The DEM (Discrete Element Method) technique for simulating the grinding media motion in a wet stirred mill has been developed. Additional parameters related to the flow of slurry inside a grinding chamber have been introduced to the standard DEM code. The grinding beads motion was simulated and compared with real motion recorded with a video camera. From the beads motion the specific impact energy of the beads was calculated and compared with the grinding rate constant of a gibbsite powder sample obtained experimentally. It was shown that the correlation between experimental and simulated data makes possible to predict the grinding performance of the mill for given conditions on the base of the computer simulation.

Bioactive polymeric microspheres can be produced by coating with a calcium silicate solution and the subsequent soaking in a simulated body fluid (SBF). Such combination should allow for the development of bioactive microspheres for several applications in the medical field including tissue engineering. Four types of polymeric microspheres with different sizes were used: (i) ethylenevinyl alcohol co-polymer (20-30μm), (ii) polyamide 12 with 10% of hematite (100mm), (iii) polyamide 12 (10-30μm) and (iv) polyamide 12 (300μm). These microspheres were soaked in a calcium silicate solution at 36.5oC for different periods of time under several conditions. Afterwards, they were dried in air at 60 and 100oC for 24 hrs. Then, the samples were soaked in SBF for 1, 3 and 7 days. Fourier transformed infrared spectroscopy, thin-film X-ray diffraction, and scanning electron microscopy showed that after the calcium silicate treatment and the subsequent soaking in SBF, the microspheres successfully formed a apatite layer on their surfaces in SBF within 7 days due to the formation of silanol (Si-OH) groups effective for apatite formation.

　Colloidal cerium oxide (CeO₂) nanoparticles prepared by hydrothermal synthesis were characterized by high-resolution transmission electron microscopy (HRTEM) and three-dimensional electron tomography (3D-ET). The HRTEM images showed that the CeO₂ particles were slightly truncated revealing {220} facets. 3D-ET revealed that the CeO₂ nanoparticles exposed predominantly {200} cubic facets. The nanoparticles were truncated at the corners exposing {111} octahedral facets and at the edges {220} dodecahedral facets. Furthermore, 3D-ET revealed the presence of some tetragonal-shaped CeO₂ nanoparticles.

Numerical simulation of impact of particles on a tubular wall in turbulent air flow has been conducted. It is found that the impact velocity normalized by the friction velocity decreased with the particle- Schmidt number. However, for larger Shmidt number, the impact velocity could not be expressed by the Schmidt number because the motion of particle depends not only on the turbulent diffusion but also on the inertia. The total impact velocity, V_total, increases with the air velocity, u₀, and can be expressed by V_total = k u₀^1.1. The result agrees qualitatively with Masda’s experimental data of the impact charge. The distribution of the total impact velocity agrees qualitatively with the experimental charge distribution.

The authors have succeeded in developing the highly polarization-axis oriented piezoelectric ceramics with superlattice structure by electrophoretic deposition (EPD) method under a strong magnetic field. Although this material has a small anisotropy of the crystal magnetic properties, the use of a magnetic field of 12T enables us to obtain the highly oriented ferroelectric ceramics. The increase in the grain size of the powder used for EPD resulted in a higher degree of orientation of the sintered ceramics, which is attributed to a higher rotation moment of larger grains. The highly polarization-axis oriented ceramics exhibited superior ferroelectric properties with a large remanent polarization of 26μC/cm² and a piezoelectric strain without hysteresis.

We have performed modification of yttrium iron oxide nanoparticle films in high-density RF plasmas sustained at high operating gas pressure. Experiments for argon plasma showed phase separation which occurred by oxygen deficiency and no phase transformation to YIG. Modification by adding Ar gas to oxygen gas resulted in significant structure change. These results suggest that the plasma sustained for argon/oxygen mixture gas have enough enthalpy for phase transformation to YIG. The addition of oxygen in Ar plasmas is effective for suppression of phase separation and enhancement of phase transformation to YIG.

