Analytical methods for evaluating crystallite size distribution by powder diffraction method have been investigated. A rapid numerical method for evaluating the exact theoretical diffraction peak profiles from collection of spherical crystallites with log-normal size distribution has been developed. The method is based on an efficient computer algorithm to evaluate the integral formula for peak profile functions, and it can be applied to estimate the broadness of the size distribution by a least squares curve-fitting method to the experimental size-broadened diffraction peak profiles within practical computing time. Theoretical frameworks and practical numerical methods for simulating the experimental diffraction peak profiles affected by the instrumental aberration have also been developed. It has been found that the observed powder diffraction peak profiles are reasonably simulated by convolution of intrinsic profiles with the instrumental functions. Accurate formulas for the instrumental aberration function of a high-angular-resolution synchrotron powder diffractometer with flat analyzer crystals as well as a laboratory powder X-ray diffractometer have been derived. Even though the spectroscopic distribution of the monochromated synchrotron beam is narrower than the laboratory X-ray source, it is still the dominant factor affecting the experimental diffraction profile. The asymmetric spectroscopic distribution of the X-ray provided by the beamline 4B2 at the KEK Photon Factory (PF) in Tsukuba was evaluated by measuring the diffraction peak profiles of standard reference crystalline powder of Si (NIST SRM640b). A new analytical method based on deconvolution by fast-Fourier-transform to remove instrumental aberration from experimental data has been developed. The segmented intensity data collected with the multiple-detector-system of the synchrotron powder diffractometer (MDS) at the beamline 4B2 at KEK-PF are affected by the different instrumental function for each detection system. The variations of the instrumental functions have been successfully adjusted by applying a Fourier-based modification on the raw diffraction intensity data.
This study investigates the characteristic of single-layered and multi-layered compacts made by selective laser sintering using blended bimodal titanium powders. The surface texture and tensile strength were investigated by using single-layered compact. There were few defects in the surface of specimen sintered in vacuum, and the roughness was smoother than that of specimen sintered in argon. Maximum tensile strength of single-layered compact sintered in vacuum was about 200MPa. The shrinkage and mechanical strength were investigated by using multi-layered compact. There was a unique tendency in the shrinkage of multi-layered compacts, which the density was around 76% and the adhesive bonding was not observed between layers, resulted in 70MPa of maximum bending strength and 50MPa of maximum tensile strength.
Recently, the present authors have found that egg-type powders with a single-core are easily obtained in the alloy systems possessing a miscibility gap in the liquid phase using conventional gas atomizing technique, and clarified that this behavior results from the Marangoni motion due to temperature change of interfacial energy between the liquid phases. In the present project, this effect was applied for fabrication of Bi-Cu based Pb-free solder materials and the following results were obtained.
(1) Both single-core and dispersion structures were obtained in the Bi-Cu-Sn, Bi-Cu-Sb and Bi-Cu-Zn systems, where the kind of structures depended on the alloy composition. From this research, a basic guideline for microstructural control of the atomizing powder in the Bi-Cu based alloy systems was established.
(2) Some Pb-free solder materials with a high melting point over 540K were developed in the Bi-Cu based systems. These materials showed a good wettability with Cu or Ni substrate and the microstructure including fine dispersed particles did not coarse during heating for joint.
Spark plasma sintering (SPS) method was applied to prepare dense compacts of high-temperature proton-conducting phosphates such as rare earth orthophosphates LnPO4 and rare earth polyphosphates LnP3O9 (Ln: rare earth). In the case of Sr-doped LaPO4, the relative density higher than 98% could be achieved with the SPS method when sintering temperatures above 1050℃ were employed, whereas only 94% at the highest was obtained with the conventional pressure less sintering (PLS) method at 1200-1300℃. Mechanical properties of the SPS samples were considerably improved compared with those of the PLS samples. The SPS samples prepared at 1050-1100℃ exhibited the bending strength of 240 MPa and the Vickers hardness of 6.7 GPa, and these values were much better than those of the conventional high-temperature proton-conducting oxides. Sr- doped LaPO4 prepared with the SPS method exhibited dominant proton conduction regardless of the sintering conditions, and the conductivities were comparable with those of the PLS samples. These results demonstrated that the SPS method was an effective tool to prepare proton-conducting phosphates with a high density and excellent mechanical properties while keeping a feature of proton conduction.
