• 한국산학기술학회논문지
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• 제21권4호
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• pp.588-595
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• 2020

반도체 산업용 9N 이상의 초고순도 N₂, Ar 등 불활성 가스 제조를 위해 가스 정제공정에 사용되고 있는 Ni 촉매의 물성 평가 및 촉매적 특성을 확인하였다. 조성이 다른 원기둥 형태의 C1, 츄러스 형태의 C2의 두 가지 Ni 촉매에 대해 비교 평가를 진행하였다. Ni 촉매의 형상과 미세구조를 분석하기 위해 광학현미경과 FE-SEM을 이용하였으며, 조성 확인 및 물성을 분석하기 위해 EDS, XRD, 그리고 micro-Raman 분석을 이용하였다. 또한 Ni 촉매의 비표면적 및 촉매적 특성을 확인하기 위해 BET, Pulse Titration 분석을 진행하였다. 조성 분석결과, C1의 경우, 상대적으로 graphite가 불순물로 다량 포함되어 있는 것을 확인하였으며, C2는 C1에 비해 Ni의 함량이 높은 것을 확인하였다. 비표면적 분석 결과, C2의 비표면적이 C1보다 약 1.69배 정도 큰 것을 확인할 수 있었다. 촉매적 특성분석 결과, 상온에서 O₂와 CO 불순물 제거 정도가 C2가 우수함을 확인하였다. 따라서 반도체 산업용 초고순도 불활성 기체 제조를 위한 Ni 촉매로는 불순물이 적고, 비표면적이 크며, 상온에서 O₂와 CO 제거 성능이 우수한 C2가 적합함을 확인하였다.

• 한국주조공학회지
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• 제41권1호
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• pp.3-10
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• 2021

알루미늄 합금과 주철의 복합주조 공정 중에는 주철로부터 철 성분이 용해되어 알루미늄 용탕에 혼입될 수 있으므로 다양한 Fe함유 금속간 화합물이 형성되며, 이로 인해 알루미늄 합금의 인장 특성이 크게 저하 될 수 있다. 반면 불순물로 첨가되는 Fe와 는 달리 Cu의 경우 알루미늄 합금의 기계적 물성을 향상시키기 위해 첨가되는 합금원소이다. 본 연구에서는 Fe와 Cu의 첨가로 인한 알루미늄 합금의 미세조직 및 인장특성의 변화를 조사하였다. 첨가된 Fe 함량이 1% 이상일 경우 조대한 Al₅FeSi 상과 같은 Fe 함유 화합물들이 다량 형성되어 인장 특성이 현저히 감소하는 것으로 나타났다. Cu가 첨가 된 알루미늄 합금의 경우 Al2Cu 상이 추가로 형성되었으며, 인장 강도가 뚜렷하게 향상되는 결과를 보였다.

• Journal of the Korean Physical Society
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• 제73권10호
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• pp.1555-1560
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• 2018

$AlFe_2B_2$ produced by using a conventional arc melter has a ferromagnetic material with a Curie temperature ($T_C$) of around 300 K, but the arc-melt generates paramagnetic $Al_{13}Fe_4$ impurities during the synthesis of $AlFe_2B_2$. Impurities are brought to cause a decrease in magnetocaloric effects (MCEs). To investigate the effects of $Al_{13}Fe_4$ impurities on MCEs, we prepared and compared ascast and acid-treated samples, where the acid treatment was performed to remove the $Al_{13}Fe_4$ impurities. For the structural analysis, powder X-ray diffraction was carried out, and the measured data were subjected to a Rietveld refinement. The presence of $Al_{13}Fe_4$ impurities in the as-cast sample was observed in the phase analysis measurements. Magnetic properties were investigated by using Superconducting Quantum Interference Device (SQUID) measurements for the as-cast and the acid-treated $AlFe_2B_2$ samples. From isothermal magnetization measurements, Arrott plots were obtained showing that the transition of $AlFe_2B_2$ has a second-order magnetic phase transition (SOMT). The $T_C$ and the saturation magnetization increased for the acid-treated sample due to removal of the paramagnetic impurities. As a consequence, the magnetic entropy change ($-{\Delta}S$) increased in the pure $AlFe_2B_2$ samples, but the full width at half maximum in the plot of $-{\Delta}S$ vs. T decreased due to the absence of impurities.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2004년도 동계학술연구발표회 논문개요집
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• pp.223-224
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• 2004

