• Environmental Engineering Research
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• 제15권4호
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• pp.183-190
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• 2010

Biogenic Mn oxides are expected to have great potential in the control of water pollution due to their high catalytic activity, although information on biological Mn oxidation is not currently sufficient. In this study, the growth of a Mn oxidizing microorganism, Pseudomonas putida MnB1, was examined, with the Mn oxides formed by this strain characterized. The growth of P. putida MnB1 was not significantly influenced by Mn(II), but showed a slightly decreased growth rate in the presence of Pb(II) and EE2, indicating their insignificant adsorption onto the cell surface. Mn oxides were formed by P. putida MnB1, but the liquid growth medium and resulting biogenic solids were poorly crystalline, nano-sized particles. Biogenic Mn oxidation by P. putida MnB1 followed Michaelis-Menten kinetics, with stoichiometric amounts of Mn oxides formed, which corresponded with the initial Mn(II) concentration. However, the formation of Mn oxides was inhibited at high initial Mn(II) concentration, suggesting mass transfer obstruction of Mn(II) due to the accumulation of Mn oxides on the extracellular layer. Mn oxidation by P. putida MnB1 was very sensitive to pH and temperature, showing sharp decreases in the Mn oxidation rates outside of the optimum ranges, i.e. pH 7.43-8.22 and around 20-$26^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• 제7권1호
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• pp.29-35
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• 1986

An empirical formula for semiconductive metal oxides is proposed relating nonstoichiometric value x to a temperature or an oxygen partial pressure such that experimental data can be represented more accurately by the formula than by the well-known Arrhenius-type equation. The proposed empirical formula is log x = A + $B{\cdot}1000/T\;+\;C{\cdot}$exp$(-D{\cdot}1000/T)$ for a temperature dependence and $log\;{\times}\;=a\;+b{\cdot}log\;Po_2\;+\;c{\cdot}$exp$(-d{\cdot}log\;Po_2)$ for an oxygen partial pressure dependence. The A, B, C, D and a, b, c, d are parameters which are evaluated by means of a best-fitting method to experimental data. Subsequently, this empirical formula has been applied to the n-type metal oxides of $Zn_{1+x}O,\; Cd_{1+x}O,\;and\;PrO_{1.8003-x}$, and the p-type metal oxides of $CoO_{1+x},\; FeO_{1+x},\;and\;Cu_2O_{1+x}$. It gives a very good agreement with the experimental data through the best-fitted parameters within 6% of relative error. It is also possible to explain approximately qualitative characters of the parameters A, B, C, D and a, b, c, d from theoretical bases.

• 약학회지
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• 제44권4호
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• pp.325-333
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• 2000

The 1,3-dipolar cycloaddition reaction of the quinoxaline 4-oxides 2 with 2-chloroacrylonitrile gave the 2,3-dihydro-1H-1,2-diazepino[3,4-b]quinoxalines 3, which were converted into the 2,3,4,6-tetrahydro-1H-1,2-diazepino[3,4-b]quinoxalines 5-7. The reaction of compounds 3 with selenium dioxide in acetic acid/water resulted in ring transformation to give the 1,4-dihydro-4-oxopyridazino[3,4-b]quinoxalines 8.

• 센서학회지
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• 제22권1호
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• pp.1-17
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• 2013

Metal oxides designed for application in conductometric gas sensors and approaches used for synthesis of metal oxides with improved gas sensing characteristics are discussed in present article.

