• Title, Summary, Keyword: pore forming agent

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Fabrication of Porous Alumina Ceramics Using Hollow Microspheres as the Pore-forming Agent

  • Nie, Zhengwei;Lin, Yuyi
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.24 no.4
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    • pp.368-373
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    • 2015
  • Porous alumina ceramics with two different pore sizes were fabricated using hollow microspheres as the pore-forming agent. The relative density, total porosity, and microstructure of the obtained alumina ceramics were studied. It was found that the total porosity of sintered samples with different amounts of hollow microsphere content, from 2.0 to 4.0 wt%, was 69.3-75.6%. The interconnected and spherical cell morphology was obtained with 3.0 wt% hollow microsphere content. The resulting ceramics consist of a hierarchical structure with large-sized cells, and small-sized pores in the cell walls. Moreover, the compressive strength of the sintered samples varied from 8.3-11.5 MPa, corresponding to hollow microsphere contents of 2.0-4.0 wt%.

Preparation and Characterization of Chemically Stable PVDF-HFP Asymmetric Microfiltration (MF) Membranes

  • Lee, Yeon-Ee;JeGal, Jong-Geon
    • Membrane Journal
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    • v.22 no.2
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    • pp.104-112
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    • 2012
  • Chemically stable Polyvinylidene fluoride-hexa-fluoropropane (PVDF-HFP) copolymer asymmetric membranes were prepared by the conventional phase inversion process, using Dimethyacetamide (DMAc) as a solvent and water as a non-solvent. To control the pore size and porosity of the PVDF-HFP membranes, tetra-ethoxysilane (TEOS) was used as a pore-forming agent. The prepared membranes were characterized, using several analytical methods such as Fourier Transform Infrared spectroscopy (FTIR), Thermo-gravimetric analyzer (TGA), Field Emission Scanning Electronic Microscopy (FESEM). TEOS turned out to increase porosity and make homogeneous pores on the membranes. Depending on the composition of the dope solutions, the pore size was ranged from 0.1 to 1.0 ${\mu}m$. The flux of the PVDF-HFP membranes prepared by using TEOS as a pore forming agent was increased substantially without much decrease in the rejection. When 15 wt% PVDF-HFP solution was blended with 13 wt% TEOS solution at composition ratio of 70/30 in wt%, the water flux at 2 bars was about 2 $m^3/m^2day$.

Fabrication and Characterization of Porous Non-Woven Carbon Based Highly Sensitive Gas Sensors Derived by Magnesium Oxide

  • Kim, Yesol;Cho, Seho;Lee, Sungho;Lee, Young-Seak
    • Carbon letters
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    • v.13 no.4
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    • pp.254-259
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    • 2012
  • Nanoporous non-woven carbon fibers for a gas sensor were prepared from a pitch/polyacrylonitrile (PAN) mixed solution through an electrospinning process and their gas-sensing properties were investigated. In order to create nanoscale pores, magnesium oxide (MgO) powders were added as a pore-forming agent during the mixing of these carbon precursors. The prepared nanoporous carbon fibers derived from the MgO pore-forming agent were characterized by scanning electron microscopy (SEM), $N_2$-adsorption isotherms, and a gas-sensing analysis. The SEM images showed that the MgO powders affected the viscosity of the pitch/PAN solution, which led to the production of beaded fibers. The specific surface area of carbon fibers increased from 2.0 to $763.2m^2/g$ when using this method. The template method therefore improved the porous structure, which allows for more efficient gas adsorption. The sensing ability and the response time for the NO gas adsorption were improved by the increased surface area and micropore fraction. In conclusion, the carbon fibers with high micropore fractions created through the use of MgO as a pore-forming agent exhibited improved NO gas sensitivity.

Fabrication of Porous W by Heat Treatment of Pore Forming Agent of PMMA and WO3 Powder Compacts (기공형성제 PMMA와 WO3 분말 성형체의 열처리를 이용한 W 다공체 제조)

  • Jeon, Ki Cheol;Kim, Young Do;Suk, Myung-Jin;Oh, Sung-Tag
    • Journal of Korean Powder Metallurgy Institute
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    • v.22 no.2
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    • pp.129-133
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    • 2015
  • Porous W with controlled pore structure was fabricated by thermal decomposition and hydrogen reduction process of PMMA beads and $WO_3$ powder compacts. The PMMA sizes of 8 and $50{\mu}m$ were used as pore forming agent for fabricating the porous W. The $WO_3$ powder compacts with 20 and 70 vol% PMMA were prepared by uniaxial pressing and sintered for 2 h at $1200^{\circ}C$ in hydrogen atmosphere. TGA analysis revealed that the PMMA was decomposed at about $400^{\circ}C$ and $WO_3$ was reduced to metallic W at $800^{\circ}C$. Large pores in the sintered specimens were formed by thermal decomposition of spherical PMMA, and their size was increased with increase in PMMA size and the amount of PMMA addition. Also the pore shape was changed from spherical to irregular form with increasing PMMA contents due to the agglomeration of PMMA in the powder mixing process.