The synthesis of CeO₂/ZrO₂ core/shell nanocrystals (NCs), which are CeO₂ NCs overcoated by a thin ZrO₂ layer, has been studied together with CeO₂, Sm₂O₃ and Gd₂O₃ doped CeO₂ and ZrO₂ NCs by a hot-surfactant colloidal method. Colloidal oleylamine solutions of the CeO₂, and doped CeO₂ NCs with an approximately 2.0 nm diameter and ZrO₂ NCs with a 2.5～3.5 nm diameter were respectively synthesized by the thermolysis of metallic acetylacetonates and the nonhydrolytic sol-gel reaction of Zr[OCH(CH₃)₂]₄ and ZrCl₄. The CeO₂/ZrO₂ core/shell NCs have been successfully synthesized by the addition of CeO₂ NCs as seed crystals to the ZrO₂ source solution and its reaction at 300□. The core/shell nanostructure, which consists of a 2.4 nm diameter CeO₂-core and 1.2 nm thick ZrO₂-shell, was determined by its XRD and HREM results.

The synthesis of Y₂O₃-stabilized zirconia was attempted by the following procedure: Zirconium isopropoxide, zirconium chloride and yttrium isopropoxide were dissolved in oleylamine at 60□ for a hour. The Y-concentration of the starting solution were varied as 10, 20, 30 at% and then the solutions were heated at 340□ for 2 h under Ar atmosphere. The products were transparent and colloidal solutions. Average particle sizes of the product powders extracted from the solutions were ranged in 2.0～2.6nm diameter. The lattice parameter, calculated from XRD patterns, increased with the analytical concentration of Y in the obtained powders. Based on these results, it was concluded that the YSZ nanocrystals were successfully synthesized. The grain growth behavior of the obtained YSZ nanocrystals was also investigated. Distinct grain growth was not observed below 800□; steep grain growth occurred above 850□. The low temperature sintering at 600□ of the YSZ nanocrystals using SPS technique was attempted, however, the resulting compact showed 69% of the theoretical density. Further study was needed in order to obtain the high density sample with several nm in grain size.

Waste incineration fly ash could be successfully recycled into calcium phosphate hydrogel, a type of fast proton conductor. Various properties of the intermediate and calcium phosphate hydrogel from incineration fly ash were characterized and compared with those from calcium carbonate reagent. It was found that the intermediate from the incineration ash, calcium phosphate glass has lower strength than that from calcium carbonate reagent.

The electrical conductivity of amorphous and crystallized hydrogel obtained from any raw material increases exponentially with increasing temperature. However, the amorphous hydrogel from incineration ash shows higher electrical conductivity than that from the reagent. On the other hand, the crystallized hydrogel from incineration ash has lower electrical conductivity and lower crystallinity than that from the reagent. Moreover, the difference in electrical conductivity between these crystallized hydrogels decreases with temperature. These experimental results suggest that the incineration fly ash is a useful calcium source for the synthesis of calcium phosphate hydrogel.

W/O microemulsions prepared with sodium bis (2-ethylhexyl) sulfosuccinate (AOT) have been used to form nano particles. Properties of the particles such as the shape and size are different from those of the particles formed with aqueous solutions. One of the possible causes of the properties is peculiar properties of the water pool of W/O microemulsions. However, the relationship between the properties of the water pool and those of the particles has not been investigated. In this study, as a first step to clarify the relationship, the peculiar properties of the water pool were investigated as a function of the size of the water pool. Light water (normal water) and heavy water were used to prepare the W/O microemulsions. Polarity, supercooling point and hydrogen bonding of the water pool and bulk water (light and heavy) were measured using fluorescent probe 1-anilino-8-naphthalene sulfonate (ANS), differential scanning calorimeter (DSC) and Fourier transform infrared spectroscopy (FT-IR) respectively. It was found that polarity, supercooling point and hydrogen bonding of the water pool are lower than those of bulk water. When light water is used to prepare W/O microemulsions, those properties are uniform at the size > 7nm, whereas they gradually become lower at the size < 7nm. In the case of heavy water, such a transition of the properties are observed at the size < 5nm. These peculiar properties may be due to the interaction between sulfonate groups of AOT and water molecules at the interface of W/O microemulsions.

