• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.3
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• pp.147-152
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• 2007

This study investigates the aging characteristics of NOx storage and reduction(NSR) catalyst on the emission conditions of lean burn natural gas vehicles. We designed various NSR catalysts using by the double-layer washcoat technology to increase of a surface area and a thermal durability performance of the catalysts. The experiments were conducted with 3 kinds of the NSR catalysts, which were manufactured using by a honeycomb cordierite substrate. It was found that Ba is weak in the thermal aging because it has lower melting temperature than that of precious metals (PMs). The suitable loading amount of Ba in this study should be about 42 g/L from the results of the NOx adsorption and the NOx reduction efficiency. The major reason in deactivation of the NSR catalyst is the decrease of the adsorption site owing to the agglomeration and sintering of Ba rather than PM aging by hydrothermal aging. It was confirmed by results of BET, SEM and TEM.

• Journal of Surface Science and Engineering
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• v.51 no.5
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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.

• Membrane Journal
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• v.34 no.3
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• pp.163-171
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• 2024

Growing demand on clean energy to control environmental pollution is growing rapidly. Rechargeable battery such as lithium ion battery is excellent source of clean energy but there is rapid depletion of lithium metal due to high demand and supply mismatch. Recovery of the precious metal from the battery waste is one of the possible solution along with the environmental pollution control. Membrane based separation method is highly successful commercial process available to recover lithium from the waste. This work will cover various methods reported recently and will be compiled in the form of a review.

• Journal of Environmental Science International
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• v.20 no.2
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• pp.251-260
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• 2011

$TiO_2$- and $SiO_2$-supported $Co_3O_4$, Pt and $Co_3O_4$-Pt catalysts have been studied for CO and $C_3H_8$ oxidations at temperatures less than $250^{\circ}C$ which is a lower limit of light-off temperatures to oxidize them during emission test cycles of gasoline-fueled automotives with TWCs (three-way catalytic converters) consisting mainly of Pt, Pd and Rh. All the catalysts after appropriate activation such as calcination at $350^{\circ}C$ and reduction at $400^{\circ}C$ exhibited significant dependence on both their preparation techniques and supports upon CO oxidation at chosen temperatures. A Pt/$TiO_2$ catalyst prepared by using an ion-exchange method (IE) has much better activity for such CO oxidation because of smaller Pt nanoparticles, compared to a supported Pt obtained via an incipient wetness (IW). Supported $Co_3O_4$-only catalysts are very active for CO oxidation even at $100^{\circ}C$, but the use of $TiO_2$ as a support and the IW technique give the best performances. These effects on supports and preparation methods were indicated for $Co_3O_4$-Pt catalysts. Based on activity profiles of CO oxidation at $100^{\circ}C$ over a physical mixture of supported Pt and $Co_3O_4$ after activation under different conditions, and typical light-off temperatures of CO and unburned hydrocarbons in common TWCs as tested for $C_3H_8$ oxidation at $250^{\circ}C$ with a Pt-exchanged $SiO_2$ catalyst, this study may offer an useful approach to substitute $Co_3O_4$ for a part of platinum group metals, particularly Pt, thereby lowering the usage of the precious metals.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.8
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• pp.714-721
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• 2016

This paper proposes a simple process to fabricate tin and brass metal discs with a large surface area from molten droplets for the wet-refining process of nonferrous metals by assuming they have precious metal elements. To optimize the droplet condition in a graphite crucible, the appropriate nozzle size was determined using a simulation program (STAR-CCM+) by varying the diameters (0.5, 1.0, and 2.0 mm). The simulation results showed that both tin and brass do not fall out with a 0.5 mm diameter nozzle but they do fall out in continuous ribbon mode with a 2.0 mm nozzle. Only the 1.0mm nozzle was expected to fabricate droplets. Finally, solidified metal discs were fabricated successfully with the 1.0 mm nozzle within 10 minutes by impacting the droplets with a cooling water flowing over a Ti plate placed at the $40^{\circ}$ falling direction. The weight, average thickness, and surface area of the tin discs were 0.15 g, $107.8{\mu}m$, and $3.71cm^2$, respectively. The brass discs were 1.16 g, $129.15{\mu}m$, and $23.98cm^2$, respectively. The surface area of the tin and brass disc were 8.2 and 17.6 times the size of the tin and brass droplets, respectively. This process for precious metal extraction is expected to save cost and time.