Grain refinement of metal microstructure is effective for the progress of mechanical property. It is essential technology for weld structure in which matrix materials is highly improving. In order to control a grain size of weld, the refinement mechanism under thermal cycle must be made clear. For the weld metal of High Strength and Low Alloy (HSLA) steel consisting of ferrite and pearlite microstructure, a lot of works about the refinement mechanism were presented. Those were postweld characterization but recently our research groups presented in situ observation of acicular ferrite formation for HSLA steel weld metal and discussed with grain refinement mechanism. On the other hand, there is little corresponding work for titanium weld. In the present work, microstructure development of pure and inoculated titanium were in situ observed along thermal cycle of Tungsten Inert Gas (TIG) welding, using laser scanning confocal microscopy. Under the in situ observation of inoculated titanium, heterogeneous nucleation of ・-phase at inclusion was clearly confirmed and kinetic information of plate growth was shown in high time-resolution. Furthermore, It was shown that grain boundary of ・-phase was pinned by the inoculated inclusion. Microstructure difference between pure and inoculated titanium was explained based on those in situ observations.
Bone has a well-organized microstructure at a nano-scale level and is composed of mineral apatite (Ap) and collagen (Col) fibril, providing reinforcement and pliability, respectively. Since Ap crystallizes under an anisotropic hexagonal lattice, the mechanical properties of an Ap crystallite are expected to depend on crystal orientation. The preferential alignment of the Ap c-axis along the extended collagen fibrils in bones depends strongly on the portion of bone. Therefore, new materials for bone replacement should possess the preferential alignment of Ap c-axis and Col fibril. In this study, we have developed Ap/Col composites with their preferential alignment on the basis of self-organization process by soaking a CaCl2/Tris-HCl buffer solution and a Na2HPO4 solution alternately (an alternate soaking process developed by Prof. M. Akashi). Deposition of Ap crystallites with preferential alignment of the c-axis was finally achieved in collagen matrix with preferred fibril direction.
We have investigated the relationship between a sintering condition of TiAlSi mixed powder and microstructure of the sintered compact for the purpose of fabricating large target (such as 160mm x 100mm). The pulse current pressure sintering (PCPS) method was employed in order to consolidate the mixed powders consisting of Ti50:Al40:Si10 (atomic %). The Ti50Al40Si10 compacts were sintered under the variation of pressure (49～98MPa) and temperature (773K ～873K). When sintering temperature was 833K or higher, Al-Si liquid oozed out from the sintered compact. On the contrary, when the temperature was 833K or higher, many micro pores have formed in the sintered compact. Higher sintering pressure (60MPa or higher) increased the relative density of the compact and caused the formation of metallic compound in the interface of Ti and Al/Si. Relatively high density consolidation of 97% for Ti50Al40Si10 mixed powder was obtained from the compact sintered at 823K under the pressure of 60MPa. Water quenching test revealed that this sintered compact had relatively high resistance of thermal shock due to the formation of little amount of metallic compound. Disk compacts of Φ190mm ×8mm were obtained and 160mm ×100 mm rectangular sputtering targets were fabricated from these disk compacts under the proper condition of PCPS.
Then we investigated that microstructure and mechanical properties of Ti-Al-Si-N films deposited from the rectangular targets to confirm whether the targets are useful for sputtering. The Ti50Al40Si10 targets were sputtered in a mixture of argon and nitrogen using an r.f. sputtering apparatus of Facing Target-type Sputtering. The highest hardness of 43GPa was obtained for the Ti-Al-Si-N films deposited at 573k without substrate bias. The hardness or the films is～20% higher than that for Ti-Al-N films. These results indicate that the Ti50Al40Si10 compact sintered by PCPS was useful and favorable for the sputtering target.
Present transparent conductive films utilized for solar cells are produced mainly by using ITO (Indium tin oxide). The main component of ITO, indium is rare metal and is said to become lack in near the future. Therefore the development of the new transparent conductive film is the urgent business.
