• Journal of Korean Society for Atmospheric Environment
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• v.23 no.5
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• pp.575-584
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• 2007

The adsorption capability of iron phthalocyanine derivatives were investigated by means of X-ray diffractometor (XRD), IR (infrared) spectroscopy, scanning electron microscopy (SEM) and temperature programmed desorption (TPD). According to TPD results, iron phthalocyanine derivatives showed two desorption peaks at low temperature ($100{\sim}150^{\circ}C$) and high temperature ($350{\sim}400^{\circ}C$) indicating that there were two kinds of acidities. Tetracarboxylic iron phthalocyanine (Fe-TCPC) have a stronger desorption peak (chemical adsorption) at the high temperature and a weaker desorption peak (physical adsorption) at the low temperature than iron phthalocyanine (Fe-PC). The specific surface areas of Fe-TCPC and Fe-PC were $26.46\;m^2/g\;and\;11.77\;m^2/g$, respectively. The pore volumes of Fe-TCPC and Fe-PC were $0.14\;cm^3/g\;and\;0.06\;cm^3/g$, respectively. The adsorption capability of triethyl amine calculated by breakthrough curve at 220 ppm of equilibrium concentration was 29.2 mmoL/g for Fe-TCPC and 0.8 mmoL/g for Fe-PC. The removal efficiency of dimethyl sulfide of Fe-TCPC and Fe-PC in batch experiment of 225 ppm of initial concentration were 44.9% and 28.9%, respectively. The removal efficiency of trimethyl amine of Fe-TCPC and Fe-PC in batch experiment of 118 ppm of initial concentration were approximately 100.0% and 33.9%, respectively.

• Journal of the Korean Magnetics Society
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• v.9 no.2
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• pp.98-103
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• 1999

We have studied changes of coercivity $(H_c)$, exchange anisotropy field $(H_{ex})$ and MR ration in glass/Ta/NiFeI/CoI(t)/Cu/CoII(3/4 t)/NiFeII/FeMn spin valve structures by changing Ar pressure and thicknesses of Co layers using DC, RF sputtering methods. We obtained minimum coercivity of 2.8 Oe at 4 mTorr of Ar pressure, exchange anisotropy field of 50.0 Oe at 6 mTorr and 5.3 % of MR ratio at 10 mTorr. Also, we obtained 3.0 Oe of coercivity at 40 $\AA$ of CoI layer, 65.9 Oe at 13 $\AA$ and 4.7 % of MR ratio at 27 $\AA$ and 34 $\AA$ by changing the thicknesses of Co layers.

• Journal of the Korean Magnetics Society
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• v.16 no.6
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• pp.276-278
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• 2006

The switching characteristics of magnetic tunnel junctions (MTJs) comprising amorphous ferromagnetic CoFeSiB free layer have been investigated. CoFeSiB was used for the free layer to enhance the switching characteristics. The typical junction structure was $Si/SiO_{2}/Ta$ 45/Ru 9.5/IrMn 10/CoFe $7/AlO_{x}/CoFeSiB\;(t)/Ru\;60\;(in\;nm)$. CoFeSiB has low saturation magnetization ($M_{s}$) of $560\;emu/cm^{3}$ and high anisotropy constant ($K_{u}$) of $2800\;erg/cm^{3}$. These properties caused low coercivity ($H_{c}$) and high sensitivity in MTJs, and it also confirmed in submicrometer-sized elements by micromagnetic simulation based on the Landau-Lisfschitz-Gilbert equation. By increasing CoFeSiB free layer thickness, the switching characteristics became worse due to increase of the demagnetization field.

