• Journal of the Korean Ceramic Society
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• v.26 no.5
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• pp.705-711
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• 1989

The glass-ceramics was prepared with the scoria(CaO-MgO-Al2O3-SiO2 system) of the locally occurring volcanic ejecta containing 10-13w/o of (FeO＋Fe2O3) by melting at 140$0^{\circ}C$ for 4 hours and thermally treated for nucleation and crystallization. The sucrose was added to the scoria to adjust the Fe2+/Fe3+ ratio during the melting process. The addition of 1-2w/o of sucrose showed the glass-ceramics body with the finest particle developed and dispersed over the entire range. It is concluded that the impurity content of iron oxide and titanium oxide play the most-influencial effect on the crystallization. When 1-2w/o of sucrose was added to the scoria, the value of Fe2+/Fe3+ ratio was 0.93-1.32 and showed the best result of crystallization. The nucleation temperature and time were calculated by the measurements of exothermic peak temperatures of DTA for quenched and thermally treated glasses. The nucleation temperature of scoria glass without the addition of sucrose was estimated as 75$0^{\circ}C$, but the addition of sucrose by 2w/o showed the nucleation temperature 6$25^{\circ}C$. The nucleation time was calculated with the same DTA curves. The nucleation times estimated were about 150min. for both of glasses without and with sucrose added. Finally, the activation energies for crystallization were calculated with the DTA data. The calculated activation energies were 143 Kcal/mole for the glass without addition of sucrose and 90Kcal/mole, 87Kcal/mole, 85Kcal/mole and 71Kcal/mole for the glasses of 1w/o, 2w/o, 3w/o and 4w/o addition respectively.

• Journal of Korea Foundry Society
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• v.24 no.5
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• pp.295-303
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• 2004

The effects of three minor elements, S, Ce and Bi, on the inoculation ability and fading behavior of 1.0 wt%Ba-Fe-Si were investigated through thermal analysis. The performance of 1.0 wt%Ba-Fe-Si inoculant was better and more consistant at the high temperature range of $1,450{\sim}1,500^{\circ}C$ than that of low one of $1,300{\sim}1,400^{\circ}C$. That was improved with individual addition of three minor elements. The optimum amount of addition was 1.0% of the weight of inoculant added, respectively. That was improved also by the simultaneous addition of two or three kinds of minor elements. Even though worse with the addition of two kinds of them simultaneously than with individual addition, that was improved with the simultaneous addition of all three kinds over that with the individual one.

• Applied Microscopy
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• v.45 no.1
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• pp.32-36
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• 2015

The microstructural features of FeCoCrNi, FeCoCrNiAl and FeCoCrNiSix (x=0, 5, 10, 15, 20) alloys have been investigated in the present study. The microstructure of FeCoCrNi alloy changes dramatically with equiatomic addition of Al. The fcc irregular shaped grain structure in the as-cast FeCoCrNi alloy changes into the bcc interconnected structure with phase separation of Al-Ni rich and Cr-Fe rich phases in the as-cast FeCoCrNiAl alloy. The microstructure of FeCoCrNi alloy changes with the addition of Si. With increasing the amount of Si, the fcc structure of the grains is maintained, but new phase containing higher amount of Si forms at the grain boundary. As the amount of Si increases, the fraction the Si-rich grain boundary phase increases.

• Journal of Powder Materials
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• v.20 no.1
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• pp.13-18
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• 2013

In the present study, we systematically investigated the effect of Mn addition on nitrogenation behavior and magnetic properties of Sm-Fe powders produced by reduction-diffusion process. Alloy powders with only $Sm_2(Fe,Mn)_{17}$ single phase were successfully produced by the reduction-diffusion process. The coercivity of $Sm_2(Fe,Mn)_{17}$ powder rapidly increased during nitrogenation and reached the maximum of 637 Oe after 16 hours. After further nitrogenation, it decreased. In contrast, the coercivity of $Sm_2Fe_{17}$ powder gradually increased during nitrogenation for 24 hours. The coercivity of $Sm_2(Fe,Mn)_{17}$ powder was higher than that of $Sm_2Fe_{17}$ powder at the same condition of nitrogenation. It was considered that the Mn addition facilitates the nitrogenation of $Sm_2Fe_{17}$ powder and enhances the coercivity.

• Economic and Environmental Geology
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• v.46 no.1
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• pp.29-37
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• 2013

In order to apply the silver cementation method using Fe powder from pregnant thiourea leaching solution. Parameters such as the amount of Fe powder addition, agitation speed, and temperature were investigated. The silver cementation rate was increased by the increasing of Fe powder addition, agitation speed, and temperature. The highest silver cementation rate was found when the addition of Fe powder was 50 g/L at the agitation speed of 500 rpm. The silver cementation rate increase with increasing temperature according to the Arrhenius equation and obeys $1^{st}$ order kinetics. The activation energy from the kinetics data was found to be between 13.73 KJ/mol and 17.02 KJ/mol. In the XRD analysis, goethite was detected in the precipitate of the thiourea leach solution. This indicates that an oxidation-reduction reaction had occurred in the thiourea solution due to the addition of the Fe powder.

