• Korean Chemical Engineering Research
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• 제50권2호
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• pp.229-237
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• 2012

Fischer-Tropsch 합성용 Co/$Al_2O_3$ 촉매에서 알루미나 지지체에 인산 용액으로 알루미나 표면을 개질하여 촉매적 활성은 물론이고, 기계적 강도와 수열 안정성을 개선하였다. FT-IR과 같은 촉매 표면 분석법을 통하여 P 첨가로 알루미나 표면에 $AlPO_4$ 상이 생성되어 촉매인 코발트와 지지체인 알루미나 사이의 상호작용이 약화되어 촉매의 환원도가 높아졌음을 보였다. 이에 따른 촉매성능을 평가하기 위하여 $C_{5+}$ productivity와 turnover frequency를 계산하였다. 또한, 2 wt.% P 첨가 알루미나를 대상으로 지지체의 소성온도가 촉매활성에 미치는 영향도 살펴보았다. 한편, 고온 가압 하에서 물을 이용하여 P 첨가 알루미나(P-알루미나)를 지지체로 한 촉매의 수열 특성을 살펴보았으며, 실험 전후의 XRD 패턴을 분석함으로써 P 첨가 알루미나 기반 촉매가 수열 안정성이 우수하다는 것을 증명하였다. 뿐만 아니라, 촉매의 기계적 강도를 측정하기 위하여 유동화 반응기를 직접 제작하여 P-알루미나 기반 촉매의 P 함량이 증가할수록 마모도가 감소함을 확인하였다. 촉매 활성, 수열 안정성, 그리고 기계적 강도를 모두 고려하면, 알루미나에 첨가된 P의 함량이 1~2 wt.% 이고, 지지체를 $500^{\circ}C$에서 소성하여 제조한 촉매가 가장 좋은 성능을 보였다.

• 보존과학연구
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• 통권26호
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• pp.165-188
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• 2005

From the ancient to these days, there have been used many kinds of pigment which have two types that are inorganic pigment and organic pigment. At the ancient times, natural pigment had been used but the artificially mixed pigment has been used in modern times. By the way, searching for studies has been studied recently, it would be said the ancient pigments such as Danchung, Wall painting and Mural painting are the mainthema. However, studies about the pigments used in modern pictured relics have rarely can be found. Therefore, this analysis of Ilweolokdo would be important at the point of the pigments used in pictures of royal family in modern times and the results can be briefly summarized as below; Firstly, the results of qualitative analysis of the pigments that base or all pigments of picture was detected components of Ca, Fe and As, this results meaning that picture was used filler and basic paint. Secondly, a result of the analysis on the composition elements of the pigments shows that the main components in their composition are ;White - Lead Cyanamide($2PbCO_3$.$Pb(OH)_2$) or Titanium Oxide($TiO_2$)Blue - Ultramarine($2(Na_2O$.$Al_2O_3$ .$2Si_O2$).$Na_2S_2$)Green - Emerald green($C_2H_3A_s3Cu_2O_8$)Gold - Gold(Au), Red-Red Lead($Pb_3O_4$) or Cinnabar(HgS)Black - Carbon(C)Thirdly, X-ray diffraction analysis of crystalline structure for the blue and green pigment peeling off in picture shows that the components of blue pigment is Ultramarine($2(Na_2O$.$Al_2O_3$ .$2Si_O2$).$Na_2S_2$) and green pigment is Emerald green($C_2H_3A_s3Cu_2O_8$). Especially, microcrystalline structure of the green pigment was the shape like a cross section of wood. Consequently, we knew through the analysis of qualitative and microcrystallinestructures seen on the cross section of analyzed pigments layer that the all pigments used in the Ilweoloakdo is possible to use synthetic pigments in modern.

• 한국수소및신에너지학회논문집
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• 제35권2호
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• pp.152-161
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• 2024

In this study, a fuel cell system for future defense unmanned vehicles was designed and validated. A Co/Al₂O₃-Ni foam catalyst for NaBH₄ hydrolysis was characterized using several analytical methods. A NaBH₄ hydrogen generation system with the Co/Al₂O₃-Ni foam catalyst continuously generated hydrogen at elevated reaction temperatures. The fuel cell system with the NaBH₄ hydrogen generation system was designed and tested. The performance of the fuel cell system was comparable to that of the fuel cell system using pure hydrogen. Therefore, the fuel cell system with the NaBH₄ hydrogen generation system is a suitable power source for future defense unmanned vehicles owing to its easy refueling and simple system.

