• 대한환경공학회지
• /
• 제22권11호
• /
• pp.2085-2095
• /
• 2000

적니는 보오크사이트로부터 수산화알루미늄/알루미나를 제조하는 공정에서 발생되는 부산물이다. 본 연구에서는 적니를 여러 가지 조건으로 산처리하여 적니에 포함되어 있는 알루미늄과 철을 산으로 침출시켜 무기응집제를 제조하였다. 적니와 산의 비율이 1/10(g/mL)인 경우 5M $H_2SO_4$와 $85^{\circ}C$에서 반응할 때, 9M HCl과 $25^{\circ}C$에서 반응할 때 알루미늄과 철의 최적 침출효율을 얻을 수 있었다. 또한 수용액에서 중금속이온($Pb^{2+}$, $Cd^{2+}$, $Cu^{2+}$, $Zn^{2+}$, $Cr^{3+}$), 탁도, 인산염인($PO_4{^{3-}}-P$) 제거실험을 여러 가지 실험조건으로 수행하였다. 실험결과, 본 연구에서 개발된 응집제는 수용액에서 중금속이온, 탁도와 인산염인에 대해 우수한 제거능력을 보이는 것으로 확인되었다.

• 한국대기환경학회지
• /
• 제32권6호
• /
• pp.603-612
• /
• 2016

The objective of this study was to estimate the emission characteristics for PM, $PM_{10}$, and $PM_{2.5}$ in the various stationary sources. The particulate matters collected in the various stationary sources such as power plants (Coal and B-C oil), incinerators(municipal and industrial waste), and glass furnaces. The PM and $PM_{10}$, PM and $PM_{2.5}$, $PM_{10}$ and $PM_{2.5}$ samples were collected using the cyclone type $PM_{10}$, $PM_{2.5}$ samplers and 30 species(19 inorganic species, 9 ionic species, OC and EC) were analyzed by ICP, IC, and TOR/IMPROVE methods. The mass concentrations of PM, $PM_{10}$, $PM_{2.5}$ from nine stationary sources ranged $0.63{\sim}9.58mg/Sm^3$, $0.26{\sim}7.47mg/Sm^3$ and $0.13{\sim}6.34mg/Sm^3$, respectively. The level of $PM_{10}$, $PM_{2.5}$ portion in PM calculated 0.63~0.99, 0.38~0.94, respectively. In the case of emission trend for species, power plant showed high concentrations for Al, Mg, Na, Si, V and $SO_4{^{2-}}$, respectively. Also, Ca, Fe, K, Si, $Cl^-$, and $K^+$ showed high in incinerator. In the case of glass furnace, Na, Pb, K, Si, $Na^+$ and $SO_4{^{2-}}$ represented high concentrations. Power plant showed higher EC/OC concentrations than other sampling sites. These results suggest the possible role for complement establishment process of emission inventory and emission management for PM.

• 한국분말재료학회지
• /
• 제23권3호
• /
• pp.240-246
• /
• 2016

In order to improve the high-temperature oxidation stability, sintered 434L stainless steel is studied, focusing on the effect of the addition of metallic oxides to form stable oxide films on the inner particle surface. The green compacts of Fecralloy powder or amorphous silica are added on STS434L and oxidized at $950^{\circ}C$ up to 210 h. The weight change ratio of 434L with amorphous silica is higher than that of 434L mixed with Fecralloy, and the weight increase follows a parabolic law, which implies that the oxide film grows according to oxide diffusion through the densely formed oxide film. In the case of 434L mixed with Fecralloy, the elements in the matrix diffuse through the grain boundaries and form $Al_2O_3$ and Fe-Cr oxides. Stable high temperature corrosion resistance and electrical resistivity are obtained for STS434L mixed with Fecralloy.

• The Korean Journal of Ceramics
• /
• 제1권2호
• /
• pp.91-95
• /
• 1995

Polycrystalline bismuth- and aluminum- substituted dysporsium and yttrium iron garnet (Bi2R3-xAlyFe5-yO12, R=Dy or Y, $0\leqx\leq3, \; 0\leqy\leq3$) films have been prepared by pyrolysis. The crystallization temperatures, the solubility limit of bismuth ions into the garnet phase, and magnetic and magneto-optic properties of the films have been investigated as a function of bismuth and aluminum concentration. It was found that the crystallization temperatures as a function of bismuth and aluminum concentration. It was found that the crystallization temperatures of these films rapidly decreased as bismuth concentration. It was found that the crystallization temperatures of these films rapidly decreased as bismuth concentration (x) increased up to x=1.5 and then remained temperatures of these films rapidly decreased as bismuth concentration (x) increased up to x=1.5 and then remained unchanged at x>1.5, whereas, showed no changes as aluminum concentration (y) increased up to y=1.0 and then gradually increased at y>1.0. The solubility limit of bismuth ions was x=1.8 when y=0 but increased to x=2.3 when y=1.0. It was demonstrated that the magnetic and magneto-optic properties of the dysprosium iron garnet films could be tailored by bismuth and aluminum substitution suitable for magneto-optic recording as follows. The saturation magnetization and coercivity data obtained for the films indicated that the film composition at which the magnetic compensation temperature became room temperature was y=1.2 when x=1.0. Near this composition the coercivity and the squareness of the magnetic hysteresis loop of the films were several kOe and unit, respectively. The Curie temperatures of the films increased with the increase of x but decreaed with the increase of y, and was 150-$250^{\circ}C$ when x=1.0 and y=0.6-1.4. The Faraday rotation at 633 nm of the films increased as x increased but decreased as y increased, and was 1 deg/$\mu\textrm{m}$ when x=1.0 and y=1.0. Based on the data obtained, the appropriate film composition for magneto-optic recording was estimated as near x=1.0 and y=1.0 or $BiDy_2AlFe_4O_{12}$.