• Journal of the Korean Magnetics Society
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• v.8 no.4
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• pp.210-215
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• 1998

$Nd_{15}Fe_{77}B_8$ and $Nd_{16}Fe_{76}B_8$ powders were prepared by mechanical alloying in Ar atmosphere, and their phases and magnetic properties were investigated with as a function of the annealing temperature. It was found that the mechanical alloyed $Nd_{16}Fe_{76}B_8$ powder for 450 hours was amorphous phase with a part of $\alpha$-Fe crystallites. The obtained powders at 700 $^{\circ}C$ for 30 minute resulted in two phase of $Nd_2Fe_{14}B$ and $NdB_6$ by the solid-state reaction. The mechanical alloyed $Nd_{16}Fe_{76}B_8$ powder for 450 hour and annealed at 700 $^{\circ}C$ for 30 minute was showed $_iH_c\;of\;9.91\;kOe,\; B_{max}\;of\;12.93\;kG,\;Br\;of\;7.6\;kG\;and\;(BH)_{max}\;10.1\;MGOe$.

• The Korean Journal of Pharmacology
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• v.21 no.1
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• pp.62-77
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• 1985

In tile Iron-catalyzed Haber-Weiss reaction to produce OH., the requirement for $O^{-}_{2}{\cdot}$ is only to reduce $Fe^{+++}$. Possibly, the role of $O^{-}_{2}{\cdot}$ can be replaced by other reducing agents. Ascorbate is one of them in biological system. In the present study, the ability of ascorbate to produce $OH{\cdot}$ in the presence of $Fe^{++}$ and $H_2O_2$ was investigated by observing the degradation of hyaluronic acid and ethylene production from methional. Ascorbate stimulated the degradation of hyaluronic by $Fe^{++}$ and $H_2O_2$. That was confirmed by both viscosity change and gel-permeation chromatographic analysis. The observed degradation was almost completely prevented by catalase and $OH{\cdot}$ scavengers. In support of the above results, ascorbate enhanced the prouction of ethylene from methional in the presence of $Fe^{++}$ and $H_2O_2$. Other reducing agents (cysteine, glutathione, NADH and NADPH) showed similar activities to ascorbate in the degradation of hyaluronic acid and ethylene production. But no stimulatory effects were observed with their oxidized forms such as NAD and NADP. Thus, it appears that reduction of the metal ion was needed for $OH{\cdot}$ production. Among the metal ions tested, $Fe^{++}$ showed most potent catalytic action in the production of $OH{\cdot}$ The results obtained support that ascorbate can substitute $O^{-}_{2}{\cdot}$ in the metal-catalyzed reactions, particularly with $Fe^{++}$ by which $OH{\cdot}$ is produced with $H_2O_2$. The significance of the ascorbate-dependent production of $OH{\cdot}$ was considered with respect to possible role of ascorbate in the damage of inflamed joints.

• Korean Journal of Materials Research
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• v.7 no.4
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• pp.295-302
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• 1997

금속분말 Fe와 Si에 KNO$_{3}$(Fe+Si)무게비=0.2로 점화촉매 KNO$_{3}$를 혼합하고 50MPa로 성형한 후 점화시키는 비기체연소합성(SHS; Self propagating High temperature Synthesis)법으로 출발 분말을 얻었다. 점화분위기를 공기 및 Ar으로 한 경우 XRD결과에서 특별한 차이가 없었고 두 경우 모두 SiO$_{2}$피크가 검출되었다. 합성된 분말을 성형한 후 119$0^{\circ}C$환원분위기에서 소결하고 포석온도이하에서 열처리하여 반도성 FeSi$_{2}$가 주상인 Fe-Si계 열전재료를 제조하였다. Fe/Si무게비=46/54,44/56 및 42/58시편의 제벡계수는 Si함량이 증가할수록 증가하였다. 점화후의 세척처리를 2단계로 하는 경우 제벡계수의 부호가 변화하여 p-type에서 n-type으로 변화하며 소결밀도가 크게 상승하였다. 조성에 관계없이 공통적으로 발견되는 SiO$_{2}$는 점화시의 분위기보다는 점화촉매에 포함된 K성분이 소결 및 열처리시 산화제로 작용하여 형성되는 것이 확인되었다.

