Faculty Profiles - NAKANISHI Kazuki

Papers - NAKANISHI Kazuki

Division display 221 - 240 of about 412 ／ All the affair displays >>

Macro- and microporous carbon monoliths with high surface areas pyrolyzed from poly(divinylbenzene) networks Reviewed

Joji Hasegawa, Kazuyoshi Kanamori, Kazuki Nakanishi, Teiichi Hanada

COMPTES RENDUS CHIMIE Vol. 13 ( 1-2 ) page： 207 - 211 2010.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER

Carbon monoliths with well-defined macropores and high surface areas were prepared by carbonization of macroporous poly(divinylbenzene) (PDVB) monoliths The carbonization reactions of PDVB networks are studied by thermal analysis and FT-IR measurements. According to the measurement results. the PDVB networks are mostly pyrolyzed at 430 degrees C and their structures dynamically change to graphite-like structure between 600 and 700 degrees C The macropore structure retained while the mesopores disappeared after carbonization In addition, the surface area of the obtained carbons dramatically increased over 900 degrees C The typical carbon monolith carbonized at 1000 degrees C for 2 h had a surface area of 1500 m(2) g(-1) and uniform macropores with a diameter of jam To cite this article: J. Hasegawa et al., C. R. Chunk 13 (2010). (C) 2009 Academic des sciences. Published by Elsevier Masson SAS All rights reserved

DOI： 10.1016/j.crci.2009.04.003

Facile preparation of transparent monolithic titania gels utilizing a chelating ligand and mineral salts Reviewed

George Hasegawa, Kazuyoshi Kanamori, Kazuki Nakanishi, Teiichi Hanada

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY Vol. 53 ( 1 ) page： 59 - 66 2010.1

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

Highly homogeneous transparent titania gels have been successfully prepared from titanium alkoxide by a sol-gel method utilizing chelating agent, ethyl acetylacetate (EtAcAc), in the presence of strong acid anions. Only catalytic amount of a strong acid anion suppress the rapid hydrolysis of titanium alkoxide by blocking the nucleophilic attack of HO(-) and H(2)O, and the resultant moderate sol-gel reactions thus afford homogeneous gelation, leading to transparent monolithic titania gels. Gelation time can be widely controlled by changing amounts of water, chelating agent and salt. The ability of salts to suppress the too abrupt sol-gel reactions is strongly dependent on the electronegativity of anions and valence of cations. With employing NH(4)NO(3) as a suppressing electrolyte, the obtained titania gels can be converted to pure TiO(2) by simple washing and heat-treatment, and transformations to anatase and rutile structures were found to start at 400 and 600 A degrees C, respectively.

DOI： 10.1007/s10971-009-2056-5

Hierarchically porous carbon monoliths with high surface area from bridged polysilsesquioxanes without thermal activation process Reviewed

George Hasegawa, Kazuyoshi Kanamori, Kazuki Nakanishi, Teiichi Hanada

CHEMICAL COMMUNICATIONS Vol. 46 ( 42 ) page： 8037 - 8039 2010

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

Hierarchically porous carbon monoliths with high specific surface areas have been fabricated by removing nano-sized silica phase from carbon/silica composites pyrolyzed from bridged polysilsesquioxane. This activation method improves the homogeneity between inner and outer parts of the monoliths compared to the conventional thermal activation methods.

