• Title/Summary/Keyword: Mesopores

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Formation and Control of Dual Porous Structures of Metal by an Electrochemical Method (전기화학적 방법을 통한 금속 이중기공구조 형성 및 제어)

  • Ha, Seong-Hyeok;Shin, Heon-Cheol
    • Korean Journal of Materials Research
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    • v.29 no.2
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    • pp.65-72
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    • 2019
  • Dual porous structures are observed for the first time on a metallic Cu surface underneath anodic Cu oxide by the application of an anodizing voltage to Cu in oxalic acid. The as-prepared porous Cu surface contains macropores of less than $1{\mu}m$ diameter and mesopores of about tens of nanometers diameter with circular shapes. The size and density (number of pores/area) of the macropores are dependent on the applied voltage. It is likely that the localized dissolution (corrosion) of Cu in oxalic acid under the anodizing voltages is responsible for the formation of the mesopores, and the combination of a number of the mesopores might create the macropores, especially under a relatively high anodizing voltages or a prolonged anodizing time. The variations of pore structure (especailly macropores) with applied voltage and time are reasonably explained on the basis of the proposed mechanism of pore formation.

Preparation and Application of ACFs Derived from the Petroleum Pitch and the Organometallic Compounds

  • Hong, Ik-Pyo;Ha, Baik-Hyon
    • Carbon letters
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    • v.3 no.3
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    • pp.146-151
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    • 2002
  • Activated carbon fibers were prepared from the petroleum isotropic pitch and organometallic compounds. The metalsvwere dispersed uniformly in the ACFs. The specific surface area and pore size distributions of metal containing ACFsvwere measured. The mesopores of ACFs were developed by Co, Ni, and Mn metals addition and the catalytic reactivityvof ACFs'SOx removal was increased by adding Ni and Pd metals. It was found that the mesopores did not work forvthe improvement of catalytic reactivity of ACFs' SOx removal with the blank experiment using the metal removedvACFs.

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Fabrication of Mesoporous Carbon from Polyvinylidene Chloride(PVDC)-resin Precursor with Mg(OH)2 Template for Supercapacitor Electrode (슈퍼 커패시터용 전극을 위한 Polyvinylidene chloride(PVDC)-resin과 Mg(OH)2 템플릿으로부터 메조기공 탄소의 제조)

  • Hwang, Beodl;Chun, Sang-Eun
    • Journal of the Korean institute of surface engineering
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    • v.52 no.6
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    • pp.326-333
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    • 2019
  • The microporous carbon derived from PVDC-resin by a simple heat-treatment under an inert atmosphere exhibits a reasonable specific capacitance for a supercapacitor's electrode. However, the capacitance was rapidly decreased at high charge/discharge rate. The micropores present in an electrode surface hinder the entrance of an electrolyte ion onto the entire surface. To induce the meso-sized pores during the carbonization of PVDC-resin, Mg(OH)2 was utilized as a hard template. The porous carbon made from the mixture of PVD-Cresin and Mg(OH)2 include mesopores as well as micropores. The induced mesopores does not homogeneously distributed on the entire surface of the synthesized carbon. The PVDC-resin and Mg(OH)2 are dissolved in the dimethylformamide for the hard template to evolve the pores on the synthesized carbon uniformly. The carbon made from PVDC-resin with solvent and a hard template contains mostly mesopores resulting in the high power performance. The reduced amount of solvent in the precursor derives the carbon with high specific surface area and high power density.

Influence of calcination temperature on the structure of freeze-dried silica gel (동결건조 실리카 젤의 구조에 미치는 하소온도의 영향)

  • 최성준;박상희;박홍채
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.13 no.2
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    • pp.73-78
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    • 2003
  • The influence of calcination temperature on the pore structure of freeze dried silica gel derived from tetraethyl orthosilicate (TEOS) was investigated using $N_2$adsorption and mercury intrusion techniques. Freeze dried material contained not only 4-6 nm sized mesopores and 6-10 $\mu\textrm{m}$ sized macropores, but minor micropores. The change of pore structure due to the increase of calcination temperature was dependant upon the degree of densification.

Studies on Pyrolysis Behaviour of Banana Stem as Precursor for Porous Carbons

  • Manocha, Satish;Bhagat, Jignesh H.;Manocha, Lalit M.
    • Carbon letters
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    • v.2 no.2
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    • pp.91-98
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    • 2001
  • Porous carbons have been prepared from different parts of banana stems using two different routes, viz., by pyrolysing the mass at different temperatures as well as by treating the dried mass with chemicals followed by pyrolysis. The pyrolysis behaviour of all these materials has been studied up to $1000^{\circ}C$. Samples treated with acids exhibit more increase in surface area as compared to those treated with alkalies or salts. Analysis of BET surface area shows that the carbon prepared at low temperature shows mixed porosity, i.e., micro and mesopores. Samples heated to high temperature above $700^{\circ}C$ show decrease in macroporosity and increase in microporosity. Liquid adsorption studies have been made using methylene blue and heavy oil. The activated carbons so prepared exhibit higher oil adsorption mainly in the macro and mesopores.

