• Journal of the Korean Magnetics Society
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• v.16 no.5
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• pp.245-248
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• 2006

[ $Tb_{3-x}Bi_xFe_5O_{12}$ ] has been studied by x-ray diffraction (XRD), vibrating sample magnetometer, $M\"{o}ssbauer$ spectroscopy. The crystal structures were found to be a cubic garnet structure with space group Ia3d. The lattice constants increase linearly with increasing bismuth concentration. With increase of bismuth substitution, the $N\'{e}el$ temperature increases but the compensation temperature decreases. We have observed the negative magnetization in Bi-TbIG system which has not been reported in garnet systems. $M\"{o}ssbauer$ spectra were measured at various temperatures from 4.2 K to $N\'{e}el$ temperature. The isomer shifts at room temperature are ${\sim}0.26mm/s$ which is consistent with ferric state.

• Corrosion Science and Technology
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• v.3 no.4
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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.

• Journal of the Korean Ceramic Society
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• v.13 no.3
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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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• v.9 no.2
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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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• v.31 no.3
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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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• v.24 no.3
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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.

• Journal of the Korean Magnetics Society
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• v.22 no.2
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• pp.37-41
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• 2012

The Ag nanoparticles attached $La_{0.7}Sr_{0.3}Co_{0.3}Fe_{0.7}O_{3-{\delta}}$ (LSCF) perovskites were prepared by plasma method. The Ag nanoparticles with size of several nanometers deposited from the Ag target were coated on the surface of LSCF powders with size range from 0.2 to 3 ${\mu}m$. The agglomeration of Ag particles annealed at $800^{\circ}C$ under inert gas of Ar were rarely observed. The inter-diffusion between surface Ag and core LSCF is effectively strong to prevent aggregation of Ag nanoparticles. The wave number of FT-IR spectra for LSCF were largely shifted as the concentration of Ag on LSCF up to 2.11 wt.%. The ionic states of irons in LSCF were measured by M$\ddot{o}$ssbauer spectroscopy. The small amount of $Fe^{4+}$ ions are converted to $Fe^{3+}$ ions after Ag nanopartcles were coated on LSCF.

• Applied Chemistry for Engineering
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• v.4 no.1
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• pp.144-152
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• 1993

Immobilized polyethylene glycols onto metal oxides such as ${\gamma}-Al_2O_3$, ${\alpha}-Al_2O_3$, $SiO_2$ and $TiO_2$ were used as phase transfer catalysts for the room temperature synthesis of aniline from nitrobenzene and ironpentacarbonyl. The amount of attached PEG molecules increased with specific surface area of metal oxides. Among the immobilized catalysts tested PEG/${\gamma}-Al_2O_3$ showed the highest activity. The reaction rate increased with the chain length of PEG mole-cules and the aqueous NaOH concentration. Mechanistic study carried out using infrared spectrometer revealed that the role of PEG was to increase the formation of $HFe(CO)_4{^-}$ ion, which is known as active species, and its movement from aqueous to organic phase.

• Journal of Korean Society on Water Environment
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• v.21 no.3
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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.

• Journal of the Korean Society of Safety
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• v.11 no.2
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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.