Faculty Profiles - NAKANISHI Kazuki

Papers - NAKANISHI Kazuki

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Structure and properties of polymethylsilsesquioxane aerogels synthesized with surfactant n-hexadecyltrimethylammonium chloride Reviewed

Gen Hayase, Kazuyoshi Kanamori, Kazuki Nakanishi

MICROPOROUS AND MESOPOROUS MATERIALS Vol. 158 page： 247 - 252 2012.8

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Structure and physical properties of monolithic polymethylsilsesquioxane (PMSQ CH3SiO1.5) aerogels have been systematically examined with varied starting compositions using a sol-gel system containing surfactant n-hexadecyltrimethylammonium chloride (CTAC). The precursor methyltrimethoxysilane (MTMS) undergoes hydrolysis and polycondensation under an acid-base two-step reaction to obtain uniform gels as a one-pot reaction. To compare the samples, each factor of starting composition, such as amount of CTAC, concentration of aqueous acetic acid solution, volume of solvent and amount of urea, is independently varied. With appropriate concentrations of surfactant CTAC, the aerogels with high light transmittance (at 550 nm) are obtained, owing to the effective suppression of macroscopic phase separation. Acid-base catalysts, acetic acid and urea also impose significant effects on the properties of obtained aerogels including their molecular-level structures. The aerogel with 91% of light transmittance was obtained under an optimized condition. The lowest density of the PMSQ aerogel in this system reaches 0.045 g cm(-3). (C) 2012 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.micromeso.2012.03.049

Synthesis of Monolithic Hierarchically Porous Iron-Based Xerogels from Iron(III) Salts via an Epoxide-Mediated Sol-Gel Process Reviewed

Yasuki Kido, Kazuki Nakanishi, Akira Miyasaka, Kazuyoshi Kanamori

CHEMISTRY OF MATERIALS Vol. 24 ( 11 ) page： 2071 - 2077 2012.6

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Various iron-based polycrystalline monoliths, Fe3O4, iron, and Fe3C, with hierarchically distributed pores have been synthesized from ionic precursors using a sol-gel process accompanied by phase separation. Propylene oxide acts as a proton scavenger to increase pH moderately and uniformly in a reaction solution, which leads to homogeneous gelation. On the other hand, poly(acrylamide) works as a phase separation inducer as well as a precipitation inhibitor. Appropriate choice of iron precursor, solvent, polymer, and epoxide allowed the formation of iron(III)-based xerogels with cocontinuous macroporous structures. The dried gels were amorphous, whereas heating in air above 300 degrees C led to the formation of alpha-Fe2O3. Calcination under an inert condition above 400 degrees C formed Fe3O4, iron, and Fe3C without collapse of macrostructures. Examination has been carried out using SEM, TG-DTA, FT-IR, Hg diffraction, and N-2 adsorption-desorption.

DOI： 10.1021/cm300495j

Facile preparation of macroporous graphitized carbon monoliths from iron-containing resorcinol-formaldehyde gels Reviewed

George Hasegawa, Kazuyoshi Kanamori, Kazuki Nakanishi

MATERIALS LETTERS Vol. 76 page： 1 - 4 2012.6

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

In this report, we demonstrate the facile preparation of macroporous monolithic materials based on graphitized carbon by utilizing catalytic graphitization at relatively low temperature (1000 degrees C). The precursor polymer, macroporous resorcinol-formaldehyde (RF) xerogel, can be obtained without any surfactants or polymeric additives in water/ethanol mixed solvent via the sol-gel reaction accompanied by phase separation. The use of iron chloride as an acid catalyst for polymerization provides the RF monoliths incorporated with Fe, which catalyzes the graphitization. The effects of the starting composition on the morphologies of the resultant RF gels and the characteristics of the graphitized carbon monoliths have been discussed. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matlet.2012.02.069

Pore properties of hierarchically porous carbon monoliths with high surface area obtained from bridged polysilsesquioxanes Reviewed Open Access