DOI： 10.1039/c0cc02974b

Effects of Starting Compositions on the Properties of Methylsilsesquioxane Aerogels Reviewed

Gen Hayase, Kazuyoshi Kanamori, Kazuki Nakanishi, Teiichi Hanada

MRS Online Proceedings Library Archive Vol. 1247 page： 1247-C08-17 2010

Sol-gel synthesis, porous structure, and mechanical property of polymethylsilsesquioxane aerogels Reviewed

Kazuyoshi Kanamori, Kazuki Nakanishi, Teiichi Hanada

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN Vol. 117 ( 1372 ) page： 1333 - 1338 2009.12

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Organic-inorganic hybrid aerogels with polymethylsilsesquioxane (PMSQ, CH3SiO15) composition have been synthesized by A modified two-step sol-gel process. The precursor alkoxysilane is hydrolyzed in weakly acidic condition, and subsequently allowed to undergo polycondensation in a weakly basic condition which is brought up fly the hydrolysis of urea. Two kinds of surfactant (nonionic and cationic) have been utilized to suppress macroscopic phase separation. The resultant porous morphology could be modified by the kind of surfactant used small angle X-ray scattering (SAXS) and nitrogen adsorption have been employed to assess the porous morphology and it is found that the obtained PMSQ aerogels consist of aggregated particles and each particle contains micropores. Compressive mechanical properties have also been discussed based oil tie obtained information oil porous morphology. (C) 2009 The Ceramic Society at Japan All rights reserved

DOI： 10.2109/jcersj2.117.1333

ワイドポアモノリスシリカカラムによるネイティブタンパク質の分離性能評価 Reviewed

森坂裕信, 桐野彩, 水口博義, 中西和樹, 植田充美

Chromatography Vol. 30 ( Supplement 2 ) page： 42 - 43 2009.10

Semi-micro-monolithic columns using macroporous silica rods with improved performance Reviewed

Kei Morisato, Shota Miyazaki, Masayoshi Ohira, Masahiro Furuno, Masahiko Nyudo, Hiroyuki Terashima, Kazuki Nakanishi

JOURNAL OF CHROMATOGRAPHY A Vol. 1216 ( 44 ) page： 7384 - 7387 2009.10

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

Monolithic silica columns in semi-micro-format have been synthesized using poly(acrylic acid) as a phase-separation inducer Via a Sol-gel route. The absence of a thick skin layer accompanied by deformation of the micrometer-sized gelling skeletons on the outermost part of the macroporous silica rod contributed to improve the efficiency of monolithic silica columns as thick as 2.4 mm in diameter The kinetic plot analysis revealed that monolithic silica columns with macropore diameter of 1 mu m and skeleton thickness of 1 mu m with decreased macroporosity behave similarly to columns packed with 3 mu m particles with slightly lower back pressure. (C) 2009 Elsevier B V. All rights reserved.

DOI： 10.1016/j.chroma.2009.05.028

Sol-gel synthesis of macro-mesoporous titania monoliths and their applications to chromatographic separation media for organophosphate compounds Reviewed

Junko Konishi, Koji Fujita, Kazuki Nakanishi, Kazuyuki Hirao, Kei Morisato, Shota Miyazaki, Masayoshi Ohira

JOURNAL OF CHROMATOGRAPHY A Vol. 1216 ( 44 ) page： 7375 - 7383 2009.10

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

We have developed a method of independently tailoring the macro- and mesoporous structres in titania (TiO(2)) monoliths in order to achieve liquid chromatographic separations of phosphorous-containing compounds Anatase TiO(2) monolithic gels with well-defined bicontinuous macropores and microstructured skeletons are obtained via the sol-gel process in strongly acidic conditions using poly(ethylene oxide) as a phase separator and N-methylformamide as a proton scavenger Aging treatment of (lie wet gels in the mother liquor at temperatures of 100-200 degrees C and subsequent heat treatment at 400 degrees C allow the formation and control of mesoporous structures with uniform pore size distributions in the gel skeletons, without disturbing the preformed macroporous morphology The monolithic TiO(2) rod columns with bimodal macro-mesoporous structures possess the phospho-sensitivity and exhibit excellent chromatographic separations of phosphorus-containing compounds (C) 2009 Elsevier B V. All rights reserved.

