• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2288-2292
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• 2007

The catalytic activities of nickel-based catalysts were estimated for oxidizing acetaldehyde of VOCs exhausted from industrial facilities. The catalysts were prepared by sol-gel methods of SiO2 and SiO2-TiO2 as a xerogel followed by impregnating Al2O3 powder with the nickel nitrate precursor. The crystalline structure and catalytic properties for the catalysts were investigated by use of BET surface area, X-ray diffraction (XRD), Xray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR) techniques. These results show that nickel oxide is transformed to NiAl2O4 spinel structure at the calcination temperature of 400 °C in response to the steps with after- and co-impregnation of Al2O3 powder in sol-gel process. The NiAl2O4 could suppress the oxidation reaction of acetaldehyde by catalysts. The NiO is better dispersed on SiO2-TiO2/Al2O3 support than SiO2/Al2O3 and SiO2-TiO2-Al2O3 supports. From the testing results of catalytic activities for oxidation of acetaldehyde, Catalysts showed a big difference in conversion efficiencies with the way of the preparation of catalysts and the loading weight of nickel. The catalyst of 8 wt.% Ni/TiO2-SiO2/Al2O3 showed the best conversion efficiency on acetaldehyde oxidation with 100% conversion efficiency at 350 °C.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.917-921
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• 2002

In this paper, we made different types of non-thermal plasma reactors such as Metal-particle reactor with $Al_2O_3$ to measure NOx removal characteristic and the dielectric effect for NOx removal. NOx removal rate is not so good when we use just dielectric of $Al_2O_3$ at the Metal-particle reactor, also we just put sludge pellets(100%) without Metal-particle reactor with $Al_2O_3$ and dielectric such as $TiO_2$, $BaTiO_3$ to measure the effect of sludge for NOx removal so that NOx removal rate is almost the same. However NOx removal rate is more than 90% in case of the reactor of composition shape used both dielectric of $Al_2O_3$ and sludge pellets at the same time. In case of the shape of plasma reactor with dielectric, the Metal-particle reactor with $Al_2O_3$, and the metal-particle reactor with both $Al_2O_3$ and dielectric such as $TiO_2$, $BaTiO_3$ at the same time, they are almost the same effect for NOx removal, so we made MNPR(Metal-particle Non-thermal Plasma Reactor with $Al_2O_3$) to reduce these kinds of demerits. Finally, we think MNPR should be much better than other reactors for NOx removal.

• Korean Journal of Materials Research
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• v.5 no.3
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• pp.280-287
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• 1995

첨가제로 $Al_{2}$$O_{3}$가 포함된 ZnO 소결체가 타깃을 이용하여 RF 마그네트론 스퍼터링법으로 Al이 첨가된 ZnO박막을 증착하고, 타깃에 첨가된 $Al_{2}$$O_{3}$의 농도와 증착시 스퍼터링장치내의 기판위치에 따른 박막의 물성 변화를 고찰하였다. 타깃의 $Al_{2}$$O_{3}$ 첨가농도가 2wt%인 경우에 비저항치 8 $\times$ $10_{-3}$ $\Omega$-cm인 박막이 증차되었다. 또한 $Al_{2}$$O_{3}$가 2wt%이상 첨가된 경우는 모든 Al이 박막내부에서 Zn를 치환하여 전자주게로의 역할을 하지 못하고, 오히려 치환되지 못한 Al원자의 중성 불순물 산란효과에 의해 박막의 비저항이 증가하였다. 타깃의 마모영역 위에서 증착된 Al을 첨가한 ZnO 박막은 그 영역 KR에서 증착된 박막보다 높은 비저항값을 나타냈으며, 이는 큰 에너지를 가지는 산소입자의 충돌에 기인한 것으로 여겨진다.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2003.04a
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• pp.59-59
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• 2003