In these days, die sensitized solar cells are anticipated to become new major solar cells. Their electrode is composed with titania crystals coated on the transparent conductive film. It is said that its best manufacturing process is the wet type procedure, that is, the nucleation and crystal growth. However it is said to be difficult to develop it. I think the difficulty come from the lack of the knowledge to control its real behaviors. In this study, as the first state of the development of transparent semiconductor electrode, the nucleation process of tin oxide generated by the hydrolysis of tin chloride (IV) was investigated.
Through this study, following conclusions were obtained.
1. Larger crystals can be obtained by the calcination of the amorphous precursor than fine crystals.
2. A transparent conductive film were successfully developed by spreading and calcinating the hydrolysis product of tin chloride under high concentration and low pH conditions.
The particle packing state and surface charge condition of the cake layer formed during microfiltration of PMMA latex beads were characterized by the streaming potential method. It was confirmed that in later stage of the cake filtration the streaming potential depended on particles forming the filtration cake regardless of membranes used. The packing state and surface charge condition of the cake layer were characterized by the analyzing the conductivity dependence of the streaming potential of the cake layer with a space charge model as fitting parameters of 2rp , which is an index of the distance between particles in the cake layer, and qp , which is the surface charge density of the particles. These fitting parameters reflected the effects of the particle size and voidage of the cake layer and the change in 2rp was consistent with the change in the cake structure. These observations showed that the streaming potential method for filter cakes can be used for the characterization of the packing state and surface charge condition of particles.
We have synthesized epitaxially-grown iron disilicide (FeSi2) nanoparticles using an electron-beam evaporation technique and characterized them by transmission electron microscopy (TEM). An Fe film was deposited on a Si(100) substrate, followed by thermal annealing at 1073 K for 2 h. It was found that epitaxially-grown nanoparticles with an average size of ～10 nm were formed just beneath the Si surface, suggesting that the deposited Fe atoms diffuse into the substrate. Every single phase of nanoparticles was examined in detail by high-resolution TEM observation, nano-beam electron diffraction, and energy-dispersive x-ray spectroscopy. Plane-view and cross-sectional TEM observations revealed that these nanoparticles consist of α-, β-, and γ-FeSi2. It was found that the morphology of nanoparticles is closely related to the phases. The α- and β- phases consist of angled hemisphere and asymmetric triangle-shaped nanoparticles, respectively, while γ-phase is hemispherical or columnar-shaped nanoparticles. These particle morphologies are discussed with respect to the lattice mismatches between the particles and the matrix.
I propose a simple and economical method for producing free-form microchannels in metal bodies. The concept for my process is based on a microscopic infiltration phenomenon that often occurs during liquid phase sintering of a mixture of metal powders with different melting points. A shaped compound of the metal powder with lower melting point and an organic binder are used as the sacrificial core that gives the shape of the microchannel. A body-metal powder compact that includes the sacrificial core is sintered at a temperature between the melting points of the sacrificial-core metal and body metal. The organic binder is removed during heating of the powder compact, and infiltration of molten sacrificial-core metal into the body-metal powder produces a microchannel and a lining layer. I examined following combinations of metal powders: titanium-aluminum, nickelaluminum, copper-tin, and iron-copper. Metallographic observations confirmed that microchannels were produced in the metallic bodies in all these systems. Furthermore, in the case of the titanium body metal with an Al-Cu alloy sacrificial-core metal, the inner wall of the microchannel was smoother than the case of titanium with aluminum. Content of alloying element such as copper or silicon in an aluminum alloy sacrificial-core metal influenced the composition and structure of the microchannel lining. This new insight indicates the potentiality of this microchanneling process for producing functional microchannel lining.
