• Membrane Journal
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• 제27권3호
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• pp.263-272
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• 2017

There are several different methods to characterize membrane pore size distribution, however, it is yet difficult to accurately measure pore size range of 10-50 nm. In this work, we employed gas-liquid displacement porometer (GLDP) and liquid-liquid displacement porometer (LLDP) to characterize in-house alumina hollow fiber membrane (K-100) and commercial membranes (A-100, A-20) that exhibit pore sizes between 10-100 nm. GLDP method was more suitable for measuring the maximum pore size, and the measured mean pore size of the membranes by LLDP were better correlated with water permeability and solute rejection. It was determined that LLDP is effective for measuring pore sizes between 10-50 nm; however, the method holds intrinsic disadvantages such as low precision and high sensitivity compared to that of GLDP. Nevertheless, it is expected that the recently commercialized LLDP technique can provide useful data that other methods cannot.

• Applied Chemistry for Engineering
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• 제20권4호
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• pp.381-385
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• 2009

A basic objective is the preparation and surface studies of supported molten salt catalysts because molten salts can stay as the liquid phase in the range of the ordinary reaction temperature. Many kinds of metal salt mixtures for the formation of molten salt phase are appliable but CuCl and KCl were selected in this study because Cu is considered catalytically reactive in many reactons. The loading of the molten salt was selected as 25 vol% of the total pore volume of ${\gamma}-alumina$ to provide reasonable exposed surface area. The surface structure of catalysts containing molten salts in the ${\gamma}-alumina$ was studied using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). CuCl and KCl were added into the ${\gamma}-alumina$ using concentrated hydrochloric acid solution by the impregnation technique. The surfaces of the prepared catalysts before and after heat treatments were compared and they suggested that the heat treatment of catalysts helped the formation of molten-salt although the surface compositions of CuCl and KCl were not uniform.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제19권3호
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• pp.576-583
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• 2018

Silicon carbide is considered to be a potentially useful material for high-temperature electronic devices, as its band gap is larger than that of silicon and the p-type and/or n-type conduction can be controlled by impurity doping. Particularly, porous n-type SiC ceramics fabricated from ${\beta}-SiC$ powder have been found to show a high thermoelectric conversion efficiency in the temperature region of $800^{\circ}C$ to $1000^{\circ}C$. For the application of SiC thermoelectric semiconductors, their figure of merit is an essential parameter, and high temperature (above $800^{\circ}C$) electrodes constitute an essential element. Generally, ceramics are not wetted by most conventional braze metals,. but alloying them with reactive additives can change their interfacial chemistries and promote both wetting and bonding. If a liquid is to wet a solid surface, the energy of the liquid-solid interface must be less than that of the solid, in which case there will be a driving force for the liquid to spread over the solid surface and to enter the capillary gaps. Consequently, using Ag with a relatively low melting point, the junction of the porous SiC semiconductor-Ag and/or its alloy-SiC and/or alumina substrate was studied. Ag-20Ti-20Cu filler metal showed promise as the high temperature electrode for SiC semiconductors.

• Korean Journal of Pharmacognosy
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• 제2권1호
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• pp.39-40
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• 1971

An alkaloidal component was extracted from the root of Aconitum koreanum R. $R_{AYMOND}$ of the commercial origin. Crude extract was obtained in ca. 2% yield out of dried root with ether-methanol (10:1). White amorphous compound was precipitated out from the HCl solution upon the addition of ammonia water, and crude base was obtained by extraction of its mother liquid with chloroform. This crude base was purified by the alumina-column chromatographic method. A pure alkaloidal component(500mg) was yielded from its crude base. Its pure base comes as needle crystals melting at $250{\sim}252^{\circ}C$ (decomp.), $[\alpha]^{20}_D$ D+9.82 (methanol) and Anal. calcd. for $C_{19}H_{27}O_{8}N$.

• Ceramist
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• 제9권6호
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• pp.7-11
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• 2006

The status of structural ceramics in Japan is presented. Use of ceramics for structural components had been limited due to their brittleness, and the successful application was wear resistant parts such as thread guides and ceramic cutting tools up to around 1980. Since then, considerable work has been done for applying ceramics to mechanical parts, and automotive components made of silicon nitride were developed and commercialized in 1980s. Unfortunately, the application of silicon nitride to automotive engines is not so popular in these days. Instead, a variety of structural ceramics such as alumina, silicon carbide and zirconia have recently extended the market, and the expanded application includes vacuum process parts for manufacturing semiconductor and liquid crystal devices, refractory tubes for casting aluminum alloy, and dies for optical lens forming. In addition, cordierite honeycombs and diesel particulate filters are widely used in automobiles. In the present review, the recent application of structural ceramics to automobiles and industries in Japan is summarized.

