particle size). Clay D consisted of lager particles than other clays. Major elements of the four clays were $SiO_2$ (45.3~62.8%), $Al_2O_3$ (18.5~29.7%) and $Fe_2O_3$ (5.4~7.9%). They contained kaolinite (clay mineral), quartz, muscovite, and so on. Clay C and D contained montmorillonite, one of the clay minerals improving clay-cell aggregation. For clay A, B and C, removal efficiency of Microcystis spp. was over 60% at 2 g/L. It reached about 100% at over 5 g/L. For clay D, it was over 60% and 95~100% at 5 g/L and 20 g/L respectively. After adding clays, pH decreased. The greatest drop of pH appeared at clay C. Except for addition of 100 g/L clay C, ecotoxicity on D. magna and V. fischeri didn't appeared at all dose of clays.

• Nuclear Engineering and Technology
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• 제52권10호
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• pp.2230-2237
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• 2020

Self-priming venturi scrubber is one of the most effective devices used to collect aerosols and soluble gas pollutants from gaseous stream during severe accident in a nuclear power plant. The present study focuses on investigation of dust particle removal efficiency of the venturi scrubber both experimentally and theoretically. Venturi scrubber captures the dust particles in tiny water droplets flowing into it. Inertial impaction is the main mechanism of particles collection in venturi scrubber. The water injected into venturi throat is in the form of jets through multiple holes present at venturi throat. In this study, aerosols removal efficiency of self-priming venturi scrubber was experimentally measured for different operating conditions. Alumina (Al₂O₃) particles with 0.4-㎛ diameter and 3950 kg/㎥ density were treated as aerosols. Removal efficiency was calculated for different gas flow rates i.e. 3-6 ㎥/h and liquid flow rates i.e. 0.009-0.025 ㎥/h. Experimental results depict that aerosols removal efficiency increases with the increase in throat velocity and liquid head. While at lower air flow rate of 3 ㎥/h, removal efficiency decreases with the increase in liquid head. A theoretical model of venturi scrubber was also employed and experimental results were compared with mathematical model. Experimental results are found to be in good agreement with theoretical results.

• The Journal of Advanced Prosthodontics
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• 제6권4호
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• pp.272-277
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• 2014

PURPOSE. The purpose of this study was to investigate the impact of different surface treatment methods and thermal ageing on the bond strength of autopolymerizing acrylic resin to Co-Cr. MATERIALS AND METHODS. Co-Cr alloy specimens were divided into five groups according to the surface conditioning methods. C: No treatment; SP: flamed with the Silano-Pen device; K: airborne particle abrasion with $Al_2O_3$; Co: airborne particle abrasion with silica-coated $Al_2O_3$; KSP: flamed with the Silano-Pen device after the group K experimental protocol. Then, autopolymerized acrylic resin was applied to the treated specimen surfaces. All the groups were divided into two subgroups with the thermal cycle and water storage to determine the durability of the bond. The bond strength test was applied in an universal test machine and treated Co-Cr alloys were analyzed by scanning electron microscope (SEM). Two-way analysis of variance (ANOVA) was used to determine the significant differences among surface treatments and thermocycling. Their interactons were followed by a multiple comparison' test performed uing a post hoc Tukey HSD test (${\alpha}=.05$). RESULTS. Surface treatments significantly increased repair strengths of repair resin to Co-Cr alloy. The repair strengths of Group K, and Co significantly decreased after 6,000 cycles (P<.001). CONCLUSION. Thermocycling lead to a significant decrease in shear bond strength for air abrasion with silica-coated aluminum oxide particles. On the contrary, flaming with Silano-Pen did not cause a significant reduction in adhesion after thermocycling.

• 접착 및 계면
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• 제21권1호
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• pp.27-33
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• 2020

유리섬유강화 복합재료 (GFRC)의 표면거칠기에 따른 에폭시 접착제의 접착강도를 평가하였고 최적의 표면거칠기를 선정하였다. 서로 다른 입자크기의 알루미나 (Al2O3) 입자를 GFRC의 표면에 분사하였고 이를 통하여 서로 다른 표면거칠기를 부여하였다. 표면거칠기를 정량화 하였고 표면거칠기에 따른 표면관찰을 진행하였다. 각 표면거칠기에 따른 접촉각을 측정하였고 이를 통하여 표면에너지를 계산하였으며, 에폭시 접착제와의 접착일을 계산 및 비교하여 접착력을 예측하였다. 단일랩전단 시험을 통해 접착강도를 평가하였고 거칠기에 따라 접착강도가 증가된다는 것을 확인하였다. 박리 후 표면을 관찰해 보았을 때 기지재인 GFRC의 박리 정도가 다른 것을 확인하였고 최종적으로 표면거칠기의 최적조건을 확인할 수 있었다.

• 헤리티지:역사와 과학
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• 제46권4호
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• pp.108-125
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• 2013

경주 동천동 출토 토제범(土製范)에 대한 실측복원도, 조성광물 분석, 입도 및 물성시험, 미세조직관찰, 색도차 및 주성분 분석결과를 알아보았다. 연구대상 내범과 외범의 단면은 내측(제1층위)과 외측(제2층위)으로 구분되고 외측에는 유기물이 혼합되어 있다. 단면에는 열적 경험과 탈형제로 인한 변화 양상이 확인되며, X-선 촬영에서는 내측인 제1층위가 투과율이 높은 광물로 구성되었고 편광현미경에서 석영만이 관찰되었다. SEM 관찰에서 단면의 내측은 공극이 확대된 양상을 나타내고 중앙은 균열이 발달하였으며 외측에서는 변화를 관찰할 수 없었다. 구성입자의 입도는 내범과 외범이 거의 유사하며 미사질식양토로 구분되고, 미사질과 점토의 구성비는 약 2.7 : 1과 약 2.9 : 1이었다. 물성시험에서 내범과 외범의 밀도와 흡수율은 유사하고 공극률만이 내범이 27.36%와 외범은 31.09%로 다소 차이가 있었다. 단면의 색도차는 제1층위의 표면에 탈형을 위해 그을음을 입히거나 제1층위를 먹물로 수비하였을 가능성이 있다. 조성광물 분석에서는 내범과 외범의 조성광물이 동일하나 내범에서만 자철석이 동정되었다. 주성분 분석에서는 $SiO_2$의 평균함량이 71.64%, $Al_2O_3$는 14.59%이고, 부성분 중 $Fe_2O_3$는 4.51%, $K_2O$는 3.06%이며, $Na_2O$, MgO, CaO, $TiO_2$, $P_2O_5$, MnO는 2% 이하를 나타내었다.