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Author: search.filters.author.Tamon, HajimeSubject: search.filters.subject.Porosity

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    HCl treatment on micropore and mesopore structures of carbon cryogels from resorcinol and formaldehyde
    (2011-02-25)
    Kraiwattanawong, Kriangsak
    ;
    Tamon, Hajime
    ;
    Praserthdam, Piyasan
    The effect of HCl treatment on the porous properties of carbon cryogels synthesized from resorcinol and formaldehyde (RF) is investigated in this work. The treated and untreated carbon cryogels were analyzed with a nitrogen adsorption-desorption apparatus, scanning electron microscope (SEM) and high performance liquid chromatograph (HPLC). The results show that the HCl treatment can enlarge the micropore diameter which is advantageous to electric double layer capacitors, and can broaden the mesopore diameter, which is advantageous to mesoporous carbon supports of catalysts. The micropore volume, mesopore volume and weight loss of the carbon cryogel are not significantly changed by the HCl treatment. Moreover, SEM images and HPLC chromatograms support that the HCl treatment can promote the Ostwald ripening effect for RF carbon cryogels. © 2011 The Society of Chemical Engineers, Japan.
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    Influence of solvent species used in solvent exchange for preparation of mesoporous carbon xerogels from resorcinol and formaldehyde via subcritical drying
    (2011-02-01)
    Kraiwattanawong, Kriangsak
    ;
    Tamon, Hajime
    ;
    Praserthdam, Piyasan
    Carbon cryogels are dried by 3 days of freeze drying with 6 h of pre-freezing whereas the carbon xerogels are prepared by 1 day of subcritical drying in the selective range of synthesis condition, but the mesoporosity of carbon xerogels are not well controlled. This research is to study the influence of solvent species in the solvent exchange for the preparation of carbon xerogels cooperated by the evaporation drying and the vacuum drying. The good solvent for the high mesoporous properties of carbon xerogels is desirable in the wide range of synthesis condition. The carbon xerogels prepared from resorcinol and formaldehyde were characterized by the nitrogen adsorption apparatus and the field emission scanning electron microscope (FE-SEM). The results illustrate that the mesoporous carbon xerogels in the two subcritical dryings can be easily prepared by solvent exchange. Among the solvents, t-butanol allows the great results in the preparation of high mesoporous carbon xerogels and is well applied in the wide range of synthesis conditions. The FE-SEM images elucidate that the carbon xerogels dried by the vacuum drying contain the particles interconnection larger than the evaporation drying. © 2010 Elsevier Inc. All rights reserved.
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    Control of mesoporous properties of carbon cryogels prepared from wattle tannin and furfural
    (2008-12-01)
    Kraiwattanawong, Kriangsak
    ;
    Mukai, Shin R.
    ;
    Tamon, Hajime
    ;
    Lothongkum, Anchaleeporn W.
    Wattle tannin-furfural (TFu) carbon cryogels are synthesized by sol-gel polycondensation of wattle tannin with furfural by using sodium hydroxide (NaOH) as a catalyst, dried by freeze-drying technique and then pyrolyzed under inert atmosphere, respectively. The amounts of wattle tannin (T), furfural (Fu), NaOH (C) and distilled water (W) are changed for preparing the mesoporous TFu carbon cryogels. The mole ratio of tannin to catalyst T/C plays a crucial role for the synthesis of TFu organic and carbon cryogels. The results suggest that the T/C ratio should be above 0.25 but <1.0 to prepare the mesoporous and homogeneous cryogels. Although TFu carbon cryogels have the broad mesopore size distribution, the mesoporous structure is controllable by the synthesis conditions. The carbon cryogels possess the mesopore volume less than 0.56 cm<sup>3</sup>/g and the BET surface area less than 600 m<sup>2</sup>/g. Moreover, the ratio of catalyst to water C/W can be used to prepare the homogeneous and mesoporous carbon cryogels, and to control the mesopore radius of carbon cryogels in the range of 1.6-9.6 nm. © 2007 Springer Science+Business Media, LLC.
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    Improvement of mesoporosity of carbon cryogels by acid treatment of hydrogels
    (2008-11-01)
    Kraiwattanawong, Kriangsak
    ;
    Mukai, Shin R.
    ;
    Tamon, Hajime
    ;
    Lothongkum, Anchaleeporn W.
    Wattle tannin-furfural (TFu) gels are synthesized by the sol-gel polycondensation of wattle tannin with furfural by using sodium hydroxide as a catalyst and cured at 363 K. After cured, the TFu hydrogels are treated in hydrochloric acid (HCl) solutions with various variables as follows: aging temperature, HCl concentration and pH. TFu cryogels aged are then freeze-dried and pyrolyzed under an inert atmosphere to obtain TFu carbon cryogels. The TFu and carbon cryogels were characterized by N<inf>2</inf> adsorption and scanning electron microscope. The high HCl concentration yields the increase of mesopore volume almost twice especially at high temperature and the mesopore size distribution can be greatly developed sharper and narrower when the high concentration of HCl or/and the high temperature are used. Moreover, this method is the versatile approach for developing the mesopore structure of the low and high porous TFu hydrogels and has no serious problem of weight loss after treatment. © 2008 Elsevier Inc. All rights reserved.