• Bulletin of the Korean Chemical Society
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• v.32 no.2
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• pp.536-540
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• 2011

This study reports the origin of the electrochemical improvement of $LiFePO_4$ when synthesized by wet milling using acetone without conventional carbon coating. The wet milled $LiFePO_4$ delivers 149 $mAhg^{-1}$ at 0.1 C, which is comparable to carbon coated $LiFePO_4$ and approximately 74% higher than that of dry milled $LiFePO_4$, suggesting that the wet milling process can increase the capacity in addition to conventional carbon coating methods. UV spectroscopy, elemental microanalysis, and evolved gas analysis are used to find the root cause of the capacity improvement during the mechanochemical reaction in acetone. The analytical results show that the improvement is attributed to the conductive residual carbon on the surface of the wet milled $LiFePO_4$ particles, which is produced by the reaction of $FeC_2O_4{\cdot}2H_2O$ with acetone during wet milling through oxygen deficiency in the precursor.

• Applied Microscopy
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• v.25 no.3
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• pp.90-98
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• 1995

In the Fe-Si system, a mixture of a($Fe_{2}Si_5$) - and ${\epsilon}$(FeSi)-composition powders was sintered and heat-treated subsequently at various temperatures and time to get thermoelectric ${\beta}$-phase($FeSi_2$) compacts. The different transformational sequences depending on the heat treating temperature were found through the investigation into phase transformation and microstructural development. That is, a rapid eutectoid decomposition of ${\alpha}{\to}{\beta}+Si$ occurred together with a accompanying slow reaction between the dispersed Si formed by above decomposition and the preexisted ${\epsilon}$ phase at temperatures below $830^{\circ}C$. The unreacted Si and the micropores formed due to the density change upon the transformation coarsened as heat treating time elapsed. At temperatures above $880^{\circ}C$, however, transformation was proceeded by a peritectoid reaction of ${\alpha}+{\epsilon}{\to}{\beta}$. It took at least 200min. to achieve 90% volume fracion of transformed ${\beta}$ phase, and the growth of micro-pores was also observed in this transformational sequence with prolonged heat treating time.

• Journal of the Korean Ceramic Society
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• v.45 no.6
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• pp.324-330
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• 2008

Activated carbon/$TiO_2$ (AC/$TiO_2$) composites modified with different concentrations of Fe were prepared. The $N_2$ adsorption data showed that the composites had decreased surface area compared with the pristine activated carbon. This indicated the blocking of the micropores on the surface of AC, which was further supported by observation via SEM. XRD results showed patterns for the composites and an anatase typed titanium dioxide structure with a small part of rutile in a higher Fe concentration (> 1.0 mol/L). EDX results showed the presence of C and, O, with Ti peaks on the composites of Fe-AC/$TiO_2$ with relatively lower Ti concentration, which may be due to the higher Fe concentration incorporated into the composites. Subsequently, the photocatalytic effects on methylene blue (MB) were investigated. The improved decomposition of MB showed the combined effects of adsorptions and photodegradation. Especially, the composites modified by Fe revealed enhanced photodegradation behaviors of MB.

• Journal of Powder Materials
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• v.15 no.2
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• pp.148-155
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• 2008

Nano magnetite particles have been prepared by two step reaction consisting of urea hydrolysis and ammonia addition at certain ranges of pH. Three different concentrations of aqueous solution of ferric ($Fe^{3+}$) and ferrous ($Fe^{2+}$) chloride (0.3 M-0.6 M, and 0.9 M) were mixed with 4 M urea solution and heated to induce the urea hydrolysis. Upon reaching at a certain pre-determined pH (around 4.7), 1 M ammonia solution were poured into the heated reaction vessels. In order to understand the relationship between the concentration of the starting solution and the final size of magnetite, in-situ pH measurements and quenching experiments were simultaneous conducted. The changes in the concentration of starting solution resulted in the difference of the threshold time for pH uprise, from I hour to 3 hours, during which the akaganeite (${\beta}$-FeOOH) particles nucleated and grew. Through the quenching experiment, it was confirmed that controlling the size of ${\beta}$-FeOOH and the attaining a proper driving force for the reaction of ${\beta}$-FeOOH and $Fe^{2+}$ ion to give $Fe_3O_4$ are important process variables for the synthesis of uniform magnetite nanoparticles.