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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.
  • Pengfei CHEN (D3): Activation of alkane for CVD synthesis of CNTs.
  • Shun TANAKA (M2): Development of a safe and low-damage dry purification method for CNTs.
  • Yuki NAOTSUKA (M2): Stable and continuous synthesis of carbon nanotubes by floating catalyst CVD with enhanced decomposition of catalyst sources
  • Koyo ANDO (M1): Synthesis of CNTs by floating catalyst CVD method and development of transparent thin films.
  • Daiki KITAJIMA (M1): Coating of carbon nanotube with boron nitride for lithium-ion battery application.
  • Koki AKIYAMA (B4): Morphology control of vertically aligned CNT films and application to electron emitters for small X-ray tubes.
  • Yoshiyuki MATSUKAWA (B4): Fluidized bed synthesis of long, high-purity CNTs and co-production of low-carbon fuels.

Rapid SWCNT growth
Larger Movie.


Continuous production by fluidized bed: Movie

Functional Films

In many devices made of solids, the interface between solids often governs performance. As the performance of electrical and electronic devices increases dramatically, the density of energy input into the device increases, and how to dissipate the heat generated is an important issue. On the other hand, LEDs and sensors are mounted on various devices such as automobiles, and their anti-fog and anti-snow protection is also becoming important. Various types of thin films are required to connect solid interfaces and add functionality to surfaces.
Strong chemical bonds create stiffness as well as heat resistance and chemical stability in ordinary bulk materials. On the other hand, CNTs and BNNTs are thin, one-dimensional materials with diameters of a few nm that have flexibility with strong and stable chemical bonds. They also have a large specific surface area and van der Waals interactions between nanotubes, which intertwine with each other in a sponge-like free-standing film. The material with unique features of softness, thermal stability, and thermal conductivity can be produced, and is expected to have diverse applications in solar cells, in-vehicle devices, and semiconductor device manufacturing.
Evaporation of solids in an inert gas such as Ar allows the synthesis of solid particulates with a clean surface, and these particulate films easily sinter and return to the bulk. We have created novel materials with high thermal stability once bonded while bonding at low temperatures.
  • (Koyo ANDO (M1): Synthesis of CNTs by floating catalyst CVD method and development of transparent thin films.)
  • Sakurako TACHIBANA (M1): Low-damage high-yield dispersion and filtration of CNTs to develop transparent thin films.
  • Kentaro NAKA (M1): Creation of metal aerogel films by gas evaporation and particle deposition for interface bonding.
  • Kana AOSHIMA (B4): Highly heat-resistant interface bonding using metal aerogel films and thermosetting resins
CNT transparent conductive film with polystyrene
sulfonate (PSS) as dispersant and doping agent

Aerogel film consisting solely of silver

Next-generation rechargeable batteries

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.
Silicon (Si), silicon monoxide (SiO), and sulfur (S), which are made of abundant light elements, have a capacity that is an order of magnitude greater than conventional anode and cathode active materials. On the other hand, a large amount of lithium flows in and out of a small amount of active material, resulting in a large volume change and degradation problems. By encapsulating these active materials in a flexible sponge-like CNT film, we are working on the development of lightweight batteries with reversible volume change.
  • Tomotaro MAE (Lecturer): Development and environmental impact assessment of high energy density Li secondary battery.
  • S. NATARAJAN (PD): Upcycling of spent lithium ion batteries.
  • Yihua TANG (PD): Creation of carbon scaffolds with spatially controlled sodiophilicity for sodium metal batteries.
  • Ben HUANG (D3): Research on pre-lithiation and performance improvement of SiO anode materials for lithium ion batteries.
  • Chun Wen CHUNG (M2): Developmenet of SiO||S full cell using 3D current collector of CNTs.
  • Masaya KAWAGUCHI (M2): Fluidized bed synthesis of long CNTs, CNT structure control and lithium-ion battery applications.
  • Soma ARAI (M1): Development of porous carbon-carbon nanotube composite materials by chemical vapor deposition for lithium ion battery anode.
  • Sungjun KIM (B4): Development of Li-Li2S8 full-cells based on three-dimensional current collectors made of various CNTs.
Highly heat-resistant LIB consisting of CNT current collector and BNNT separator.

Reversibly expandable-shrinkable SiO-CNT anode.