We have developed a unique method for direct numerical simulations (DNS) of dense colloidal dispersions. This method enables us to compute the time evolutions of colloidal particles, ions, and host fluids simultaneously by solving Newton, advection-diffusion, and Navier-Stokes equations so that the electro-hydrodynamic couplings can be fully taken into account. The electrophoretic mobilities of charged spherical particles are calculated in several situations. The comparisons with approximation theories show quantitative agreements for dilute dispersions without any empirical parameters; however, our simulation predicts notable deviations in the case of dense dispersions. Recently, our DNS code was modified to take into account the effect of Brownian motions of the particles. The new code has been applied to several cases where coupling between hydrodynamic interaction and the thermal fluctuation becomes important. Striking examples include chain formations of likely charged particles due to the application of external electric fields and dynamics of chain conformations fluctuating in host fluids. We also observed clear tendency of the shear thickening behavior when we apply shear flow to dense colloidal dispersions. The origin of the thickening will be studied in future.

Liquid crystals composed of colloidally dispersed inorganic nanosheets were prepared by exfoliation of layered titanium and niobium oxides, and orientation of the nanosheets was controlled. Dispersed state of the nanosheets in the liquid crystalline colloids prepared from K₄Nb₆O₁₇ was irreversibly modified with concentrating the colloid, the modification which was monitored at different hierarchies: molecular to sub-mm level. A cationic porphyrin was added to the colloid as a spectroscopic probe, and its spectral profile successfully detected the modification of the dispersed state; the spectral response indicated alteration of molecular-level environment given by the nanosheets. Macroscopic observations with fluorescence optical microscopy and TEM showed buckling and aggregation of the nanosheets upon the concentration, indicating macroscopic change of the dispersed state of nanosheets. Moreover, macroscopic ordering of the nanosheets was aligned with external forces. Nanosheets were successfully aligned homeotropically on various substrates at cm level. This alignment was transformed to homogeneous under an external AC electric field. On the other hand, the colloidally dispersed nanosheets exhibited photocatalytic activity that is an intrinsic property of the titanium and niobium oxides. The nanosheet colloids generated hydrogen under UV irradiation. Sacrificial hole scavengers were unnecessary for the hydrogen generation because propylammonium ions used as the exfoliating reagent were present near the nanosheets to work as the hole scavenger.

Core/shell microspheres (core : polymethylmethacrylate (PMMA, ca. 90 μm in diameter), shell : hydroxyapatite (HA) mixed with a small amount of fumed silica) could be prepared by employing a mechanofusion system. The shell thickness and surface roughness of hollow microspheres, which were obtained by heat-treatment (1200℃ in air) of the core/shell microspheres, could be controlled by adjusting the mixing ratio of HA-based powders and PMMA microspheres in the raw materials. A mixture of the core/shell composites and a HA sol was subjected to firing at 1200℃ in air to prepare porous HA bodies. The amount of protein adsorbed increased with an increase in pore volume of the porous HA bodies.

Nowadays according to developments of micromachine, biotechnology and micro-fabrication technology, manipulation of small objects has become more and more recognized as an important technology. Manipulation technology using an acoustic radiation force by ultrasound has a number of advantages such that wide handling range is available, and has been studied by many researchers. However, for small objects with the size of μm order which are considered to be remarkably influenced by viscosity of the surrounding fluid and are the target of the recent micromanipulation, little studies have been carried out to date. There still remain several questions how viscosity of the surrounding fluid, elasticity of the object influence the acoustic radiation force.

In this study, measurements are made for acoustic radiation force acting on small particles in a progressive wave with a frequency of 400 kHz which is not plane. In order to see the influence of elasticity of the particles, three kinds of material with different properties are used and the experiment is made in the condition of ka « 1, where k is the wave number of sound waves and a is the radius of a particle on which the radiation force is exerted. It is well known that acoustic field interacts not only with objects as the acoustic radiation force but with the surrounding fluid through which the sound is carried to cause acoustic streaming. A small particle in the acoustic field is affected by the radiation force and the streaming. Acoustic streaming is numerically calculated and its effect is attempted to be eliminate in the experiment.

From experimental results, it is found that the acoustic streaming couldn't be neglect to estimate the acoustic radiation force and very larger forces were exerted on small particles than some theories of the radiation force.

