Kazuhisa Yano

Bio: Kazuhisa Yano is an academic researcher from Toyota. The author has contributed to research in topics: Mesoporous silica & Mesoporous material. The author has an hindex of 29, co-authored 92 publications receiving 4373 citations. Previous affiliations of Kazuhisa Yano include Toyota Motor Engineering & Manufacturing North America & Denso.

Synthesis and properties of polyimide–clay hybrid

Abstract: A polyimide hybrid with montmorillonite clay mineral has been synthesized from a dimethylacetamide (DMAC) solution of poly(amic acid) and a DMAC dispersion of montmorillonite intercalated with an ammonium salt of dodecylamine. Montmorillonite consists of stacked silicate sheets about 2000 A in length, 10 A in thickness. In this hybrid, montmorillonite is dispersed homogeneously into the polyimide matrix and oriented parallel to the film surface. Thanks to this special structure, this hybrid showed excellent gas barrier properties. Only 2 wt % addition of montmorillonite brought permeability coefficients of various gases to values less than half of those of ordinary polyimide. Furthermore, this hybrid had low thermal expansion coefficient. © 1993 John Wiley & Sons, Inc.

Synthesis and properties of polyimide-clay hybrid films

Abstract: Polyimide-clay hybrid films with four different sizes of clay minerals have been synthesized to investigate the effect of the size of clay minerals to the properties of the hybrids. Hectrite, saponite, montmorillonite, and synthetic mica were used as clay minerals. Those clays consist of stacked silicate sheets about 460 A (hectrite), 1650 A (saponite), 2180 A (montmorillonite), and 12300 A (synthetic mica) in length, 10 A in thickness. The longer the length of clay mineral was, the more effectively properties of polyimide were improved. In the case of polyimide-mica hybrid, only 2 wt % addition of synthetic mica brought permeability coefficients of water vapor to value less than one-tenth of that of ordinary unfilled polyimide, and thermal expansion coefficient was lowered at the level of 60% of the original one. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2289–2294, 1997

Synthesis of mono-dispersed mesoporous silica spheres with highly ordered hexagonal regularity using conventional alkyltrimethylammonium halide as a surfactant

Abstract: Mono-dispersed mesoporous silica spheres with highly ordered hexagonal regularity were obtained with tetramethoxysilane (TMOS)–alkyltrimethylammonium chloride–methanol–water–sodium hydroxide. Just by changing the methanol ratio in the solvent, mono-dispersed particles were obtained with C14TMACl, C16TMACl and C18TMACl as surfactants under the same reactant concentrations. The adsorption properties of the samples were specific surface areas of 1150–1200 m2 g−1 and pore volumes of 0.60–0.81 cm3 g−1. Work is underway to explore new potential applications of these materials which possess both mono-dispersion characteristics and ordered mesoporous regularity with various mean pore sizes and particle diameters.

Particle size control of mono-dispersed super-microporous silica spheres

Abstract: The particle size of mono-dispersed super-microporous silica spheres synthesized from tetramethoxysilane and n-decyltrimethylammonium bromide was successfully controlled by variation of the synthesis temperature, methanol ∶ water ratio in solvent and silica source in the range of 0.52 to 1.25 µm, while their mono-dispersion characteristics were retained. The adsorption properties of the samples were a specific surface area of 700–1000 m2 g−1 and a pore volume of 0.32–0.41 ml g−1, and were mainly affected by the synthesis temperature. The mono-dispersed super-microporous silica spheres obtained had a particle diameter equivalent to the wavelength of visible light, and thus their optical use, for example, as photonic crystals, is expected.

Polyimide composite material and process for producing the same

Abstract: Disclosed herein is a polyimide composite material which comprises a polyimide-containing resin and a layered clay mineral which is intercalated with organic onium ions and dispersed in the polyimide. Owing to the intercalated clay mineral, the composite material has improved gas and water vapor barrier properties and a small thermal expansion coefficient. Disclosed also herein is a process for producing a polyimide composite material which comprises the steps of intercalating a layered clay mineral with organic onium ions, adding by mixing the intercalated clay mineral to a solution of a monomer or prepolymer for polyimide, removing the solvent, and forming a polyimide. This process makes the layered clay mineral miscible with and dispersible in polyimide.

