• 한국세라믹학회지
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• 제33권1호
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• pp.92-100
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• 1996

Amorphous alumina(AA) the precursor of ${\gamma}$-alumina for catalyst support was made in the newly designed ball filled heating column. Some properties of AA as precursor were investigated. In observation of microstruc-ture and pore structure of AA and its derivatives scanning electronic microscope(SEM) and transmission electronic microscope(TEM) were used. It was found that the width of one particle in AA was 45~60$\AA$ and the average distance among the particles ranged 9~12 $\AA$ which suggested a micropore structure. When AA was reacted with water the shape of the surface was found to be altered and acicular bioehmite was formed inside AA which contributed inproved formability. Pore distribution was evaluated for the three samples of AA ground and granulated lump and La2O3 coated alumina. Acid sites were quantitatively determined by ammonia TPD method and the effect of impurity of Na on acid sites was discussed. Water adsorption capacity was evaluated in terms of a desiccant.

• Korean Chemical Engineering Research
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• 제53권3호
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• pp.382-390
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• 2015

Poly(methyl methacrylate) (PMMA) supports and amine additives were investigated to adsorb $CO_2$. PMMA supports were fabricated by using different ratio of pore forming agents (porogen) to control the BET specific surface area, pore volume and distribution. Toluene and xylene are used for porogens. Supported amine sorbents were prepared by wet impregnation of tetraethylenepentamine (TEPA) on PMMA supports. So we could identify the effect of the pore structure of supports and the quantity of impregnated TEPA on the adsorption capacity. The increased amount of toluene as pore foaming agent resulted in the decreased average pore diameter and the increased BET surface area. Polymer supports with huge different pore distribution could be fabricated by controlling the ratio of porogen. After impregnation, the support with micropore structure is supposed the pore blocking and filling effect so that it has low $CO_2$ capacity and kinetics due to the difficulty of diffusing. Macropore structure indicates fast adsorption capacity and low influence of amine loading. In case of support with mesopore, it has high performance of adsorption capacity and kinetics. So high surface area and meso-/macro- pore structure is suitable for $CO_2$ capture.

• 대한건축학회논문집:구조계
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• 제33권12호
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• pp.63-70
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• 2017

When industrial by-products like slag and fly ash are using in concrete with cement, it improves strength and durability against external deterioration factors by densifying the structure through potential hydraulic and pozzolanic reaction. But it has been pointed out that high dependence on the quality variation and the curing condition using a admixure material for concrete. In this study, the characteristics of internal micropore structure according to curing condition were analyzed for pastes and mortar specimens under using blast furnace slag powder. As a result, the variation of compressive strength and the internal microstructure were observed according to curing conditions by binder type. Particularly, using blast furnace slag powder, decrease in compressive strength were clearly observed in indoor and carbonation curing compared with water curing. The pore structure analysis also clearly observed the decrease of the gel pore existing in the CSH hydrate layer and the increase of the capillary pore in indoor and carbonation curing compared with water curing condition.

• 펄프종이기술
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• 제29권1호
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• pp.36-42
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• 1997

비건조 화학펄프의 세포벽공 속으로 충전제의 충전을 요체로 하는 소위 섬유벽 충전기술은 제지 공정의 충전공정을 개선하는데 기여해 왔다. 섬유 세포벽 충전기술이라 함은 펄프섬유의 세포벽공에 두가지 이상의 수용성 염의 이온용액을 1차와 2차로 차례로 흡착시켜 충전제를 침착시키는 기술이다. 즉 이들 두 이온 용액의 세포벽 내에서의 화학반응에 의해 세포벽 세포벽공내에서 물에 부용의 침전을 유발케하는 공정이다. 비록 이 섬유 세포벽 충전기술이 제지공정상 비건조 화학펄프에 적용하도록 고안되었지만, 본 연 구에서는 폐지의 재활용을 위해 폐지에 이 충전기술을 시도하였다. 그 결과 무게비율로 폐지섬유의 약 5-6%와 4-5%의 CaCO$_3$와 SrCO$_3$가 각각 충전되었다. 비건조 화학펄프의 그들 값이 17-18% 와 16-18%를 나타내는 결과와 비교하여 매우 낮은 값이긴 하지만, 여전히 주목할 만한 결과로 간주되었다. 또한 이 세포벽 충전기술은 실험결과 재래의 충전방식보다 광학적 성질, 물리적 성질 및 강도적 성질이 훨씬 우수함을 보여 주었다.

• Journal of Electrochemical Science and Technology
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• 제9권3호
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• pp.163-168
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• 2018

Biomass waste-derived carbon is an attractive alternative with environmental benignity to obtain carbon material. In this study, we prepare carbon from coffee grounds as a biomass precursor using a simple, inexpensive, and environmentally friendly method through physical activation using only steam. The coffee-derived carbon, having a micropore-rich structure and a low extent of graphitization of disordered carbon, is developed and directly applied to lithium-ion battery anode material. Compared with the introduction of the Ketjenblack (KB) conducting agent (i.e., coffee-derived carbon with KB), the coffee-derived carbon itself achieves a reversible capacity of ~200 mAh/g (0.54 lithium per 6 carbons) at a current density of 100 mA/g after 100 cycles, along with excellent cycle stability. The origin of highly reversible lithium storage is attributed to the consistent diffusion-controlled intercalation/de-intercalation reaction in cycle life, which suggests that the bulk diffusion of lithium is favorable in the coffee-derived carbon itself, in the absence of a conducting agent. This study presents the preparation of carbon material through physical activation without the use of chemical activation agents and demonstrates an application of coffee-derived carbon in energy storage devices.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.74-74
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• 2018