• Journal of Electrochemical Science and Technology
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• 제12권2호
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• pp.237-245
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• 2021

Atomic layer deposition (ALD) enhances the stability of cathode materials via surface modification. Previous studies have demonstrated that an Ni-rich cathode, such as LiNi_0.8Co_0.1Mn_0.1O₂, is a promising candidate owing to its high capacity, but is limited by poor cycle stability. In this study, to enhance the stability of the Ni-rich cathode, synthesized LiNi_0.8Co_0.1Mn_0.1O₂ was coated with Al₂O₃ using ALD. Thus, the surface-modified cathode exhibited enhanced stability by protecting the interface from Ni-O formation during the cycling process. The coated LiNi_0.8Co_0.1Mn_0.1O₂ exhibited a capacity of 176 mAh g^-1 at 1 C and retained up to 72% of the initial capacity after 100 cycles within a range of 2.8-4.3 V (vs Li/Li⁺. In contrast, pristine LiNi_0.8Co_0.1Mn_0.1O₂ presented only 58% of capacity retention after 100 cycles with an initial capacity of 173 mAh g^-1. Improved cyclability may be a result of the ALD coating, which physically protects the electrode by modifying the interface, and prevents degradation by resisting side reactions that result in capacity decay. The electrochemical impedance spectra and structural and morphological analysis performed using electron microscopy and X-ray techniques establish the surface enhancement resulting from the aforementioned strategy.

• 대한치과기공학회지
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• 제23권1호
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• pp.55-64
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• 2001

This study is focusing on the improvement of problems of Ti-6Al-4V alloy. A new Ti based alloy, Ti-15Sn-4Nb, have designed to examine any possibility of improving the mechanical properties and biocompatibility. Specimens of Ti alloys were melted in vacuum arc furnace and homogenized at $100^{\circ}C$ for 24h. All specimens were solution treated at $812^{\circ}C$ and aged at $500^{\circ}C$ for 10h. The corrosion resistance of Ti alloys was evaluated by potentiodynamic polarization test and immersion test inl%Lactic acid solutions. Ti-15Sn-4Nb system alloys showed Widmanstatten microstructure after solution treatment which is typical microstructure of ${\alpha}+{\beta}$ type Ti alloys. Analysing the corrosion resistance of Ti alloys, it was concluded that the passive films of Ti-15Sn-4Nb system alloys are more stable than that of Ti-6Al-4V alloys. Also, the corrosion resistance of Ti-15Sn-4Nb system alloys was improved with adding elements, Hf. It was analysed that the passive film of the Ti-15Sn-4Nb alloy which was formed in air atmosphere was consisted of TiO2, SnO and NbO through X-ray photoelectron spectroscopy(XPS) analysis.

• 자원환경지질
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• 제34권1호
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• pp.39-53
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• 2001

이 연구는 토현광산 수계의 환경오염에 관하여 지질, 광물 및 지구화학적으로 고찰한 것이다. 과안부근에 분포하는 토양과 퇴적물의 ${Al_2}{O_3}/{Na_2O}$와 ${K_2}O/{Na_2}O$의 비는 ${SiO_2}/{Al_2}{O_3}$에 대하여 부분적인 부의 상관관계를 갖는다. 또한 일부 미량 및 희토류 원소의 지구화학적 특성(V/Ni, Ni/Co, La/Ce, Th/Yb, Th/U, La/Th, ${La_N}/{Yb_N}$, Co/Th, La/Sc 및 Sc/Th)들은 비교적 좁은 범위를 보이며 균질한 조성을 갖는다. 이는 광산의 모암인 셰일의 근원암이 중성 또는 염기성 화성암에서 기원한 퇴적물이 우세하였던 것임을 지시하는 것이다. 토양과 퇴적물의 대표적인 광물종은 석영, 운모, 장석, 각섬석, 녹니석 및 점토광물 등이나, 함량비는 시료에 따라 다소 차이가 있다. 독성원소의 함량이 높은 토양과 퇴적물에서는 황철석, 유비철석, 섬아연석, 황동석, 방연석, 침철석 등의 중광물과 다양한 종류의 수산화물이 많이 산출된다. 기반암의 조성으로 표준화한 주원소의 부화지수는 퇴적물 = 1.0, 침전물 = 1.7, 밭 토양 =0.9, 논 토양 = 0.8이다. 이 광산 수계에서 검출된 중금속의 최대함량은 Ag = 186 ppm, As = 17,100 ppm, Bi = 127 ppm, Cd = 77 ppm, Cu = 12,299 ppm, Pb = 8,897 ppm, Sb = 1,350 ppm, W = 599 및 Zn = 12,250 ppm 이다. 이 독성원소들은 광폐석 야적장 주변의 퇴적물과 침전물에서 특히 높고, total FeO의 함량과 밀접한 관계가 있다. 기반암의 조성을 기준으로 이 독성원소(As, Bi, Cd, Cu, Pb, Sb, W, Zn)들의 부화지수를 구하면, 퇴적물 = 106.0, 침전물 = 279.6, 밭토양 = 3.5, 논 토양 = 1.6 이나, EPA의 기준치로 표준화된 부화지수는 각각 40.7, 121.4, 1.3 및 0.6 이다.