• Bulletin of the Korean Chemical Society
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• 제30권7호
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• pp.1563-1566
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• 2009

One-dimensional aluminum nitride (AlN) nanostructures were synthesized by calcining an Al(OH)(succinate) complex, which contained a very small amount of iron as a catalyst, under a mixed gas flow of nitrogen and CO (1 vol%). The complex decomposed into a homogeneous mixture of alumina and carbon at the molecular level, resulting in the lowering of the formation temperature of the AlN nanostructures. The morphology of the nanostructures such as nanocone, nanoneedle, nanowire, and nanobamboo was controlled by varying the reaction conditions, including the reaction atmosphere, reaction temperature, duration time, and ramping rate. Iron droplets were observed on the tips of the AlN nanostructures, strongly supporting that the nanostructures grow through the vapor-liquid-solid mechanism. The variation in the morphology of the nanostructures was well explained in terms of the relationship between the diffusion rate of AlN vapor into the iron droplets and the growth rate of the nanostructures.

• Journal of ILASS-Korea
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• 제17권1호
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• pp.9-13
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• 2012

This study investigates experimentally evaporation characteristics of nanofluid droplets containing 50 nm alumina($Al_2O_3$) particles and the wettability changes on a hydrophilic glass surfaces. From the captured digital images by using a CMOS camera and a magnifying lens, we examined the effect of particle concentration on droplet evaporation rate which can be indirectly deduced from the measured droplet volumes varying with time. In particular, with the use of a digital image analysis technique, the present study measured droplet perimeters and the contact angles to study the wetting dynamics during evaporating process. In addition, we compared the measured total evaporation time with theoretically estimated values. It was found that as the volume fractions of nanofluid increased, the total evaporation time and the initial contact angles decreased, while the droplet perimeters increased.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.28-29
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• 2006

High-Speed Centrifugal Compaction Process (HCP) is a wet compacting method, in which powders are compacted under a huge centrifugal force. The HCP was well applied to small alumina specimens, but the compact easily cracked when we applied the HCP to other materials. We clarified how the cracks introduced and found that the formation of such a flow pattern was related to the Colioli's force in the centrifugal field.

• Journal of Korea Foundry Society
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• 제17권4호
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• pp.379-384
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• 1997

Al-15Cu-lMg alloys have been directionally solidified in 3mm diameter alumina tubes under the conditions of $760^{\circ}C$ of furnace temperature and 12 cm/hr of furnace moving velocity(V). By analyzing the evolution of the temperature profiles along the alloy length, the position of the solid/liquid interface, temperature gradient(G) and local growth velocity (R) were determined. These growth characteristics were compared for 6, 10, 14 cm length alloys. Steady state growth region was obtained in 15 cm length alloy, not in 6, 10 cm.

• Nuclear Engineering and Technology
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• 제52권10호
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• pp.2230-2237
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• 2020

Self-priming venturi scrubber is one of the most effective devices used to collect aerosols and soluble gas pollutants from gaseous stream during severe accident in a nuclear power plant. The present study focuses on investigation of dust particle removal efficiency of the venturi scrubber both experimentally and theoretically. Venturi scrubber captures the dust particles in tiny water droplets flowing into it. Inertial impaction is the main mechanism of particles collection in venturi scrubber. The water injected into venturi throat is in the form of jets through multiple holes present at venturi throat. In this study, aerosols removal efficiency of self-priming venturi scrubber was experimentally measured for different operating conditions. Alumina (Al₂O₃) particles with 0.4-㎛ diameter and 3950 kg/㎥ density were treated as aerosols. Removal efficiency was calculated for different gas flow rates i.e. 3-6 ㎥/h and liquid flow rates i.e. 0.009-0.025 ㎥/h. Experimental results depict that aerosols removal efficiency increases with the increase in throat velocity and liquid head. While at lower air flow rate of 3 ㎥/h, removal efficiency decreases with the increase in liquid head. A theoretical model of venturi scrubber was also employed and experimental results were compared with mathematical model. Experimental results are found to be in good agreement with theoretical results.