• 공업화학
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• 제24권6호
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• pp.656-662
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• 2013

원자력발전소의 2차 계통수 중에 존재하는 철산화물(magnetite)은 열전달 튜브의 표면에 침착(fouling)되어 열전달 성능을 떨어뜨리거나 부식을 유발한다. 이와 같은 문제를 방지하기 위해, 원전 2차 계통수 중에 고분자 분산제(polymeric dispersant) 주입을 통해 철산화물의 분산 안정성 향상을 도모하는 연구를 수행하였다. 카르복실기(-COOH, carboxyl group)를 함유한 3종의 음 이온성 고분자(PAA, PMA, PAAMA)를 선정하였으며, 이들에 농도변화(1~1000 ppm)에 의한 마그네타이트 분산 특성을 평가하기 위해 침강시험, 투과율 측정, 입도 측정, 제타전위 측정을 수행하였다. 고분자 분산제는 수용액 중 철산화물 분산안정성에 큰 영향을 미쳤다. 분산제가 주입되면 분산 안정성이 향상되는 경향을 보였으나, 분산제 농도 증가에 따라 마그네타이트의 분산 안정성이 선형적으로 비례하여 증가하지 않았다. 이는 임계 분산제 농도 이상에서는 철산화물 사이의 응집(agglomeration)이 발생하기 때문인 것으로 사료된다. 분산안전성 향상 효과는 분산제-철산화물의 농도비(ppm, 분산제/마그네타이트)가 0.01~0.1 범위에서 현저하였다. 분산제 주입을 통한 철산화물 제거 효과를 최대화하기 위해서는 적용 환경 특성, 철산화물 농도, 분산제 농도 및 철산화물-분산제 농도비의 최적화가 필요한 것으로 판단된다.

• 한국자기학회지
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• 제4권1호
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• pp.25-31
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• 1994

코발트와 철의 이온을 혼합한 산성수용액 중에서, 알루미늄 양극산화피막에 전해석출 하여 제작된 자성막은, 코발트조성이 증가함에 따라 발크합금의 경우와 마찬가지로 상전이(phase shifting) 하였다. 입자직경이 $150\;{\AA}$의 시료의 경우 조성이 25-35 at% Co에서 큰 포화자화, 고항자력, 큰 자기이방성 에너지 및 우수한 각형비 등에 기인하는 큰 자기에너지 적($BH_{max}$)이 얻어진다. 그러나 입자직경이 $450\;{\AA}$의 경우에는, 코발트가 50-70 at% 일때 초기석출부 에 강자성체인 FeC가 아주 강하게 배향하므로, 입자의 큰 형상이방성(수직자기이방성)이 없어지고 면내 방향의 자기이방성을 나타낸다. 그리고 같은 조성에서 초기석출부를 제거하여 FeC의 영향을 없앨때, 주직자기이방성이 회복되었다.

• 대한화학회지
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• 제38권2호
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• pp.92-100
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• 1994

초미립 코발트 치환 산화철 분말을 새로운 유기금속 전구체인 $Co_xFe_{1-x}(N_2H_3COO)_2(N_2H_4)_2$ (x = 0, 0.01, 0.02, 0.03, 0.05, 0.10, 1.00)을 열분해화 산화과정으로 제조하였다.유기금속 전구체는 몰비 x : 1-x인 Co(II)와 Fe(II)를 hydrazinocarboxylic acid와 반응시켜서 합성하였고, 합성을 정량분석, 및 적외선분광기를 사용하며, 합성을 정량분석, 원소분석 및 적외선분광기를 사용하여 확인하였다. 유기금속 전구체의 열분해 과정은 TG-DTG 와 DSC로 살펴보았다. 코발트치환 산화철 분말은 유기금속 전구체를 대기 중에서 $350^{\circ}C$ 와 $450^{\circ}C$에서 6시간 열처리하여 제조하였다. 산화철의 결정상은 각각 ${\gamma}-Fe_2O_3$ 및 ${\gamma}-Fe_2O_3$ 와 ${\alpha}-Fe_2O_3$의 혼합상이었다. 입자의 형태는 구형에 가까운 모양이었고 크기는 $0.05{\mu}m$ 이하의 초미립이었다. 코발트 치환 산화철의 보자력과 각형비는 코발트 함량 또는 열처리 온도가 높아질 수록 증가하였다.

