Effect of morphology on shear viscosity for binary blends of polycarbonate and polystyrene

The structure and rheological properties of binary blends of polycarbonate (PC) and polystyrene (PS) were investigated using various PS samples with different molecular weights, namely PS1k (M_w = 1,000), PS53k (M_w = 53,000), and PS240k (M_w = 240,000). The blends with PS53k and PS240k show phase-separated structures, whereas the blend with PS1k is miscible. The shear viscosity decreases greatly on addition of PS53k and PS240k, especially at high shear rates, which would be a great advantage at processing operations. Because the nonlinear response occurs in the small strain region for multilayered films of PC and PS240k, the origin of the significant viscosity drop for the phase-separated system is interfacial slippage at the phase boundary.     

Solidification of Al2O3–YAG eutectic composites with off-metastable eutectic composition from undercooled melt produced by melting Al2O3–YAP eutectics

It has been reported that solidification of the Al₂O₃–YAG equilibrium eutectic structure follows melting of the Al₂O₃–YAP metastable eutectic structure. Since the exothermic heat due to solidification was consumed by the endothermic heat due to melting, a fine and uniform eutectic structure was obtained. However, the composition of the Al₂O₃–YAG eutectic structure is restricted to the metastable eutectic composition. In this paper, Al₂O₃–YAG eutectic compacts with an off-metastable eutectic composition were prepared by the addition of Al₂O₃ particles to Al₂O₃–YAP eutectic particles with diameters less than 20 μm. In compositions ranging from 18.5 mol%Y₂O₃ to 13.5 mol%Y₂O₃, dense Al₂O₃–YAG eutectic compacts were formed without any Al₂O₃ segregation. The flexural strength and the fracture toughness remained almost unchanged with the increase in the Al₂O₃ phase. The addition of Al₂O₃ particles to the Al₂O₃–YAP eutectic particles enabled the matrix phase to change from the YAG phase to the Al₂O₃ phase.     

Non‐Enzymatic Geometry‐Selective Acylation of Tri‐ and Tetrasubstituted α,α′‐Alkenediols

A highly geometry‐selective organocatalytic acylation of tri‐ and tetra‐substituted 2‐alkylidene‐1,3‐propanediols has been developed. The highly E‐selective acylation of various tetrasubstituted 2‐alkylidene‐1,3‐propanediols was achieved in 96 to >99% selectivity for the first time by a non‐enzymatic protocol.     

Composition Regulation by Flow Copolymerization of Methyl Methacrylate and Glycidyl Methacrylate with Free Radical Method

It is important to match the feeding ratio of comonomers to the composition ratio in the resulting copolymers as closely as possible in industrial production, where the goal is often to produce more a homogeneous composition in copolymers. In this study, a flow copolymerization system with a conventionally initiated free radical method, together with randomly selected polymerization conditions is investigated. It is succeeded in achieving a closer match between the composition ratio and feeding ratio than previously reported in the copolymerization of styrene with methyl methacrylate and of glycidyl methacrylate with methyl methacrylate, which will widen the range of applications, by precisely controlling the mixing and heating in a flow polymerization apparatus. This is confirmed by the fact that the estimated values of reactivity ratios, r₁ and r₂, which are used in the reaction kinetics of copolymerization, are close to 1.     

A Novel KCaNi/α-Al2O3 Catalyst for CH4 Reforming with CO2

A potassium and calcium co-promoted nickel catalyst (KCaNi/-Al₂O₃) prepared by a direct impregnation method possessed a high activity, high stability and excellent coke resistance properties in CH₄ reforming with CO₂. XRD, XPS and H₂-TPR characterizations indicated that (i) Ca and K strengthened the interaction between Ni and -Al₂O₃ and promoted the formation of a unique NiAl₂O₄ phase on the surface of the catalyst and (ii) Ca and K increased the dispersion of Ni and retarded its sintering. Coking reactions (CH₄ temperature-programmed decomposition and O₂-TPO) disclosed that K reduced carbon formation via CH₄ decomposition.     