DOI： 10.1016/j.chroma.2009.06.016

Structural characterization of hierarchically porous alumina aerogel and xerogel monoliths Reviewed

Yasuaki Tokudome, Kazuki Nakanishi, Kazuyoshi Kanamori, Koji Fujita, Hirofumi Akamatsu, Teiichi Hanada

JOURNAL OF COLLOID AND INTERFACE SCIENCE Vol. 338 ( 2 ) page： 506 - 513 2009.10

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

Detailed nanostructures have been investigated for hierarchically porous alumina aerogels and xerogels prepared from ionic precursors via sol-gel reaction. Starting from AlCl(3)center dot 6H(2)O and poly(ethylene oxide) (PEO) dissolved in a H(2)O/EtOH mixed solvent, monolithic wet gels were synthesized using propylene oxide (PO) as a gelation initiator. Hierarchically porous alumina xerogels and aerogels were obtained after evaporative drying and supercritical drying, respectively. Macroporous structures are formed as a result of phase separation, while interstices between the secondary particles in the micrometer-sized gel skeletons work as mesoporous structures. Alumina xerogels exhibit considerable shrinkage during the evaporative drying process, resulting in relatively small mesopores (from 5.4 to 6.2 nm) regardless of the starting composition. For shrinkage-free alumina aerogels, on the other hand, the median mesopore size changes from 13.9 to 33.1 nm depending on the starting composition; the increases in PEO content and H(2)O/EtOH volume ratio both contribute to producing smaller mesopores. Small-angle X-ray scattering (SAXS) analysis reveals that variation of median mesopore size can be ascribed to the change in agglomeration state of primary particles. As PEO content and H(2)O/EtOH ratio increase, secondary particles become small, which results in relatively small mesopores. The results indicate that the agglomeration state of alumina primary particles is influenced by the presence of weakly interacting phase separation inducers such as PEO. (C) 2009 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcis.2009.06.042

Performance of wide-pore monolithic silica column in protein separation Reviewed

Hironobu Morisaka, Kengo Kobayashi, Aya Kirino, Masahiro Furuno, Hiroyoshi Minakuchi, Kazuki Nakanishi, Mitsuyoshi Ueda

JOURNAL OF SEPARATION SCIENCE Vol. 32 ( 15-16 ) page： 2747 - 2751 2009.8

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

A monolithic wide-pore silica column was newly prepared for protein separation. The wide distribution of the pore sizes of monolithic columns was evaluated by mercury porosimetry. This column, as well as the conventional monolithic column, shows high permeability in the chromatographic separation of low-molecular-sized substances. In higher-molecular-sized protein separation, the wide-pore monolithic silica column shows better performance than that of the conventional monolithic column. Under optimized conditions, five different proteins - ribonuclease A, albumin, aldolase, catalase, and ferritin - were baseline-separated within 3 min, which is faster than that using the particle-packed columns. In addition, the monolithic wide-pore silica column could also be prepared in fused silica capillary (600 min long, 0.2 mm i.d.) for highly efficient protein separation. The peak capacity of the wide-pore monolithic silica capillary column is estimated to be approximately 300 in the case of protein separation, which is a characteristic performance.

DOI： 10.1002/jssc.200800653

Rigid Crosslinked Polyacrylamide Monoliths with Well-Defined Macropores Synthesized by Living Polymerization Reviewed

Joji Hasegawa, Kazuyoshi Kanamori, Kazuki Nakanishi, Teiichi Hanada, Shigeru Yamago

MACROMOLECULAR RAPID COMMUNICATIONS Vol. 30 ( 12 ) page： 986 - 990 2009.6

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

Rigid crosslinked polyacrylamide monoliths with well-defined macropores have been successfully fabricated by organotellurium-mediated living radical polymerization (TERP) accompanied by spinodal decomposition. The TERP forms homogeneous networks derived from N,N-methylenebis(acrylamide) (BIS), in which spinodal decomposition is induced to form macropores. Macropore diameter can be controlled from submicrons to a few microns, and also the obtained networks contain mesopores in the macroporous skeletons, which are collapsed by evaporative drying. They are promising materials with hydrophilic polyacrylamide surfaces and have enough strength to preserve the macropores from the surface tension arising in the repetitive swelling and drying that may occur in many applications.