Ti-6Al-4V alloys have been widely used as orthopedic materials because of their excellent corrosion resistance and mechanical properties. However, it does not bind directly to the bone, so it requires a surface modification. This problem can be solved by nanotube and micropore formation. Plasma electrolytic oxidation (PEO) treatment for micropore, which combines high-voltage spark and electrochemical oxidation, is a new way of forming a ceramic coating on light metals such as titanium and its alloys. This method has excellent reproducibility and can easily control the shape and size of the Ti alloy. In this study, formation of bioactive surface by PEO-treatment after $2^{nd}$ ATO technique of Ti-6Al-4V alloy was invesgated by various instrument. Nanotube oxide surface structure was formed on the surface by anodic oxidation treatment in 0.8 wt.% NaF and 1M $H_3PO_4$ electrolytes. After nanotube formation, nanotube layer was removed by ultrasonic cleaning. PEO-treatment was carried out at 280V for 3 minutes in the electrolytic solution containing the bioactive substance (Mg, Zn, Mn, Sr, and Si). The surface of Ti-6Al-4V alloy was observed by field emission scanning electron microscopy (FE-SEM, S-4800 Hitachi, Japan). An energy dispersive X-ray spectrometer (EDS, Inca program, Oxford, UK) was used to analyze the spectra of physiologically active Si, Mn, Mg, Zn, and Sr ions. The PEO film formed on the Ti-6Al-4V alloy surface was characterized using an X-ray diffractometer (TF-XRD, X'pert Philips, Netherlands). It is confirmed that bioactive ions play an essential role in the normal bone growth and metabolism of the human skeletal tissues.

• 한국분말재료학회지
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• 제4권4호
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• pp.304-309
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• 1997

The synthesis of W-l5wt%Cu nanocomposite powder by hydrogen reduction of ball milled W-Cu oxide mixture was investigated in terms of powder characteristics such as particle size, mixing homogeneity and micropore structure. It is found that the micropores in the ball milled oxide (2-50 nm in size) act as an effective removal path of water vapor, followed by the formation of dry atmosphere at reaction zone. Such thermodynamic condition enhances the nucleation of W phase but suppresses the growth process, being in favor of the formation of W nanoparticles (about 21 nm in size). In addition, the superior mixing homogeneity of starting oxide mixture turned out to Play a significant role for forming extraordinary chemical homogeneity of W-l5wt%Cu nanocomposite powder.

• Macromolecular Research
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• 제10권2호
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• pp.127-134
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• 2002

Microporous polypropylene hollow fiber membrane was fabricated from isotactic polypropylene-soybean oil system by melt spinning process. Addition of nucleating agent accelerated the crystallization rate and elevated the crystallization temperature. Nucleating agent increased the number of nuclei and spherulites, which offered more inter-spherulitic amorphous sites for stretching. Benzoic acid, adipic acid, and dibenzylidene sorbitol were selected as nucleating agents, and their characteristics and effects were investigated by thermal and optical analyses. Spherulite growth and micropore formation characteristics were correlated with the kind of nucleating agent. Benzoic acid and adipic acid showed the remarkable nucleating effect, while dibenzylidene sorbitol was less effective than those. Nucleating agents also helped the sample have uniform microporous structure. Increase of nucleating agent composition enhanced the nucleation effect to some extent. Nucleating agents played very important roles in enhancing the membrane porosity and water flux.

• 한국분말재료학회지
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• 제16권1호
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• pp.22-27
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• 2009

To improve the filtration efficiency of porous materials used in filters, an extensive specific surface area is required to serve as a site for adsorption of impurities. In this paper, a method for creating a hybridized porous alloy using a powder metallurgical technique to build macropores in an Al-4 wt.% Cu alloy and subsequent surface modification for a microporous surface with a considerably increased specific surface area is suggested. The macropore structure was controlled by granulation, compacting pressure, and sintering; the micropore structure was obtained by a surface modification using a dilute NaOH solution. The specific surface area of surface-modified specimen increased about 10 times compare to as-sintered specimen that comprised of the macropore structure. Also, the surface-modified specimens showed a remarkable increase in micropores larger than 10 nm. Such a hybridized porous structure has potential for application in water and air purification filters, as well as membrane pre-treatment and catalysis.

• 대한토목학회논문집
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• 제14권5호
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• pp.1081-1089
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• 1994

최근에 폴리프로필렌 섬유를 첨가하여 콘크리트의 인성을 증가시키고, 균열에 대한 저항성을 향상시키고자 하는 노력이 경주되어 왔다. 그러나 첨가된 섬유의 작동 구조에 대한 이해 부족으로 인하여 연구자들 간에 실험 결과에 대한 해석이 상이한 경우가 많았다. 섬유의 첨가에 따른 콘크리트 물성의 변화는 콘크리트의 미세 공극구조의 변화가 외부적으로 관측된 것이기 때문에 본 연구에서는 주로 투수성 실험과 공극분포 측정 등을 통한 공극구조의 변화를 분석하여 섬유의 첨가로 인한 콘크리트의 물성 변화가 발생하는 메카니즘에 대하여 분석하였다. 분석결과, 섬유의 첨가는 수분의 이동을 촉진하는 통로를 제공하며, 이에따라 건조수축을 증가시키고 공극의 크기를 증가시키는 효과를 나타내고 있으며, 섬유의 주변에 형성된 공극의 크기는 $0.05{\mu}m$에서 $5.0{\mu}m$ 사이에 분포되어 있음이 관측되었다.