Takashi Ogihara

Structure and thermal/mechanical properties of poly(l‐lactide)‐clay blend

Organophilic montmorillonite was obtained by the reaction of montmorillonite (MON) and distearyldimethylammonium chloride (DSAC). The modified clay and poly(l-lactide), (PLLA), were solvent-cast blended using chloroform as cosolvent. The structure and properties of the PLLA-clay blends were investigated. Thermal measurements revealed that cold crystallization took place in the as-cast PLLA, and that the clay served as a nucleating agent. From small and wide-angle x-ray scattering measurements, it was found that silicate layers forming the clay could not be individually well dispersed in the PLLA-clay blends prepared by the solvent-cast method. In other words, the clay existed in the form of tactoids, which consist of several stacked silicate monolayers. However, these tactoids formed a remarkable geometrical structure in the blend films. That is, their surfaces lay almost parallel to the film surface, and were stacked with the insertion of PLLA crystalline lamellae in the thickness direction of the film. During the blend drawing process, fibrillation took place with the formation of plane-like voids developed on the plane parallel to the film surface. Furthermore, delamination of the silicate layers did not occur even under the application of a shearing force. Finally, Youngs modulus of the blend increased with the addition of a small amount of the clay.

Structure and thermal/mechanical properties of poly (∈-caprolactone)-clay blend

Montmorillonite was organically modified with distearyldimethylammonium chloride. This organically modified clay (OMON) and poly (ϵ-caprolactone) (PCL) were solvent-cast blended with chloroform, and the structure and properties of the resulting PCL-clay blends were investigated. From isothermal crystallization experiments, it was found that a small amount of OMON in the blend accelerated the crystallization of PCL, whereas a large amount of the organophilic clay delayed it. From small-and wide-angle X-ray scattering measurements, it was found that the silicate layers forming the clay could not be dispersed individually in the PCL blends. In other words, the clay seemed to exist as the tactoids consisting of some silicate layers. These tactoids formed a remarkable geometric structure; that is, their surface planes lay almost parallel to the blend film surface. Furthermore, the tactoids were stacked with insertion of PCL lamellae in the film-thickness direction. Preferred orientation of the PCL crystallites was induced by the presence of the clay. During the drawing process of the blends, fibrillation took place with formation of planelike voids developed on the plane parallel to the film surface. From dynamic viscoelastic measurements, it was shown that intercalation of PCL chains into the layered silicates did not take place in the blends prepared by the solvent-cast method used in this work.

Poly(vinyl alcohol)-clay and poly(ethylene oxide)-clay blends prepared using water as solvent

Montmorillonite (MON) was solvent-cast blended with poly(vinyl alcohol) (PVA) and poly(ethylene oxide) (PEO) using water as cosolvent. The structure and properties of the blend films have been investigated. From small- and wide-angle X-ray scattering measurements of the blends, the silicate layers of MON are found to be well dispersed individually in the PVA-MON blends, while the silicate layers in PEO-MON blends are found to exist in the form of a large clay tactoid. Furthermore, for both blends, it is found that the silicate layers are parallel to the film surface of the blends, and that preferred orientation of polymer crystallites is induced by the presence of MON. The effects of the MON content on the thermal behavior of the PVA- and PEO-MON blends have been studied with a differential scanning calorimeter. Furthermore, the effects of geometry of the silicate layers on dynamic behavior of the blends have been studied.

Structure and thermal/mechanical properties of poly(ethylene oxide) : clay mineral blends

Montmorillonite was organically modified with distearyldimethyl-ammonium chloride. This organically modified clay mineral and poly(ethylene oxide), (PEO), were solvent-cast blended with chloroform, and the structure and properties of the resulting blends were investigated. The effects of the clay mineral content on the isothermal crystallization of PEO are discussed. From small and wide angle X-ray scattering measurements of the blends, it was found that the clay mineral forms a remarkable geometrical structure in the blend and induces a preferred orientation of PEO crystallites. The effects of the clay mineral content on dynamic behaviour were also studied.

Structure and physical properties of poly(butylene succinate)/cellulose acetate blends

Polybutylene succinate (Bionolle) and cellulose triacetate (CTA) were solvent-cast blended with chloroform. Homogeneous blend films were obtained over a wide range of composition. The structure and properties of the blend films were investigated using various apparatuses. From Fourier transform infrared spectroscopy, wide-angle X-ray, and thermal measurements, it was found that the miscibility of Bionolle (BN) with CTA is excellent. In other words, in CTA-rich samples, it was found that BN molecules in the CTA matrix do not form a crystalline state, but forms an amorphous state. Therefore, the mechanical properties of the CTA-rich samples do not indicate the singularity before and after the melting point of pure BN. When CTA-rich samples were heated above the glass transition temperature of CTA, the BN molecules were eluted from the CTA matrix.

