• The Korean Journal of Ceramics
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• 제4권2호
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• pp.156-161
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• 1998

We have measured changes of the non-stoichiometry, $\Delta\delta$, in Fe-doped nicked oxide , by thermogravimetry for four iron fractions, x=0.01, 0.031, 0.057 and 0.10, and three temperatures, T=1273, 1373 and 1473 K. The obtained data can be modelled by a defect structure in which substitutional trivalent iron ions, FeNi, are compensated by cation vacancies, $V_{Ni}$", and (4:1)-clusters. These clusters consist of tetravalent interstitial iron, $Fe_i\;^4$

• 한국결정성장학회지
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• 제24권2호
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• pp.77-83
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• 2014

본 연구는 순환자원인 저회, 잔사회 그리고 준설토로 인공 경량골재를 제조할 때 철분의 종류와 양이 발포기구에 미치는 영향을 분석하는 것이다. 원료의 화학적 특성을 X선 회절 분석과 X선 형광 분석으로 측정하였다. 준설토 50 %, 저회 15 % 그리고 잔사회 35 %를 무게비로 혼합하고 철분함량을 5 % 단위로 30 %까지 첨가하였으며, 철분의 종류는 $Fe_2O_3$와 $Fe_3O_4$로 선정하였다. 성형된 골재는 급속 소성법으로 $40^{\circ}C$ 간격으로 $1060^{\circ}C$에서 $1180^{\circ}C$까지 소결하고, 비중과 흡수율을 측정하였다. 인공 경량골재는 철분 함유량이 10~15 %일 때 가장 낮은 비중을 보이며, 철분량이 증가할수록 액상 소결이 되어 비중이 증가하였다.

• 한국안전학회지
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• 제35권5호
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• pp.128-136
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• 2020

In the present experimental study, the effect of water-based iron(III) oxide nanofluid on the MFB(Minimum Film Boiling) point during quenching was investigated. As the highly heated test specimen, the cylindrical stainless steel rod was used, and as the test fluids, the water-based iron(III) oxide nanofluids of 0.001 and 0.01 vol% concentrations were prepared with the pure water. To examine the effect of location in the test specimen, the thermocouples were installed at the bottom and middle of wall, and center in the test specimen. Through a series of experiments, the experimental data about the influences of nanofluid concentrations, the number of repeated experiments, and locations in the test specimen on the reaching time to MFB point, MFBT(Minimum Film Boiling Temperature), and MHF(Minimum Heat Flux) were obtained. As a result, with increasing the concentration of nanofluid and the number of repeated experiments, the reaching time to MFB point was reduced, but the MFBT and MHF were increased. In addition, it was found that the effect of water-based iron(III) oxide nanofluid on the MFB point at the bottom of wall in the test specimen was observed to be greater than that at the middle of wall and center. In the present experimental ranges, as compared with the pure water, the water-based iron(III) oxide nanofluid showed that the maximum reduction of reaching time to MFB point was about 53.6%, and the maximum enhancements of MFBT and MHF were about 31.1% and 73.4%, respectively.

• 보존과학회지
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• 제36권5호
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• pp.393-404
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• 2020

본 연구는 도자기 유약 내 철산화물의 함량에 따라 유약층에서 나타나는 미세조직적 특성변화의 비교분석을 통해 과거 흑유자기들의 제작 과정에서 사용된 재료의 성분 함량과 제작 방법을 유추해보고자 하였다. 먼저 산화철과 장석, 석회석, 참나무재의 성분비를 달리한 유약을 사용하여 온도와 소성조건을 달리한 재현시편을 제작하였고, 색차와 단면관찰, 성분분석, 결정구조분석을 통해 발현 특성을 알아내고자 하였다. 분석 결과 산화조건에서는 유약의 특성이 5개 그룹으로 분류된 것을 관찰할 수 있었으며, 1200℃ 이상의 환원환경에서는 각자 다른 양상의 유약 특성을 확인하였다. 실험을 통해 확인한 결정형태는 출토 흑유자기에서 나타나는 유약특성과 유사한 것을 확인하였다. 철 산화물의 농도 변화에 따라서도 산화조건에서는 결정상이 띠모양, 원형, 수지상, 침상 등 4개의 그룹으로 나타났으나, 고온에서는 결정의 차이가 크게 나타나지 않았다. 또한 성분비에 따라서 유약의 결정상이 2개의 그룹으로 나뉘었다. 이는 장석의 유무가 결정성과 무정형의 철산화물을 만드는데 영향을 주는 것으로 판단되며, 이들의 양에 따라서도 단면에서 나타나는 변화 양상이 극명하게 달라졌다. 특히 산화조건과 환원환경에서 나타나는 철산화물의 조직 양상이 다르게 나타나는 것으로 보아 소성조건으로 인한 결정상 또한 광학적으로 나타나는 발색특성에 영향을 미치는 것을 확인할 수 있었다.

• 한국주조공학회지
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• 제10권2호
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• pp.154-161
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• 1990

The microstructures of sintered products of $Fe_2O_3$or $Fe_3O_4$-Oxide added cast iron powder was investigated. And the effects of particle size distribution was investigated too. As the result, the structures of sintered products did not related to the species of Fe-Oxide. Th porosity of sintered products was decreased in size and spherodized with increasing sintering temperature, decreasing Fe-Oxide quantity. Fe-Oxide itself did not hinder sintering of cast iron powder particularly, therefore sintering could be occurred without termination of reduction of it. And the sintered products of finer particle size distribution had finer and more spherodized porosity, and had minimized the deviation of size and shape of porosity.

