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A new foaming apparatus, which can depressurize the vessel that contains polymer + gas from 100 MPa to atmospheric pressure in 50 ms, was developed to generate a high degree of supersaturation. The influences of the saturation conditions and the molecular weight of the polymer were studied with the new rapid decompression system using the polymethyl methacrylate (PMMA) - CO2 system as a model. It is found that the Sub-micron cellular structures could be produced by using the apparatus. The results confirm the effectiveness of the high degree of supersaturation achieved in decreasing the cell size and increasing the cell nucleation density of foams. Moreover, it was revealed that the cell size and the cell nucleation density do not always vary as expected as the saturation pressure is increased at the decompression rate and the saturation temperature conditions used in this work.

A new flexible thermal insulation sheet, a composite of silica aerogel with polypropylene (PP) foam, has been developed. Even though a large volume ratio of silica aerogel (97%) was included, the composite showed high flexibility. Thermal conductivity of the composite was 0.016 W/(m⋅K) at 298 K, which is as low as silica aerogel monolith. Silica aerogel flaking, which has been a problem in practical applications, is very low in this composite due to skin layers of the polymer-foam composite. A supercritical drying process for rolled sheets of the material for large-scale production is also described. Simulations of extraction of 2-propanol from a silica alcogel revealed that rolled composite sheets with small spaces between the sheet composite are able to dry in a reasonable extraction time. These findings led to effective on production of this material on a pilot industrial scale.

Densities and viscosities of methanol-water, ethanol-water and n-propanol-water mixtures were measured over the entire range of compositions at temperatures from 523.2 to 618.2 K and at pressures up to 40 MPa. The excess molar volume calculated from the measured density changed negative to positive with increasing alcohol composition at some conditions studied, and this behavior was observed at lower temperature with increasing alkyl chain length. Maxima in composition dependence of viscosity, which is generally observed in ambient conditions, were not present at 618.2 K. Viscosities could be correlated with the Eyring's theory to within 6.4% at temperatures up to 476.2 K. The Peng-Robinson equation of state and Redlich-Kister mixing rule were used to obtain the excess Gibbs energy included in the Eyring's theory, and two binary interaction parameters in the mixing rules were determined by fitting of viscosity data. The densities were predicted using the volume translated Peng-Robinson equation of state to within 3.2% with parameters being determined by viscosity data at temperatures up to 476.2 K. A switching of fitting parameters from binary interaction parameters of the equation of state mixing rule to a proportionality constant, σ, of Eyring's theory was introduced, and viscosities and densities of the normal alcohol-water mixtures could be correlated and predicted to within 4.6% and 8.9%, respectively at temperatures above 476.2 K.

We investigated magnetic properties of spinel oxides Zn (Cr1-xFex)2O4 to study element substitution effects on magnetism of spin-frustrated spinel oxides ZnCr2O4 and ZnFe2O4. The present study revealed that an antiferromagnetic order of ZnCr2O4 (TN ~ 13 K) is suppressed by Fe doping. Zn (Cr1-xFex)2O4 with x = 0.1, 0.5, and 0.7 exhibits spin-glass-like behavior below ~ 10 K. On the other hand, Zn (Cr1-xFex)2O4 with x = 0.3 exhibits the absence of magnetic order or spin-glass-like behavior down to low temperature (3 K), which is probably due to the competition of geometrical and bond frustrations.

Dynamical features of hydrogen bonds in methanol–water mixtures have been analysed in terms of lifetime in the wide range of conditions, including supercritical states, using a molecular dynamics simulation with flexible potential models. Hydrogen bond characteristics in methanol–water mixtures were investigated by considering the combination of molecular species and donor–acceptor of hydrogen-bonded molecules. The hydrogen bond lifetimes mainly depend on temperature, and those in supercritical condition were about 1/10th of that at ambient condition. Focusing on the composition dependence of the hydrogen bond lifetime, the unique behaviour of that resulting from hydration structure was observed. Moreover, the molecular combination, which showed the largest hydrogen bond lifetime, was different for ambient and high temperature and high pressure conditions. The relationship between hydrogen bond lifetime and molar volume was also calculated to discuss the hydrogen bond lifetime in terms of the coll...

Viscosities and self-diffusion coefficients of methanol–water mixtures were calculated via molecular dynamics simulation from 298.2 to 476.2 K and at pressures up to 40 MPa. The periodic perturbation method (non-equilibrium molecular dynamics) and the Green-Kubo method with three-site flexible potential models were adopted for evaluating the viscosities and the diffusion coefficients, respectively. The calculated viscosities and diffusion coefficients of methanol–water mixtures agreed qualitatively with literature experimental values. The three-site flexible potential models used in this study provided similar performance to the previous studies that used rigid models. Results correlated with the Stokes–Einstein relation show the possibility that the effective hydrodynamic radii were approximately constant for the studied condition and might be little affected by the clathrate-type structure at lower methanol compositions.

A two-step foaming process was developed that uses different temperatures in each step and combines ultra-high saturation pressure (Ps > 50 MPa) and rapid depressurization (> 1.25 GPa/s) for production of nanocellular polymer foams. The effect of process conditions were investigated using polymethylmethacrylate (PMMA) and carbon dioxide. Foams with small cells ( 1015 nuclei cm−3) were obtained, which were of a finer structure than those made by previous one-step foaming process. N0 tended to increase even at Ps =100 MPa. A fine cell structure (30.5 nm ± 10.4 nm) was observed with scanning transmission electron microscopy (STEM), and was confirmed when two-step process conditions were used. The process and advantages of ultra-high pressure are discussed with regard to porosity, cell size and N0.

A flow-type cell was developed for measuring Compton scattering spectra of heat-sensitive aqueous solution. Compton scattering spectra of water and ethanol were measured in the region from ambient conditions to 623 K and 20 MPa. Compton profiles derived from measurement with the flow-type cell were comparable with those in the literature. Results obtained from the flow-type cell showed that delocalization of electronic charge density of water and ethanol at high temperatures occurred. Delocalization of the electronic charge density of ethanol was greater than that of water at high temperature, which is consistent with the prior works that use proton NMR chemical shifts to describe hydrogen bonding.