Monodisperse, submicron-sized spherical metal oxide particles have been widely investigated due to their importance in many areas of science and technology, e.g., pigments, catalyst, raw materials of advanced ceramics, and opal-based photonic crystals. A number of methods have been developed to prepare them. Among these methods, hydrolysis of metal alkoxide in homogeneous solution is one of the most effective methods to prepare high purity spherical metal oxide particles with narrow size distribution. However, application of this method has been limited to relatively inactive metal alkoxide. Here, we report the synthesis of monodisperse, submicron-sized spherical V2O5 particles with narrow size distribution via hydrolysis of vanadium isopropoxide (VO(OiPr)3) in acetone/pyridine mixture solution under air. The formed particles had almost perfect spherical shape and were nonagglomerated as revealed by transmission electron microscopic observations. Their size could be easily controlled from 200 to 800 nm by changing the concentration of pyridine while keeping narrow size distribution (standard deviation, ca. 7%). Elemental and Fourier Transform Infrared analyses revealed that these particles have a composition of V2O5 ·xPy ·yH2O (x≈0.8, y≈0.9) independent of their size. X-ray diffraction studies revealed that these particles have layered structure similar to that of V2O5·nH2O xerogel with an interlayer spacing of ca. 1.05 nm independent of their size, possibly due to the intercalation of H2O and pyridine between the V2O5 sheets. Since V2O5 has been extensively studied as an important material in many areas, e.g., catalysis, lithium ion battery, electrochromic device, sensors and actuators, these monodisperse spherical V2O5 particles may be highly appreciated in such areas.
The slurries studied were characterized by a conventional apparent viscosity measurement, a constant rate filtration and a stress relaxation test proposed in this study in order to identify the most affective property of a slurry on the crack formation of a green sheet during drying.
We evaluated the packing ability of the slurry from the constant rate filtration and stress relaxation rate of a cake form by the stress relaxation test. Slurries were also tape cast, dried at room temperature and then cracks formed in green sheets were observed. Slurry properties were controlled by changing the pH value of the slurry or the additive amount of the binder.
It was shown that there is not a good correlation between the apparent viscosity, packing ability of slurry and crack formation in the green sheet, while the number of cracks decreased with an increase in the stress relaxation rate of the cake. The stress relaxation test can be useful to predict crack formation during drying regardless of the slurry preparation method such as the pH adjusted or binder containing slurries.
In the particle-related engineering equipment such as circulated fluidized bed and pneumatic conveyer, it is well-known that particles form a spontaneous structure. This is the “particle cluster”. Clustering particles have significant interactions with the surrounding flows and enhance the transport performance of flows drastically. For the innovative designing and advanced controlling of such equipment, it is important to know the characteristics of the particle cluster in detail. However, it is not easy to investigate it by an experiment and a reliable and cost-effective numerical model has been highly demanded. In this project, for the development of new averaged-models, spatial-scale characteristics of particle cluster are investigated by using flow field data obtained by large-scale discrete particle model simulations. The extraction of dominant flow structures is attempted by applying Fourier and wavelet filtering techniques that are the basis of modern turbulent flow simulation techniques to the flow field data. The results show that the particle cluster consists of multiple-spatial scale components and dominant structures are successfully extracted by the two filtering techniques.
Regulations for small dust particles in exhaust gases are getting more and more stringent because epidemiologic studies have revealed the hazards of suspended particulate materials (SPM) in ambient air. Dust particles were electrically charged with unipolar ion flow from a barrier discharging electrode and then collected in an electrified packed bed, i.e., a packed bed to which a strong electric field is applied. The collection efficiency of the electrified packed bed turned out very high, namely, the efficiency for submicron particles was higher than 99% for a bed of 8 cm high packed with 3 mm alumina spherical particles. The electric field across the bed was 3 kV/cm, the superficial velocity, 0.63 m/s with 0.43 kPa pressure drop.
To examine refreshment and regeneration of used packed beds, soil dust (Kanto loam, JIS No.11) and DEPM (diesel exhaust particulate matter) were collected continually in the electrified packed bed until the collection efficiency deteriorated appreciably. Then the bed was backwashed with fresh air blows, which blew three times for one second at a superficial velocity of 2.5 m/s. The backwashing was effective for soil dust, but wasn’t for DEPM (tar and soot) because the electric resistivity of the packed bed could not be recovered enough by the backwashing.
As is well known, DEPM is oxidizable by ozone and radicals generated from electric plasma. The suitable temperature for the chemical reaction is believed to be higher than 150℃, preferably 250℃. In this experiment, however, the temperature of the bed was kept below 70℃ because the bed container was made of transparent plastics. Nevertheless it was found that some chemically active species (probably OH radical) generated from the barrier discharging electrode helped to oxidize DEPM.