경사기능 재료는 위치에 따른 특성 변화를 갖고 있어 변화하는 주변 환경에서 사용되는 재료의 응용성을 높일 수 있는 장점이 있다. 적합한 경사기능 재료의 제조를 위해서는 탄성률, 강도, 인성 등의 위치에 따른 변화를 예측하는 것이 필요하다. 그러나 재료 내에서의 탄성률 변화 등으로 인해 경사기능 재료에서 인성을 정량적으로 표현하는데는 어려움이 있으므로 이를 정량적으로 측정하고, R-curve를 결정하는 것은 재료의 응용성에 중요한 인자가 된다. 본 연구에서는 폴리우레탄 스폰지를 이용하여 밀도의 분포가 연속적으로 다른 폴리 우레탄 스폰지를 제조하고 이에 알루미나 분말 슬러리를 이용하여 slip casting을 행하였다. 그 후 폴리 우레탄 스폰지를 탈지한 후 알루미나 성형체를 소결하여 연속적인 기공률 분포가 다른 다공성 알루미나를 제조하였으며, 이에 Al을 용침하여 $Al_2O_3-Al$ 경사기능 재료를 제조하였다. 이러한 $Al_2O_3-Al$ 경사기능 재료에 대해 파괴인성 및 R-curve 특성을 CT(conpact tension)시편으로 측정하였으며, 이를 균일한 복합체의 파괴인성과 비교하였다. 또한 잔류 응력 특성을 파악하기 위해 실험적이 응력 데이터를 Moire interferometry를 이용하여 결정하였다. 또한 이를 유한요서 해석법(FEM)에 의한 계산치와 비교하였다. 서로 다른 조성 분포를 갖는 $Al_2O_3-Al$ 경사기능 재료와 균일한 복합체의 파괴인성을 비교한 결과 동일한 Al조성에서도 서로 다른 파괴 인성치가 나타났다. $Al_2O_3-Al$ 경사기능 재료에서 파괴인성에 영향을 줄 수 있는 인자로는 술수한 $Al_2O_3$의 파괴인성에 Al금속의 소성변형에 의한 인성증진 효과, 그리고 경사기능 재료에서 상호 조성차이에 따른 잔류응력을 고려할 수 있을 것이다. 이중 $Al_2O_3-Al$ 경사기능 재료의 파괴인성에 미치는 잔류응력의 영향을 고려하기 위해 이의 잔류응력에 대해 실험에 의한 유추된 잔류응력과 FEM계산에 의해 유추된 잔류 응력을 비교, 분석하였다.

• Journal of the Korean Ceramic Society
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• v.20 no.1
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• pp.37-42
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• 1983

An attempt was made to derive a possible synthetic mechanism of Fluoro-phlogopite (Mica, 4Mg.$Al_2O_3$.$6SiO_2$.$K_2O$.$2MgF_2$) The pevention of fluorine vaporization turned out to be the key in the synthesis of Mica in question.l Consequently the quinary system of Mica was seperately synthesized ; frist 4MgO.$Al_2O_3-6SiO_2$(ternary system) was sintered at 135$0^{\circ}C$ and $K_2O$ and $MgF_2$ were added and second 4MgO.$Al_2O_3-6SiO_2$.$K_2O$ (quarternary system) was heat-treated at 135$0^{\circ}C$ and $MgF_2$ was added. The ternary system resulted in Proto-enstatite Cordierite and Spinel phases while Forsterite and Leucite were shown in the quarternay system . In both methods Fluoro-phlogopite was systhesized but the solid state reactions to form Mica from the ternary system and the quarternary system were different. High temperature reactions in the formation of Mica were investigated employing XRD, DTA and SEM The study of the synthesis of Mica indirectly suggested a method of phase analysis of quinary system(MgO-$Al_2O_3-SiO_2-K_2O-MgF_2$) and quarternary system(MgO-$Al_2O_3-SiO_2-K_2O-MgF_2$) at various temperatures.

• Journal of the Korean Ceramic Society
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• v.35 no.2
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• pp.129-136
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• 1998

The effects of MgO on the resistance to corrosion and oxidation of Al2O3-SiC-C refractory have been in-vestigated. The resistance to oxidation was improved as the amount of MgO increased. The resistance to corrosion was enhanced until 2 wt% MgO content but degraded over that content. From the dependence of temperatuer on the oxidation resistance oxidation was suppressed by the microstructural densification caused by spinel formation over 1200~130$0^{\circ}C$and the formation MgO-Al2O3-SiO2 liguid-phase over 130$0^{\circ}C$ The weight loss of specimens containing MgO with various purity at range of 95 to 99% and par-ticle size of -0.045 mm to -0.074 mm was examined. The oxidation resistance was not changed signficantly with the particle size and purity of MgO powders.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.145-156
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• 1997