• 청정기술
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• 제18권3호
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• pp.259-264
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• 2012

페롭스카이트형 산화물을 능금산법으로 합성하여 TG/DTA, XRD, XPS, TEM 및 $H_2$-TPR 등에 의해 특성분석을 하였고, 벤젠의 연소반응에서의 활성을 조사하였다. 대부분의 촉매들은 페롭스카이트 결정구조를 잘 가지고 있었으며 15에서 70 nm의 크기를 나타내었다. $LaMnO_3$ 촉매가 가장 높은 활성을 보여주었고 $350^{\circ}C$에서 거의 100%의 전환율을 나타내었다. 반응활성을 증가시키기 위해 페롭스카이트 산화물의 A-와 B-위치에 다른 금속이온의 치환을 행하였다. $LaMnO_3$ 촉매의 A-위치에 Sr을 일부분 치환시키면 벤젠의 전환율이 증가하였다. 또한, B-위치에 Co 및 Cu 이온의 치환 역시 촉매 활성을 증가시켰고, $LaMn_{1-x}B_xO_3$ (B = Co, Fe, Cu)형 페롭스카이트에서 촉매활성은 Co > Cu > Fe의 순서로 감소하였다.

• 한국환경보건학회지
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• 제2권1호
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• pp.29-31
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• 1975

This experiment Was carried out under two points of view, from May 1st to the end of 1973. One was the comparative determination of the activation factor of Lead dioxide by kinds in measuring of Sulfur oxides concentration by $PbO_2$ cylinder method, and the other was the comparison that result with the record of auto analyzer. Five measuring sites were selected out of Seoul City. Three kinds of Lead dioxide made in Japan (B,C and D) were compared with Standard $PbO_2$ (A for use in Determination of Sulphur in the atmosphere, purity 99% up) made in British Institution, and monthly measuring was conducted at every sampling site. The recording by auto analyzer (Beckman Model 906-A $SO_2$ Analyzer) was conducted once or twice a month for 24 hours at each sampling site during the same period. And some significant results were obtained. 1. In comparative experiments to determine the activation degree of three kinds of Lead dioxide (B,C and D), the obtained correction factor of B reagent was 1.09, 1.16 in C and 1.30 in D against Standard $PbO_2$ (A). Therefore, it should be in need of standardization or clear statement about the reagents for use, in determination sulfur oxides by $PbO_2$ cylinder method. 2. Generally, the concentration of Sulfur dioxide by wilkins' convertion method from $SO_3$ showed about 20-30% higher than those by Auto analyzer.

• Journal of Preventive Medicine and Public Health
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• 제6권1호
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• pp.27-41
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• 1973

In order to provide some basic data for the control of air and water pollution in Korea, the authors have estimated the amount of air and water pollutants emitted from industries which are employed over 20 employees. This study have done from July 1, 1972 to the end of March 1973. The results are as followings; 1. Total number of establishments with over 20 employees is 5,197 in Korea and the largest group establishments was the manufacturing of textiles with 1,363 establishments (26.2%). 2. By order of number of employees it was observed that there 2,800 industries with 20-59(53.9%) employees, 1,101 with 50-99 (21.2%), 571 with 100-199 (11.0%), 501 with 200-499 (9.6%) and 225 with over 500 (4.3%) respectively. 3. By order of regional distribution, it was observed that there were 2,257 industries in Seoul (43.2%) and 736 industries in Pusan(14.2%). 4. Industrial coal consumption was 596,154 M/T in 1972, but it' 11 be 315,000 M/T in 1980. Fuel consumption was 4,972,000 K1 in 1972, and estimated volume will be 19,370,000 K1 in 1980. 5. Total amounts of air polutants entitled from industries by fuel combustion were sulfur oxides 79,459 tons, carbon monoxide 33,908 tons, particulate 31,304 tons and hydrocarbon 30,280 tons in 1972 but in 1990 there will be sulfur oxides 1,010,474 tons, nitrogen oxides 204,575 tons, carbon monoxide 68,014 tons, particulate 64,820 tons and hydrocarbon 67,622 tons, respectively. 6. Annual emitted air pollutants through the working processes were sulfur oxides 91,250 tons and nitrogen oxides 32,485 tons in 1972, but sulfur oxides 118,625 tons and nitrogen oxides 42,555 tons will be present in 1980, respectively. 7. Annual emitted air pollutants by national unit area amounted to $0.77ton/km^2/year$ in 1965 and $14.7ton/km^2/year$ in 1980. 8. Total industrial wastes from all industries in Korea were estimated at 810,360 tons/day in 1972; manufacturing of chemicals and plastic products showed the highest amount of wastes at 470,000 tons/day. 9. The amounts of water pollutants due to industrial wastes were the B.O.D., 471.5 tons/day, suspended solid 331.5 tons/day, CN, 2.3 tons/day, and Cr. 3.4 tons/day in 1972, but it might be evident of a B.O.D. of 3,388 tons/day, suspended solid 2,544 tons/day, CN 20.1 tons/day, and 26.5 tone/day in 1990. 10. Total population equivalent of B.O.D. was 943,000 in 1972, and the estimated value in 1950 will be 6,780,000.