In this project, wet chemical approaches for synthesizing metal nanocubes were investigated together with their applications. As one of the typical results, a facile synthetic method of monodisperse 85-nm Pd nanocubes in aqueous solution at room temperature was developed. By using cetyltrimethylammonium bromide (CTAB) as a capping reagent and reducing K₂PdCl₆ by ascorbic acid, the formation of 85-nm Pd nanocubes was clearly confirmed by observing the images with a field-emission scanning electron microscopy (FE-SEM). After the dispersion into pure water and the casting on the glassy carbon surfaces, Pd nanocubes were found to assemble to form the two-dimensional square array presumably due to the effect of CTAB. In addition, after just allowing the Pd nanocubes lie onto a smooth glassy carbon surface in solution, a flat and continuous structure of assembled Pd nanocubes could be formed on the glassy carbon surface. As the second example, we demonstrated a facile method for the preparation of the Pd nanobricks which comprised of atomic-step defects on the nanocrystals surface for the first time. By simply controlling the reaction parameters including the CTAB to hexamethylenetetramine (HMT) ratio and the ascorbic acid concentration, large scale Pd nanobricks structure could be prepared. These new structures should find extensively used in catalysis, surface-enhanced Raman scattering, magnetic and opto-electronics, due to their unique shapes and surface structure. Furthermore, some trials were performed for wet chemical preparation of Cu₂O nanocubes. While suitable conditions to form Cu₂O nanocubes were established, sphere and star-shaped Cu₂O nanocubes were formed depending on the synthetic conditions. These results imply the possibilities of wet chemical approaches to control the shapes of metal nanoparticles by just changing the synthetic conditions.

To develop the water photolysis into hydrogen and oxygen gases, photoinduced hydrogen production with the system consisting of photosynthesis dye molecule, Mg chlorophyll-α (MgChl-α) from Spinach as a visible light photosensitizer, NADH, methylviologen (MV²⁺) and platinum nano-particle in trimethyl alkyl bromide (CH₃(CH₂)_nN(CH₃)₃⁺. Br^-; n=8, 12 and 14) micellar media was investigated. Consequently, the effective MV²⁺ photoreduction and hydrogen production systems were accomplished using MgChl-α in CH₃(CH₂)₁₄N(CH₃)₃⁺ . Br^- micellar media.

The ultimate goal of the present study is to develop less invasive, locally injectable microdevices as a prolonged-release depot for peptide- or protein-based drugs. In order to fabricate such devices, a biodegradable coating material and nanoporous spherical core particles with high density and biocompatibility applicable for spouted bed spray coating were prepared; hydroxyapatite (HAp) and chitosan were selected for the sources of those materials.

HAp slurry was prepared by ball-milling of HAp powders with distilled water and dispersant for 4h. The slurry was spray-dried and the resultant products were sintered at various temperature. The spray-dried HAp microparticles showed porous and spherical shape. The pore size was dependent on the sintering temperature. The protein absorption study of HAp microparticles was carried out using bovine serum albumin (BSA) as a model protein-drug. The results demonstrated that The Hap microparticles possessed the adsorption capacity of BSA around 6 mass% at least.

Chitosan nanoparticles (CNPs) were prepared by a novel aqueous neutralization-precipitation technique as a biodegradable coating material. In a typical formulation, the CNPs with 300-400 nm in size were obtained. Using the CNPs thus prepared, microencapsulation of BSA-layered CaCO₃ core particles (63-75μm) was carried out using a spouted-bed spray-coating process to evaluate the coating performance of the CNPs. The mass median diameter of microcapsules and the %fraction of agglomerates were 96μm and below 5%, respectively, indicating that the CNPs have a low agglomeration tendency. It was found on the SEM observation that the microcapsules had a smooth surface without any post-thermal curing, indicating a good film-formability. In vitro release studies revealed that BSA was released from the microcapsules in a prolonged manner over a week in phosphate buffered saline (pH 7.4); no burst effect in the initial release period was observed when the feed weight percent of CNPs was 50 wt%.

