• Bulletin of the Korean Chemical Society
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• 제20권1호
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• pp.49-52
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• 1999

Various metal oxides such as Fe2O3, FeO, TiO2, MnO2, MoO3, WO3 and ZnO have been used as a catalyst for Gif-KRICT type cyclohexane oxidation. In this reaction, the conversion of cyclohexane to cyclohexanone and cyclohexanol and the selectivity ratio of cyclohexanone to cyclohexanol were greatly affected by the acidity of metal oxides. When metal oxide has more acidic property, the reactivity on oxidation is increased and the formation of cyclohexanone is more favored. From this result, we proposed a new mechanism for the biomimetic Gif-KRICT oxidation system.

• 한국세라믹학회지
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• 제14권2호
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• pp.78-81
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• 1977

The effects of variation in composition and the addition of small amount of the rare-earth oxides La2O3, CeO2 and Sm2O3 on the magnetic properties of Mn-Zn system ferrites, 0.5MnO.0.5ZnO.(1＋0.1X) Fe2O3(X=-1, 0, 1, 2), were investigated in the range of frequencies of 0.1~100 kHz. It was shown that the magnetic permeability of the specimens with the composition Mn 0.5 Zn 0.5 Fe2O4 was maximum in the Mn-Zn system ferrites, and that the addition of a small amount of the rare-earth oxides to the composition 0.5 MnO.0.5ZnO.0.9 Fe2O3 caused the sharp increase of magnetic permeability and the decrease of the loss factors.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2003년도 가을 학술논문집
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• pp.447-452
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• 2003

산화물 핵연료의 리튬환원공정에서 생성되는 $Li_2O$와 희토류원소 산화물($RE_2O_3$)의 화학적 반응을 밝혔다. 스칸듐, 이트륨, 프라세오디뮴, 네오디뮴, 사마륨, 유러퓸, 가돌리늄, 이테르븀 및 루테튬의 산화물은 각각 어떤 $Li_2O$의 임계농도 이상에서 $Li_2O$와 반응하여 복합산화물($LiREO_2$)을 형성하고, 이들 산화물이 복합산화물을 형성하는 각각의 $Li_2O$ 임계농도는 0.1 wt%, 1.9 wt%, 5.3 wt%, 5.0 wt%, 3.0 wt%, 3.9 wt%, 2.9 wt%, 2.6 wt% 및 0.3 wt%로 나타났다. $CeO_2$ 및 란타늄 산화물은 $Li_2O$와 반응하지 않는 것으로 나타났다. 실험에서 얻은 이들 희토류원소 복합산화물의 LiCl 용융염에 대한 용해도는 매우 작았다.

• 한국세라믹학회지
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• 제43권11호
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• pp.680-687
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• 2006

An overview is given to optimize the solid state processes toward phase pure and well-crystallized fine particulates of mixed oxides, serving as electroceramic materials in various genres. Elevation of the reactivity and preservation of stoichiometry of the starting mixture are of universal importance. Mechanical activation is versatile for these purposes, particularly when an oxygen atom as a hinge promotes formation of hetero-bridging bonds between dissimilar cationic species prior to calcination. Case studies carried out recently in the author's laboratory are displayed and compared for ferroelectric materials, i.e. $PbMg_{1/3}Nb_{2/3}O_3$ $xPbTiO_3$(PMN-PT), $(1-y)Pb(Zn_xMg{1-x})_{1/3}$ $yNb_{2/3}O_3$ (PZN-PMN), $BaBi_2Ta_2O_9$ (BBT), $Ba(Mg_{1/3}Ta_{2/3})O_3$ (BMT), and ferromagnetics, i.e. M-, Y-, and Z-phases of Ba-hexaferrites.

• 자연과학논문집
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• 제14권2호
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• pp.41-54
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• 2004

$LaMnO_3$(a=$5.51\AA$, c=$13.33\AA$) 페로브스카이트형 복합산화물에서 A site인 La자리에 Sr을 치환시킨 $La_{0.9}Sr_{0.1}MnO_3$(a=$5.33\AA$, c=$13.27\AA$)와 B site인 Mn을 Cu로 치환시킨 $LaMn_{0.9}Cu_{0.1}O_3$(a=$5.52\AA$, c=$13.31\AA$) 복합산화물을 Citrate sol-gel법을 이용하여 합성하였으며 분말 X-ray회절 분석기(XRD)을 이용하여 Rhombohedral의 페로브스카이트 구조임을 확인하였다. 수소 환원분위기에서의 TRR결과에 의하면 이들 산화물의 산소 화학양론은 $LaMnO_{3.16}$, $La_{0.9}Sr_{0.1}MnO_{3.10}$, $LaMn_{0.9}Cu_{0.1}O_{3.14}$의 조성을 갖는다. $LaMnO_3$는 2단계 환원반응을 일으키지만 각 자리를 치환시킨 $LaMnO_3$ 복합산화물은 3단계 환원반응을 일으켰다.