Cold spray is a new coating method for the deposition of metal, alloy, polymer, or composite powder material onto various substrates. In the cold spray method, a coating is formed by exposing a substrate to high velocity (300 to 1200 m/s) solid-phase particles, which have been accelerated by the supersonic gas flow at a temperature (ambient temperature to 700K) much lower than the melting or softening temperature of the feedstock.
Development of low pressure vacuum chamber in cold spray and the performances of cold-sprayed copper coating are presented in this report.
Porous ceramic composites consisting of SiC whiskers (W) and mullite particles (M) were fabricated by a combined procedure of homogeneous dispersion in aqueous media, forced sedimentation and high temperature heating. Green bodies of the W-M composites with W:M = 3:1, 1:1 and 1:3 in volume ratio were formed by filtration of aqueous W-M mixed suspensions under reduced pressure. Heating the green bodies at 1250℃ in air caused the reaction bonding between mullite particles and SiO2 produced by the oxidation of SiC whiskers. Porosities of the W-M composites could be controlled by changing the mixing ratio of W and M, ranging from 68% to 82% for the W:M=1:3 to 3:1 composites, respectively. The examination on the stability at higher temperatures (1450° ～1550℃) was also conducted for the composites thus fabricated. The weight loss of the composites was observed after heat-treatment in Ar atmosphere, which might be due to the reaction SiC(s)+2SiO2(s) → 3SiO(g)+ CO(g). This reaction could be inhibited by HfO2-coating on the surface of SiC whiskers, which would lead to the fabrication of the porous W-M composites with improved high-temperature performance.
We investigate the spectral reflectivity of micro-periodic structures self-assembled with silica spheres. The propagation of electromagnetic wave can be controlled by periodic structures known as photonic crystals. Therefore photonic crystals are anticipated for advanced control of thermal radiation beyond solid state properties. The close-packed photonic crystals well-defined thickness are rapidly made on a Si wafer by using self-assembly of colloidal silica spheres. We measure spectral reflectivities of the samples with an FT-IR (Fourier Transform-Infrared Spectroscopy). The spectral reflectivity is enhanced at specific wavelength designed with numerical analysis. The peak of spectral reflectivity shifts to shorter wavelength with increasing incident angle. The angular dependency of the spectral reflectivity can be roughly calculated by the modified Bragg’s equation taking into account Snell’s law of refraction. We show that the reflectivity in infrared range is well enhanced by using large photonic crystals assembled with silica micro-spheres.
New evaluation method of particle adhesion characteristics based on fluid penetration method has been proposed. We presumed that the pressure drop of airflow in a particle bed is equivalent to the stress on the particles induced by the airflow passing through the void in the particle bed. It was also assumed that the particle bed collapses when the stress is equal to the strength of the particle bed expressed by Rumpf equation. Based on these assumptions, we defined the adhesion characteristic value as a ratio of adhesive force to particle surface area. It was confirmed that the adhesive characteristic values measured for spherical Silica particles having different sizes were equivalent to the theoretical values of van der Waals force. The fact implies that the proposed method can be applied to the evaluation of the adhesion characteristics.
This study investigates the barnacle settlement on several micro-textured surfaces manufactured by FPB (Fine Particle Bombardment) treatment. All of the modified surfaces possessed a microscopic surface roughness. The attachment of barnacles Amphibalunus amphitrite on micro-textured surfaces and polished controlled surface was observed in laboratory environment. In comparison with the polished surface, barnacles inclined to settle on the treated surface. In these experiments, surface roughness under the submicrometer scale, the larger the surface roughness was and the less the texture density was, more cypris larvae settled. We measured diameter of the first antenna head, and it was about 30 micrometers. This result investigates there is a gap which width is nearly the same size of the antenna head, it may be difficult for barnacles to settle on.
