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Nanomaterials & Self-Organization

Nanotechnology brings innovations to the society in wide fields of energy/environment, information/communication, etc., by adding novel functions to materials by controlling their structures at nanometer-scale. We are trying to establish the base of materials nanotechnology.

Let us think about the future clean energy systems. For large-scale electric power generation by solar cells, efficient use of high purity silicon is the key. We are trying to improve the efficiency several-ten times by making highly-crystalline films in one minute instead of bulk substrates. Transparent electrodes are important for both solar cells (yielding electricity from light) and display & lighting devices (generating lights from electricity). We try to replace rare-metal-based oxide semiconductors with carbon nanotubes or graphene. Nanotube-silicon hybrids are promising to realize Li ion batteries of larger capacities for (hybrid) electric vehicles. In this way, nanotechnology can bring innovations widely even with abundant carbon and silicon elements, and contributes to sustainable technological society.

But nanomaterials can never be made in macro-scale if we artificially manipulate atoms/molecules one-by-one. Self-organization, i.e. spontaneous formation of materials from numerous atoms/molecules, is the key. We are trying to understand the processes of chemical reactions of atoms/molecules, formation of nanostructures, and evolution of higher-order structures fundamentally. Based on the fundamental understandings with flexible thinking and idea, we are proposing and developing novel processes for nanomaterials and their devices.

Carbon Nanotubes

Carbon nanotubes (CNTs) are a unique 1D nanomaterial as thin as ~nm and as long as ~mm. They have good electrical conductivity, high tensile strength, thermal and chemical stability similarly with inorganic materials, and have small mass, flexibility, and compatibility with printing process similarly with organic materials. Thus, many applications have been proposed for them.
On the other hand, as their price (higher than gold) shows, their fabrication process is still under development and their practical applications are very much limited. Chemistry & engineering should lead the innovations for their production and manufacturing. We have developed rapid growth process of millimeter-long single-wall CNTs and are trying to realize their practical production. Please click here for details.
We are developing mass-production processes of CNTs by utilizing three-dimensional space of reactors, and direct fabrication of various devices by growing CNTs on device substrates.
    (3D Synthesis)
  • Shohei OKADA (M2): Flame synthesis of single-wall CNTs.
  • Katsuya NAMIKI (M1): Continuous production of single-wall CNTs and their fibers by floating catalyst CVD method.
  • Yohei MAEDA (M1): Development of gas-phase continuous production process of carbon nanoparticle-nanotube hybrids.
  • Risa MAEDA (M1): Quick wet preparation of catalysts on ceramic powders and fluidized-bed synthesis of long CNTs.
  • Masahiro YOSHIDA (M1): In situ dry preparation of catalysts on ceramic powders and fluidized-bed synthesis of long CNTs.
  • Kaisheng FENG (B4): Continuous gas-phase synthesis of CNTs by floating supported catalyst.
  • (2D Synthesis & Applications)
  • Shunji KOBAYASHI (M2): Creation of metal nanoparticle-CNT composites for thermal interface materials.
  • Michiko EDO (M1): Combinatorial screening of binary metal catalyst for chirality controlled synthesis of CNTs.
  • Sae KITAGAWA (M1): Fabrication of self-organized CNT spike arrays for electron emitter application.
  • Toshihiro SATO (M1): Understanding and engineering of catalytic growth of long CNTs on substrates.
  • Mayu ASAKA (B4): On-aluminum synthesis, morphology control, and heat-transfer application of CNTs.
  • Yuki KANAZAWA (B4): Filling polymer sheet with high-density, vertically-aligned carbon fibers for thermal interface materials.
  • Satoru KAWAKAMI (B4): Creation of soft, anisotropic electric conductors by hybridization of CNTs with metals.
  • Rei NAKAGAWA (B4): Catalysts and mechanisms for vertically aligned growth of long CNTs.

Rapid SWCNT growth
Larger Movie.