• 에너지공학
• /
• 제2권3호
• /
• pp.258-267
• /
• 1993

본 연구에서는 초고온 잠열 축열재를 이용한 에너지 저장 시스템을 개발하기 위한 첫 단계로 에너지 저장 시스템 내부를 구성하는 단일 축열재 모듈에 대한 축방열 특성에 관한 수치모델을 개발하였다. 잠열축열재는 Si와 Al이 각각 96.8%와 2.7%인 합금으로 Ca, Fe 및 Ti 등의 불순물을 함유하고 있으며, 그것을 둘러 싼 캡슬은 SiC와 흑연이 각각 58%와 42%인 합금으로 융점은 약 1673 K다. 재료분석 결과에 준하여 수치모델 개발에 필요한 물리·화학적 데이타를 참고문헌으로부터 인용하였으며 유체의 온도와 속도를 축열재의 축방열 특성에 관한 변수로 사용하였다. 상전이에 관한 해석은 겉보기 열용량 법(apparent capacity method)과 postiterative 법의 장점들을 이용하여 해석하였다. 수치해석 결과 가스의 온도가 실제 조업에 가까운 1773 K의 경우 잠열재가 축방향으로 빨리 용융되고 상대적으로 가스의 온도가 높아 온도 차이가 큰 3000 K의 경우 잠열재가 반경방향으로 빨리 용융되는 현상이 일어났다. 가스의 유속은 온도에 관계없이 느린 경우에만 용융시간에 영향을 주고 빠른 경우에는 융용시간이나 용융형태에 거의 영향을 주지 못하며, 유속이 느릴수록 축열재 내부 온도구배의 앞·뒤 비대칭성이 심해지는 것이 예측되었다.

• 대한치과보철학회지
• /
• 제54권4호
• /
• pp.354-363
• /
• 2016

목적: 본 연구는 지르코니아 도재 표면의 나노구조 알루미나 코팅이 지르코니아와 레진 시멘트와의 전단결합강도에 미치는 영향을 알아보고자 하였다. 재료 및 방법: 지르코니아 원판 80개를 표면처리방법(산화알루미늄 분사처리(A), 산화알루미늄 분사 후 Rocatec 처리(R), 연마 후 나노구조 알루미나 코팅(PC), 산화알루미늄 분사 후 나노구조 알루미나 코팅(AC))에 따라 4개의 군으로 나누었다. 알루미나 코팅은 질산 알루미늄을 가수분해시킨 용액에 침적 후 $900^{\circ}C$에서 열처리 하여 시행하였다. 지르코니아 표면 코팅은 주사전자 현미경을 이용하여 관찰하였다. 레진 블럭을 레진 시멘트를 이용하여 각 실험군의 지르코니아 표면에 합착하고 열순환처리 전, 후의 전단결합강도를 측정하였다. 결과: 알루미나 코팅을 한 지르코니아 표면은 균일하고 치밀한 나노구조 알루미나가 관찰되었다. PC, AC 군은 열순환처리 전과 후 모두 A와 R 군에 비해 현저하게 높은 전단결합 강도를 보였다. A, R 군은 열순환처리 후에 급격한 결합강도의 감소를 보였으나, PC와 AC군은 열순환처리에 의해 유의할만한 결합강도의 감소를 보이지 않았다. 결론: 지르코니아 표면에 나노구조 알루미나 코팅처리하는 것은 레진시멘트와의 결합강도를 증가시키는 방법이다.