Polymer-layered silicate nanocomposites: preparation, properties and uses of a new class of materials

Abstract: This review aims at reporting on very recent developments in syntheses, properties and (future) applications of polymer-layered silicate nanocomposites. This new type of materials, based on smectite clays usually rendered hydrophobic through ionic exchange of the sodium interlayer cation with an onium cation, may be prepared via various synthetic routes comprising exfoliation adsorption, in situ intercalative polymerization and melt intercalation. The whole range of polymer matrices is covered, i.e. thermoplastics, thermosets and elastomers. Two types of structure may be obtained, namely intercalated nanocomposites where the polymer chains are sandwiched in between silicate layers and exfoliated nanocomposites where the separated, individual silicate layers are more or less uniformly dispersed in the polymer matrix. This new family of materials exhibits enhanced properties at very low filler level, usually inferior to 5 wt.%, such as increased Young’s modulus and storage modulus, increase in thermal stability and gas barrier properties and good flame retardancy.

Progress, Challenges, and Opportunities in Two-Dimensional Materials Beyond Graphene

Abstract: Graphene’s success has shown that it is possible to create stable, single and few-atom-thick layers of van der Waals materials, and also that these materials can exhibit fascinating and technologically useful properties. Here we review the state-of-the-art of 2D materials beyond graphene. Initially, we will outline the different chemical classes of 2D materials and discuss the various strategies to prepare single-layer, few-layer, and multilayer assembly materials in solution, on substrates, and on the wafer scale. Additionally, we present an experimental guide for identifying and characterizing single-layer-thick materials, as well as outlining emerging techniques that yield both local and global information. We describe the differences that occur in the electronic structure between the bulk and the single layer and discuss various methods of tuning their electronic properties by manipulating the surface. Finally, we highlight the properties and advantages of single-, few-, and many-layer 2D materials in...

Polymer Layered Silicate Nanocomposites

Abstract: Polymer nanocomposites with layered silicates as the inorganic phase (reinforcement) are discussed. The materials design and synthesis rely on the ability of layered silicates to intercalate in the galleries between their layers a wide range of monomers and polymers. Special emphasis is placed on a new, versatile and environmentally benign synthesis approach by polymer melt intercalation. In contrast to in-situ polymerization and solution intercalation, melt intercalation involves mixing the layered silicate with the polymer and heating the mixture above the softening point of the polymer. Compatibility with various polymers is accomplished by derivatizing the silicates with alkyl ammonium cations via an ion exchange reaction. By fine-tuning the surface characteristics nanodispersion (i. e. intercalation or delamination) can be accomplished. The resulting polymer layered silicate (PLS) nanocomposites exhibit properties dramatically different from their more conventional counterparts. For example, PLS nanocomposites can attain a particular degree of stiffness, strength and barrier properties with far less inorganic content than comparable glass- or mineral reinforced polymers and, therefore, they are far lighter in weight. In addition, PLS nanocomposites exhibit significant increase in thermal stability as well as self-extinguishing characteristics. The combination of improved properties, convenient processing and low cost has already led to a few commercial applications with more currently under development.

Effects of particle size, particle/matrix interface adhesion and particle loading on mechanical properties of particulate–polymer composites

Abstract: There have been a number of review papers on layered silicate and carbon nanotube reinforced polymer nanocomposites, in which the fillers have high aspect ratios. Particulate–polymer nanocomposites containing fillers with small aspect ratios are also an important class of polymer composites. However, they have been apparently overlooked. Thus, in this paper, detailed discussions on the effects of particle size, particle/matrix interface adhesion and particle loading on the stiffness, strength and toughness of such particulate–polymer composites are reviewed. To develop high performance particulate composites, it is necessary to have some basic understanding of the stiffening, strengthening and toughening mechanisms of these composites. A critical evaluation of published experimental results in comparison with theoretical models is given.