ZrO2 phase transformations depending on the type and amount of dopants and the sintering temperatures were studied for the 2 components (CaO-, Y2O3-, MgO-ZrO2) and the 3 components(MgO-ZrO2-Al2O3)ZrO2 powder by X-ray diffraction and Raman spectroscopy. In the CaO- and Y2O3-ZrO2 systems, as the CaO and Y2O3 contents increased to 6~15mol% and 3~15mol% respectively, we were not able to identify between tetragonal and cubic in the X-ray diffraction patterns. On the other hand, all Raman modes shifted to lower wavenumbers, decreasing in intensity and the number of bands, markedly. These phenomena were caused by tetragonallongrightarrowcubic phase transformation and interpreted by the breakdown of the wave vector selection rule(k=0) and the structural disorder associated with the formation of oxygen sublattice which was caused by the substitution between Zr4+ ion and Ca2+ or Y3+ ion in ZrO2 matrix. The monoclinic to cubic phase transformation occurred in 10mol% MgO-ZrO2 system. As the Al2O3 content increased from 0 to 20mol% in the MgO-ZrO2-Al2O3 systems, cubic phase transformed to monoclinic phase, this is because the MgO didn't play a role in a stabilizer because of the formation of the spinel(MgAl2O4) by the reaction between MgO and Al2O3, Also, the ZrO2 phase transformation was explained by the change of it's lattice parameters depending on the type and amount of dopants. Namely, as the amount of dopant increased to 10~13mol%, the axial ra-tio c/a came close to unity with increasing the lattice parameter a and decreasing the lattice parameter c. At that time, the tetragonallongrightarrowcubic phase transformation occurred.

• Journal of the Korean Ceramic Society
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• v.28 no.6
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• pp.465-470
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• 1991

AlN powder was synthesized by carbothermal reduction and nitridation of aluminum hydroxides precipitated in 5∼11 pH range from Al2(SO4)3$.$18H2O aqueous solution. Nitridation reactivity of hydroxide, which depends on precipitation pH, reaction temperature and time, was examined by XRD analysis at 1200∼1350$^{\circ}C$ and compared with that of commercial ${\alpha}$-Al2O3. Hydroxides obtained at higher pH could be more easily nitridated and, considering DTA/TG and BET results, the reason seems to be specific surface area difference of reactants depending on the content of decomposed structural water and the transition rate from transition-Al2O3 to ${\alpha}$-Al2O3.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.4
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• pp.341-349
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• 2002

Electrical, mechanical and sinterability properties of yttria-stabilized zirconia doped with 5.35wt% $Y_2$O$_3$(Y$_2$O$_3$- containing stabilized zirconia : YSZ) were studied as a function of $Al_2$O$_3$, CoO, Fe$_2$O$_3$ and MnO$_2$ addition. The ratio of monoclinic phase to tetragonal phase was changed by the addition of $Al_2$O$_3$, CoO, Fe$_2$O$_3$ and MnO$_2$ to 8.00 wt% and sintered density decreased with increasing $Al_2$O$_3$, CoO, Fe$_2$O$_3$ and MnO$_2$ addition. Fracture toughness increased with the increase of monoclinic to tetragonal phase ratio and was maximum at about 18%. When transition metals such as CoO, Fe$_2$O$_3$ or MnO$_2$ was added more than 1.5 wt%, the electrical conductivity of YSZ increased. But $Al_2$O$_3$ hardly affected the electrical conductivity of YSZ. The addition of $Al_2$O$_3$, CoO, Fe$_2$O$_3$ and MnO$_2$ into YSZ resulted in the more complex behavior of fracture toughness and hardness variation and the specimen with 1.5wt%-Fe$_2$O$_3$, 3.0wt%-Al$_2$O$_3$ and 1.5wt%-CoO showed the monoclinic to tetragonal phase ratio of 18% and the highest toughness of 10.8 MPa.m$^{1}$2/ and Vickers hardness of 1201 kgf/mm$^2$.

• Journal of environmental and Sanitary engineering
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• v.15 no.1
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• pp.95-101
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• 2000

This study was investigated to the reaction of alumina sintering with alkaline. The soluble $NaAlO_2$ was made after the commercial ${\alpha}-Al_2O_3$ was calcinated with NaOH. The reaction of alumina was carried out to be based on the effects of calcination temperature, time, and the mixing ratio of ${\alpha}-Al_2O_3/NaOH$. The alumina was calcined over $500^{\circ}C$ with NaOH powder after it was sieved with 170/270 mesh. The calcined alumina with NaOH powder was dissolved into $25^{\circ}C$ distilled water and filtrated, and HCI was added to adapt pH 6.5~7.5. The residue was separated with vacuum pump for filtration after it was adapted to proper pH, and aluminum compound was precipitated with $Al(OH)_3$. The investigation was carried out with the variables; the calcination temperature($500-900^{\circ}C$), the calcination time (30~90 min), and the concentration of HCI when leaching(0.5~3.0N) respectively. In this investigation, the main product of ${\alpha}-Al_2O_3$ and NaOH was $NaAlO_2$ and the maximum conversion ratio was 91.4% under the optimum conditions as followed ; the ratio of NaOH/${\alpha}-Al_2O_3$ was 1.5 and the calcination conditions were $800^{\circ}C$ and 90 min.