• 한국환경과학회지
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• 제13권7호
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• pp.619-626
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• 2004

We have studied the catalytic combustion of soot particulates over perovskite-type oxides prepared by malic acid method, The catalysts were modified to enhance the activity by substitution of metal into A or B site of perovskite oxide. In addition, the reaction conditions such as temperature and $O_2$ concentration were investigated. The partial substitution of alkali metals into A site in the $LaMnO_3$ catalyst, enhanced the catalytic activity in the combustion of carbon particulate and the activity was shown in the order: Cs > K > Na. For the $La_{1-x}Cs_{x}MnO_{3}$ catalysts, the catalytic activity showed the maximum value with x=0.3 but no more increase on the catalytic activity was shown with x > 0.3. For the $La_{0.8}Cs_{0.2}MnO_{3}$ catalyst, the substitution of Fe or Ni increased the ignition temperature. The ignition temperature decreased with an increase of $O_2$ concentration, however, no more increase in the catalytic activity was shown with $O_2$ concentration > 0.2. The introduction of NO into reactants showed no effect on the catalytic activity.

• 대한화학회지
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• 제55권4호
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• pp.697-702
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• 2011

새로운 층상구조인 페로브스카이트 망가나이트 $La_{0.5}Sr_{1.5}Mn_{0.5}Cr_{0.5-x}Fe_xO_4$ (x=0.15, 0.3) 를 세라믹 방법에 의해 합성하였다. 분말 X-선 측정을 통하여 I4/mmm 의 정방정계 단위세포를 확인하였다. 전기전도도 측정을 통하여 부도체의 특성을 확인하였으며 전기전도도는 3D 홉핑 메커니즘에 의해 나타난다. 자기적 특성은 모두 반강자성의 특성을 보인다.

• 한국표면공학회지
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• 제34권6호
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• pp.568-574
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• 2001

Mixed powders of Fe + 0.7% C, Fe + 0.7% C + 1.6% Cu, and Fe + 0.7% C + 0.3% MnS were pressed in a mold so that the green-compact densities were 6.3, 6.5, 6.7, and 6.9 g/㎤, respectively. Then, the compacts were sintered at $1125^{\circ}C$ for 30 minutes and subsequently steam treated at $600^{\circ}C$ for 60 minutes. From the results, it was found that the overall properties of the steam-treated compacts, such as the weight gain of the sintered compacts, the diffusion of oxides into the sintered compacts, the surface hardness, and the formation of surface oxide layer, were primarily influenced by the density of the compacts and the oxides that were formed on the surface of the compacts by the steam treatment.

• Corrosion Science and Technology
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• 제11권1호
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• pp.9-14
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• 2012

The formation of the Fe-Al inhibition layer in hot-dip galvanizing is a confusing issue for a long time. This study presents a characterization result on the inhibition layer formed on C-Mn-Cr and C-Mn-Si dual-phase steels after a short time galvanizing. The samples were annealed at $800^{\circ}C$ for 60 s in $N_{2}$-10% $H_{2}$ atmosphere with a dew point of $-30^{\circ}C$, and were then galvanized in a bath containing 0.2 %Al. X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) was employed for characterization. The TEM electron diffraction shows that only $Fe_{2}Al_{5}$ intermetallic phase was formed. No orientation relationship between the $Fe_{2}Al_{5}$ phase and the steel substrate could be identified. Two peaks of Al 2p photoelectrons, one from metallic aluminum and the other from $Al^{3+}$ ions, were detected in the inhibition layer, indicating that the layer is in fact a mixture of $Fe_{2}Al_{5}$ and $Al_{2}O_{3}$. TEM/EDS analysis verifies the existence of $Al_{2}O_{3}$ in the boundaries of $Fe_{2}Al_{5}$ grains. The nucleation of $Fe_{2}Al_{5}$ and the reduction of the surface oxide probably proceeded concurrently on galvanizing, and the residual oxides prohibited the heteroepitaxial growth of $Fe_{2}Al_{5}$.

• 대한환경공학회지
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• 제32권2호
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• pp.193-200
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• 2010

복합 오염물질 처리를 위해 제조한 다기능성 흡착제인 철과 망간이 동시에 코팅된 모래(Iron and Manganese Coated Sand, IMCS)를 이용하여 용존 Mn(II) 처리 특성을 평가하였다. 실험에 사용된 IMCS는 0.05 M의 Mn(II)과 Fe(III) 용액을 pH 7에서 혼합하여 담체로 쓰인 모래에 코팅하여 제조하였다. IMCS는 ${\gamma}-MnO_2$ 형태의 Mn 산화물과 goethite 및 magnetite($F_{e3}O_4$) 형태의 철산화물이 동시에 존재하는 것으로 나타났다. Mn과 Fe의 함유량은 각각 826 및 1676 mg/kg으로 분석되었으며 $pH_{pzc}$는 6.40으로 측정되었다. IMCS와 산화제로서 NaOCl과 $KMnO_4$를 이용하여 Mn(II)의 제거에 관한 회분식 실험을 pH, 시간, 주입 농도를 변수로 하여 수행하였다. IMCS를 이용하여 Mn(II)을 처리하였을 때, pH 7.4에서 약 34%의 제거율을 나타내었고, 산화제인 NaOCl(13.6 mg/L)을 주입 후 IMCS와 반응시킨 결과 pH 7.0에서 96%의 제거율을 나타냈고, $KMnO_4$(4.8 mg/L)을 이용한 경우 pH 7.6에서 89%의 제거율을 나타내었다. IMCS와 산화제를 이용하여 Mn(II)을 제거할 경우, 용액의 pH가 증가함에 따라 제거율이 증가하는 양이온 형태의 제거 경향을 따랐으며, 반응 시간 6시간이 경과 후 거의 일정한 상태에 도달하는 것으로 나타났다. IMCS만을 이용하여 Mn(II)을 제거한 경우 833.3 mg/kg의 최대제거량을 나타냈고, 산화제로 NaOCl(13.6 mg/L), $KMnO_4$(4.8 mg/L)를 주입 후 IMCS와 반응시킨 경우 최대제거량은 각각 1428.6 및 1666.7 mg/kg으로 나타났다. IMCS에 의한 Mn(II)의 제거는 2차 반응속도식 및 Langmuir 식으로 잘 표현되었다.