Processing of monodispersed ZrO2 powders

Abstract Monodispersed ZrO 2 fine particles were synthesized by the hydrolysis of the metal alkoxide in alcohol solution. Differential thermal analysis-thermogrametric analysis (DTA-TG) revealed that the weith loss of bound water with an endothermic reaction occurred below 320°C, and that the crystallization to the tetragonal phase from an amorphous phase occurred at 430°C. Calcined ZrO 2 powders were crystallized and consisted of spherical monodispersed ZrO 2 fine particles similar to their precursors. The state of dispersed particles in suspension was modified by pH adjustment. In a neutral suspension, particles were agglomerated, but in a basic medium they were well dispersed by a high negative charge in their zeta potential. Ordered compacts were produced by gravitational settling from the basic suspension. Three-dimensional close-packed arrays of particles were also observed in ordered compacts.

Formation of monodispersed Ta2O5 powders

The Ta2O5 powders synthesized by the hydrolysis of tantalum pentaethoxide, Ta(OC2H5)5 in alcoholic solution were monodispersed fine oxide particles, which were a uniform, spherical shape, non-agglomerate, and had a narrow size distribution. They grew to 1.2μm after ageing for 1 h after hydrolysis. Powder X-ray diffraction and differential thermal analysisthermogravimetric analysis showed the particles were amorphous and hydrated. These particles lost the water at 290° C and gave well-crystalline Ta2Oμ at 740° C. Throughout these thermal processes, the particle morphology was kept almost the same.

Preparation of monodispersed Y-doped ZrO2 powders

Abstract3 mol% Y-doped ZrO2 powders prepared by the controlled hydrolysis of metal alkoxides were monodispersed and grown to 0.5μm after 5 h ageing. The as-prepared powder was amorphous and hydrate but transformed into a tetragonal single phase by heating. Furthermore, the Y2O3 concentration of each particle was almost the same in all particles. The synthesis conditions such as ageing time, ageing temperature and water concentration greatly affected the particle morphology. The refluxing of the alkoxide solution was particularly necessary to prepare the monodispersed particles. On the basis of the variation of size distribution with ageing time, the mechanism of particle growth was discussed.

Synthesis of non-stoichiometric lithium manganate fine powders by internal combustion-type spray pyrolysis using gas burner

Non-stoichiometric lithium manganate fine powders were continuously produced by internal combustion-type spray pyrolysis. As-prepared particles were crystallized to a spinel structure with a Fd3m space group. The crystal phase and morphology of as-prepared particles were influenced by the flame temperature during pyrolysis. When the flame temperature was more than 1000°C, the crystal phase of Mn2O3 was observed. The discharge capacity of a lithium secondary battery was about 110 mAh/g at the rate of 1 C. The discharge capacity of a lithium secondary battery decreased at the rate of 1 to 9 C, but exhibited stable cycle performance at the rate of 9 C.

Synthesis and sintering of barium titanate fine powders by ultrasonic spray pyrolysis

Crystalline, spherical barium titanate fine powders with a narrow particle size distribution were prepared by ultrasonic spray pyrolysis. The stability of the starting solution was influenced by type of barium source and peptizer. The particle structure was influenced by the pyrolysis temperature of the barium source. The particle structure derived from barium acetate was dense, while powders derived from barium nitrate involved a lot of hollow particles. As-prepared powders were crystallized to a perovskite structure. Inductively coupled plasma analysis showed that the BaO/TiO2 molar ratio of as-prepared powders was 50.5:49.5. The effects of the concentration of the starting fluid, pyrolysis temperature and flow rate of carrier air through the furnace on powder characteristics such as particle size, size distribution and crystal phase were investigated. The particle size depended on the concentration of starting solution and the flow rate of carrier air, but the particle size distribution was independent of these variables. Single-phase BaTiO3 was obtained at more than 700°C. The relative density of barium titanate sintered at 1200°C was 98%. The hollow particles in the powders resulted in a low sintering density and a large grain size. The dielectric constant and tan δ of barium titanate at 25°C were 4500 and 0.02, respectively.