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1997년도 Proceedings of the 13th KACG Technical Meeting `97 Industrial Crystallization Symposium(ICS)-Doosan Resort, Chunchon, October 30-31, 1997
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• pp.111-115
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• 1997

Iron-doped LiNbO$_3$ crystals were grown by floating zone(FZ) method with different [Li]/[Nb] ratio in order to investigate doping effects of transition metal impurity in LiNbO$_3$ crystal. The grown crystals were analyized edge in UV/VIS/IR spectrometry and EPMA(electron probe micro-analysis). The absorption edge in UV-VIS region and OH-absorption peak in IR region were investigated. The change of Fe concentration along the solidification direction was also investigated

• 산업기술연구
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• 제4권
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• pp.55-60
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• 1984

Silicastone of Hongcheon in Kangweon province was characterized by means of chemical analysis, scanning electron microscope, polarization microscope and x-ray diffractometer. The results showed that the purity of $SiO_2$ is over 97.64 in Wt-%. It also contains 0.046-0.417 Wt-% $Fe_2O_3$ and some others as impurity. The impuity exist as a isolated mineral type of hematite, sericite, apatite etc.

• 한국세라믹학회지
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• 제26권5호
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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.

• The Korean Journal of Ceramics
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• 제6권4호
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• pp.401-404
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• 2000

Mimicking the bacterial synthesis of magnetosomes, in which the functionalized surface of a cytoplasmic (lipid) membrane is considered to be stimulating the crystal growth of magnetite, we have successfully grown magnetite films at $30^{\circ}C$ using an arachic acid monomolecular layer as a functionalized surface. The lipid monomolecular layer was spread on an aqueous solution of FeCl$_2$ which was oxidized by flowing a mixed gas, with ratio $O_2$/$N_2$=1/2000, on the surface of the lipid layer. Mossbauer and X-ray diffraction analyses revealed that the Fe$_3$O$_4$ films contain small amounts of ferric hydroxyl impurity phases of ${\alpha}$-FeOOH and ${\tau}$-FeOOH. This is because the oxygen partial pressure at the ferrite/aqueous interface changed as the film (through which the gas penetrated) increased in thickness. Methods to obtain single phase magnetite films are proposed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 하계학술대회 논문집
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• pp.227-230
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• 1990

The addition of titanium has come to produce an increase in the conductivity of ${\alpha}-Fe_2O_3$ and has been shown NTC ( negative temperature coefficient ) characteristics. Titanium enters the ${\alpha}-Fe_2O_3$ lattice substitutionally as $Ti^{4+}$,thus producing an $Fe^{2+}$ and maintaining the average charge per cation at three. Thus the $Fe^{2+}$ acts as a donor center with respect to the surrounding $Fe^{3+}$ ions. The sintering temperature, compacting pressure and sintering tire have an effect on the electrical properties. C-V and other properties have been measured on polycrystalline samples of ${\alpha}-Fe_2O_3$ containing small deviations from stoichiometry and small amounts of added Titanium. This measurment was made in the course of an investigation of the NTC mechanism in oxides whose cations have a partially filled d-level. C-V and frequency properties have been applied to the measurement of the trap barrier properties at the grain boundary. The double Schottky barrier at the grain boundary is the major cause of the NTC mechanism in NTC thermistor of ${\alpha}-Fe_2O_3$ containing N-type impurity.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.99-101
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• 1999

To improve the texture and the hardness of Ni substrates, we added impurities such as Mn, Fe, Co, Cu and Cr and investigated the effect of impurities on the texture and the hardness of Ni tapes. The Ni tapes with 0.2% Co, Cr, Cu, showed poor in-plane textures. However, the Ni tapes with 0.1 ${\sim}$ O.2% Mn (or Fe), showed much better textures. We'll describe the detailed effects of the amount of Mn impurities.