• Title, Summary, Keyword: Porous Alumina Membrane

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Thermally Stabilized Porous Nickel Support of Palladium Based Alloy Membrane for High Temperature Hydrogen Separation

  • Ryi, Shin-Kun;Park, Jong-Soo;Cho, Sung-Ho;Hwang, Kyong-Ran;Kim, Sung-Hyun
    • Corrosion Science and Technology
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    • v.6 no.3
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    • pp.133-139
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    • 2007
  • Nickel powder was coated with aluminum nitrate solution to increase the thermal stability of a porous nickel support and control the nickel content in the Pd-Cu-Ni ternary alloyed membrane. Raw nickel powder and alumina coated nickel powder were uniaxialy pressed by home made press with metal cylindrical mold. Though the used nickel powder prepared by pulsed wire evaporation (PWE) method has a good thermal stability, the porous nickel support was too much sintered and the pores of porous nickel support was plugged at high temperature (over $800^{\circ}C$) making it not suitable for the porous support of a palladium based composite membrane. In order to overcome this problem, the nickel powder was coated by alumina and alumina modified porous nickel support resists up to $1000^{\circ}C$ without pore destruction. Furthermore, the compositions of Pd-Cu-Ni ternary alloy membrane prepared by magnetron sputtering and Cu-reflow could be controlled by not only Cu-reflow temperature but also alumina coating amount. SEM analysis and mercury porosimeter analysis evidenced that the alumina coated on the surface of nickel powder interrupted nickel sintering.

Effect of Electrolyte on Preperation of Porous Alumina Membrane by Anodic Oxidation (양극산화에 의한 다공성 알루미나 막의 제조시 전해질의 영향)

  • Lee, Chang-Woo;Hahm, Yeong-Min;Kang, Hyun-Seop;Chang, Yoon-Ho
    • Applied Chemistry for Engineering
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    • v.9 no.7
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    • pp.1047-1052
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    • 1998
  • The porous alumina membrane was prepared from aluminum metal(99.8%) by anodic oxidation using DC power supply of constant current mode in aqueous solution of sulfuric, oxalic, phosphoric and chromic acid. Pore size and distribution, membrane thickness, morphology and crystal structure were examined with several anodizing conditions : reaction temperature, electrolyte concentration, current density and electrolyte type. It was found that ultrafiltration membrane was fabricated in electrolyte of sulfuric, and oxalic acid. On the other hand, microfiltration membrane was fabricated in electrolyte of phosphoric, and chromic acid. Also, it was shown that crystal structure of porous alumina membrane prepared in sulfuric, oxalic, and phosphoric acid was amorphous, whereas porous alumina membrane prepared in chromic acid had ${\gamma}$ type of crystal structure.

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Gas Permeation Characteristics of Porous Alumina Membrane Prepared by Anodic Oxidation (양극산화에 의한 다공성 알루미나 막의 기체투과 특성)

  • 함영민
    • Journal of environmental and Sanitary engineering
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    • v.13 no.3
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    • pp.72-78
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    • 1998
  • For investigation into gas permeation characteristics, the porous alumina membrane with asymmetrical structure, having upper layer with 10 nanometer under of pore diameter and lower layer with 36 nanometer of pore diameter, was prepared by anodic oxidation using DC power supply of constant current mode in an aqueous solution of sulfuric acid. The aluminium plate was pre-treated with thermal oxidation, chemical polishing and electrochemical polishing before anodic oxidation. Because the pore size depended upon the electrolyte, electrolyte concentration, temperature, current density, and so on, the the membranes were prepared by controling the current density, as a very low current density for upper layer of membrane and a high current density for lower layer of membrane. By control of current quantity, the thicknesses of upper layer of membranes were about $6{\;}{\mu}m$ and the total thicknesses of membranes were about $80-90{\;}{\mu}m$. We found that the mechanism of gas permeation depended on model of the Knudsen flow for the membrane prepared at each condition.