DOI： 10.1002/marc.200900066

Effect of La addition on thermal microstructural evolution of macroporous alumina monolith prepared from ionic precursors Reviewed

Yasuaki Tokudome, Kazuki Nakanishi, Teiichi Hanada

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN Vol. 117 ( 1363 ) page： 351 - 355 2009.3

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Porous alumina monoliths with high thermal stability have been prepared using sol-gel processing from ionic precursors. Samples were synthesized from AlCl3 center dot 6H(2)O and LaCl3 center dot 7H(2)O dissolved in a H2O/etanol solution containing poly(ethylene oxide) (PEO) via propylene oxide (PO) involved sol-gel reaction accompanied by phase separation. The heat-treated gels consist of controllable size of macropores and La-doped alumina skeletons. Doped lanthanum ions are homogeneously embedded in the gel matrix, which retards the phase transition from gamma-alumina to alpha-alumina during the sintering. The 3 mol% La-doped aluminate exhibits the BET surface area of 55.3 m(2)/g, after the heat treatment at 1100 degrees C for 24 It. Drying condition are also related to the thermal stability of obtained gels. Aluminate aerogels show higher thermal stability than corresponding xerogels due to relatively large mesopore size and high porosity. As a result, the 3 mol% lanthanum doped aluminate aerogel shows BET surface area as high as 82.5 m(2)/g even after heat treatment at 1100 degrees C for 24 h. (C) 2009 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.117.351

Pore Formation in Poly(divinylbenzene) Networks Derived from Organotellurium-Mediated Living Radical Polymerization Reviewed

Joji Hasegawa, Kazuyoshi Kanamori, Kazuki Nakanishi, Teiichi Hanada, Shigeru Yamago

MACROMOLECULES Vol. 42 ( 4 ) page： 1270 - 1277 2009.2

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

Macroporous cross-linked polymeric dried gets have been obtained by inducing phase separation in a homogeneous poly (divinylbenzene) (PDVB) network formed by organotellurium-mediated living radical polymerization (TERP). The living polymerization reaction of DVB with the coexistence of a nonreactive polymeric agent, poly(dimethylsiloxane) (PDMS), in solvent 1,3,5-trimethylbenzene (TMB) resulted in polymerization-induced phase separation (spinodal decomposition), and the transient structure of spinodal decomposition has been frozen by gelation. Well-defined macroporous monolithic dried gels with bicontinuous structure in the micrometer scale are obtained after removing PDMS and TMB by simple washing and drying. Inside the skeletons that comprise the macroporous structure, "skeletal pores" with various sizes in nanometer scale have also been found by gas sorption measurements. The skeletal pores are deduced to be formed by secondary phase separation in the skeletons due to the thermodynamic instability that arises in the separated phases during the polymerization. The properties of the macropores and the skeletal pores have been controlled by changing starting composition, molecular weight of PDMS, and reaction temperature.

