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The volume change, ΔVh,, accompanying the hydrophobic hydration associated with the volume phase transition in Poly(N-isopropylacrylamide) gels was measured by a simple method. The hydration accompanies a negative ΔVh′−2.5 cm3/mol. The P-T phase diagram, the coexistence curve, for the gels was determined from the swelling ratio-pressure curves up to 350 MPa for various constant temperatures. The contour of the coexistence curve is shaped like an ellipsoid on the P-T plain, which is a feature peculiar to the reversible pressure-temperature denaturation of a protein. The thermodynamic analysis of the Clausius–Clapeyron relation for the measured ΔVh elucidates that the obtained coexistence curve represents the phase boundary between thermodynamic different phases like the two phases, native and denatured, of a protein and gives the transition enthalpy, ΔH, 5.2kJ/mol by estimate, which well coincides with the transition heat measured by a calorimetric method. Considering the volume-dependent free energy, Δvmi · P, for the mixing free energy of the gel, we can fit the calculated curve to the measured swelling ratio-pressure curve of PNIPA gels. The value of Δvmi changes the sign from negative to positive above around 100MPa. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 405–412, 2005

The swelling behavior of poly(N-isopropylacrylamide) (PNIPA) gels in seawater at high pressures up to ∼40 MPa is examined in terms of human activity at deep sea. The neutral gel in seawater undergoes a continuous volume transition at 26°C at atmospheric pressure. Addition of the ionic group (sodium acrylate) does not have much effect on the swelling properties of the gels in seawater except that the transition temperature is somewhat increased. At high constant pressures up to ∼40 MPa, the gels undergo a continuous volume transition at 26–28°C as the temperature varies. Normally, the gel takes a swollen state at deep sea. The ratio of the volume change associated with the transition is more than 10, which is 3 times larger than that obtained by changing the pressure at a constant temperature. The results suggest a possibility that the phase transition of PNIPA gels is utilized for producing mechanochemical energy at deep sea. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1069–1072, 2005

The volume phase transition of neutral poly( N -isopropylacrylamide) gels in aqueous solutions of pyridine was studied by means of depolarized Rayleigh and Raman scattering. The Rayleigh reorientational relaxation time, τ Ray , of pyridine, calculated from the half-width of the depolarized Rayleigh spectrum, attains a maximum at approximately x =0.2 at which the gel undergoes the abrupt volume change. As the gel shrinks, the ratio, I G / I S , of the intensity of the spectrum of the gel to that of the aqueous solution abruptly decreases, reflecting the decrease in the number of free pyridine in the gel network. A new Raman band, which shifts by 130 cm −1 , appears for the shrunken gels. This new band is assigned to the C–H stretching vibrations of pyridine bound to the PNIPA chains by the hydrogen-bonding interaction. As the gel shrinks, the intensity, I B , of the new Raman band abruptly increases, on the contrary, the intensity, I F , of the free pyridine band decreases. The intensity ratio, I F /( I F + I B ), which represents the number fraction of free pyridine in the network, excellently agrees with I G / I S . The results show that the hydrophilic solutes such as pyridine in PNIPA gels are bound by the hydrogen-bonding interaction between the solutes and the chains.

The effect of phosphorus on microstructure and mechanical properties of dephosphorised JIS AC3A alloys was investigated. In 3 ppm phosphorus alloy, eutectic silicon crystallizes in very fine and lamellar structure, and iron base intermetallic compounds crystallizes in very fine one. In case of 12 ppm phosphorus alloy, eutectic silicon takes a coarse acicular shape, and iron base intermetallic compounds are also coarse. Strength of 3 ppm phosphorus alloy is larger than that of 12 ppm phosphorus one. Particularly elongation and absorbed energy of 3 ppm phosphorus alloy are over three times as large as those of 12 ppm phosphorus alloy. By dephosphorising commercial alloys, we removed the deleterious effect of phosphorus on microstructure of eutectic silicon and iron base intermetallic compounds and improved mechanical properties.

In the present study, an attempt is made to prepare a highly c-axis oriented thin film with the composition of Bi4Ti3O12 (BIT). Bismuth nitrate and titanium tetrabutoxide were used as raw materials. Acetylacetone and ethylene glycol were used as the solvents. The thin film was a single phase of BIT completely oriented along the c-axis on Pt substrate with good ferroelectric properties at room temperature: coercive field of 25kV/cm, remanent polarization of 2.5μC/cm2, dielectric constant of 130. The key technique to highly c-axis oriented thin films was heat treatment of sol prepared by optimum combination of raw materials and solvents.