• 자연과학논문집
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• 제14권2호
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• pp.41-54
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• 2004

$LaMnO_3$(a=$5.51\AA$, c=$13.33\AA$) 페로브스카이트형 복합산화물에서 A site인 La자리에 Sr을 치환시킨 $La_{0.9}Sr_{0.1}MnO_3$(a=$5.33\AA$, c=$13.27\AA$)와 B site인 Mn을 Cu로 치환시킨 $LaMn_{0.9}Cu_{0.1}O_3$(a=$5.52\AA$, c=$13.31\AA$) 복합산화물을 Citrate sol-gel법을 이용하여 합성하였으며 분말 X-ray회절 분석기(XRD)을 이용하여 Rhombohedral의 페로브스카이트 구조임을 확인하였다. 수소 환원분위기에서의 TRR결과에 의하면 이들 산화물의 산소 화학양론은 $LaMnO_{3.16}$, $La_{0.9}Sr_{0.1}MnO_{3.10}$, $LaMn_{0.9}Cu_{0.1}O_{3.14}$의 조성을 갖는다. $LaMnO_3$는 2단계 환원반응을 일으키지만 각 자리를 치환시킨 $LaMnO_3$ 복합산화물은 3단계 환원반응을 일으켰다.

• 한국재료학회지
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• 제12권3호
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• pp.220-224
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• 2002

The oxide scales formed on $Ni_3Al$-7.8%Cr-1.3%Zr-0.8%Mo-0.025%B after oxidation at 900, 1000 and 110$0^{\circ}C$ in air were studied using XRD, SEM, EPMA and TEM. The oxide scales consisted primarily of $NiO,\; NiAl_2O_4,\;{\alpha}-Al_2O_3,\; monoclinic-ZrO_2,\; and \;tetragonal-ZrO_2$. The outer layer of the oxide scale was rich in Ni-oxides, whereas the internal oxide stringers were rich in Al-oxides and $ZrO_2$. Within the above oxide scales, Cr and Mo tended to exist as dissolved ions.

• 한국재료학회지
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• 제20권7호
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• pp.370-373
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• 2010

In fabricating plasma display panels, the photolithographic process is used to form patterns of barrier ribs with high accuracy and high aspect ratio. It is important in the photolithographic process to control the refractive index of the photosensitive paste. The composition of this paste for photolithography is based on the $B_2O_3-SiO_2-Al_2O_3$ glass system, including additives of alkali oxides and rare earth oxides. In this work, we investigated the density, structure and refractive index of glasses based on the $B_2O_3-SiO_2-Al_2O_3$ system with the addition of $Li_2O$, $K_2O$, $Na_2O$, CaO, SrO, and MgO. The refractive index of the glasses containing K2O, Na2O and CaO was similar to that of the [BO3] fraction while that of the SrO, MgO and Li2O containing glasses were not correlated with the coordination fraction. The coordination number of the boron atoms was measured by MAS NMR. The refractive index increased with a decrease of molar volume due to the increase in the number of non-bridging oxygen atoms and the polarizability. The lowest refractive index (1.485) in this study was that of the $B_2O_3-SiO_2-Al_2O_3-K_2O$ glass system due to the larger ionic radius of $K^+$. Based on our results, it has been determined that the refractive index of the $B_2O_3-SiO_2-Al_2O_3$ system should be controlled by the addition of alkali oxides and alkali earth oxides for proper formation of the photosensitive paste.