• Bulletin of the Korean Chemical Society
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• 제31권1호
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• pp.100-103
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• 2010

In this study, NO reduction behaviors of copper-loaded mesoporous molecular sieves (Cu/MCM-41) have been investigated. The Cu loading on MCM-41 surfaces was accomplished by a chemical reduction method with different Cu contents (5, 10, 20, and 40%). $N_2/77$ K adsorption isotherm characteristics, including the specific surface area and pore volume, were studied by BET's equation. NO reduction behaviors were confirmed by a gas chromatography. From the experimental results, the Cu loading amount on MCM-41 led to the increase of NO reduction efficiency in spite of decreasing the specific surface area of catalysts. This result indicates that highly ordered porous structure in the MCM-41 and the presence of active metal particles lead the synergistical NO reduction reactions due to the increase in adsorption energy of MCM-41 surfaces by the Cu particles.

• 한국표면공학회지
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• 제51권5호
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• pp.332-336
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• 2018

Alkaline oxygen electrocatalysis, targeting anion exchange membrane alkaline-based metal-air batteries has become a subject of intensive investigation because of its advantages compared to its acidic counterparts in reaction kinetics and materials stability. However, significant breakthroughs in the design and synthesis of efficient oxygen reduction catalysts from earth-abundant elements instead of precious metals in alkaline media still remain in high demand. One of the most inexpensive alternatives is carbonaceous materials, which have attracted extensive attention either as catalyst supports or as metal-free cathode catalysts for oxygen reduction. Also, carbon composite materials have been recognized as the most promising because of their reasonable balance between catalytic activity, durability, and cost. In particular, heteroatom (e.g., N, B, S or P) doping on carbon materials can tune the electronic and geometric properties of carbon, providing more active sites and enhancing the interaction between carbon structure and active sites. Here, we focused on boron and nitrogen doped nanocarbon composit (BNC nanocarbon) catalysts synthesized by a solution plasma process using the simple precursor of pyridine and boric acid without further annealing process. Additionally, guidance for rational design and synthesis of alkaline ORR catalysts with improved activity is also presented.

• 공업화학
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• 제10권8호
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• pp.1161-1168
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• 1999

3주기 전이금속(Cr~Zn)의 산화물 및 V, Mo, W의 산화물에 대하여 temperature-programmed reduction/trmperature-programmed oxidation(TPR/TPO) 실험을 통하여 그 산화-환원 특성을 조사하였다. TPO 곡선의 산화피크는 TPR 곡선의 환원피크와 비슷하거나 약간 낮은 온도에서 나타났으며, 환원피크에 비하여 온도 폭이 넓었다. 3주기 전이금속한화물의 산화 및 환원 과정의 활성화에너지는 33~149 kJ/mol 범위에 있는 반면, V, Mo, W 산화물에서는 더 컸다. 금속산화물의 산화 및 환원 과정의 활성화에너지 변화는 금속-산소 결합세기에 비례하였다. 환원(TPR) 및 산화(TPO) 과정에 대한 활성화에너지 차이(${\Delta}E_a$)가 작을수록 o-자일렌 산화반응에서 금속산화물 촉매의 활성화에너지도 작았다. 금속한화물 촉매에서 o-자일렌 산화반응은 금속산화물 표면의 산화-환원 과정을 반복하는 Mars-van Krevelen 반응 메카니즘으로 설명될 수 있음을 확인하였다.

• 한국생산제조학회지
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• 제26권4호
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• pp.430-435
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• 2017

The effect of the surface profile on CFRP and aluminum metal bonding was studied. A small number of steps were made on the aluminum surface, and the shear stress and elongation were measured using a shear test after bonding with an autoclave method. As the number of surface steps increased, the shear stress and elongation increased. The surface bonding strength increased because of the effect of the mechanical and chemical bonding. When the number of effective stages was exceeded, the shear strength decreased again due to the aspect ratio of the step and the reduction of the penetration effect of the resin into the groove.