Electrochemistry for Energy & Environment

The use of lithium ion batteries (LIBs) is expanding every year. Establishment of recycling is essential to prevent depletion of scarce resources, fires in garbage incineration plants, and environmental pollution due to improper disposal. We are aiming to realize direct recycling of spent LIB materials back to functional materials without returning them to raw materials, while maintaining their crystalline structure. Conventional battery fabrication methods require a large amount of active materials (several grams or more) for testing, which is one of the factors that make recycling research difficult. We are working on the construction of a simple recycling process by utilizing CNT film current collector technology, realizing battery fabrication with only a few milligrams of active material, and conducting efficient experiments.
Hydrogen, on the other hand, is also expected to be a clean secondary energy source that does not emit CO2 when used. Especially, hydrogen produced by water electrolysis using renewable electricity is attracting attention as green hydrogen. However, the usable electric energy is reduced to less than half during the conversion process from electricity to hydrogen to electricity. In water electrolysis, hydrogen is generated at the cathode and oxygen at the anode, but the problem is the high overvoltage of the oxygen generation reaction. Here, we focus on the impurities contained in various types of wastewater, which can be used as reducing agents. By replacing the oxidation of water at the anode with the oxidation of impurities, we aim to achieve energy efficient hydrogen production and simultaneous wastewater treatment.
  • Nobuhiro KURODA (M2): Development of direct recycling technology of NCM powders from spent lithium ion batteries.
  • Junyi LIU (M2): Development of simple technology for separation and activation of NCM cathode material from spent lithium ion batteries.
  • Aldo Gregarious DIONDIHON (M1): Development of direct recycling technology of NCA cathode of lithium ion battery.
  • RyosukeISHIBASHI (B4): Recycling of spent Gr-LFP full cells via resource-saving simple processes.
  • Hiroki RI (M2): Energy efficient hydrogen production and simultaneous waste-water treatment via hydrazine-assisted water electrolysis.
  • Riho NAKANO (B4): Enhancing water electrolysis using CNT-based three-dimensional electrodes with controlled bubble desorption.
  • Miki HAYAKAWA (B4): Energy efficient hydrogen production and simultaneous waste-water treatment via water electrolysis assisted by organic impurities.

    • Various recycling methods for LIB cathode materials

    CO2-absorbing concrete

    Concrete is indispensable for the construction and maintenance of social infrastructure, but the production of cement emits large amounts of greenhouse gases (5% of Japan's total and 8% of the world's total). This is because CaCO3 is heated by burning fossil fuels to form a compound of CaO and SiO2, which then reacts with H2O to harden as Ca(OH)2, producing a large amount of CO2 in terms of both material and energy. Recently, CO2-absorbing cement materials have been developed that hardens to CaCO3 through the reaction of CaO and CO2. CaCO3 is also the main ingredient of marble and is characterized by its high strength and stability. If CaO, a by-product of blast furnace slag and incinerator ash, is used as a raw material, it may be possible to shift from emissions to absorption of CO2. However, since this reaction is slow. To put it into wide practical use, it is essential to develop reaction acceleration technology based on the clarification of the reaction mechanism. Although this is a complex reaction in a gas-liquid-solid system, we are working on research and development based on our unique approach, utilizing our knowledge of chemical engineering, reaction engineering, and material processes.
  • Katsuya NAMIKI (Research Associate): In-situ reaction analysis and CO2-fixation evaluation of CO2 absorbing concrete using a batch reactor.
  • Yuli WEN (PD): In-situ reaction analysis and CO2-fixation evaluation of CO2 absorbing concrete using a flow reactor.
  • Daisuke MOTOHASHI (M2): In-situ measurement of CO2 absorption in a CO2-absorbing cement admixture using a flow reactor.
  • Ruri MATSUI (M1): Mixing effects of various powders on carbonation of CO2-absorbing cement admixture.
  • Yuya YOKOI (M1): Effects of porosity and powder addition on carbonation of cement pastes.
  • Keita MATSUOKA (B4): Evaluation of carbonation rate and mechanism of various industrial by-products

    • 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.
    • Tomotaro MAE (Lecturer): Environmental impact assessment of CNT-Based SiO||NCM batteries.
    • S. NATARAJAN (PD): Environmental impact assessment of recycling various components of spent lithium-ion batteries.
    • Yihua TANG (PD):
    • Daisuke MOTOHASHI (M2), Yuya YOKOI (M1): Assessment of greenhouse gas emissions including transportation of CO2-absorbing concrete.
    • Hiroki RI (M1): Efficient hydrogen production and waste water treatment by substrate-assisted water electrolysis.
    • Yoonho CHO (B3): Scientific research.

    Assessment of GHG emissions related with CNT production

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