In this work, the experimental equipment to measure the mechanical properties of particle aggregates has been developed, where one aggregate of fine particles can be mechanically compressed with a glass fiber probe which is attached to the force transducer and can be moved downward at a speed of 50 nm/s～ by the micromanipulation technique. Hydrofluoric acid etching was applied to make the glass fiber probe with a tip diameter of less than 100μm, and then the tip surface was optically polished. Also, the deformation behavior of the aggregate during the compression test can be observed three-dimensionally using a confocal laser scanning microscope (CLSM). Using such an equipment, the mechanical properties of an aggregate of polystyrene particles with a diameter of 2 mm in NaCl aqueous solutions were measured, where the aggregate was formed under a simple shear flow, and then the relationship between the aggregate size and breakage strength of aggregate was investigated experimentally. As a result, it was found that the breakage strength of aggregate in the projected area range from 20μm2 to 40μm2 is divided into two groups. The observation using CLSM suggested that this is due to the structure difference of the aggregates classified in two groups: The larger porosity the aggregate has, the smaller the breakage strength is. While, the breakage strength of the aggregate with a projected area of more than 40μm2 increases monotonously with the aggregate size.
New method to fabricate the organic or inorganic non-woven cloth that can be applied to the filters was successfully developed. The obtained fiber of silica gel was extremely flexible. The diameter of fiber was about ５mm and the specific volume was about 500m2/g.
Monodisperse particles of tungsten(VI) oxide monohydrate were prepared in a hydrothermal system, where 20 ml of HCl solution (1.50 mol/l) was added at 40℃ to the same volume of Na2WO4 aqueous solution (0.50 mol/l) with magnetic stirring, followed by standing in an air oven for 168 h. The shape of particles was square platelet and the mean size was 0.72μm with 10% of the coefficient of variation. The XRD pattern was in good agreement with the standard JCPDS data for WO3・H2O. The particles, immobilized on ITO electrode, showed color alternation by electrochemical redox reaction in acid solution, indicating a possibility of application to new electrochromic display devices on the basis of monodisperse particles.
Nanocrystalline PbTiO3 particle/polymer hybrid was synthesized in situ through hydrolysis of modified metal-organics below 100℃. PbTiO3 precursor was synthesized from lead acetate, titanium isopropoxide and polymerizable diketonate ligand in 2-methoxyethanol. The modified PbTi alkoxide was hydrolyzed yielding PbTiO3 particles embedded in polymer matrix through chemical bonds. The nanocrystalline particles were identified to be PbTiO3 by EDX and electron diffraction. A fluid consisting of PbTiO3 particle/polymer hybrid and silicone oil revealed a typical electrorheological (ER) behavior on applying DC field. The ER behavior was found to depend upon the synthesis conditions of the hybrid.
Nanostructures are the gateway into a realm in physical, chemical, biological and materials science. In particular, optically transparent nanostructured materials showing optical nonlinearity or ferroelectricity have received much attention, because such materials have a high potential for applications in photonic devices such as optical switching. Crystallization of glass is one of the effective methods for fabrication of nanostructures, and many studies on crystallized glasses consisting of nanocrystals have been carried out. It is also of importance to develop techniques for enhancing optical properties of nanocrystallized glasses. In this study, we applied a high magnetic field of 10 T in the crystallization of the BaO-TiO2-SiO2 glass and examined whether the application of such a high magnetic field has the effect on the second-order optical nonlinearity of Ba2TiSi2O8 nanocrystals. We also examined the effect of thermal poling on the second harmonic intensity of transparent nanocrystallized glasses consisting of Ba2TiSi2O8 nanocrystals. It was clarified that the formation of Ba2TiSi2O8 nanocrystals is depressed in the crystallization under 10T and the c-axis orientation of nanocrystals occurs along to the applied magnetic field. The prominent enhancement in the second harmonic (SH) intensity is observed due to the thermal poling (DC electric voltage: 8.8kV/cm, temperature: 110～300℃，time: 1 h), demonstrating that a thermal poling is an effective method in enhancing anisotropic polarization of ferroelectric Ba2TiSi2O8 nanocrystals in the crystallized glasses. The present study proposes that the Maker fringe pattern for the SH intensity of nanocrystallized glasses is very sensitive to the anisotropic polarization of nanocrystals at the surface.
