• Title/Summary/Keyword: Aqueous chemistry

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PHOTOCATALYTIC ACTIVITY OF ARTIFICIAL TITANIUM(IV) OXIDE-$TIO_2(B)$-AND TITANATES SUSPENDED IN AQUEOUS SOLUTION OF ALIPHATIC ALCOHOLS

  • Bunsho Ohtani;Koujiro Tennou;Nishmoto, Sei-ichi;Tomoyuki Inui
    • Journal of Photoscience
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    • v.2 no.1
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    • pp.7-11
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    • 1995

  • Powders of artificial crystallites of titanium(IV) oxide, TiO$_2$(B), were synthesized by the calcination of tetratitanic acid (hydrate, $H_2Ti_4O_9H_2O$; TTA). The relating titanates, potassium octatitanate ($K_2Ti_8O_{17}$) and octatitanic acid($H_2Ti_8O_{17}$), were also prepared. These powders, loaded with small amount of Pt, were suspended in an aqueous solution of 2-propanol and irradiated under argon atmosphere at 298 K + 0.5 deg. All the photocatalysts tested in this study produced almost equimolar amount of acetone and molecular hydrogen (H$_2$). Among them TiO$_2$(B) and TYA showed the higher photocatalytic activity but rather lower than commercial titanium(IV) oxide (TiO$_2$) powders. The photocatalytic activity of TiO$_2$(B) for 2-propanol dehydrogenation in deaerated aqueous suspension increased with the elevating calcination temperature. Comparison of rate of H$_2$ formation from methanol and 2-propanol solutions by the TiO$_2$(B) photocatalyst suggested a possibility of selection of substrate with its molecular size by TiO$_2$(B)

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Flexible poly(vinyl alcohol)-ceramic composite separators for supercapacitor applications

  • Bon, Chris Yeajoon;Mohammed, Latifatu;Kim, Sangjun;Manasi, Mwemezi;Isheunesu, Phiri;Lee, Kwang Se;Ko, Jang Myoun
    • Journal of Industrial and Engineering Chemistry
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    • v.68
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    • pp.173-179
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    • 2018

  • Electrochemical characterization was conducted on poly(vinyl alcohol) (PVA)-ceramic composite (PVA-CC) separators for supercapacitor applications. The PVA-CC separators were fabricated by mixing various ceramic particles including aluminum oxide ($Al_2O_3$), silicon dioxide ($SiO_2$), and titanium dioxide ($TiO_2$) into a PVA aqueous solution. These ceramic particles help to create amorphous regions in the crystalline structure of the polymer matrix to increase the ionic conductivity of PVA. Supercapacitors were assembled using PVA-CC separators with symmetric activated carbon electrodes and electrochemical characterization showed enhanced specific capacitance, rate capability, cycle life, and ionic conductivity. Supercapacitors using the $PVA-TiO_2$ composite separator showed particularly good electrochemical performance with a 14.4% specific capacitance increase over supercapacitors using the bare PVA separator after 1000 cycles. With regards to safety, PVA becomes plasticized when immersed in 6 M KOH aqueous solution, thus there was no appreciable loss in tear resistance when the ceramic particles were added to PVA. Thus, the enhanced electrochemical properties can be attained without reduction in safety making the addition of ceramic nanoparticles to PVA separators a cost-effective strategy for increasing the ionic conductivity of separator materials for supercapacitor applications.

  • https://doi.org/10.1016/j.jiec.2018.07.043 인용 KSCI

Oxidations of Cyclohexanols by N-Bromosuccinimide and Sodium Hypochlorite

  • Chung, Kyoo-Hyun;Kim, Seong-Jin
    • Bulletin of the Korean Chemical Society
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    • v.7 no.2
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    • pp.111-113
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    • 1986

  • The axial alcohol in trans-3,3,5-trimethylcyclohexanol was oxidized more readily than the equatorial alcohol in cis-3,3,5-trimethylcyclohexanol by NBS in aqueous dioxane. On the contrary, the equatorial alcohol was preferentially oxidized to the axial one by 10% aqueous sodium hypochlorite in the presence of tetrabutylammonium hydrogen sulfate (TBHS). The specificity indicates the presence of two different mechanism. In acidic medium, the cleavage of C-H bond is rate determining step while the reactivity of the alcohol is important in the presence of TBHS. The mechanism in basic medium without TBHS will be discussed.

  • https://doi.org/10.5012/bkcs.1986.7.2.111 인용 PDF

Double Ion-Pair Formation in Aqueous Solutions of Methylene Blue and Tetraphenylborate

  • Yoon, Kil-Joong;Kim, Kang-Jin
    • Bulletin of the Korean Chemical Society
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    • v.6 no.3
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    • pp.149-152
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    • 1985

  • Spectrophotometric and spectrofluorimetric methods of analysis were conducted in dilute aqueous solutions of methylene blue and tetraphenylborate. The formation of double ion-pair was confirmed and its overall formation constant, ${\Delta}H^{\circ}$, and ${\Delta}S^{\circ}$ were obtained. The irradiation with wavelengths over visible region resulted in bleaching the mixed solution. The bleaching reaction was also proceeded at $55^{\circ}C$. The reactions of the double ion-pair were briefly discussed.

  • https://doi.org/10.5012/bkcs.1985.6.3.149 인용 PDF