• Korean Journal of Materials Research
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• v.22 no.5
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• pp.253-258
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• 2012

Activated magnetite ($Fe_3O_{4-{\delta}}$) was applied to reducing $CO_2$ gas emissions to avoid greenhouse effects. Wet and dry methods were developed as a $CO_2$ removal process. One of the typical dry methods is $CO_2$ decomposition using activated magnetite ($Fe_3O_{4-{\delta}}$). Generally, $Fe_3O_{4-{\delta}}$ is manufactured by reduction of $Fe_3O_4$ by $H_2$ gas. This process has an explosion risk. Therefore, a non-explosive process to make $Fe_3O_{4-{\delta}}$ was studied using $FeC_2O_4{\cdot}2H_2O$ and $N_2$. $FeSO_4{\cdot}7H_2O$ and $(NH_4)_2C_2O_4{\cdot}H_2O$ were used as starting materials. So, ${\alpha}-FeC_2O_4{\cdot}2H_2O$ was synthesized by precipitation method. During the calcination process, $FeC_2O_4{\cdot}2H_2O$ was decomposed to $Fe_3O_4$, CO, and $CO_2$. The specific surface area of the activated magnetite varied with the calcination temperature from 15.43 $m^2/g$ to 9.32 $m^2/g$. The densities of $FeC_2O_4{\cdot}2H_2O$ and $Fe_3O_4$ were 2.28 g/$cm^3$ and 5.2 g/$cm^3$, respectively. Also, the $Fe_3O_4$ was reduced to $Fe_3O_{4-{\delta}}$ by CO. From the TGA results in air of the specimen that was calcined at $450^{\circ}C$ for three hours in $N_2$ atmosphere, the ${\delta}$-value of $Fe_3O_{4-{\delta}}$ was estimated. The ${\delta}$-value of $Fe_3O_{4-{\delta}}$ was 0.3170 when the sample was heat treated at $400^{\circ}C$ for 3 hours and 0.6583 when the sample was heat treated at $450^{\circ}C$ for 3 hours. $Fe_3O_{4-{\delta}}$ was oxidized to $Fe_3O_4$ when $Fe_3O_{4-{\delta}}$ was reacted with $CO_2$ because $CO_2$ is decomposed to C and $O_2$.

• Korean Journal of Materials Research
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• v.28 no.7
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• pp.371-375
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• 2018

The manganese-, nickel-, and aluminum-doped cobalt ferrite powders, $Mn_{0.2}Co_{0.8}Fe_2O_4$, $Ni_{0.2}Co_{0.8}Fe_2O_4$, and $Al_{0.2}CoFe_{1.8}O_4$, are fabricated by the sol-gel method, and the crystallographic and magnetic properties of the powders are studied in comparison with those of $CoFe_2O_4$. All the ferrite powders are nano-sized and have a single spinel structure with the lattice constant increasing in $Mn_{0.2}Co_{0.8}Fe_2O_4$ but decreasing in $Ni_{0.2}Co_{0.8}Fe_2O_4$ and $Al_{0.2}CoFe_{1.8}O_4$. All the $M{\ddot{o}}ssbauer$ spectra are fitted as a superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. The values of the magnetic hyperfine fields of $Ni_{0.2}Co_{0.8}Fe_2O_4$ are somewhat increased in the A and B sites, while those of $Mn_{0.2}Co_{0.8}Fe_2O_4$ and $Al_{0.2}CoFe_{1.8}O_4$ are decreased. The variation of $M{\ddot{o}}ssbauer$ parameters is explained using the cation distribution equation, superexchange interaction and particle size. The hysteresis curves of the ferrite powders reveal a typical soft ferrite pattern. The variation in the values of saturation magnetization and coercivity are explained in terms of the site distributions, particle sizes and the spin magnetic moments of the doped ions.

• Proceedings of the Korean Magnestics Society Conference
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• 2004.12a
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• pp.202-203
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• 2004

• Proceedings of the Korean Magnestics Society Conference
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• 1994.10a
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• pp.98-99
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• 1994

• Proceedings of the Korean Magnestics Society Conference
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• 2002.04a
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• pp.44-45
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• 2002

• Proceedings of the Korean Magnestics Society Conference
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• 2002.04a
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• pp.106-107
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• 2002

• Proceedings of the Korean Magnestics Society Conference
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• 1998.10a
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• pp.20-21
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• 1998

• Proceedings of the Korean Magnestics Society Conference
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• 2001.04a
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• pp.58-59
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• 2001

• Journal of the Korean Electrochemical Society
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• v.8 no.3
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• pp.125-129
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• 2005

We have investigated the electrochemical factors affecting the magnetic properties of hard magnetic CoP nanowires and soft magnetic CoFe nanowires fabricated by ac electrodeposition into self-made AAO(anodic aluminum oxide) nano-templates. AAO template having nano scale pores of high aspect ratio has been prepared through 2-step anodizing of aluminum foil in sulfuric acid. Hard Magnetic properties of CoP nanowires were highly conditional on the applied ac potential which could be a decisive factor to make CoP nanowires made up of either pure hcp crystals or a mixture of hop crystals and fcc crystals. On the contrary to CoFe films, there was no anomalous codeposition in the electrodeposition of soft magnetic CoFe nanowires which exhibited their best saturation magnetization of 238 emu/g at the composition of $Co_{30}Fe_{70}$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2390-2395
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• 2009

In the condition of GHSV=$30000\;hr^{-1}$, $NO_x$ removal yield was higher as mole ratio of $SiO_2/Al_2O_3$ for Fe/ZSM-5 was lower regardless of preparation method such as CVD (chemical vapor deposition) and dry impregnation. In addition to this, Fe/ZSM-5 catalyst showed about 50% $NO_x$ removal yield between $350^{\circ}C$ - $400^{\circ}C$ while CO formed significantly. To remove newly formed CO over Fe/ZSM-5, Co-Pt/ZSM-5 was used in conjunction with Fe/ZSM-5 in the series and this demonstrated over 90% removal yield of both NOx and CO at $250^{\circ}C$ and GHSV=$30000\;hr^{-1}$.