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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. We have also started the synthesis of boron nitride nanotubes (BNNTs) having similar structure as CNTs and insulative property.
    (3D Synthesis)
  • Mochen LI (PD): Fluidized-bed synthesis of long CNTs.
  • Itsuki CHIKAARASHI (M2): Continuous gas-phase synthesis and collection with controlled shape of highly crystalline single-wall carbon nanotubes via rapid heating of catalyst source.
  • Riko TOYAHARA (M2): Catalyst preparation by chemical vapor deposition for fluidized-bed production of highly pure and long carbon nanotubes.
  • Takuma GOTO (M1): Development of a low-damage dry purification method for CNTs.
  • Vincentius WILSON (B4): Reaction rate analysis and carbonation enhancement of CO2 absorbing concrete.
  • Misuzu TAKASE (B4): Quantifying CO2 absorption effect of CO2-absorbing concrete.

  • (2D Synthesis & Applications)
  • Pengfei CHEN (D2): Activation of alkane for CVD synthesis of CNTs.
  • Sota EBISU (M2): Development of synthesis method of boron nitride nanotubes using low-cost sources and templates.
  • Shiori NAKAMURA (M2): Development of fabrication method of boron nitride nanotube thin films.
  • Junya OKA (M1): Synthesis of free-standing films of highly crystalline graphene using molten metal catalysts.
  • Takazumi KAIDA (M1): CVD synthesis of BNNTs from vapor source generated from solid boron.
  • Wataru KITAHARA (B4): Morphology control of vertically aligned CNT films afor small X-ray tubes with enhanced life.

Rapid SWCNT growth
Larger Movie.


Continuous production by fluidized bed: Movie

Soft Films and Solar Cells

Strong chemical bonds make bulk materials stable and mechanically hard. Whereas CNTs and BNNTs, one dimensional materials with strong chemical bonds and a-few-nm diameters, are stable yet mechanically soft. They easily form self-supporting, sponge-like films owing to the large specific surface areas, strong van der Waals interaction, and high aspect ratio for interwoven structure. When we integrate materials into devices, it is important how to make connections between materials. Our goal is to connect the interfaces as we like using these soft nanomaterials.
By the way, promoting the use of natural/renewable energy is essential to realize sustainable society. Japan has once been the leader for the solar cell technology and industry, however, we are now behind the world innovating this field. It is now widely recognized that renewable energy such as solar and wind powers are cheaper than nuclear and fire powers, there still remain vast areas with no electric power supply. Whether shall we install and use coal power plant or levelized renewable energy? The future will be much different. Various types of solar cells have been extensively researched, but the bulk crystalline silicon solar cells still account for >90% owing to their balanced cost, performance, reliability, and stability. Aiming at further cost reduction, 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 are also working on a simple cell fabrication process coating the Si film with CNTs and/or organic conductors. And we started technology assessment of their environmental, energy, and economical aspects.
    (Thin films+PV)
  • Yumi OSHIMA (M2): Interface materials based on nanosponges with various guest materials.
  • Misako OHASHI (M1): Fabrication of single-crystalline silicon films at low environmental burden and their solar cell applications.
  • Yurin KANAI (M1): Creation of Ag aerogel films by gas evaporation and particle deposition for interface bonding.
  • Yoshihiro TAKAHASHI (B4): Low thermal resistance and high heat resistance interfacial bonding between solids.
  • Ryosuke NAKAJIMA (B4): Stable p/n-doping of carbon nanotubes
  • Naoumi HASUMI (B4): Development of CNT transparent heater by spray coating and liquid surface transfer.

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

Materials, devices, and processes for clean energy

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.
Hydrogen is expected as a clean secondary energy, which does not emit CO2 upon usage. Renewable energy is getting cheaper drastically, and large-scale production of CO2-free hydrogen is expected in future. However, breakthrough still is needed in its storage and transportation for their efficient use for production of energy and chemicals. Various technologies such as hydrogen storage alloys and hydrogen carriers have been researched, in which the chemical conversion of hydrogen via interfacial reaction is important. We are developing new materials by hybridization of hydrogen storage alloys and electrocatalysts with carbon nanotubes, and apparatuses and processes based on those materials.
    (Batteries and electrochemistry)
  • S. NATARAJAN (PD): Upcycling of spent lithium ion batteries
  • Kentaro KANEKO (D3): Development of BNNT separators and lithium-ion batteries/all-solid-state batteries with high thermal stability.
  • Tomotaro MAE (D2): CNT-based lithium metal anodes for high-capacity lithium secondary battery.
  • Ben HUANG (D1): Research on pre-lithiation and performance improvement of SiO anode materials for lithium ion batteries.
  • Hiroki SAKURAI (M2): Composite of metal oxide and CNT for positive electrode of lithium ion batteries.
  • Ki CHOU (M2): Development of CNT current collector-based anode suitable for lithium polysulfide cathode.
  • Kaito NAKAMAE (M1): New fabrication method of Li-S battery via preloading of active materials and salts onto CNT sponge and injection of solvent.
  • Yukako OGINO (B4): Application of CNT/BNNT sponge film structure for rechargeable batteries.
  • Eun KO (B4): Structural control of CNT-based 3D current collector and its application to lithium polysulfide cathode.

  • (hydrogen)
  • S. ANANTHARAJ (PD): Development of high-performance non-noble-metal electrocatalysts for electrochemical conversion reactions
  • Keisuke YOSHIDA (D1): Design and demonstration of hydrogen-storage tank using MgH2-CNT composite material.
  • Kana KUTSUNUGI (M2): Development of anode and integrated cell for aqueous ammonia electrolysis.
  • Tomoki HAMASAWA (M1): Fabrication process of alloy-CNT composite for hydrogen storage with cycle stability.
  • Sumire MIYAKOSHI (M1): Development of anode catalyst structure for hydrogen production by electrolysis of liquid ammonia.
  • Hajar abdullah yasir AL ABRI (B4): Energy-efficient catalytic production of hydrogen from ammonia.
  • Shunsuke OBANA (B4): Highly efficient hydrogen production via water electrolysis using layered double hydroxide catalysts and CNT three-dimensional electrodes
  • Kazuo OHNO (B4): Development of a simple synthesis process for catalyst-doped Mg hydrogen storage materials using Mg nanoparticles
  • Ryota ZUKERAN (B4): Development of AB5-based hydrogen storage alloy-polymer resin structure for high-speed hydrogen absorption and desorption
  • Luke MURAKAMI (B4): Revealing cathodic reaction mechanism and enhancing current efficiency of liquid ammonia electrolysis

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

Assessment of Emerging Technologies

Extensive efforts and budgets are being paid to research and development in application fields. However, the rapid expansion of knowledge and technology has resulted in excessive specialization of fields, complication of systems, and distance between technology and society, sometimes causing the technologies unused even when they are successfully developed. Subjective research and development are inefficient and insufficient. It is essential to assess the technologies quantitatively by setting them to systems and estimating the performance change of the systems in society, comparing them with existing/competitive technologies objectively, and making feedback the results to research and development. It is important to shift from the ggood mattersh to guseful mattersh, develop methodologies and theories, and cultivate professionals.
We are developing new technologies for innovations in fields including energy and environment, and trying to conduct development and assessment of emerging technologies concurrently.
  • Ki CHOU, Tomotaro MAE: Life-cycle assessment of lithium-sulfur batteries.
  • Misako OHASHI: Life-cycle assessment of CO2-absorbing concrete.

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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