• 공업화학
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• 제20권5호
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• pp.522-526
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• 2009

다양한 금속(Ru, Mn, Co, Fe)을 $Al_2O_3$와 $CeO_2$에 담지한 촉매를 이용하여 1,2-Dichlorobenzen (1,2-DCB) 제거를 위한 촉매산화 실험을 실시하였다. 이와 더불어 동시에 NOx 제거가 이루어져 단일 촉매층에서 산화/환원 이원 기능이 가능한 촉매를 연구하고자 하였다. 실험결과 1,2-DCB 산화제거효율은 Ru/Co/$Al_2O_3$, Mn-Fe/$CeO_{2}$, 상용촉매인 Cr/$Al_2O_3$ 순으로 나타났다. 또한 1,2-DCB 산화제거효율이 가장 우수하였던 Ru/Co/$Al_2O_3$는 Chlorobenzene (CB)의 분해실험에서도 VOC 제거에 있어서 잘 알려진 Pt-Pd/$Al_2O_3$ 보다 우수한 활성을 나타내었다. 또한 $Cl_2$와 같은 생성물에 의하여 활성의 저하 및 황에 대한 내피독성과 내구성에서 우수한 결과를 얻을 수 있었다. NOx 제거에 있어서도 $260^{\circ}C$에서 NOx 전환율이 70% 정도로 나타났다.

• 한국재료학회지
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• 제20권7호
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• pp.370-373
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• 2010

In fabricating plasma display panels, the photolithographic process is used to form patterns of barrier ribs with high accuracy and high aspect ratio. It is important in the photolithographic process to control the refractive index of the photosensitive paste. The composition of this paste for photolithography is based on the $B_2O_3-SiO_2-Al_2O_3$ glass system, including additives of alkali oxides and rare earth oxides. In this work, we investigated the density, structure and refractive index of glasses based on the $B_2O_3-SiO_2-Al_2O_3$ system with the addition of $Li_2O$, $K_2O$, $Na_2O$, CaO, SrO, and MgO. The refractive index of the glasses containing K2O, Na2O and CaO was similar to that of the [BO3] fraction while that of the SrO, MgO and Li2O containing glasses were not correlated with the coordination fraction. The coordination number of the boron atoms was measured by MAS NMR. The refractive index increased with a decrease of molar volume due to the increase in the number of non-bridging oxygen atoms and the polarizability. The lowest refractive index (1.485) in this study was that of the $B_2O_3-SiO_2-Al_2O_3-K_2O$ glass system due to the larger ionic radius of $K^+$. Based on our results, it has been determined that the refractive index of the $B_2O_3-SiO_2-Al_2O_3$ system should be controlled by the addition of alkali oxides and alkali earth oxides for proper formation of the photosensitive paste.

• 한국세라믹학회지
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• 제30권11호
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• pp.925-932
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• 1993

The perovskite phase in PZN-PMN-PT (Pb(Zn, Mg)1/3Nb2/3O3-PbTiO3) pseudoternary ceramics was stabilized by the addition of excess constituent divalent oxides (PbO, MgO and ZnO). The excess addition of 5mol% MgO or 7.5mol% PbO fully stabilized the perovskite phase. The enhanced diffuse phase transition (DPT) and the decrease in the electrical resistivity observed in the presence of excess ZnO or MgO were interpreted in terms of the additional formation of negatively charged, short-range ordered 1:1 domains with a concomitant generation of charge carriers, holes.

• 한국표면공학회지
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• 제39권6호
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• pp.288-294
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• 2006

Alloys of TiAl-Mn-(0, 5, 10)wt.% $Y_2O_3$ were prepared by a powder metallurgical route, and their oxidation behavior was studied at 800, 900 and $1000^{\circ}C$ in 1 atm of air. The scale formed on the alloys consisted of $TiO_2$ and $Al_2O_3$ oxides. During oxidation, Mn tended to diffuse outward, whereas oxygen diffused inward. The dispersoids of $T_2O_3$, which segregated at the matrix grain boundaries, acted as a diffusion channel for cations and oxygen ions, nucleation sites for oxides, and vacancy annihilation sites. $T_2O_3$ increased the scale thickness, but improved the scale adherence.

• 한국재료학회지
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• 제12권3호
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• pp.220-224
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• 2002

The oxide scales formed on $Ni_3Al$-7.8%Cr-1.3%Zr-0.8%Mo-0.025%B after oxidation at 900, 1000 and 110$0^{\circ}C$ in air were studied using XRD, SEM, EPMA and TEM. The oxide scales consisted primarily of $NiO,\; NiAl_2O_4,\;{\alpha}-Al_2O_3,\; monoclinic-ZrO_2,\; and \;tetragonal-ZrO_2$. The outer layer of the oxide scale was rich in Ni-oxides, whereas the internal oxide stringers were rich in Al-oxides and $ZrO_2$. Within the above oxide scales, Cr and Mo tended to exist as dissolved ions.