A novel microfabrication method for L1₀-FePt nanoparticles ultrathin films that utilizes fluoroalkylsilane monolayer patterned substrates was developed. A line-patterned high wettability contrast surface which consists of lyophobic fluoroalkylsilane and lyophilic Si-OH phases was prepared via the local photodecomposition of the fluoroalkylsilane monolayer. Due to high wetting contrast between these phases, anisotropic condensing behavior of the solution was observed. Xylene solutions of the L1₀-FePt nanoparticles were used to coat the patterned surface. The L1₀-FePt nanoparticles ultrathin films were selectively formed on the lyophilic areas.

Microbial adhesion to solid surface is known to play an important role in a wide variety of situations. In this study, the early stage of microbial adhesion to solid surface was investigated using the lactic acid bacterium. Microbial cells were washed using the sterile NaCl aqueous solution to remove the extracellular polymeric substances (EPS). The washed and intact cells were used for the experiments. Two types of beads were used as support materials: untreated silica (NTsilica) and AmP-silica with amino groups. The surface propeties of NT-silica and AmP-silica are negative/hydrophilic and positive/hydrophilic at the neutral pH, respectively. The surface potential and surface tension of microbial cells were analyzed by the measurements of electrophoretic mobility and contact angle. The percentage of cells adhering to support materials was calculated using the absorbance of microbial suspension before and after mixing. As a result, the percentage of cells adhering to AmP-silica was higher than to NT-silica. The percentage of cells adhering to AmP-silica decreased with an increase in the ionic strength. In contrast, the result of NT-silica was a tendency opposite to that of AmP-silica. These results could be explained by the extended DLVO theory using measured physico-chemical properties. Moreover, although there were slightly differences in the physico-chemical properties between washed and intact cells, the percentage of intact cells adhering was higher than that of washed cells. This result indicated that the EPS promoted the adhesion of the microbial cell to solid surface. Furthermore, the system to measure the adhesion force between the microbial cell and solid surface was constructed. As a result, it was found that the adhesion forces of the cell to slide glass at the ionic strength 5 mM was ca 3.4 pN.

An entirely new idea of using powdered material as propellant is suggested for the space propulsion system. Since powdered propellant does not need any high pressure system and temperature control for storage in spacecraft, it is very manageable propellant especially for small satellites and deep space probes. Moreover, although powdered propellant is one kind of solid propellant, it has controllability of propellant supply. The thruster we suggest consists of the propellant supply part using electrostatic adsorption and electromagnetic acceleration part. First we performed a fundamental experiment about electrostatic adsorption and showed the usefulness of this propellant supply system. Second, we made an experimental pulsed plasma thruster and compared some performances of thruster using solid propellant and powdered propellant. The thrust measurement instrument was newly developed in order to detect the impulse bit, average thrust and propellant consumption rate simultaneously.

The handling of nanoparticles is quite difficult, and still remains as a challenging topic for researchers as well as engineers. One method to enable fairly easy handling of this material is to mold it into microstructures which can be easily handled. Nanoparticles can be molded quite easily to have a spherical morphology. However, if the resulting spheres are large, the diffusion paths within them will tend to become long, and therefore generally, it will become very difficult to utilize the unique properties of the nanoparticles included within them. On the other hand, if the resulting spheres are small, a severe pressure drop will occur when fluids are passed through a column packed with them. Therefore, it is necessary to develop a method to mold such nanoparticles to have a morphology which has short diffusion paths, and which do not cause significant pressure drops during usage.

One ideal morphology is a microfiber which has a diameter in the μm range. Another ideal morphology is a monolithic microhoneycomb having channels which sizes are also in the μm range. However, it is very difficult, if not impossible, to mold nanoparticles to have such morphologies using conventional methods.

Recently in our laboratory, we found that silica hydrogels can be molded into fibers or into a monolithic microhoneycomb by freezing them unidirectionally. As ice crystals which grow within the hydrogels during freezing act as the template, we named this method the ice templating method. In this work, we applied this method to silica hydrogels including nanoparticles. We found that the nanoparticles could be molded into microfibers and monolithic microhoneycombs using this newly developed freezing method. The properties of the obtained microstructures were also investigated in detail.