Continuous production by fluidized bed: Movie

Graphene and Thin Films

Graphene is a unique 2D nanomaterial of a single atomic layer having excellent conducting, transparent, and mechanical properties. But their practical production method has not been developed yet. We are developing new processes including direct synthesis of graphene films on substrates for electronic device applications, and low-cost production of its transparent conductive films for solar cells and touch panels. Such thin films can also be fabricated easily by dispersion and printing of CNTs. We are developing a loss-free fabrication process of thin films of CNTs from their powder.
Solar cells are one of the important application target of these studies. Although various types have been extensively researched, bulk single- or poly-crystalline Si type still accounts for >90% of all solar cells. To make solar cells cheaper and install them at larger scale, we are developing a rapid vapor deposition process of highly crystalline Si films at >10 times larger area than the conventional Si substrates in 1 minute. We also work on a simple cell fabrication process coating the Si film with CNTs. And we started technology assessment of their environmental, energy, and economy aspects.
  • Hiroyuki SHIRAE (D3/LD5): Loss-free fabrication process of highly-conductive, flexible CNT thin films.
  • Rongbin XIE (D1): Simple fabrication of silicon solar cells based on heterojunction with carbon nanomaterials.
  • Yukuya NAGAI (M2): Precisely controlled synthesis of graphene by CVD.
  • Kohki HAMADA (M2): Novel dry purification method of CNTs.
  • Makoto FUJITA (M2): Rapid vapor deposition of crystalline Si films for solar cells and its technology assessment by LCA.
  • Kei OHASHI (M1): Investigation of catalyst metals for direct synthesis of graphene on SiO2 substrates by etching-precipitation method.
  • Naoya ISHIJIMA (M1): Rapid vapor deposition of crystalline Si films and simple fabrication of flexible solar cells by coating Si with CNTs.
  • Kazuya TAKAHASHI (B4): Novel transfer-less synthesis method of graphene.
  • Mizuki MORI (B4): Novel synthesis method of free-standing graphene films.

1-min-epitaxy and lift-off of Si films for solar cells

Novel Rechargeable Batteries and Fabrication Processes

Energy devices must be produced at low cost and installed at large scale in order to contribute to the sustainable energy and environmental systems. We are developing next-generation, high energy and power density rechargeable batteries via rapid, high-yield fabrication process using low-cost sources.
Self-supporting, sponge-like films of single-wall and few-wall CNTs can be easily obtained by dispersion and filtration. For example, 0.1 mm-thick paper of our few-wall CNTs by fluidized-bed CVD is as light as 0.3 mg/cm3 and 3 mg/cm2, has a 80-90% porosity and 100 S/cm electrical conductivity. Differently from the conventional electrodes fabricated by coating active materials on heavy current collectors of Cu or Al foils with binder and conductive fillers, we are developing light-weight, high-capacity electrodes by capturing various active materials in the CNT papers.
Especially, Si has a huge theoretical capacity 10-times as large as the current graphite anode, however is suffering from the degradation due to the volumetric change during charge-discharge cycles. Vapor deposition is a common method in basic research in preparing thin films slowly and carefully under ultrahigh vacuum. But it enables rapid, low-cost fabrication of aluminum thin films for gas barriers in snack packaging in industry. We elevate the vapor pressure of the evaporation source by heating it to a temperature much higher than the melting point, deposit the vapor on substrates at lower temperature, and realize several micrometer-thick porous films quickly in 1 minute. We are applying this method also for various metals to realize high-performance battery electrodes via simple, low-cost processes.
  • Keisuke HORI (D1): Development of high-capacity lithium secondary batteries by capturing high-capacity cathode and anode materials in CNT sponge films.
  • Sohki KUZUHARA (M2): Development of self-supporting composite films of MnO2 nanoparticles and CNTs for electrochemical capacitor electrodes.
  • Yoichiro HONDA (M2): Development of self-supporting composite films of lithium titanate and CNTs for lithium ion battery anodes.
  • Go YAMAGATA (M1): CNT-based hybrid electrodes of transition metal oxides for cathodes of Li ion batteries.
  • Tatsuya TOMINAGA (M1): On-foil growth, structure control, and capacitor application of vertically-aligned CNTs.
  • Yuta HASHIZUME (M1): Rapid vapor deposition of self-supporting Si/metal/Si films and their application to lithium secondary battery anodes.
  • Kentaro KANEKO (B4): Creation of functional separator for lithium ion batteries.
  • Yusuke KOHASE (B4): Nanoparticle catalyst supported on CNT sponge films for electrolysis of ammonia for hydrogen recovery.
  • Kazuya TSUNODA (B4): Rapid, high-yield synthesis of platelet Si particles and their composite with CNTs for lithium secondary battery anodes.

1-min deposition of porous Si films for Li ion batteries

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Noda-Hanada Laboratory,
Department of Applied Chemistry,
School of Advanced Science and Engineering,
Waseda University,
3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan