• 한국자기학회지
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• 제16권5호
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• pp.245-248
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• 2006

Sol-gel법을 이용하여 단일상을 갖는 $Tb_{3-x}Bi_xFe_5O_{12}$ 분말 시료를 제조하였으며, 그 결정학적 및 자기적 특성을 x-선 회절법(XRD), 진동 시료 자화율 측정법(VSM), $M\"{o}ssbauer$ 분광법으로 연구하였다. XRD 분석 결과 결정구조는 Ia3d의 공간그룹을 갖는 cubic 구조임을 알 수 있었고, Bismuth의 치환량이 x=0.5, 0.75, 1.0 및 1.25로 증가할수록 격자상수가 각각 $a_0=12.466{\AA},\;12.487{\AA},\;12.499{\AA},\;12.518{\AA}$으로 선형적으로 증가함을 확인할 수 있었다. VSM을 이용한 온도에 따른 자기모멘트 측정 결과 Bismuth의 치환량이 증가하면 $N\'{e}el$ 온도는 증가하며 compensation 온도는 감소함을 확인할 수 있었다. 또한 field cooled 조건에서 비정상적인 음의 자화값이 관측되었다. $M\"{o}ssbauer$ 스펙트럼은 4.2 K에서부터 $N\'{e}el$ 온도까지 측정하였으며, 분석 결과 상온에서 모든 시료의 이성질체 이동치의 값은 평균적으로 0.27mm/s로 철의 이온상태가 +3가 임을 확인할 수 있었다.

• Corrosion Science and Technology
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• 제3권4호
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• pp.161-165
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• 2004

Aluminum source in an Al-Fe coating reacts with molten carbonate and develops a protective $LiAlO_2$ layer on the coating surface during operation of molten carbonate fuel cells (MCFC). However, if aluminum content in an Al-Fe coating decreases to a critical level for some reasons during MCFC operation, a stable and continuous $LiAlO_2$ protective layer can no longer be maintained. The aluminum content in an Al-Fe coating can be depleted by two different processes; one is by corrosion reaction at the surface between the aluminum source in the coating and molten carbonate, and the other is inward-diffusion of aluminum atoms within the coating into a substrate. In these two respects, therefore, the decreasing rate of aluminum concentration in an Al-Fe coating was measured, and then the influences of these two aspects on the lifetime of Al-Fe coating were investigated, respectively.

• 한국세라믹학회지
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• 제13권3호
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• pp.13-20
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• 1976

The magnetic properties, especially the magnetostriction, of ferroxplana $Zn_{1-x}$$M_X$Y(x=0.0, 0.2, 0.4, 0.6) were investigated at room temperature. In general, the Curie temperature and the permeability of ferroxplana $Zn_{1-X}$$Mn_X$Y increased while the amount of the other phase decrease with increased concentration of dopant $Mn^{2+} for $Zn^{2+}. The magnetostriction constnats K1, K2, K3 and K4 for ZnY were ＋0.3, -5.0, -4.3 and $-4.8{\times}$$10^{-6} while that for 4Zn^0.8$ $Mn^0.2$Y were ＋2.5, -5.4, -6.0 and $-3.4{\times}10^{-6}$, respectively.

• Journal of Electrochemical Science and Technology
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• 제9권2호
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• pp.133-140
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• 2018

$Sr_{0.92}Y_{0.08}Ti_{0.5}Fe_{0.5}O_{3-{\delta}}$ (SYTF0.5) is investigated as an alternative anode in $H_2$ fuels containing $H_2S$ (0-200 ppm). Although additional ionic conductivity is introduced by aliovalent substitution of $Ti^{4+}$ by $Fe^{3+}$ in the B-site, the SYTF0.5 has lower electrical conductivity than that of the $Sr_{0.92}Y_{0.08}TiO_{3-{\delta}}$. Due to the mixed ionic and electronic conductive (MIEC) property exhibited in the SYTF0.5 anode, the electrochemical performance of the SYTF0.5 anode is improved, as well as the sulfur tolerance. The maximum power densities in $H_2$ at $900^{\circ}C$ for the SYT anode and the SYTF0.5 anode were 56.9 and $98.6mW/cm^2$, respectively. The maximum power density in the SYTF0.5 anode at 200 ppm of $H_2S$ concentration decreased by only 12.9% (86.3 to $75.2mW/cm^2$).

• Journal of Microbiology and Biotechnology
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• 제31권3호
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• pp.419-428
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• 2021

To efficiently recycle GH78 thermostable rhamnosidase (TpeRha) and easily separate it from the reaction mixture and furtherly improve the enzyme properties, the magnetic particle Fe3O4-SiO2-NH2-Cellu-ZIF8 (FSNcZ8) was prepared by modifying Fe3O4-NH2 with tetraethyl silicate (TEOS), microcrystalline cellulose and zinc nitrate hexahydrate. FSNcZ8 displayed better magnetic stability and higher-temperature stability than unmodified Fe3O4-NH2 (FN), and it was used to adsorb and immobilize TpeRha from Thermotoga petrophilea 13995. As for properties, FSNcZ8-TpeRha showed optimal reaction temperature and pH of 90℃ and 5.0, while its highest activity approached 714 U/g. In addition, FSNcZ8-TpeRha had better higher-temperature stability than FN. After incubation at 80℃ for 3 h, the residual enzyme activities of FSNcZ8-TpeRha, FN-TpeRha and free enzyme were 93.5%, 63.32%, and 62.77%, respectively. The organic solvent tolerance and the monosaccharides tolerance of FSNcZ8-TpeRha, compared with free TpeRha, were greatly improved. Using naringin (1 mmol/l) as the substrate, the optimal conversion conditions were as follows: FSNcZ8-TpeRha concentration was 6 U/ml; induction temperature was 80℃; the pH was 5.5; induction time was 30 min, and the yield of products was the same as free enzyme. After repeating the reaction 10 times, the conversion of naringin remained above 80%, showing great improvement of the catalytic efficiency and repeated utilization of the immobilized α-L-rhamnosidase.

• Environmental Engineering Research
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• 제24권3호
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• pp.474-483
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• 2019

In this study, iron (Fe) impregnated granular activated carbon (Fe-GAC) has been synthesized and characterized for various properties. Comparative studies have been performed for use of Fe-GAC as an adsorbent as well as a catalyst during catalytic oxidation of hydroquinone (HQ). In the batch adsorption study, effect of process parameter like initial HQ concentration ($C_o=25-1,000mg/L$), pH (2-10), contact time (t: 0-24 h), temperature (T: $15-45^{\circ}C$) and adsorbent dose (w: 5-50 g/L) have been studied. Maximum HQ adsorption efficiency of 75% was obtained at optimum parametric condition of: pH = 4, w = 40 g/L and t = 14 h. Pseudo-second order model best-fitted the HQ adsorption kinetics whereas Langmuir model best-represented the isothermal equilibrium behavior. During oxidation studies, effect of various process parameters like initial HQ concentration ($C_o:20-100mg/L$), pH (4-8), oxidant dose ($C_{H2O2}:0.4-1.6mL/L$) and catalyst dose (m: 0.5-1.5 g/L) have been optimized using Taguchi experimental design matrix. Maximum HQ removal efficiency of 83.56% was obtained at optimum condition of $C_o=100mg/L$, pH = 6, $C_{H2O2}=0.4mL/L,$ and m = 1 g/L. Overall use of Fe-GAC during catalytic oxidation seems to be a better as compared to its use an adsorbent for treatment of HQ bearing wastewater.