• 한국재료학회지
• /
• 제20권4호
• /
• pp.181-186
• /
• 2010

Since it was developed by Joseph Aspdin, cement has been a common construction materials up to the present time. However, there are trace constituents in cement clinker. One of the trace constituents included in cement clinker, chromium, has become prominent and highly noticed lately as a social issue both inside and outside of this country because it affects the human body negatively. The aim of the present study was to investigate the concentration of water-soluble hexavalent chromium in cement clinker by using industrial by-products. For that reason, raw materials were prepared to add different $SiO_2$, $Al_2O_3$, and $Fe_2O_3$ sources. After the raw materials such as the limestone, the sand and the clay, iron ore was pulverized and mixed, and the raw meal was burnt at about $1450^{\circ}C$ in a furnace with an oxidizing atmosphere. The part in the raw materials of the clinker was substituted with slag, sludge, etc. and this was used to manufacturing cement clinker. To investigate the water-soluble hexavalent chromium content in clinker, raw meal was prepared by changing the modulus, the type, and the content of clinker materials and tested concentrations of hexavalent chromium in the clinkers. To determine $Cr^{+6}$ formation of the clinker, tests were done with raw meals adding chromium by using different industrial by-products. Consequently because the chromium was to be included in the raw materials of the clinker, production of Portland cement clinker was included with the chromium. Also, the chromium was converted into hexavalent chromium in the burning process.

• 한국대기환경학회지
• /
• 제19권6호
• /
• pp.701-717
• /
• 2003

The objective of this study was to extensively estimate the air quality trends of the study area by surveying con-centration trends in months or seasons, after analyzing the mass concentration of PM-10 samples and the inorganic lements, ion, and total carbon in PM-10. Also, the study introduced to apply the PMF (Positive Matrix Factoriza-tion) model that is useful when absence of the source profile. Thus the model was thought to be suitable in Korea that often has few information about pollution sources. After obtaining results from the PMF modeling, the existing sources at the study area were qualitatively identified The PM-10 particles collected on quartz fiber filters by a PM-10 high-vol air sampler for 3 years (Mar. 1999∼Dec.2001) in Kyung Hee University. The 25 chemical species (Al, Mn, Ti, V, Cr, Fe, Ni, Cu, Zn, As, Se, Cd, Ba, Ce, Pb, Si, N $a^{#}$, N $H_4$$^{+}$, $K^{+}$, $Mg^{2+}$, $Ca^{2+}$, C $l^{[-10]}$ , N $O_3$$^{[-10]}$ , S $O_4$$^{2-}$, TC) were analyzed by ICP-AES, IC, and EA after executing proper pre - treatments of each sample filter. The PMF model was intensively applied to estimate the quantitative contribution of air pollution sources based on the chemical information (128 samples and 25 chemical species). Through a case study of the PMF modeling for the PM-10 aerosols. the total of 11 factors were determined. The multiple linear regression analysis between the observed PM-10 mass concentration and the estimated G matrix had been performed following the FPEAK test. Finally the regression analysis provided source profiles (scaled F matrix). So, 11 sources were qualitatively identified, such as secondary aerosol related source, soil related source, waste incineration source, field burning source, fossil fuel combustion source, industry related source, motor vehicle source, oil/coal combustion source, non-ferrous metal source, and aged sea- salt source, respectively.ively.y.

• 한국분말재료학회지
• /
• 제22권3호
• /
• pp.197-202
• /
• 2015

In this study, porous stainless steel (STS316L) sintered body was fabricated by powder metallurgy method and its properties such as porosity, compressive yield strength, hardness, and permeability were evaluated. 67.5Fe-17Cr- 13Ni-2.5Mo (wt%) powder was produced by a water atomization. The atomized powder was classified into size with under $45{\mu}m$ and over $180{\mu}m$, and then they were compacted with various pressures and sintered at $1210^{\circ}C$ for 1 h in a vacuum atmosphere. The porosities of sintered bodies could be obtained in range of 20~53% by controlling the compaction pressure. Compressive yield strength and hardness were achieved up to 268 MPa and 94 Shore D, respectively. Air permeability was obtained up to $79l/min{\cdot}cm^2$. As a result, mechanical properties and air permeability of the optimized porous body having a porosity of 25~40% were very superior to that of Al alloy.

• 한국염색가공학회지
• /
• 제22권3호
• /
• pp.194-206
• /
• 2010

This study was carried out to identify the optimum dyeing conditions for maximum dye uptake of Prunus yedoensis Matsumura flower extract on silk fabric and to investigate hue/tone characteristics and fastness properties of the dyed fabrics. As results, the flower extract was found to contain flavonoids by FT-IR and to show yellowish shade by UV-vis spectrum. Silk fabric was optimized for maximum dye uptake to five repetitions of dyeing at $80^{\circ}C$ for 60 min with an extract concentration of 600% owf in terms of both K/S and color differences. Pre-mordanting was more effective to dye uptake than post-mordanting for all of the mordants used. Un-mordanted and pre-mordanted fabric showed YR(Yellow Red) while most of post-mordanted ones did Y(Yellow). Main tones of dyed fabrics were sf(soft) and lt(light) in the case of unmordanting or Al-mordanting whereas they were d(dull) and g(grayish) by post-mordanting with Cu, Cr, and Fe, respectively. The fastness grades to rub and dry cleaning were reasonably good for most dyeing conditions while those to light were poor. Finally dyeing condition for each hue/tone of the dyed silk with the flower extract was optimized considering fastness properties.