• 한국표면공학회지
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• 제44권5호
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• pp.201-206
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• 2011

Fe-2%Mn-0.5%Si alloys were corroded at 600, 700 and $800^{\circ}C$ for up to 70 h in 1 atm of $N_2$ gas, or 1 atm of $N_2/H_2O$-mixed gases, or 1 atm of $N_2/H_2O/H_2S$-mixed gases. Oxidation prevailed in $N_2$ and $N_2/H_2O$ gases, whereas sulfidation dominated in $N_2/H_2O/H_2S$ gases. The oxidation/sulfidation rates increased in the order of $N_2$ gas, $N_2/H_2O$ gases, and, much more seriously, $N_2/H_2O/H_2S$ gases. The base element of Fe oxidized to $Fe_2O_3$ and $Fe_3O_4$ in $N_2$ and $N_2/H_2O$ gases, whereas it sulfidized to FeS in $N_2/H_2O/H_2S$ gases. The oxides or sulfides of Mn or Si were not detected from the XRD analyses, owing to their small amount or dissolution in FeS. Since FeS was present throughout the whole scale, the alloys were nonprotective in $N_2/H_2O/H_2S$ gases.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제2권1호
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• pp.69-78
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• 1998

Contents of heavy metals (Cr, Cu, Zn, Cd, and Pb) in the sediments of Ulsan Bay were investigated by the sequential extraction methods that classifies heavy metals into five types of chemical forms: exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter and residual. The analytes were determined by using an ICP-MS. Total Cr concentrations in the sediments were in the range of 41.6-96.4, Cu 60.7-680, Zn 189-1954, Cd 33.1-83.4, and Pb 138-567 mg/kg. Results of sequential fractionation indicates that relatively high proportion $(\~44\%)$ of Cu is associated with organic matter A large proportion of Pb is associated with three types of chemical forms: Fe-Mn oxides, organic matter, and residual. There were significant correlation in concentrations between the exchangeable components and total organic carbons. The heavy metals in the residual phase cannot be easily released to the environment since these are bound to the crystal lattice. But, reducible and organic Phases cfn a significant amount of most heavy metals. Therefore. there is potential danger of a substantial amount of metals becoming chemically mobile with environmental changes.

• 한국환경과학회지
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• 제2권1호
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• pp.69-78
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• 1993

Contents of heavy metals (Cr, Cu, Zn, Cd, and Pb) in the sediments of Ulsan Bay were investigated by the sequential extraction methods that classifies heavy metals into five types of chemical forms: exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter and residual. The analyses were determined by using an ICP-MS. Total Cr concentrations in the sediments were in the range of 41.6-96.4, Cu 60.7-680, Zn 189-1954, Cd 33.1-83.4, and Pb 138-567 mg/kg. Results of sequential fractionation indicates that relatively high proportion ( ~44%) of Cu is associated with organic matter. A large proportion of Pb is associated with three types of chemical forms: Fe-Mn oxides, organic matter, and residual. There were significant correlation in concentrations between the exchangeable components and total organic carbons. The heavy metals In the residual phase cannot be easily released to the environment since these are bound to the crystal lattice. But, reducible and organic Phases con a significant amount of most heavy metals. Therefore, there is Potential dancer of a substantial amount of metals becoming chemically mobile with environmental changes.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.245-248
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• 2001

Nomura Kohsan Corp. is producing oxides, such as ZnMn$_2$O$_4$, ZnFe$_2$O$_4$, and ZnO, by burning the used dry manganese cells and by sorting out the remnant materials. It is possible to use the recycled materials of the spent dry batteries as the raw materials of deflection yoke cores. Making hish roasting temperature in the recycling system has an effect in reduction of the impurities. As a result, the loss of the cores using the recycled materials is lower. When using the recycled materials, it is required to add Mg (OH)$_2$. ZnO, and Fe$_2$O$_3$in order to rectify the composition of the MnMgZn ferrite for deflection yoke core applications. Furthermore, in order to disappear ZnMn$_2$O$_4$in the formation, it is necessary to control at higher calcining temperatures. The MnMgZn ferrite of using the recycled materials becomes Toss equivalent to the conventional material. TDK Corp. is manufacturing the deflection yoke cores from 1996 using the material recycled from the spent dry batteries.

• 한국표면공학회지
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• 제48권1호
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• pp.27-32
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• 2015

Advanced high strength steels undergo recrystallization annealing in reducing gas atmosphere before galvanizing to improve mechanical properties. The selective oxidations of elements such as Mn, Si, Cr and Al during annealing decrease wettability of liquid zinc, resulting in bare spots and other defects. In this work, Fe-3wt%Mn steel sheet was annealed at $780^{\circ}C$ for 1200 sec. in 5% $H_2-N_2$ atmosphere and then dipped into zinc bath held at $460^{\circ}C$, which contained 0.2wt% dissolved Al. MnO crystallines in the average size of 200 nm were formed on the surface after annealing. It is estimated that MnO has been detached into bath with the formation and growth of inhibition layer with longer immersion time during galvanizing. No evidence of aluminothermic reduction of MnO has been found in this study.