George Hasegawa, Kazuyoshi Kanamori, Kazuki Nakanishi

MICROPOROUS AND MESOPOROUS MATERIALS Vol. 155 page： 265 - 273 2012.6

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Hierarchically porous carbon monoliths with high specific surface area have been prepared via a nano-phase extraction technique from carbon/silica composites which had been prepared from arylene-bridged polysilsesquioxanes. The nano-sized silica phase developed in the composite has been removed to increase micropores, resulting in a similar effect to thermal activation of carbons. The resultant carbons are expected to possess homogeneously distributed micropores. Here we report the changes of the pore characteristics through the synthesis process by the nitrogen adsorption-desorption method and mercury porosimetry. In particular, the growth of silica phase in carbon/silica composites at different temperatures has been characterized by the micropore analysis using the Horvath-Kawazoe method. (C) 2012 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.micromeso.2012.02.001

Development of flexible porous materials from organotrialkoxysilanes Reviewed

Kazuyoshi Kanamori, Gen Hayase, Kazuki Nakanishi

Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy Vol. 59 ( 6 ) page： 320 - 325 2012.6

Language：Japanese Publishing type：Research paper (scientific journal)

Organosiloxane (RnSiO(4-n)/2) gels can be prepared from organoalkoxysilanes using the sol-gel process. In general,however, formation of uniform networks from these precursors is strongly inhibited due to cyclization reactions. In addition, phase separation of hydrophobic condensates from polar solvent leads to inhomogeneous gels in these systems. A careful control of the hydrolysis and polycondensation reactions is therefore required to obtain a monolithic gel with desired properties. We have been trying to control the sol-gel reactions as well as phase separation in these systems to obtain unique porous materials particularly from methyltrimethoxysilane(MTMS) and dimethyldimethoxysilane (DMDMS). Flexible aerogels and xerogels based on the methylsiloxane networks are discussed.

DOI： 10.2497/jjspm.59.320

Flower-like surface modification of titania materials by lithium hydroxide solution Reviewed Open Access

George Hasegawa, Kazuyoshi Kanamori, Yoshihiro Sugawara, Yuichi Ikuhara, Kazuki Nakanishi

JOURNAL OF COLLOID AND INTERFACE SCIENCE Vol. 374 ( 1 ) page： 291 - 296 2012.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE

Surface modification of titania materials to give flower-like structures has been achieved simply by the treatment in lithium hydroxide aqueous solution under mild conditions. The flower-like structured materials were characterized by X-ray diffraction, thermogravimetric analysis, and Raman scattering. The analyses indicate that the flower-like materials are composed of layered hydrous lithium titanate. It is suggested that the unique intercalation behavior of lithium ions into titania allows dissolution and re-precipitation of titania to form the flower-like structure. The obtained flower-like structure can be retained up to 700 degrees C, while the crystal phase transforms into Li4Ti5O12. (C) 2012 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcis.2012.02.002

New Monolithic Capillary Columns with Well-Defined Macropores Based on Poly(styrene-co-divinylbenzene) Reviewed

George Hasegawa, Kazuyoshi Kanamori, Norio Ishizuka, Kazuki Nakanishi

ACS APPLIED MATERIALS & INTERFACES Vol. 4 ( 5 ) page： 2343 - 2347 2012.5

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Macroporous polymer monoliths based on poly(styrene-co-divinylbenzene) with varied styrene/divinylbenzene ratios have been prepared by organotellurium-mediated living radical polymerization. The well-defined cocontinuous macroporous structure can be obtained by polymerization-induced spinodal decomposition, and the pore structures are controlled by adjusting the starting composition. The separation efficiency of small molecules (alkylbenzenes) in the obtained monoliths has been evaluated in the capillary format by high-performance liquid chromatography (HPLC) under the isocratic reversed-phase mode. Baseline separations of these molecules with a low pressure drop (similar to 2 MPa) have been achieved because of the well-defined macropores and to the less-heterogeneous cross-linked networks.