• 한국표면공학회지
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• 제26권3호
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• pp.109-114
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• 1993

Black magnetite film could be formed on Invar steel for shadows mask by iron electroplating in thickness of 0.46~0.63$\mu\textrm{m}$ on Invar steel and subsequent oxidation of iron by immersion in strongly alkaline soution for 30~60 minutes. blackness degreed of magnetite oxide film on Invar was C20BL90 in comparision of color chart of Dainippon Ink & Chemicals Inc. Co. and adhesion test showed excellent adhesion of oxide film on substrate. Magnetite oxide film grew up on iron in hot strongly alkaline solution according to 'Sato-Cohen' oxide film growth model.

• 한국재료학회지
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• 제16권11호
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• pp.687-691
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• 2006

Synthesis of Iron oxides by air oxidation of $FeSO_4$ solutions in the presence of NaOH, Diethylenetriamine (DETA), Butylamine (BA) and influence of ultrasonic wave were investigated by XRD, SEM and particle size analyzer. As the DETA addition increased to 0.05 mol, $Fe_3O_4$ was formed with goethite($\alpha$- FeOOH) and $Fe_3O_4$ single phase was formed above 0.18mol of DETA. As the BA addition increased, the XRD peak intensity of (020) face of lepidocrocite($\gamma$-FeOOH) was developed until the formation of $Fe_3O_4$ and reduced the size of the iron oxide particles formed. Ultrasonic wave reduced the size of the iron oxide particles but gave little effects on the iron oxide particles synthesized by amine.

• 상하수도학회지
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• 제24권3호
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• pp.341-349
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• 2010

It is well known that manganese is hard to oxidize under neutral pH condition in the atmosphere while iron can be easily oxidized to insoluble iron oxide. The purpose of this study is to identify removal mechanism of manganese in the D water treatment plant where is treating bank filtered water in aeration and rapid sand filtration. Average concentration of iron and manganese in bank filtered water were 5.9 mg/L and 3.6 mg/L in 2008, respectively. However, their concentration in rapid sand filtrate were only 0.11 mg/L and 0.03 mg/L, respectively. Most of the sand was coated with black colored manganese oxide except surface layer. According to EDX analysis of sand which was collected in different depth of sand filter, the content of i ron in the upper part sand was relatively higher than that in the lower part. while manganese content increased with a depth. The presence of iron and manganese oxidizing bacteria have been identified in sand of rapid sand filtration. It is supposed that these bacteria contributed some to remove iron and manganese in rapid sand filter. In conclusion, manganese has been simultaneously removed by physicochemical reaction and biological reaction. However, it is considered that the former reaction is dominant than the latter. That is, Mn(II) ion is rapidly adsorbed on ${\gamma}$-FeOOH which is intermediate iron oxidant and then adsorbed Mn(II) ion is oxidized to insoluble manganese oxide. In addition, manganese oxidation is accelerated by autocatalytic reaction of manganese oxide. The iron and manganese oxides deposited on the surface of the sand and then are aged with coating sand surface.

• 자원리싸이클링
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• 제21권1호
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• pp.75-81
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• 2012

선탄경석을 환경개선물질로 순환자원화하기 위해 철산화물과 혼합하여 중금속 불용화제를 제조하고 이의 적정제조 조건과 중금속에 대한 불용화 성능을 평가하였다 선탄경석을 분쇄한 후 철산화물의 분말을 혼합하여 구형의 펠릿을 제조하고 이를 가열하여 중금속 불용화제를 제조하였다. 온도별로 가열한 결과, $1100^{\circ}C$부터 선탄경석에 함유된 탄질분에 의해 영가철이 생성되었다. 제조된 불용화제는 구형의 다공체로서 공극률은 34.63%, 겉보기 밀도는 1.31 g/mL, 공극의 평균크기는 9.82 ${\mu}m$로 측정되었다. 불용화제를 비소(V), 구리(II), 크롬(VI), 카드뮴(II)이 함유된 각각의 중금속 용액과 반응시킨 결과, 영가철이 생성된 $1100^{\circ}C$에서 제조된 펠릿이 중금속 불용화도가 높고 pH를 더 높이는 것으로 나타났다. 중금속농도 10 ppm의 용액을 99.9%이상 불용화하기까지 비소의 경우 1시간, 크롬의 경우 2시간, 구리의 경우 4시간이 필요하였다. 그러나 카드뮴의 경우 불용화도가 낮게 나타났고 중금속농도가 높을수록 불용화도가 더 낮아지는 것으로 나타났다.

• 한국표면공학회지
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• 제25권2호
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• pp.66-72
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• 1992

Magnetite film on iron surface could be coated in strongly alkaline solution (12M NaH\OH) which contained additives such as NaHCO3, KCl and NaNO2, Iron plate was immersed in boiling solution ($130^{\circ}C$) contained above mentioned additives for 1 hour. There are some microcracks and these cracks proved to be the sites for the initiation of corrosion when immersed in 3% NaCl solution. To improve corrosion resistance of the coated steel plate, chromating was done as a post treatment. Chromate film was formed on magnetite oxide film potentiostatically at-918mV/SCE for five minutes at temperature of $70^{\circ}C$ in the alkaline solution containing 5g/l Na2Cr2O7.2H2O.Cr3O4 was electrodeposited on magnetite oxide film and Cr2O3 was electrodeposited on iron surface which was assumed as surface revealed due to microcracks. Increased corrosion resistance of chromated magnetite oxide film was proved in salt spray test & immersion test.