Various kinds of such new porous materials as non-oxide ceramics and intermetallic compounds, can be rapidly manufactured by combustion synthesis methods. By using combustion-synthesized materials of NiAl intermetallic compounds for a heater, it is possible to generate high temperature superheated steam. We have been able to generate superheated steam at 1000℃ by sending low temperature saturated steam at 100℃ from the bottom of a quartz tube filled with porous NiAl pellets that are heated by an electromagnetic induction coil wound outside the tube. Since superheated steam over 1000℃ was considered to be very reactive field, it was used for the fabrication of oxide ceramic powders with nano size. When mist of sakusann was induced to the superheated steam, NiO powder with the particle distribution from nanometer to subumicron could be synthesized. Such oxide nano powder as NiO was expected to using for catalyst.
TiO2‒Ag nanocomposite particles were prepared by spray pyrolysis of TiO2 (7 nm) dispersed AgNO3 solution. The structures and morphologies of powders were carefully characterized by combination of transmission electron microscopy (TEM) and three-dimensional electron tomography (3D-ET). It was clearly demonstrated by 3D-ET that the TiO2‒Ag nanocomposite particle was consisted of well-dispersed Ag nanoparticles within TiO2 matrix. Furthermore, it was shown by high-resolution TEM that the spray pyrolysis was capable of fabricating Ag particles with a few nm in size.
A nanocomposite permanent magnet, which is a nano-scale mixture of a hard magnetic phase and a soft magnetic phase, has become more and more attractive as a new magnetic material. Exchange coupling between the soft magnetic phase and the hard magnetic phase causes the magnetization vector of the soft phase to be aligned with that of the hard phase, resulting in high magnetization due to the soft phase and high coercivity due to the hard phase. Recently, mechanical alloying (MA) and the melt-spinning method have been applied to the production of nanocomposite magnets. These composite magnets, however, are magnetically isotropic, and a magnetically anisotropic composite magnet is significantly required. Therefore, in this experiment, we have tried to synthesize anisotropic nanocomposite magnetic powders by vacuum deposit method, and the corrosion behavior of them also investigated.
The photoluminescent properties of silica-coated cadmium selenide (SiO2/CdSe) nanoparticles was modified by using the size-selective photoetching technique. The irradiation of laser light caused the blue shift of the absorption spectra of SiO2/CdSe and finally the absorption onset agreed with the wavelength of irradiation light. These facts indicated that CdSe particles were photoetched to smaller ones until the irradiated photons were not absorbed by the photoetched particles and that the SiO2 shell layer surrounding the CdSe core prevented coalescence between the photoetched particles. The application of size-selective photoetching to SiO2/CdSe resulted in the development of the band gap emission, the degree being enhanced with progress of the photoetching. The peak wavelength of photoluminescence was blue-shifted with decrease in the wavelength of laser light used for the photoetching. The size selective photoetching could be applied to control the photoluminescence wavelength of the SiO2/CdS particles immobilized on a glass substrate, and the partial photoetching of SiO2/CdSe nanoparticle films produced intense band gap emission of CdSe at the photoetched area, resulting in the formation of a clear photoluminescence image under UV irradiation. This technique makes it possible to produce a multicolor photoluminescence image by irradiation with monochromatic lights having various wavelengths using a single source material.
The reaction condition for sol-gel reaction of tetraethoxysilane in natural rubber was investigated in order to prepare the green nanocomposite materials. N-hexylamine, n-heptylamine and n-oxtylamine were found to be useful for a high in situ silica filling into natural rubber, where silica particles were generated up to ca. 80 parts per hundred rubber by weight in situ. The formation of reverse micelle by the primary alkylamines with a long hydrocarbon segment was important to increase the in situ silica content in the natural rubber matrix. The primary alkylamines with a long hydrocarbon segment had also an advantage as a surfactant to disperse the generated in situ silica particles homogeneously in the rubber matrix. In the sol-gel method reported here, the solubility of catalyst in water was found to be the most influential point for controlling the in situ silica particles in natural rubber. Not only the direct use but also the diluted use of the obtained high in situ silica filled natural rubber were useful to prepare the various kinds of green nanocomposite elastomers. High stress and low hysteresis loss of these materials were achieved. These materials are expected to be new green nanocomposites for rubber industry and technology.