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Preparation of MgO with High Surface Area, and Modification of Its Pore Characteristics

  • Lee, Moon-Hee;Park, Dong-Gon
    • Bulletin of the Korean Chemical Society
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    • v.24 no.10
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    • pp.1437-1443
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    • 2003
  • Thermal decomposition of hydrated surface layer of $Mg(OH)_2$ at $500^{\circ}C$ in vacuum turned non-porous MgO into porous one with high surface area of around $270 m^2$/g. Most of its surface area, 74 %, was from micropores, and rest of it was from mesopores in wedge-shaped slits, exhibiting bimodal size distribution centered around 30 and 90${\AA}$. Rehydration followed by subsequent dehydration at $300 ^{\circ}C$ in dynamic vacuum further raised the surface area to 340 $m^2$/g. Fraction of microporous surface area was increased to 93%, and the shape of the mesopores was modified into parallel slits with a specific dimension of 32 ${\AA}$. Application of $Fe_2O_3$ over MgO via iron complex formation did not alter the pore characteristics of MgO core, except slightly increased pore dimension. Over the course of the modification, $Fe_2O_3$ stayed on the surface possibly via spill-over reaction.

Preparation of Silica Monoliths with Macropores and Mesopores and of High Specific Surface Area with Low Shrinkage using a Template Induced Method

  • Guo, Jianyu;Lu, Yan;Whiting, Roger
    • Bulletin of the Korean Chemical Society
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    • v.34 no.2
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    • pp.447-452
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    • 2013
  • In this study we report a new method for the synthesis of a silica monolithic column bed with bimodal pores (throughpores and mesopores). The template induced synthesis method was used to direct bimodal pores simultaneously instead of the usual post base-treating method. Block polymer Pluronic F127 was chosen as a dual-function template to form hierarchically porous silica monolith with both macropores and mesopores. This is a simplification of the method of monolithic column preparation. Poly(ethylene glycol) was used as a partial substitute for F127 can effectively prevent shrinkage during the monolith aging process without losing much surface area (944 $m^2/g$ to 807 $m^2/g$). More importantly, the resultant material showed a much narrower mesopore size (centered at 6 nm) distribution than that made using only F127 as the template reagent, which helps the mass transfer process. The solvent washing method was used to remove the remaining organic template, and it was proved to be effective enough. The new synthesis method makes the fabrication of the silica monolithic column (especially capillary column) much easier. All the structure parameters indicate that monolith PFA05 prepared by the above method is a good material for separation, with the merits of much higher surface area than usual commercial HPLC silica particles, suitable mesopore volume, narrow mesopore size distribution, low shrinkage and it is easily prepared.

Preparation of novolac-type phenol-based activated carbon with a hierarchical pore structure and its electric double-layer capacitor performance

  • Lee, Dayoung;Jung, Jin-Young;Park, Mi-Seon;Lee, Young-Seak
    • Carbon letters
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    • v.15 no.3
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    • pp.192-197
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    • 2014
  • A hierarchical pore structured novolac-type phenol based-activated carbon with micropores and mesopores was fabricated. Physical activation using a sacrificial silicon dioxide ($SiO_2$) template and chemical activation using potassium hydroxide (KOH) were employed to prepare these materials. The morphology of the well-developed pore structure was characterized using field-emission scanning electron microscopy. The novolac-type phenol-based activated carbon retained hierarchical pores (micropores and mesopores); it exhibited high Brunauer-Emmett-Teller specific surface areas and hierarchical pore size distributions. The hierarchical pore novolac-type phenol-based activated carbon was used as an electrode in electric double-layer capacitors, and the specific capacitance and the retained capacitance ratio were measured. The specific capacitances and the retained capacitance ratio were enhanced, depending on the $SiO_2$ concentration in the material. This result is attributed to the hierarchical pore structure of the novolac-type phenol-based activated carbon.

Adsorption of volatile organic compounds using activated carbon fiber filter in the automobiles

  • Moon, Hyung Suk;Kim, In Soo;Kang, Sin Jae;Ryu, Seung Kon
    • Carbon letters
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    • v.15 no.3
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    • pp.203-209
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    • 2014
  • The adsorption of volatile organic compounds (VOCs) was carried out using an activated carbon fiber (ACF) filter in an automobile. The adsorption capacities of formaldehyde, toluene, and benzene on an ACF filter were far better than those of a polypropylene (PP) mat filter and combined (PP+activated carbon) mat filter by batch adsorption in a gas bag. In a continuous flow of air containing toluene vapor through an ACF packed bed, the breakpoint time was very long, the length of the unused bed was short, and sharp "S" -type breakthrough curve was plotted soon after breakpoint, showing a narrow mass transfer zone of toluene on the ACF. The adsorption amount of toluene on the ACF filter was proportional to the specific surface area of the ACF; however, the development of mesopores 2-5 nm in size on the ACF was very effective with regard to the adsorption of toluene. The ACF air clarifier filter is strongly recommended to remove VOCs in newly produced automobiles.