DOI： 10.1021/am300552q

New flexible aerogels and xerogels derived from di- and trifunctional organosilanes co-precursors

Hayase Gen, Kanamori Kazuyoshi, Nakanishi Kazuki

Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan Vol. 2012 ( 0 ) page： 280-280 2012

Language：English Publishing type：Research paper (scientific journal)

We report new flexible “marshmallow-like” aerogels and xerogels with a bendable feature from the di- and trifunctional organosilane co-precursor systems. A 2-step acid/base sol–gel process and surfactant are employed to control the phase separation of the hydrophobic networks, which give porous monolithic gels. The obtained gels from methyltrimethoxysilane (MTMS) and dimethyldimethoxysilane (DMDMS) become softer and more flexible with increasing DMDMS fractions.

DOI： 10.14853/pcersj.2012S.0.280.0

612 Synthesis of Macroporous Layered Double Hydroxide with a Bulk Form for High Performance Ion Exchange Reaction

TOKUDOME Yasuaki, TARUTANI Naoki, TAKAHASHI Masahide, NAKANISHI Kazuki

Vol. 61 page： 159-160 2012

Evolution of Mesopores in Monolithic Macroporous Ethylene-Bridged Polysilsesquioxane Gels Incorporated with Nonionic Surfactant Reviewed Open Access

Atsushi Mushiake, Kazuyoshi Kanamori, Kazuki Nakanishi

INTERNATIONAL JOURNAL OF POLYMER SCIENCE Vol. 2012 2012

Language：English Publishing type：Research paper (scientific journal) Publisher：HINDAWI PUBLISHING CORPORATION

By combining the micellar templating in nanometer scale with the polymerization-induced phase separation in micrometer scale, ethylene-bridged polysilsesquioxane gels with hierarchical macropores and mesopores are prepared. The difference of mesopore structures depending on the method of the solvent removal has been observed by the X-ray diffraction and the nitrogen adsorption-desorption measurements. During the hydrothermal treatment under the basic condition, the reorganization of the polysilsesquioxane gel network occurred differently depending on the alkoxy group contained in the precursors. From Si-29 CP/MAS NMR measurements, it was revealed that the crosslinking density of the hydrothermally treated gels was increased so that the highly ordered mesostructure of the wet gel could be preserved even after the evaporative drying of solvent.

DOI： 10.1155/2012/460835

2011 Donald R. Ulrich Awards Reviewed

K. Nakanishi

Journal of Sol-Gel Science and Technology page： 1 - 2 2012

Selective Preparation of Macroporous Conductive Oxide Ti<SUB><I>n</I></SUB>O<SUB>2<I>n</I>-1</SUB> (<I>n</I> = 2, 3, 4, 6) Monoliths Reviewed

Kitada Atsushi, Hasegawa George, Kobayashi Yoji, Kanamori Kazuyoshi, Nakanishi Kazuki, Kageyama Hiroshi

Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan Vol. 2012 ( 0 ) page： 526 - 526 2012

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan

We report selective preparation of macroporous monoliths of conductive titanium oxides Ti<SUB><I>n</I></SUB>O<SUB>2<I>n</I>-1</SUB> (<I>n</I> = 2, 3, 4, 6) as a single phase, by reducing a macroporous TiO<SUB>2</SUB> monolith using zirconium getter. All the reduced monoliths have uniform pore size distribution, retaining that of the precursor TiO<SUB>2</SUB> monoliths. Furthermore, their bulk densities of 1.8 g cm<SUP>-3</SUP> are about half smaller and their porosities of 60% are about three times larger than that of commercial porous Ebonex (shaped conductive Ti<SUB><I>n</I></SUB>O<SUB>2<I>n</I>-1</SUB>). The obtained Ti<SUB><I>n</I></SUB>O<SUB>2<I>n</I>-1</SUB> (<I>n</I> = 2, 3, 4, 6) macroporous monoliths could find their applications as electrodes for many electrochemical reactions.

