• 한국세라믹학회지
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• 제19권4호
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• pp.287-292
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• 1982

Nonohmic properties of ZnO ceramics with various small amounts of additives were studied in relation to experimental methods, additive contant and sintaring temperature. The kinds of additives used to following chemicals were basic additives ($0.5Bi_2O_3$, $0.3BaCO_3$, $0.5MnCO_3$, $0.5Cr_2O_3$, $0.1KNO_3$), $TiO_2$ and $Al(OH)_3$. Expecially, this study has focused on the effectsof $TiO_2$ and $Al(OH)_3$ in ZnO ceramics with the basic additives. SEM studies indicated that the addition of TiO2 promoted grain growth but retarded grain growth with the addition of $Al(OH)_3$. Also, in the case of calcination of ZnO with $TiO_2$ and ZnO with $Al(OH)_3$ previously, grain size of ZnO with $TiO_2$ was larger and that of ZnO with Al(OH)3 was smaller in comparison to the case with out calcination. From the viewpoint of nonohmic exponent and nonohimic resistance, electrical characteristics of ZnO, $TiO_2$ and the basic additives was more effective than that of ZnO, $Al(OH)_3$ and the basic additives. Nonohmic exponent and nonohmic resistance of ZnO, $TiO_2$ and the basic additives was 11-13 and 40-65 respectively.

• 공업화학
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• 제4권1호
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• pp.144-152
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• 1993

${\gamma}-Al_2O_3$, ${\alpha}-Al_2O_3$, $SiO_2$, $TiO_2$등에 고정화된 폴리에틸렌글리콜을 $Fe(CO)_5$에 의한 니트로벤젠의 상온 환원반응에 상이동 촉매로 사용하였다. 고정화된 PEG의 몰수는 담체의 비표면적에 따라 증가하였고 PEG/${\gamma}-Al_2O_3$가 가장 좋은 활성을 나타내었다. PEG의 사슬길이가 길고 NaOH 농도가 높을수록 반응속도가 증가하였다. 적외선분광기를 이용하여 반응기구에 대한 고찰도 함께 실시하였으며 폴리에틸렌글리콜 상이동 촉매는 본 반응의 활성물질로 알려진 $HFe(CO)_4{^{-}}$이온의 생성과 이의 유기상으로의 이동을 촉진시키는 것으로 판단되었다.

• 공업화학
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• 제9권6호
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• pp.878-883
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• 1998

Pd-ZSM-5 촉매 상에서 메탄의 연소반응을 수행하였다. 담체는 저온상압법으로 합성한 ZSM-5를 이용하였다. 담체인 ZSM-5의 $SiO_2/Al_2O_3$ 몰비 변화에 따른 메탄의 전환율 변화를 조사해 보았다. 그리고 합성한 Pd-ZSM-5 촉매의 메탄 전환율을 상업화된 Pd-ZSM-5(PQ Co.) 및 $PdO/{\gamma}-Al_2O_3$와 비교하여 보았다. $SiO_2/Al_2O_3$ 몰비 변화에 따른 메탄의 연소반응실험 결과 $SiO_2/Al_2O_3$ 몰비가 작을수록 높은 메탄의 전환율을 보였으며, Pd을 정량화시켜 메탄의 연소속도를 비교한 결과, 역시 $SiO_2/Al_2O_3$ 몰비가 작을수록 빠르게 나타났다. 합성한 Pd-ZSM-5가 상업화된 Pd-ZSM-5(PQ Co.)보다 우수한 메탄 전환율을 나타냈다. 촉매 특성 분석 결과들로부터 메탄의 연소반응에서 촉매에 흡착하는 산소의 결합세기가 반응속도에 매우 큰 영향을 미침을 알 수 있었다.

• 한국환경과학회지
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• 제22권9호
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• pp.1097-1103
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• 2013

Tetrafluoromethane($CF_4$) have been widely used as etching and chemical vapor deposition gases for semiconductor manufacturing processes. $CF_4$ decomposition efficiency using microwave system was carried out as a function of the microwave power, the reaction temperature, and the quantity of $Al_2O_3$ addition. High reaction temperature and addition of $Al_2O_3$ increased the $CF_4$ removal efficiencies and the $CO_2/CF_4$ ratio. When the SA30 (SiC+30wt%$Al_2O_3$) and SA50 (SiC+50wt%$Al_2O_3$) were used, complete $CF_4$ removal was achieved at $1000^{\circ}C$. The $CF_4$ was reacted with $Al_2O_3$ and by-products such as $CO_2/CF_4$ and $AlF_3$ were produced. Significant amount of by-product such as $AlF_3$ was identified by X-ray powder diffraction analysis. It also showed that the ${\gamma}-Al_2O_3$ was transformed to ${\alpha}-Al_2O_3$ after microwave thermal reaction.

• 한국수소및신에너지학회논문집
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• 제21권5호
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• pp.390-397
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• 2010

0.5wt% Ru/$\alpha-Al_2O_3$ catalysts are prepared by deposition-precipitation method for the preferential CO oxidation In order to investigate the effect of pH on the Ru dispersion and particle size, the pH of precursor solution is adjusted to between 5.5 and 9.5. 0.5wt% Ru/$\alpha-Al_2O_3$ catalyst prepared at the pH of 6.5 has high Ru dispersion of 17.9% and small particle size of 7.7nm. In addition, 0.5wt% Ru/$\alpha-Al_2O_3$ catalyst prepared at the pH 6.5 is easily reduced at low temperatures below $150^{\circ}C$ due to high dispersion of $RuO_2$ particle and shows high CO conversion over 90% in the wide temperature range between $100^{\circ}C$ and $160^{\circ}C$. Moreover, the deposition-precipitation is a feasible method to improve the Ru dispersion as compared to the impregnation method. The 0.5wt% Ru/$\alpha-Al_2O_3$ catalyst prepared by deposition-precipitation exhibits higher CO conversion than 0.5wt% Ru/$\alpha-Al_2O_3$ catalysts prepared by impregnation due to higher metal dispersion and better reducibility at low temperature.