• International Journal of Advanced Culture Technology
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• 제12권2호
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• pp.334-344
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• 2024

In Dangjin, Chungcheongnam-do, there are not only power plants and large steel complexes, but also small and medium-sized air pollutant emission facilities. The dust generated by these facilities has a very small particle size and a large surface area due to condensation and physical and chemical reactions, and is discharged containing various harmful substances. Therefore, this study analyzed the distribution of particulate matter and heavy metal concentrations by particle size in the vicinity of the steel complex, residential area, and reference point using an eight-stage Cascade Impactor. Overall, the direct impact sites with a short distance from the steel complex had the highest concentration, followed by the indirect impact sites, and the non-impact sites had the lowest concentration, indicating that they are directly affected by the steel complex. The atmospheric dust concentration distribution showed a bimodal distribution with a minimum value around the 1.1 to 2.1 ㎛ particle diameter. However, during the yellow dust event, the maximum concentration was biased toward coarse particles. The proportion of PM2.5 in the dust tended to be higher in winter, while the ratio between PM2.5 and PM10 was relatively higher in spring. Regardless of the location of the impact point, heavy metals in the dust were dominated by iron and aluminum, followed by zinc, lead, and manganese.

• 한국산학기술학회논문지
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• 제13권12호
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• pp.6187-6195
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• 2012

네오디뮴 폐자석 침출액으로부터 희유금속인 네오디뮴을 회수하기 위해서는 네오디뮴과 같이 침출되는 철의 부가가치를 높이는 연구가 필요하다. 본 연구에서는 네오디뮴과 같이 침출되는 철의 유용자원화를 위한 기초연구로 철 나노분말 제조하는 실험을 수행하였다. 본 연구는 $FeCl_3$ 용액을 철 분말 원료로, 분산제는 $Na_4O_7P_2$와 Polyvinylpyrrolidone를 이용하였고, 환원제로는 $NaBH_4$, 철 나노분말 핵생성 촉진제 시드(seed)로 염화팔라듐을 사용하였다. 제조한 철 나노분말을 XRD, 전자현미경(SEM) 및 PSA 등을 이용하여 분말의 형상 및 크기 등을 분석하였다. 철과 $NaBH_4$의 농도비가 1 : 5이며, 반응시간이 30분 이상인 경우에서 철 분말이 제조되었으며, 이때 철 분말은 구형이었으며, 입도는 약 50 nm ~ 100 nm 크기였다. 분산제 $Na_4O_7P_2$의 경우 100 mg/L에서 철이온의 제타포텐셜이 음의 값을 가지므로 100 mg/L로 일정하게 하고, PVP와 Pd의 농도를 다양하게 하였을 경우, $FeCl_3$와 PVP와 Pd의 질량비 1 : 4 및 1 : 0.001에서, 분산이 양호하고, 입도 100 nm 크기인 철 나노분말을 합성하였다.

• Bulletin of the Korean Chemical Society
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• 제25권2호
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• pp.237-242
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• 2004

Recombinant human ferritin homopolymers (rHF and rLF) were successfully produced in the Saccharomyces cerevisiae Y2805, which was transformed with human ferritin H or L-chain genes, respectively. In order to characterize the molecular properties of the recombinant ferritins in relation to mineralization, the proteins were isolated and apoferritins were prepared. The apoferritins were reconstituted with 2000 Fe atoms per protein molecule under various experimental conditions (the concentration of the protein, the buffer concentration of the MOPS buffer, the total volume of the reaction and the reconstitution method). The structure and composition of the iron cores formed in the ferritins were examined using transmission electron microscopy. The recombinant ferritins behaved in a similar manner to other mammalian ferritins in accumulating iron in the core. Proteins of rHF and rLF showed varying reconstitution yields of 37-72% depending on the reaction conditions. In general, the rHF showed higher reconstitution yield than the rLF at the protein concentrations and the reaction volumes we examined. Iron cores with a similar mean particle size were obtained in the rHF, rLF and horse spleen ferritin reconstituted at a protein concentration of 1.0 mg/mL. Electron diffraction of all the three ferritins showed 2-3 diffuse lines, with d-spacings corresponding to those of the mineral ferrihydrite with a limited crystallinity.