DOI： 10.14853/pcersj.2012S.0.526.0

Role of block copolymer surfactant on the pore formation in methylsilsesquioxane aerogel systems Reviewed

Masayuki Kurahashi, Kazuyoshi Kanamori, Kazuyuki Takeda, Hironori Kaji, Kazuki Nakanishi

RSC ADVANCES Vol. 2 ( 18 ) page： 7166 - 7173 2012

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Transparent and low-density methylsilsesquioxane (MSQ, CH3SiO1.5) aerogels can be obtained solely from methyltrimethoxysilane (MTMS) by a one-pot two-step process under the co-presence of surfactant. In the present study, we have systematically investigated the effects of the molecular structure of triblock copolymer-type nonionic surfactants PEO-b-PPO-b-PEO (PEO and PPO denote poly(ethylene oxide) and poly(propylene oxide) units, respectively) on the properties of the resultant MSQ aerogels. Macroscopic phase separation of hydrophobic MSQ networks from polar solvent occurs when no surfactant is employed, which results in macroporous opaque aerogels. In contrast, a co-presence of appropriate surfactant effectively suppresses the phase separation and yields transparent aerogels after supercritical drying. By employing various surfactants having different molecular weight and PO/EO ratio, the mechanism of suppression of phase separation or pore formation is discussed in detail. In situ H-1 NMR suggests that the PO units of surfactant interact with the hydrophobic MSQ network enriched with methyl groups and make the MSQ network hydrophilic by extending EO chains toward the aqueous solvent in the late phase of gelation, until which hydrogen bonding dominates between the Si-OH groups of polymerizing MSQ and the ether oxygens of the EO unit. Through the comprehensive understanding of the role of surfactant, the strategy for rational design of MSQ aerogels materials has become developable.

DOI： 10.1039/c2ra20799k

Facile Preparation of Monolithic LiFePO4/Carbon Composites with Well-Defined Macropores for a Lithium-Ion Battery Reviewed

George Hasegawa, Yuya Ishihara, Kazuyoshi Kanamori, Kohei Miyazaki, Yuki Yamada, Kazuki Nakanishi, Takeshi Abe

CHEMISTRY OF MATERIALS Vol. 23 ( 23 ) page： 5208 - 5216 2011.12

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

A novel and facile method for the preparation of monolithic LiFePO4/carbon composites with well-defined macropores has been developed. The precursor macroporous gels consisting of inorganic networks as well as organic polymers were fabricated by the epoxide-mediated sol-gel method accompanied by phase separation. The inorganic-organic hybrid gels were calcined under an inert atmosphere, resulting in LiFePO4/carbon monoliths. The influence of the starting compositions on the gel morphologies has been investigated, and the constituents of the gel network were discussed. The reaction mechanism of the crystallization of LiFePO4 from green bodies during calcination has also been investigated by thermal analysis, X-ray diffraction, and Raman scattering. In addition, the electrochemical properties of the resultant LiFePO4/carbon composites were examined by the charge-discharge test.

DOI： 10.1021/cm2021438

Macroporous carbon monoliths with large surface area for electric double-layer capacitor

George Hasegawa, Mami Aoki, Kazuyoshi Kanamori, Kazuki Nakanishi, Teiichi Hanada, Kiyoharu Tadanaga

Materials Research Society Symposium Proceedings Vol. 1304 page： 38 - 43 2011.12

Language：English Publishing type：Research paper (international conference proceedings)

Macro/meso/microporous carbon monoliths doped with sulfur have been prepared from sulfonated polydivinylbenzene networks followed by the activation with CO 2 resulted in the activated carbon monoliths with high surface area of 2400 m 2 g -1. The monolithic electrode of the activated carbon shows remarkably high specific capacitance (175 F g -1 at 5 mV s -1 and 206 F g -1 at 0.5 A g -1). © 2011 Materials Research Society.