DOI： 10.1021/ma802343a

Spinodal decomposition in siloxane sol-gel systems in macroporous media Reviewed

Kazuyoshi Kanamori, Kazuki Nakanishi, Teiichi Hanada

SOFT MATTER Vol. 5 ( 16 ) page： 3106 - 3113 2009

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

Spinodal decomposition in siloxane sol-gel systems has been investigated in a macroporous silica mould (pore diameter D 2.74 mu m) with a bicontinuous structure. Methyltrimethoxysilane (MTMS) and tetramethoxysilane ( TMOS) have been employed as siloxane gel sources and as-sintered hydrophilic and octadecylsilylated hydrophobic macroporous silica were used as the confining moulds. In an MTMS-formamide system with a longer phase separation time and higher viscosity, the phase-separated gels in both moulds exhibited a similar morphology when the bulk correlation length Lambda, i.e. spinodal wavelength in a free volume, was enough shorter than D. As Lambda was made longer by altering the starting composition, a wetting transition occurred in both the hydrophilic and hydrophobic moulds. In an MTMS-methanol system with a shorter phase separation time and lower viscosity, the wetting transition unexpectedly occurred when Lambda was much shorter than D in the hydrophobic mould. In TMOS-formamide system, fine and disordered structure has formed in the hydrophilic mould and never exhibited the wetting transition. A hydrodynamic wetting transition in each system was considered to occur when the ratio D/Lambda becomes smaller than unity, whereas a diffusive wetting transition takes place in the early stage of spinodal decomposition in the case where the chemical affinity between siloxane gel and the mould is high. Additionally, when the initial wavelength of spinodal decomposition is shorter than D, spinodal decomposition is highly suppressed due to the presence of the random surfaces of macropores. These effects may interplay depending on the physical and chemical nature of the sol-gel systems and the moulds.

DOI： 10.1039/b903444g

Elastic Aerogels and Xerogels Synthesized From Methyltrimethoxysilane (MTMS) Reviewed

Kazuyoshi Kanamori, Kazuki Nakanishi, Teiichi Hanada

POLYMER-BASED SMART MATERIALS - PROCESSES, PROPERTIES AND APPLICATION Vol. 1134 page： 173 - + 2009

Language：English Publishing type：Research paper (international conference proceedings) Publisher：MATERIALS RESEARCH SOC

Transparent organic-inorganic hybrid aerogels and aerogel-like xerogels have been prepared from methyltrimethoxysilane (MTMS) respectively by supercritical drying (SCD) and ambient pressure drying (APD). The new aerogels and xerogels significantly deform without collapsing on uniaxial compression and almost fully relax when unloaded. This elastic behavior., termed as "spring-back", allows APD without noticeable shrinkage and cracking. The flexible network composed of lower cross-linking density (up to three bonds per every silicon atom) compared to silica gels (up to four bonds) and repulsion between hydrophobic methyl groups bonded to every silicon atom largely contributes to the pronounced deformability and relaxing, respectively. Lower surface silanol group density also plays a crucial role for the "spring-back" behavior.

Preparation of Macroporous Poly(divinylbenzene) Gels Via Living Radical Polymerization Reviewed

Joji Hasegawa, Kazuyoshi Kanamori, Kazuki Nakanishi, Teiichi Hanada, Shigeru Yamago

POLYMER-BASED SMART MATERIALS - PROCESSES, PROPERTIES AND APPLICATION Vol. 1134 page： 139 - + 2009

Language：English Publishing type：Research paper (international conference proceedings) Publisher：MATERIALS RESEARCH SOC

Macroporous cross-linked polymeric dried gels have been obtained by inducing phase separation in a homogeneous poly(divinylbenzene) (PDVB) network formed by organotellurium-mediated living radical polymerization (TERP). The living polymerization reaction of DVB with the coexistence of a non-reactive polymeric agent, poly(dimethylsiloxane) (PDMS), in solvent 1,3,5-trimethylbenzene (TMB) resulted in polymerization-induced phase separation (spinodal decomposition), and the transient structure of spinodal decomposition has been frozen by gelation. Well-defined macroporous monolithic dried gels with bicontinuous structure in the micrometer scale are obtained after removing PDMS and TMB by simple washing and drying. The properties of the macropores have been controlled by changing starting composition.

Fabrication of macroporous silicon carbide ceramics by intramolecular carbothermal reduction of phenyl-bridged polysilsesquioxane Reviewed

George Hasegawa, Kazuyoshi Kanamori, Kazuki Nakanishi, Teiichi Hanada

JOURNAL OF MATERIALS CHEMISTRY Vol. 19 ( 41 ) page： 7716 - 7720 2009

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

Macroporous SiC ceramics were obtained from porous phenyl-bridged polysilsesquioxane prepared by a sol-gel method accompanied by spinodal decomposition subsequently subjected to intramolecular carbothermal reduction. By this method, we can obtain macroporous SiC ceramics with improved atomic-level homogeneity and controlled pore size more easily than by intermolecular carbothermal reduction using a mixture of SiO(2) and carbon powder. Therefore, the resultant SiC ceramics have sufficiently high purity without washing with hydrofluoric acid to remove residual SiO(2).