• Resources Recycling
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• v.27 no.6
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• pp.23-29
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• 2018

Recently rapid economic growth and technological development have led to an increase in the generation of waste electrical and electronic equipment (WEEE). As the amount of electric and electronic waste generated increases, the importance of processing waste printed circuit boards (PCB) is also increasing. Various studies have been conducted to recycle various valuable metals contained in a waste PCB in an environmentally friendly and economical manner. To get anode slime containing Ag and Au, Anode copper prepared from PCB scraps was used by means of electro-refining. Ag and Au recovery was conducted by leaching, direct reduction, and ion exchange method. In the case of silver, the anode slime was leached at 3 M $HNO_3$, 100 g/L, $70^{\circ}C$, and Ag was recovered by precipitation, alkali dissolution, and reduction method. In the case of gold, the nitrate leaching residues of the anode slime was leached at 25% aqua regia, 200 g/L, $70^{\circ}C$, and Au was recovered by pH adjustment, ion exchange resin adsorption, desorption and reduction method. The purity of the obtained Au and Ag were confirmed to be 99.99%.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.1
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• pp.1-6
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• 2006

Previous to do business computerization of industry field, it isn't efficient for write down all account book. Recently many companies competitive is raised from competence improvement for a task and cost-cutting for electronic data processing system. Moreover, sudden increase of internet-user need effective management information system and share information because of network connection. Accordingly, it needs to get out of text base information system from multimedia base system and it need to introduce E-catalog system of merchandise information. In addition, it is required technological development and merchandising with movement, real time omnipresent. carrying. In this paper, established portable B2B system with movement of precious metals and jewels field's portable terminal from mobile technology.

• Journal of Korean Society for Atmospheric Environment
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• v.13 no.6
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• pp.487-495
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• 1997

The most desirable diesel oxidation catalyst (DOC) should have the properties of oxidizing CO, HC and SOF effectively at low exhaust gas temperature while minimizing the formation of sulfate at high exhaust gas temperature. Precious metals such as platinum and palladium have been known to be sufficiently active for oxidizing SOF and also to have high activity for the oxidation of sulfur dioxide $(SO_2)$ to sulfur trioxide $(SO_3)$. There is a need to develop a highly selective catalyst which can promote the oxidation SOF efficiently, on the other hand, suppress the oxidation of $SO_2$. In this study, a Pt-V catalyst was prepared by impregnating platinum and vanadium onto a Ti-Si wash coated ceramic monolith substrate. A prepared Pt-V catalytic converter was installed on a heavy duty diesel engine and the effect of fuel sulfur on particulate matter (PM) of heavy duty diesel engine was measured. The effect of fuel sulfur on PM of Pt-V was also compared with that of a commercialized Pt catalyst currently being used in some of the heavy duty diesel engines in advanced countries. Only 1 $\sim$ 3% of sulfur in the diesel fuel was converted to sulfate in PM for the engine without catalyst, but almost 100% of sulfur conversion was achieved for the engine with Pt catalyst at maximum loading condition. In the case of Pt-V catalyst, there was no big difference in conversion with the base engine even at maximum loading condition. The reason of SOF increase according to the increase of suflate emission was identified as the washing off effect of bound water in sulfate.

• The Research Journal of the Costume Culture
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• v.7 no.2
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• pp.230-241
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• 1999

The purpose of this study is to classify frequency of advertisement and types of advertisement by items and to analyze a primary factors were factors were reflected in the costumes by a policy of rule under the Japanese rule. Data was MaIl Shin Bo\`s advertisement connected with costumes from 1910 to 1945 years. The results are as follows : 1. The order of the advertisement\`s frequency was footwear, cosmetics, soap[, headgear, western style clothes, precious metals and so on. 2. The type of the advertisement was a format that transmits informs in all items. Cosmetics, hairdye and shampoo applied positive appeals. 3. In the military government, the advertisement\`s frequency connected with costumes was 37.5% and a shoe store was the first order. A shoes and headgear were high level, because of these were essential imports and were allowded as a proper articles for a western style clothes by a civilized policy. In the political periods of civilization, the advertisement\`s frequency connected with costumes was 54%. This result indicates industrial development of this period. Soap was the first order during 1924∼1933 and cosmetics was the first order during 1934∼1940. High level of the advertisement\`s frequency in these imports were reflected by a cultural policy as a link of an appeasement measure In the political periods of a racial liquidation, the advertisement\`s frequency connected with costumes was 8.5% and the advertisement\`s order by items was cosmetics, a shoe store. The reason was that reflected the phases of the times that was serious by a shortage of goods and an reinforcement of wartime\`s attitudes throughout war.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.2 no.2
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• pp.7-10
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• 2001

Recently, most jewelry design employ multiple prongs that grasp the front surface of the jewel to the metal frame To keep up with recent trends in fashion. jewelry manufacturers need to produce single-prong neckalces and earings constructed with non-precious metals. In responce to this demand, Ameth Development Division and The University of Seoul researched jointly and developed a technique for setting the jewel safely using a single prong with less weight. The setting process consists of making a small trench through the jewel at the mounting point and using a low melting point tin solder, to fill the trench and bonding with the prong. The application or this technology in the setting of a natural amethyst to a single 18K gold prong resulted in a 40% reduction in cost and weight and improvement of feeling for wearing.