• 대한금속재료학회지
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• 제47권6호
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• pp.344-348
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• 2009

Dense $4.25Co_{0.53}Fe_{0.47}-Al_{2}O_{3}$ composite was simultaneously synthesized and consolidated by pulsed current activated combustion method within 2 min from mechanically activated powders. Consolidation was accomplished under the combined effects of a pulsed current and mechanical pressure. Dense $4.25Co_{0.53}Fe_{0.47}-Al_{2}O_{3}$ with relative density of up to 96% was produced under simultaneous application of 80 MPa pressure and the pulsed current. Fracture toughness and hardness of the composite are $6MPa{\cdot}m^{1/2}$ and $570kg/mm^{2}$ respectively.

• 청정기술
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• 제28권1호
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• pp.1-8
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• 2022

미활용 저급자원인 석유코크스를 대상으로 고순도의 수소 생산을 위한 수성가스전이반응에 적용가능성을 확인하기 위하여 Cu/ZnO/MgO/Al₂O₃ (CZMA) 촉매를 공침법을 사용하여 제조하였다. 제조된 촉매는 BET, H₂-TPR을 사용하여 분석되었다. 촉매의 반응성 테스트는 고농도의 CO를 포함하는 합성가스로부터 단일 Low Temperature Shift 반응을 거치는 경우와 High Temperature Shift 반응을 거친 후 스팀의 응축 없이 즉시 LTS 반응을 거치는 두 가지의 경우를 비교 및 분석하였다. 두 조건에서 steam/CO 비, 유량 및 유속, 온도에 따른 반응특성을 확인하였다. 전환된 저농도의 CO와 스팀이 응축 없이 LTS로 즉시 주입되는 경우 많은 양의 스팀이 존재함에도 불구하고 대부분의 조건에서 다소 낮은 CO 전환율을 나타냈다. 또한 steam/CO비, 온도 및 유속에 대한 영향이 크게 나타나 최적의 조업조건을 결정하기에 추가적인 분석이 요구되었다. 반면, 고농도의 CO 기체를 포함하는 조건에서는 탄소침적 또는 촉매의 활성 저하가 나타나지 않았으며 대부분의 조건에서 높은 CO 전환율을 나타내었다. 결론적으로 Cu/ZnO/MgO/Al₂O₃ 촉매를 적용하여 고농도의 CO를 포함하는 합성가스 조성에서 적절한 조업조건을 적용시키면 단일 LTS 반응을 적용해도 고농도의 CO를 CO₂로 충분히 전환 가능함을 확인하였다.

• 한국분말재료학회지
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• 제16권2호
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• pp.91-97
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• 2009

Nanopowders of $Co_3O_4$ and FeAl were fabricated by high energy ball milling. Dense 4.25 $Co_{0.53}Fe_{0.47}-Al_2O_3$ composite was simultaneously synthesized and consolidated by high frequency induction heated combustion method within 2 min from mechanically activated powders. Consolidation was accomplished under the combined effects of a induced current and mechanical pressure of 80 MPa.

• 한국세라믹학회지
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• 제37권8호
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• pp.817-823
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• 2000

A solid-state electrochemicall cell for sensing CO2 gas was fabricated using a solid electrolyte of Li2CO3-Li3PO4-Al2O3 mixture and a reference electrode of LiMn2O4. The e.m.f. (electromotive force) of sensor showed a good accordance with theoretical Nernst slope (n=2) for CO2 gas concentration range of 100-10000 ppm above 35$0^{\circ}C$. The e.m.f. of sensor was constant regardless of oxygen partial pressure at the high temperature above 0.1 atm. It was, however, a little depended on oxygen partial pressure as the pressure decreased below 0.1 atm. The oxygen-dependency of our sensor gradually disappeared as the operating temperature increased. The sensing behavior of our CO2 sensor was affected by the presence of water vapor, but its effect was small comparing with other sensors.

• 한국재료학회지
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• 제24권7호
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• pp.370-374
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• 2014

Inorganic pigments have high thermal stability and chemical resistance at high temperature. For these reasons, they are used in clay, paints, plastic, polymers, colored glass and ceramics. $CoAl_2O_4$ nano-powder was synthesized by reverse-micelle processing the mixed precursor(consisting of $Co(NO_3)_2$ and $Al(NO_3)_3$). The $CoAl_2O_4$ was prepared by mixing an aqueous solution at a Co:Al molar ratio of 1:2. The average particle size, and the particle-size distribution, of the powders synthesized by heat treatment (at 900; 1,000; 1,100; and $1,200^{\circ}C$ for 2h) were in the range of 10-20 nm and narrow, respectively. The average size of the synthesized nano-particles increased with increasing water-to-surfactant molar ratio. The synthesized $CoAl_2O_4$ powders were characterized by X-ray diffraction analysis(XRD), field-emission scanning electron microscopy(FE-SEM) and color spectrophotometry. The intensity of X-ray diffraction of the synthesized $CoAl_2O_4$ powder, increased with increasing heating temperature. As the heating temperature increased, crystal-size of the synthesized powder particles increased. As the R-value(water/surfactant) and heating temperature increased, the color of the inorganic pigments changed from dark blue-green to cerulean blue.