Investigation of CH4 Reforming with CO2 on Meso-Porous Al2O3-Supported Ni Catalyst

Meso-porous Al₂O₃-supported Ni catalysts exhibited the highest activity, stability and excellent coke-resistance ability for CH₄ reforming with CO₂ among several oxide-supported Ni catalysts (meso-porous Al₂O₃ (Yas1-2, Yas3-8), -Al₂O₃, -Al₂O₃, SiO₂, MgO, La₂O₃, CeO₂ and ZrO₂). The properties of deposited carbons depended on the properties of the supports, and on the meso-porous Al₂O₃-supported Ni catalyst, only the intermediate carbon of the reforming reaction formed. XRD and H₂-TPR analysis found that mainly spinel NiAl₂O₄ formed in meso-porous Al₂O₃ and -Al₂O₃-supported catalysts, while only NiO was detected in -Al₂O₃, SiO₂, CeO₂, La₂O₃ and ZrO₂ supports. The strong interaction between Ni and meso-porous Al₂O₃ improved the dispersion of Ni, retarded its sintering and improved the activated adsorption of CO₂. The coking reaction via CH₄ temperature-programed decomposition indicated that meso-porous Al₂O₃-supported Ni catalysts were less active for carbon formation by CH₄ decomposition than Ni/-Al₂O₃ and Ni/-Al₂O₃.     

Syntheses of Spinon Thermal Conductivity Materials in Sr–Cu–O System by Glass‐Ceramics Technique

We have synthesized spinon thermal conductivity materials in Sr–Cu–O system by glass‐ceramics technique. The materials are promising for active control of thermal energy in microelectronic devices because of high and anisotropic thermal conduction, its controllability, and electric insulation. Nevertheless, research on these materials has been limited to that concerning theoretical perspectives and investigation of physical properties using large single crystals. In this study, we adopt glass‐ceramics technique to synthesize these materials: We prepared melt‐quenched multicomponent oxides including SrO and CuO, and checked its glass‐forming ability and crystallization behaviors by heating. As a result, we have found that SrCuO₂ and Sr₁₄Cu₂₄O₄₁, known as the spinon thermal conductivity materials, are synthesized using SrO–CuO–?Li₂O–?Al₂O₃?–Ga₂O₃ system. This synthesis process for the system will provide practical application of the spinon thermal conductivity materials.     

Hydrogen‐bonding interaction between poly(ε‐caprolactone) and low‐molecular‐weight amino compounds

The specific interactions between several low‐molecular‐weight diamino compounds and poly(ε‐caprolactone) (PCL) have been investigated by FT‐IR. It was found that PCL and 3,3′‐diaminodiphenylmethane (3,3′‐DADPM) interact through strong intermolecular hydrogen bonds in the blend. Thermal and mechanical properties of PCL/3,3′‐DADPM blends were investigated by DSC and tensile measurements, respectively. The glass transition temperature of the blend increases while both the melting point and the elongation‐at‐break of the blend decrease with the increase of 3,3′‐DADPM content. Besides 3,3′‐DADPM, several other low‐molecular‐weight compounds containing two amino groups, such as o‐phenylenediamine or 1,6‐diaminohexane, were also added into PCL and the corresponding blend systems were investigated by FT‐IR and DSC. The effect of the chemical structure of the additives on the properties of PCL is discussed. © 2001 Society of Chemical Industry     

Phase Relations and Volume Changes of Hafnia under High Pressure and High Temperature

Using multi-anvil high-pressure devices and synchrotron radiation, X-ray in situ observations of HfO₂ under high pressure and high temperature have been performed to investigate its phase relations and compression behavior. An orthorhombic phase (orthoI) is stable from 4 to 14.5 GPa below 1250°–1400°C and transforms to a tetragonal phase, which is one of the high-temperature forms of HfO₂, above these temperatures. Another orthorhombic phase (orthoII) with a cotunnite-type structure appears above 14.5 GPa. OrthoII is stable up to 1800°C at 21 GPa. OrthoII is quenchable to ambient conditions. The orthoI-to-orthoII transition is accompanied by ∼8 vol% decrease. The bulk moduli of orthoI and orthoII at room temperature are 220 and 312 GPa, respectively. This low compressibility of orthoII indicates that it is a potential candidate for very hard materials.