The effect of phosphorus on the silicon particle structure during solidification has been investigated for Al–Si eutectic alloy. Phosphorus content less than about 5 ppm refines the microstructure. The eutectic silicon exhibits a very finely divided lamellar structure. A few dendrites of primary aluminum crystal are also observed showing a slightly hypoeutectic behavior for this composition. For phosphorus content not less than 10 ppm, the coarsening of eutectic structure was observed. Then coarse crystals of plate-like silicon appear and the eutectic silicon of acicular shape becomes much coarser than that in the case of the pure alloy. Al–12.5%Si alloy containing phosphorus forms small crystals of aluminum phosphide in the molten aluminum before solidification, which act as effective nuclei for silicon and promote crystallisation of plate-like silicon at the start of solidification. The fact that undercooling of eutectic solidification becomes smaller for phosphorus containing alloy supports the above idea.

Ferroelectric polycrystalline lead germanate (Pb 5 Ge 3 O 11 , PGO) thin films were prepared by a dip-coating method in a sol-gel process. The optimum conditions for c -axis oriented films at a low process temperature were examined. The films were synthesized on glass substrates with sputtered ITO thin films. The c -axis oriented thin films were readily obtained by heating the coating solution. The dielectric constant of the thin films prepared from heated solution was twice as large as that of films prepared from non-heated solution. The c -axis orientation of the thin films was favored, and remanent polarization and coercive force of the films increased with increasing sintering temperature.

Effect of strontium addition on the gas pick-up and porosity formation in AC4CH alloys have been investigated. The alloys melt were held in the controlled humidity. It has been demonstrated that the gas pick-up occurs from the reaction between the moisture in the atmosphere and the aluminum melt rather than the reaction between the moisture and the strontium. There is less strontium loss in the moist argon atmosphere than in the noncontrolled atmosphere. The loss of strontium and the gas pick-up proceed faster in the melt of secondary alloy ingots than of new alloy ingots. Consequently much porosity is observed in the conical casting from a secondary alloy melt. Conical castings modified with strontium are more prone to exterior shrinkage in the case of lower gas content. However, the higher the gas content, the more gas pores are formed, thus reducing the volume of interior shrinkage.

Cyclic bending fatigue tests were performed on alumina short fiber reinforced AC8A aluminum alloys in order to examine the effects of volume fraction of fibers and nonfibrous inclusions (shots) on S-N curves. Fatigue limit stress increased with increasing volume fraction of fibers. The effect of shots on S-N curves was very little when shot content was less than 0.1%. Cyclic fatigue crack propagation rate was also measured on the composites. The crack propagation rate increased with increasing volume fraction of fibers when it was compared at the same stress intensity range.

In relation to the production of composite materials, the present paper studied the influence of the solidification rate on the microstructure of an unidirectionally solidified eutectic Al-Fe alloy. The results obtained are as follows:(1) When the solidification rate was less than 10cm/hr, FeAl3 rods were regularly aligned parallel to the solidification direction. However, when the solidification rate was more then 20cm/hr, the microstructure became irregular, as observed in the normal cast structure.(2) The eutectic compounds under high and low solidification rate were rods and flakes in shape, respectively. It was found that the rod diameter decreased as the solidification rate increased.(3) The interrod spacing, λ, was related to the solidification rate, R, as λ2R=K, where K was 2.7×10-9cm3/sec.

Relationship between the dynamic elastic-plastic fracture toughness and the notch root radius of high strength 7075 alloys aged in various conditions were investigated. The apparent fracture toughness is strengthened with an increase of the notch root radius, ρ, and is independent of the aging condition. The notch root radius does not affect the critical value of fracture toughness, which depends on the mean free path of the inclusions over 1μm. The experimental value of critical point is slightly higher than the calculated one.

Mechanical properties of unidirectionally solidified Al-Fe eutectic composites were compared with those of a normally cast Al-Fe eutectic alloy at various temperatures. The results obrained are as follows:(1) The linear portion of the stress-strain curves of the unidirectionally solidified alloy was enlarged and the proportional limit showed a considerable increase. When the solidification rate was 5 to 10cm/hr, the maximum ultimate tensile strength was obtained. The slower solidification rate produced the lower tensile strength.(2) The difference of the mechanical properties between the unidirectionally and the normally cast alloys was in the same trend over all the testing temperatures.(3) The fracture of the unidirectionally solidified alloy was initiated when the stress carrying FeAl3 fractured after deformation to critical elongation along the tensile direction.