• 한국정밀공학회지
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• 제26권5호
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• pp.57-63
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• 2009

Interface friction in blanking dies, cold forging and extrusion of aluminum alloys is a major cause of inefficient process. This paper describes an investigation of femtosecond laser texturing for reduction of interface friction on sliding surfaces in forming process. Femtosecond direct writing technology was used to fabricate a laser micro-machined die and to create microgroove patterns with varying size and density on metal forming dies. A systematic approach to find the optimum parameters and computer simulation comparison of friction coefficients are provided to study the relation of friction coefficients and die profiles. In metal forming tests, the effectiveness of various laser-machined patterns for enhancing interface lubrication is determined.

• Design & Manufacturing
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• 제14권4호
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• pp.52-57
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• 2020

In this study attempted to prevent defects due to blow holes among defects of sand casting products. It was intended to reduce the defect rate by reducing the blow hole of the inner surface. Currently, expectations and requirements for the quality level of non-ferrous aluminum casting in the casting industry are increasing. In addition, the shape is complex and the shrinkage precision is required. Among them, the test prototype is expensive to manufacture the mold, and the production time is also long, and the product is manufactured by sand casting. At this time, the highest defect rates are defects caused by shrinkage defects, surface defects, and blow holes.. At this study, the manufacturing time was shortened by using the shape of the fluid movement path in advance. Also, it is possible to reduce defects due to blow holes.

• 한국표면공학회지
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• 제42권1호
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• pp.34-40
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• 2009

In the study, it was carried out dissimilar metal welding on materials for Al ship. The electrochemical and mechanical characteristics evaluated for specimen welded by ROBOT. The hardness of welding zone is lower than those of heat affected zone and base metal. At the result of tensile test, the specimen welded with ER5183 welding material presented excellent property compared with ER5556. The polarization trend for the base metal and welding metal showed the effects of concentration polarization due to oxygen reduction and activation polarization due to hydrogen generation. At the Tafel experiments result, the corrosion density in welded with ER5183 welding material presented the lowest value.

• Tribology and Lubricants
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• 제25권3호
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• pp.192-196
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• 2009

This paper presents the hardness and wear characteristic of bronze metals, which are manufactured by a sintering process with a high pressuring technology. A bronze metal with a high hardness and anti-wear properties is usually used for a high pressure cylinder and a pin-bush bearing. The new bronze metal in which is manufactured for this experimental study shows very high hardness of 192${\sim}$220 Hv compared with that of a conventional bronze metal of 120${\sim}$140 Hv. The high hardness of new bronze metals is strongly related to the radical reduction of wear volumes and an improved surface roughness of operated worn surfaces. As explained by previous many research works, the improved hardness of nonferrous metals may increase a load-carrying capacity and anti-wear properties of tribological components.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.1198-1201
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• 2006

Carbon nanotubes (CNTs) have used as an electron field emitter of the field emission display (FED) due to their characteristics of high-electron emission, rapid response and low power consumption. However, to commercialize the FED with CNT emitter, some fundamental problems regarding life time and emission efficiency have to be solved. In this study, we investigated the metal coated CNT as a field emitter on which metal nanoparticles were coated by chemical modification. Metal nanoparticles, such as Ru, Pd, were synthesized by solution reduction method. The size of the metal nanoparticle has the range of 2 - 5 nm. Surface was modified chemically with the use of ionic surfactant which changed the surface charge of nanoparticles.

• 한국표면공학회지
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• 제26권6호
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• pp.327-333
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• 1993

The effect of heat treatment on the adhesion between Cu-18wt% Cr film and polyimide has been studied by using T-peel test, AES, and XRD. Cu-18wt% Cr alloy and pure Cu films were sputter deposited onto pol-yimide. Cu was electroplated before and after heat treatment at $400^{\circ}C$ for 0.5 hr and 2 hrs respectively. The adhesion of metal film onto polyimide was considerably good before heat treatment, but heat treatment re-duced the peel adhesion strength in all specimens. The reduction in adhesion in adhesion strength values in the specimens which were plated after heat treatment was mainly due to Cr-O rich pahse formed in the metal/polyimide in-terface. In the specimens which were heat treated after plating, the enhanced ductility in the metal films con-tributes the peel adhesion strength by increasing the amount of deformation in metal strips.