DOI： 10.1039/b913992c

Examination of mesopore structure of hierarchically macro/mesoporous silica by thermoporometry

E. Fukui, K. Shinohara, K. Nakanishi, K. Kanamori, T. Hanada

Materials Research Society Symposium Proceedings Vol. 1056 page： 28 - 33 2008.12

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

Thermoporometry was employed to monitor the mesopore evolution in wet, drying and heat-treatment stages of monolithic macro/mesoporous silica with SBA-15 like structure. Direct comparison of mesopores in wet state was only possible with the samples extracted with sulfuric acid. In good agreement with the preceding study, the sulfuric acid not only removed the surfactant but also modified the silica gel network into that with reduced amount of micropores and increased stability against the drying stress. Thermoporometry revealed that the structural evolution takes place completely in the wet condition, which accompanies a decrease in the thickness of non-freezable water. © 2008 Materials Research Society.

Phase separation in silica sol-gel system containing anionic surfactant

Taisuke Matsui, Kazuki Nakanishi, Kazuyoshi Kanamori, Teiichi Hanada

Materials Research Society Symposium Proceedings Vol. 1056 page： 418 - 423 2008.12

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

By inducing phase separation parallel to the sol-gel transition of alkoxy-derived silica systems, silica monoliths with well-defined co-continuous macropores were obtained from the systems containing anionic surfactants.We adopted three kinds of anionic surfactants which differ from each other in the length of alkyl chain (CH3(CH2)i7SO3Na, CH 3(CH2)i5SO3Na, CH3(CH 2)i3SO3Na).Mesopores were also found in the silica skeletons presumably by the supramolecular templating.Characterization of the dried or heat-treated samples was carried out by a scanning electron microscope (SEM) and nitrogen adsorption measurements.Experimental results showed that due to the moderate interaction between silica oligomers and surfactants, most of the surfactants are distributed to the solvent phase which determines the macropore volume.The median size and volume of the macropores could be controlled independently by the starting composition.In the absence of any additive to enhance templating by the surfactant, the samples exhibited only amorphous mesopores. © 2008 Materials Research Society.

Elastic organic-inorganic hybrid aerogels and xerogels Reviewed

Kazuyoshi Kanamori, Mamoru Aizawa, Kazuki Nakanishi, Teiichi Hanada

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY Vol. 48 ( 1-2 ) page： 172 - 181 2008.11

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

Novel aerogels and xerogels with methylsilsesquioxane (MSQ, CH(3)SiO(1.5)) networks have been prepared by a modified sol-gel process using surfactant and urea as a phase-separation inhibitor and as an accelerator for the condensation reaction, respectively. Optimized aerogels dried under a supercritical condition not only showed the similar properties as conventional pure silica aerogels such as high transparency and porosity etc, but also demonstrated outstanding mechanical strength against compression; the aerogel drastically shrank upon loading and then recovered when unloaded, which is called a "spring-back" behavior. On ambient pressure drying, the wet gel also exhibited the similar response against compression stress originated from the capillary pressure, and thus xerogels with the comparative structure and properties to those of corresponding aerogels have also been obtained. This unusual mechanical behavior is attributed to the trifunctional flexible networks of MSQ, low silanol concentration which prevents the irreversible shrinkage, and high concentration of a hydrophobic methyl group directly attached to every silicon atom which helps re-expansion after the temporal shrinkage.

DOI： 10.1007/s10971-008-1756-6

　 PREV - NEXT 　

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21