Electrochemical Properties of Carbonized Phenol Resin (탄화된 페놀레진의 전기화학적 성질)

  • 김한주;박종은;홍지숙;류부형;박수길
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.629-632
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    • 1999
  • For replacing Li metal ai Lithium ton Bakery(LIB) system. we used carbon powder material which prepared by pyrolysis of phenol resin as starting material. It became amorphous carbon by pyrolysis through it\`s self condensation by thermal treatment. Amorphous carbon can be doped with Li intercalation and deintercalation because it has wide interlayer. however it has a problem with structural destroy causing weak carbon-carbon bond. So. we used ZnCl$_2$ as the pore-forming agent. This inorganic salt used together with the resin serves not only as the pore-forming agent to form open pores, which grow Into a three-dimensional network structure in the cured material, foul also as the microstructure-controlling agent to form a loose structure dope with bulky dopants. We analyzed SEM in order to find to different of structure. and can calculate distance of interlayer. CV test showed oxidation and reduction

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Preparation of Spherical Granules of Dolomite Kiln Dust as Gas Adsorbent

  • Choi, Young-Hoon;Huh, Jae-Hoon;Lee, Shin-Haeng;Han, Choon;Ahn, Ji-Whan
    • Journal of the Korean Ceramic Society
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    • v.53 no.1
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    • pp.13-17
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    • 2016
  • It is highlighted that increasing the adsorbent surface area on volumetric basis is very important in providing an easy access for gas molecules. Fine particles around $3{\mu}m$ of soft-burned dolomite kiln dust (SB-DKD) were hydrated to wet slurry samples by ball mill process and then placed in a chamber to use spray dryer method. Spherical granules with particle size distribution of $50{\sim}60{\mu}m$ were prepared under the experimental condition with or without addition of a pore-forming agent. The relationship between bead size of the pore-forming agent and size of SB-DKD particles is the most significant factor in preparation of spherical granules with a high porosity. Whereas addition of smaller beads than SB-DKD resulted in almost no change in the surface porosity of spherical granules, addition of larger beads than SB-DKD contributed to obtaining of the particles with both 15 times larger average pore volume and 1 order of magnitude larger porosity. It is considered that spherical granules with improved $N_2$ gas adsorption ability may also be utilized for other atmospheric gas adsorption.

Viscosity Study to Optimize a Slurry of Alumina Mixed with Hollow Microspheres

  • Bukhari, Syed Zaighum Abbas;Ha, Jang-Hoon;Lee, Jongman;Song, In-Hyuck
    • Journal of the Korean Ceramic Society
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    • v.52 no.6
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    • pp.403-409
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    • 2015
  • Porous alumina ceramics are involved in many industrial applications due to the exceptional properties of these products. This study addresses the preparation of porous alumina ceramics using hollow microspheres as a pore-forming agent and slip casting as a green-body-forming technique. A uniform distribution of pores is a basic requirement of a porous material. This study investigates three different slurry systems, i.e., as-prepared alumina slurry, alumina slurry electrostatically dispersed by hydrochloric acid (HCl), and slurry dispersed by the commercial dispersant 'Darvan C-N'. At a low viscosity, the hollow microspheres in the slurry tend to float, which causes a non-uniform pore distribution. To avoid this phenomenon, the viscosity of the slurry was increased to the extent that the movement of hollow microspheres ceased in the slurry. As a result, a uniform pore distribution was achieved.

Treatment Characteristics of Acid Mine Drainage by Porous Ceramics using Wood Flour as Pore-forming Agent (목분 기포제를 이용한 산업부산물 소재 다공성 세라믹에 의한 산성광산배수의 처리특성 연구)

  • Lee, Yeong-Nam;Yim, Soo-Bin
    • Journal of Environmental Science International
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    • v.27 no.2
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    • pp.109-122
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    • 2018
  • This study was conducted to investigate the removal characteristics of heavy metals and sulfate ion from acid mine drainage by porous zeolite-slag ceramics (ZS ceramics) that was prepared by adding wood flour as pore-foaming agent while calcining the mixtures of natural zeolite and converter slag. The batch test showed that the removal efficiency of heavy metals by pellet-type porous ZS ceramics increased as the particle size of wood flour was decreased and as the weight mixing ratio of wood flour to ZS ceramics was increased. The optimal particle size and weight mixing ratio of wood flour were measured to be $75{\mu}m$ and 7~10%, respectively. The removal test with the porous ZS ceramics prepared in these optimal condition showed very high removal efficiencies: more than 98.4% for all heavy metals and 73.9% for sulfate ion. Relative to nonporous ZS ceramics, the increment of removal efficiency of heavy metals by porous ZS ceramics with $75{\mu}m$ and 10% wood flour was 5.8%, 60.5%, 36.9%, 87.7%, 10.3%, and 57.4% for Al, Cd, Cu, Mn, Pb, and Zn, respectively. The mechanism analysis of removal by the porous ZS ceramics suggested that the heavy metals and sulfate ion from acid mine drainage are eliminated by multiple reactions such as adsorption and/or ion exchange as well as precipitation and/or co-precipitation.

The Study on Foam Formation in Waterslag-Bentonite System (수광재와 백토조합물에서의 기포형성에 관한 연구)

  • 김종희;송한식
    • Journal of the Korean Ceramic Society
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    • v.14 no.4
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    • pp.248-255
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    • 1977
  • The effect of firing temperature, soaking time and batch composition upon the glass phase and pore formation as well as their distribution in slag foamed glass was investigated. Sulfur dioxide gas produced by the oxidation and reduction of metal sulfide in waterslag was attributed to foam forming agent. Slag foamed glass matrix was mainly composed of 35~60% glas phase and melilite crystalline phase. The increment of bentonite addition in batch lowered the foam forming temperature in studied system. The result showed also that the foam size distribution was broadened as th firing temperature wa inbereased.

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