• 공업화학
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• 제5권1호
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• pp.44-53
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• 1994

고성능 니켈-철 축전지를 개발하기 위하여 알칼리 축전지로 이론적 용량밀도가 높고 저공해성, 저렴한 가격, 자원의 풍부성 등의 우수한 장점을 가지고 있는 철전극에 대한 연구를 수행하였다. 충방전반응의 특성을 전위주사법, SEM, XRD 분석으로 조사하였으며, 또한 전극용량을 정전류 충방전시험법으로 조사하였다. 철의 순도와 입자크기가 전극용량에 크게 영향을 미쳤으며, 첨가제 $Na_2S$는 전극의 부동태화를 방지하고 수소과전압을 높여 전극용량을 20% 정도 증대시켰다. 전극의 안정성과 용량은 Ni-fibrex와 foamed Ni집전체를 사용하여 증대시켰으며, 또한 소결온도에 영향을 받았다. 전극용량은 350 mAh/g(0.2 C)으로 나타났는데, 이는 이용률 36%에 해당한다.

• Journal of Biosystems Engineering
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• 제42권4호
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• pp.323-329
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• 2017

Purpose: Biocompatible capsules have recently been highlighted as a novel platform for delivering various components, such as drug, food, and agriculture pesticides, to overcome the current limitations of living systems, such as those in agriculture, biology, the environment, and foods. However, few active targeting systems using biocompatible capsules and physical forces simultaneously have been developed in the agricultural engineering field. Methods: Here, we developed an active targeting delivery platform that uses biocompatible alginate capsules and controls movements by magnetic forces for agricultural and biological engineering applications. We designed and fabricated large-scale biocompatible capsules, using custom-made nozzles ejecting alginate solutions for encapsulation. Results: To develop the active target delivery platforms, we incorporated iron oxide nanoparticles in the large-scale alginate capsules. The sizes of alginate capsules were controlled by regulating the working conditions, such as concentrations of alginate solutions and iron oxide nanoparticles. Conclusions: We confirmed that the iron oxide particle-incorporated large-scale alginate capsules moved actively in response to magnetic fields, which will be a good strategy for active targeted delivery platforms for agriculture and biological engineering applications, such as for the controlled delivery of agriculture pesticides and biocontrol agents.

• Journal of Microbiology and Biotechnology
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• 제15권2호
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• pp.254-258
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• 2005

We have conducted in vitro reconstitution study of ferritin from its subunits FerH and FerL. For the reconstitution, FerH was produced from an expression vector construct in Escherichia coli and was purified from a heat treated cell extract by using one-step column chromatography. FerL was expressed as inclusion bodies. The denatured form of FerL was obtained by a simple washing step of the inclusion bodies with 3 M urea. The reconstitution experiment was conducted with various molar ratios of urea-denatured FerH and FerL to make the ferritin nanoparticle with a controlled composition of FerH and FerL. SDS-PAGE analysis of the reconstituted ferritins revealed that the reconstitution required the presence of more than 40 molar$\%$ of FerH in the reconstitution mixture. The assembly of the subunits into the ferritin nanoparticle was confmned by the presence of spherical particles with diameter of 10 nm by the atomic force microscopic image. Further analysis of the particles by using a transmission electron microscope revealed that the reconstituted particles exhibited different percentages of population with dense iron core. The reconstituted ferritin nanoparticles made with molar ratios of [FerH]/[FerL]=l00/0 and 60/40 showed that 80 to $90\%$ of the particles were apoferritin, devoid of iron core. On the contrary, all the particles formed with [FerH]/[FerL]=85/ 15 were found to contain the iron core. This suggests that although FerH can uptake iron, a minor portion of FerL, not exceeding $40\%$ at most, is required to deposit iron inside the particle.

• Journal of Magnetics
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• 제17권2호
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• pp.83-85
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• 2012

Magnetic particles in a novel, wound-healing ointment were studied using M$\ddot{o}$ssbauer spectroscopy and VSM to estimate the stability of the properties of the magnetic particles. The isomer shifts of $Fe_3O_4(A)$ were found to be 0.49-0.56 mm/s relative to iron metal, this indicates that the iron ions in $Fe_3O_4(A)$ are $Fe^{3+}$. On the other hand, the isomer shifts of $Fe_3O_4(B)$ were found to be 0.91-1.13 mm/s relative to iron metal, this shows that the ion state of $Fe_3O_4(B)$ is a mixed state of $Fe^{2+}$ and $Fe^{3+}$. It is noted that this composition, as well as that of the initial pure component in the form of a highly dispersed fraction (${\sim}10\;{\AA}$), differs from the stoichiometric one. It was found that the area ratio of the M$\ddot{o}$ssbauer subspectra of $Fe_3O_4(A)$ / $Fe_3O_4(B)$ taken at 87 and 181 K linearly increased in comparison to the initial pure magnetic particles, but the rate of increase of the area ratio at 181 K was about two times that at 87 K. From the magnetic hyperfine field, despite their small size, the particles exhibit no superparamagnetism.