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Preparation of Inorganic Ultrafiltration Membrane by Anodic Oxidation in Oxalic Acid (수산전해액하에서 양극산화에 의한 무기 UF막의 제조)

  • Lee, Chang-Woo;Hong, Young-Ho;Chang, Yoon-Ho;Hahm, Yeong-Min
    • Applied Chemistry for Engineering
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    • v.9 no.4
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    • pp.536-541
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    • 1998
  • The porous size alumina membrane was prepared by anodic oxidation with current method in an aqueous solution of oxalic acid. The aluminum metal plate was pretreated with thermal oxidation, chemical polishing and electropolishing before anodic oxidation. Membrane thickness and pore size distribution were investigated with several anodizing conditions; reaction temperature, cumulative charge, electrolyte concentration and current density. The porous alumina membrane obtained was $55{\sim}75{\mu}m$ thick with straight micropore of 45~100nm. Also, the porous alumina membrane has an uniform pore diameter and pore distribution. It was inorganic ultrafiltration membrane as a kind of the ceramic membrane.

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Hydrogen Permeance of Silica Membrane Prepared by Chemical Vapor Deposition Method on an $\alpha$-Alumina Support Tube (기상 화학증착법에 의해 $\alpha$-Alumina 지지관 상에 제조한 Silica막의 수소투과 특성)

  • 김성수;이재홍;서동수;박상욱;서봉국
    • Journal of Environmental Science International
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    • v.7 no.5
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    • pp.669-677
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    • 1998
  • A porous $\alpha$-alumina tube of 2.5 mm O.D. and 1.9 mm I.D. was used as the support of an inorganic membrane. Macropores of the tube, about 150 nm in size, were plugged with silica formed by thermal decomposition of tetraethylorthosilicate at $600^{\circ}C$. The forced cross-flow CVD method that reactant was evacuated through the porous wall of the support was very effective in plugging macropores. The H$_2$ permeance of the prepared membrane was of the order of $10^{-8}/ molㆍs^{-1}/ㆍm^{-2}/. Pa{-1}$/, while the $N_2$ permeance was below $10^{-11}/ molㆍs^{-1}/ㆍm^{-2}/ㆍPa^{-1}$/ at $600^{\circ}C$. This was comparable to that of silica-modified Vycor glass whose size was 4 nm.

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Effect of Aluminum Purity on the Pore Formation of Porous Anodic Alumina

  • Kim, Byeol;Lee, Jin Seok
    • Bulletin of the Korean Chemical Society
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    • v.35 no.2
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    • pp.349-352
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    • 2014
  • Anodic alumina oxide (AAO), a self-ordered hexagonal array, has various applications in nanofabrication such as the fabrication of nanotemplates and other nanostructures. In order to obtain highly ordered porous alumina membranes, a two-step anodization or prepatterning of aluminum are mainly conducted with straight electric field. Electric field is the main driving force for pore growth during anodization. However, impurities in aluminum can disturb the direction of the electric field. To confirm this, we anodized two different aluminum foil samples with high purity (99.999%) and relatively low purity (99.8%), and compared the differences in the surface morphologies of the respective aluminum oxide membranes produced in different electric fields. Branched pores observed in porous alumina surface which was anodized in low-purity aluminum and the size; dimensions of the pores were found to be usually smaller than those obtained from high-purity aluminum. Moreover, anodization at high voltage proceeds to a significant level of conversion because of the high speed of the directional electric field. Consequently, anodic alumina membrane of a specific morphology, i.e., meshed pore, was produced.

Effect of Additives on Preparation of Porous Alumina Membrane by Anodic Oxidation in Sulfuric Acid (황산전해조에서 양극산화에 의한 다공성 알루미나 막의 제조시 첨가제의 영향)