• 한국분말재료학회지
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• 제12권3호
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• pp.220-224
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• 2005

Boehmite (AlOOH) powder with uniform pore size and high specific surface area were synthesized via sol-gel method using metal salts, $Al_2(SO_4)_3$ and $NaAlO_2$. During these synthetic process, the effects of the aging time were investigated to determine the optimal synthetic conditions of boehmite. X-ray diffraction, BET, Raman/IR, and scanning electron microscopy techniques were used for the characterization of the powder. Boehmite gel synthesized at the first stage of the experimental procedure transformed to crystalline boehmite phase after aging for 6 hours. The specific surface area of the crystalline boehmite showed a maximum value, $350m^2/g$, at aging time of 72 hours. The pore size of the boehmite increased with increasing aging time and the boehmite with average pore diameter of 3.6 nm was obtained at aging time of 96 hours.

• Transactions on Electrical and Electronic Materials
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• 제15권4호
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• pp.213-216
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• 2014

The microstructure and varistor properties of ZPCCAE ($ZnO-Pr_6O_{11}-CoO-Cr_2O_3-Al_2O_3-Er_2O_3$) ceramics were investigated with different erbium amounts. Analysis of the microstructure indicated that the ceramics consisted of ZnO grains as a bulk phase, and intergranular layers (mixture of $Pr_6O_{11}$ and $Er_2O_3$) as a minor secondary phase. With the increase of the doped erbium amount, the densities of sintered pellets increased from 5.63 to $5.82g/cm^3$, and the average grain size decreased from 9.0 to $5.7{\mu}m$. The increase of the doped erbium amount increased the breakdown field from 2,649 to 5,074 V/cm, and the nonlinear coefficient from 27.6 to 39.1. It was found that in the range of 0.25 to 0.5 mol%, the doped erbium had little effect on the microstructure and electrical properties.

• 한국정밀공학회지
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• 제12권2호
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• pp.5-13
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• 1995

Various techniques to measure fracture toughness which is an important parameter to predict fracture behavious of structural materials have been reported. Among these mathods, this paper describes the micro-Vickers indentation crack method to estimate the fracture toughness of some WC-Co composites. Two indentation crack patterns (such as radial-median cracks (orhalf-penny cracks) and Palmqvist cracks generated during indentation) are referred precisely. The fracture toughness of WC-4.7wt%Co, WC-6wr%Co and WE-9wr%Co composites were estimated by using some equations given by Shetty et al., Nihara et al. in this study. We show the reliability of indentation method by comparing the results with those from literatures. The appropriate equation to estimate the fracture toughness in the case of WC-Co composite is given. In addition, some technical informations in terms of the crack length by indentation in estimating the existence of the surface residual stress that prevents to obtain an accurate fracture toughness are presented.

• 한국수소및신에너지학회논문집
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• 제15권4호
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• pp.274-282
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• 2004

This study focused on the development of high performance catalyst for autothermal reforming (ATR) of gasoline to produce hydrogen. The ATR was carried out over MgO/Al2O3 supported metal catalysts prepared under various experimental conditions. The catalysts before and after reaction were characterized by N2-physisorption, CO-chemisorption, SEM and XRD. The performance of supported multi-metal catalysts were better than that of supported mono-metal catalysts. Especially, it was observed that the conversion of iso-octane over prepared Ni/Fe/MgO/Al2O3 catalyst was 99.9 % comparable with commercial catalyst (ICI) and the selectivity of hydrogen over the prepared catalyst was 65% higher than ICI catalyst. Furthermore, it was identified that the sulfur tolerance of prepared catalyst was much better than ICI catalyst based on the ATR reaction of iso-octane containing sulfur of 100 ppm. Therefore, Ni/Fe/MgO/Al2O3 catalyst can be applied for a fuel reformer, hydrogen station and on-board reformer in furl cell powered vehicles.