DOI： 10.1557/opl.2011.604

Synthesis of new flexible aerogels from di- and trifunctional organosilanes

Gen Hayase, Kazuyoshi Kanamori, Kazuki Nakanishi, Teiichi Hanada

Materials Research Society Symposium Proceedings Vol. 1306 page： 68 - 73 2011.12

Language：English Publishing type：Research paper (international conference proceedings)

Recent years, although silica aerogels are expected to be the promising material for energy savings, the lack of mechanical strength prevents from commercial applications such as to low-density thermal insulators. To improve mechanical properties, methyltrimethoxysilane (MTMS) and dimethyldimethoxysilane (DMDMS) are used in this study as the co-precursor of aerogels because the network becomes flexible due to the relatively low cross-linking density and to the unreacted methyl groups. Because of the strong hydrophobicity of MTMS/DMDMS-derived condensates, phase separation occurs in aqueous sol and must be suppressed to obtain uniform and monolithic gel. We employed surfactant n-hexadecyltrimethylammonium chloride (CTAC) in starting compositions to control phase separation during a 2-step acid/base sol-gel reaction. By changing the starting composition, various microstructures of pores are obtained. In the uniaxial compression test, the aerogel showed high flexibility and spring-back to the original shape after removing the stress. © 2011 Materials Research Society.

DOI： 10.1557/opl.2011.216

Organosiloxane transparent aerogels and hierarchically porous monoliths

Yasunori Kodera, Gen Hayase, Kazuyoshi Kanamori, Kazuki Nakanishi, Teiichi Hanada

Materials Research Society Symposium Proceedings Vol. 1306 page： 54 - 59 2011.12

Language：English Publishing type：Research paper (international conference proceedings)

A transition of porous structures in monolithic poly(methylsilsesquioxane) (PMSQ, CH 3SiO 1.5) gels from uniform mesopores to hierarchical pore structures consisting of macro- and mesopores, has been investigated using a sol-gel system containing surfactant Pluronic F127. A broad variation of porous morphology is controlled by changing the concentration of F127. Sufficient concentrations of F127 inhibit the occurrence of macroscopic phase separation of hydrophobic PMSQ condensates and lead to well-defined mesoporous transparent aerogels with high specific pore volume. Mesopores are developed through microscopic phase separation of PMSQ colloid-surfactant complexes in the solvent. Macroscopic phase separation regulates well-defined macropores in the micrometer range on decreasing concentrations of F127, in which microscopic phase separation concurrently takes place in the PMSQ-rich gelling phase after the onset of macroscopic phase separation. Monolithic PMSQ gels with hierarchical macro- and mesopore structures are consequently obtained. © 2011 Materials Research Society.

DOI： 10.1557/opl.2011.96

Hierarchically Porous Materials by Phase Separation: Monoliths

Kazuki Nakanishi

Hierarchically Structured Porous Materials: From Nanoscience to Catalysis, Separation, Optics, Energy, and Life Science page： 241 - 267 2011.11

Hierarchically Structured Porous Materials: Application to Separation Sciences

Kazuki Nakanishi

Hierarchically Structured Porous Materials: From Nanoscience to Catalysis, Separation, Optics, Energy, and Life Science page： 517 - 529 2011.11

New hierarchically porous titania monoliths for chromatographic separation media Reviewed

George Hasegawa, Kei Morisato, Kazuyoshi Kanamori, Kazuki Nakanishi

JOURNAL OF SEPARATION SCIENCE Vol. 34 ( 21 ) page： 3004 - 3010 2011.11

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-BLACKWELL

Separation media based on hierarchically porous titania (TiO(2)) monoliths for high-performance liquid chromatography (HPLC) have been successfully fabricated by the sol-gel process of titanium alkoxide in a mild condition utilizing a chelating agent and mineral salt. The as-gelled TiO(2) monoliths were subjected to a simple solvent exchange process from ethanol (EtOH) to H(2)O followed by drying and calcination. The resultant monolithic TiO(2) columns consist of anatase crystallites with the typical specific surface area of more than 200 m(2)/g. The resultant monolithic TiO(2) column calcined at 200 and 400 degrees C exhibited a good separation performance for organophosphates as well as for polar benzene derivatives in the normal-phase mode.

DOI： 10.1002/jssc.201100538

Other Link： http://orcid.org/0000-0002-8069-4780

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