  • Lee, Chang-Woo;Lee, Yoong;Kang, Hyun-Seop;Chang, Yoon-Ho;Hong, Young Ho;Hahm, Yeong-Min
    • Applied Chemistry for Engineering
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    • v.9 no.7
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    • pp.1030-1035
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    • 1998
  • The porous alumina membrane was prepared from aluminum metal(99.8%) by anodic oxidation using DC power supply of constant current mode in an aqueous solution of sulfuric acid. To prevent the chemical dissolution of alumina membrane, $Al_2(SO_4)_3$, $AlPO_4$ and $Al(NO_3)_3$ which could be considered to supply $Al^{3+}$ ions were added to electrolyte solution at a reaction temperature of $20^{\circ}C$ and cumulative charge of $150C/cm^2$. Effects of these additives on the formation of porous alumina membrane were evaluated under various electrolyte concentration(5~20 wt%) and current densities($10{\sim}50mA/cm^2$). The membrane surfaces which were prepared in electrolyte solution with all the additives except $Al_2(SO_4)_3$ were damaged. However, when $Al_2(SO_4)_3$ was added to the $H_2SO_4$ solution, an uniform surface of porous alumina was obtained. Also, it was shown that the pore size of membrane was nearly independent on the quantity of $Al_2(SO_4)_3$ added at same electrolyte concentration and current density.

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Separation of ethanol/water mixtures with hydrophobic alumina membrane in vapor permeation (소수성 알루미나막의 증가투과에 의한 에탄올의 분리)

  • Lee, Sang-In;Song, Kun-Ho;Lee, Kwang-Rae
    • Journal of Industrial Technology
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    • v.20 no.A
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    • pp.179-184
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    • 2000
  • The surface of porous alumina membrane was modified with silane coupling agent in order to enhance hydrophobicity. The contact angle of water to the surface-modified alumina membrane was greater than $90^{\circ}$. The surface-modified membrane was tested in vapor permeation for the concentration of aqueous ethanol. With the increase of ethanol concentration in the feed, permeation flux increased due to the greater affinity of ethanol with surface-modified alumina membrane than that of water. The experimental results showed that the permeation rate of surface-modified alumina membrane was 15~1000 times greater than that of polymer membranes.

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Synthesis of Silica/Alumina Composite Membrane Using Sol-Gel and CVD Method for Hydrogen Purification at High Temperature (Sol-gel 및 CVD법을 이용한 고온 수소 분리용 silica/alumina 복합막의 합성)

  • 서봉국;이동욱;이규호
    • Membrane Journal
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    • v.11 no.3
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    • pp.124-132
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    • 2001
  • Silica membranes were prepared on a porous ${\alpha}$-alumina tube with pore size of 150nm by sol-gel and chemical vapor deposition(CVD) method for hydrogen separation at high temperatures. Silica and ${\gamma}$-lumina membranes formed by the sol-gel method possessed a large amount of mesopores of a Knudsen diffusion regime. In order to improve the $H_2$ selectivity, silica was deposited in the sol-gel derived silica/${\gamma}$-alumina layer by thermal decomposition of tetraethyl orthosilicate(TEOS) at $600^{\circ}C$. The CVD with forced cross flow through the porous wall of the support was very effective in plugging mesopores that were left unplugged in the membranes. The CVD modified silica/alumina composite membrane completely rejected nitrogen permeation and thus showed a high $H_2$ selectivity by molecular sieve effect. the permeation of hydrogen was explained by activated diffusion and the activation energy was 9.52kJ/mol.

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Fabrication of Nano Metal Compounds Using Porous Aluminum Oxide Films (기공성 알루미나 산화 피막을 이용한 나노 금속화합물의 제조)

  • Oh, Han-Jun;Jeong, Yong-Soo;Chi, Choong-Soo
    • Journal of the Korean institute of surface engineering
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    • v.43 no.5
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    • pp.248-254
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    • 2010
  • Porous $Al_2O_3$ film can be utilized as template for fabrication of nano-structured materials. Porous anodic alumina layer as template was prepared by anodization of aluminum in oxalic acid, and the pore diameter and barrier-type alumina layer can be controlled for proper anodizing parameter by widening process in $H_3PO_4$ solution. The $SiO_2$ nanodot and Ni nanowire was fabricated using anodic alumina template and their characteristics were investigated using SEM and TEM with EDS. Especially the growth mechanism of $SiO_2$ nanodot in alumina membrane compared with thinning of the alumina barrier layer during anodization was also investigated.