• Journal of Photoscience
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• v.1 no.2
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• pp.83-88
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• 1994

The synergic effect of iron plus blue light on the peroxidation of membrane lipid was investigated, using liposomes made of phospholipid. While strong irradiation did not affect Fe$^{+2}$-promoted lipid peroxidation that turned out to be O$_2$-dependent, ferric iron in bright light exerted a pronounced effect on the initiation of lipid peroxidation: this combined action of light and Fe$^{+3}$ on liposomal membranes was apparently independent of O$_2$. When liposomal samples containing Fe$^{+3}$ were subjected to irradiation, some portions of Fe$^{+3}$ were converted into Fe$^{+2}$. The extent of the Fe$^{+3}$-Fe$^{+2}$ conversion increased with increasing time of irradiation, which resembled the dependence of Fe$^{+3}$-promoted lipid peroxidation on irradiation. Further, it was observed that the effect of irradiation in liposomal samples containing Fe$^{+2}$ was strikingly mimicked by that of Fe$^{+2}$ addition to the same samples. The obligatory requirement of a suitable Fe$^{+3}$/Fe$^{+2}$ ratio for the genesis of iron-dependent lipid peroxidation, a controversial proposition, was also confirmed by the observation that lipid peroxidation was substantially enhanced by the addition of a mixture of Fe$^{+3}$ and Fe$^{+2}$, as compared to the addition of Fe$^{+3}$ or Fe$^{+2}$ alone. The results obtained in this study not only suggest that light acts as an effector for initiating lipid peroxidation, when Fe$^{+3}$ is present in membrane systems, but also imply that any chemical or physical factor that influences the redox states of iron in membranes can play a role in lipid peroxidation reactions.

• Journal of Magnetics
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• v.14 no.4
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• pp.150-154
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• 2009

The effect of Ga and, Nb addition on the kinetics and mechanism of the disproportionation of a Nd-Fe-B alloy were investigated by isothermal thermopiezic analysis (TPA) using $Nd_{12.5}Fe_{(81.1-(x+y))}B_{6.4}Ga_xNb_y$ (x=0 and 0.3, y= 0 and 0.2) alloys. The addition of Ga and Nb retarded the disproportionation kinetics of the Nd-Fe-B alloy significantly, and increased the activation energy of the disproportionation reaction. The disproportionation kinetics of the $Nd_{12.5}Fe_{(81.1-(x+y))}B_{6.4}Ga_xNb_y$ alloys measured under an initial hydrogen pressure of 0.02 MPa were fitted to a parabolic rate law. This suggested that during the disproportionation of $Nd_{12.5}Fe_{(81.1-(x+y))}B_{6.4}Ga_xNb_y$ alloys with an initial hydrogen pressure of 0.02 MPa, a continuous disproportionation product is formed and the overall reaction rate is limited by the diffusion of hydrogen atoms (or ions).

• Transactions of Materials Processing
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• v.28 no.3
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• pp.123-129
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• 2019

Hypereutectic Al-Si alloys have been widely utilized for wear-resistant components in the automotive industry. In order to expand the application of Hypereutectic Al-Si alloys, the addition of alloying elements forming a stable precipitate at high temperature is required. Thermally stable inter metallic compounds can be formed through the addition of transition elements such as Fe, Ni to Al alloys. However, the amount of transition element to be added to Al alloys is limited due to their low solid solubility. Also, hypereutectic Al-Si-Fe alloys form coarse primary Si phases and needle-shaped intermetallic compounds during solidification in the general casting processes. In this study, the effects of the destruction of Intermetallic compound and Si phase are investigated via hot extrusion. Both the microstructure and mechanical properties are discussed under different extrusion conditions.

• Journal of the Korean Ceramic Society
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• v.36 no.5
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• pp.471-477
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• 1999

Fe and Fe-Mo binder were used to produce TiB2 based cermet by a pressureless sintering. The densification behaviour of TiB2-Fe-Mo cermet during liquid-phase sintering in argon was studied in relation to binder phase charactertics. The effects of Mo addition and sintering condition on the sintering behaviour and mechanical properties were also investigated. TiB2-based cermets with Fe-Mo binder composition showed a better sinterability than the cermets with only Fe binder. In TiB2-Fe-Mo cermet higher densities in the wide temperature range were obtained and also fully densified sintered cermet were obtained at 1873K The enhancement in the densification phenomenon of TiB2-Fe-Mo system can be explained by improved liquid phase wettability associated with the roles of Mo components as solute atoms. When Fe-Mo binders were used cermets with a finer grain size and enhanced mechanical properties wereproduced and new phases such as Fe2B and Mo2FeB2 were observed in the sintered cermet. The highest bending strength was obtained from the 20vol% Fe-Mo cermet and these hardness-fracture toughness combination in the wide binder compositions is better than that of TiB2-Fe cermet. In order to improve mechanical properties microstructure control with high purity powders is desirable because high purity powders prevent the formation of Fe2B and Mo2FeB2 phase which comsume the ductile binder phase.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.06a
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• pp.139-143
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• 1997

The doping effects of Mg and/or Fe ions on congruent LiNbO$_3$ single crystal growth were studied in order to clarify the roles of MgO in Fe doped LiNbO$_3$ single crystals. The effective distribution coefficienct of Fe was found decreased drastically from 0.85 to 0.5 by the addition of MgO into the LiNbO$_3$ melt. M ssbauer spectra revealed that the addition of MgO reduces the occurrence of Fe2+ ions during growth in air. Therefore, it is likely that there would be two important roles of MgO in Fe doped LiNbO$_3$. One is to suppress the incorporation of all Fe ions, and the other is to reduce the concentration of Fe2+ ions among the total Fe ions.