• 한국자기학회지
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• 제22권2호
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• pp.37-41
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• 2012

DC 스퍼터를 이용하여 은(Ag) 나노입자를 입도 0.2~3 ${\mu}m$ 크기를 갖는 페롭스카이트(Perovskite) $La_{0.7}Sr_{0.3}Co_{0.3}Fe_{0.7}O_{3-{\delta}}$(LSCF) 입자 표면에 코팅하여 복합재를 제조하였다. 제조된 LSCF/Ag 복합재에서 Ag 나노입자는 수 나노입자 크기로 형성되었으며 Ar가스 분위기에서 $800^{\circ}C$ 열처리 후에도 Ag입자가 응집되는 현상이 없어 안정적으로 증착되었음을 확인하였다. LSCF 표면에 Ag나노입자 코팅양이 2.11 wt.%까지 증가함에 따라 Fourier Transform Infrared Spectroscopy(FT-IR) 분광기의 파수가 크게 변하여 강한 결합이 형성되어 있으며, Ag 코팅 전후 결정 구조의 변화는 없으나 M$\ddot{o}$ssbauer 분광 분석으로 확인한 결과 $Fe^{4+}$ 이온이 감소하면서 $Fe^{3+}$ 이온이 증가하여 LSCF의 전자 가에 변화가 생김을 확인 할 수 있었다.

• 공업화학
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• 제4권1호
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• pp.144-152
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• 1993

${\gamma}-Al_2O_3$, ${\alpha}-Al_2O_3$, $SiO_2$, $TiO_2$등에 고정화된 폴리에틸렌글리콜을 $Fe(CO)_5$에 의한 니트로벤젠의 상온 환원반응에 상이동 촉매로 사용하였다. 고정화된 PEG의 몰수는 담체의 비표면적에 따라 증가하였고 PEG/${\gamma}-Al_2O_3$가 가장 좋은 활성을 나타내었다. PEG의 사슬길이가 길고 NaOH 농도가 높을수록 반응속도가 증가하였다. 적외선분광기를 이용하여 반응기구에 대한 고찰도 함께 실시하였으며 폴리에틸렌글리콜 상이동 촉매는 본 반응의 활성물질로 알려진 $HFe(CO)_4{^{-}}$이온의 생성과 이의 유기상으로의 이동을 촉진시키는 것으로 판단되었다.

• 한국물환경학회지
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• 제21권3호
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• pp.284-288
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• 2005

In this study, photochemical advanced oxidation processes (AOPs) utilizing the Photo Fenton reaction ($Fe^{2+}+H_2O_2+UV$) were investigated in lab-scale experiments for the treatment of livestock wastewater. For the experimets, the livestock wastewater was pretreated by coagulation with $3,000mg/L\;FeCl_3$. The optimal conditions for Photo-Fenton processes were determined: pH was 5, the concentration of ferrous ion (Fe II) was 0.01 M. The concentration of hydrogen peroxide was 0.1 M, and molar ratio ($Fe^{2+}/H_2O_2$) was 0.1. The optimal reaction time was 80 min. Under the optimal condition of Photo-Fenton process, chemical oxygen demand (COD), color and fecal coliform removal efficiencies were about 79, 70, and 99.4%, respectively and sludge production was 7.5 mL from 100 mL of solution.

• 한국안전학회지
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• 제11권2호
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• pp.67-78
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• 1996

Gas sensing element, $\gamma-Fe_2O_3$was synthesized by dehydration, reduction, and oxidation of $$${\gamma}$-FeOOH, which was synthesized with $FeSO_4\;{\cdot}\;7H_2O$ and NaOH. They were produced as a bulk-type, a thick film-type. Then, their responses and mechanisms of response to the gas of liquefied-petroleum were studied. The qualities of gas sensing elements are decided by the structure and the relative surface area. In the process of $\alpha-FeOOH $synthesis, the effects of reaction conditions as the equivalent ratio, on the structure and the relative surface area of gas sensing element were observed. The changes of the structure were measured with XRD, SEM, TG-DTA and BET. The resistance changes of the synthesized gas sensor in the air were measured. The response ratio were also measured for the changes of working temperature and gas concentration. As a result of analysis with XRD, it was confirmed that the the best conditions for the synthesis of $\alpha -FeOOH$ were equivalent ratio 0.65. The thick film-type element of $\gamma-Fe_2O_3$responded more quickly than the bulk-type did. The structure and the relative surface area of the $\alpha-FeOOH $were confirmed as the important factors deciding gas response charcteristics.