We observed the three stages in water migration of spaghetti during boiling by using MRI method. From the result of two kinds of microscope observation, the structures of starch granule contained in the boiling spaghetti were mainly divided into three stages; that is non-gelatinized, gelatinized and macromolecule dispersion. Moreover, it was suggested that the water holding capacity in the system was different in these states of starch granule. Then we simulated water migration in the spaghetti during boiling by using a two-dimensional mass transfer equation in which driving force was the ratio between the water holding capacity and the real water content. Good agreement was obtained between simulating and measurement.
The gaseous diffusion coefficients of dichloromethane (CH2Cl2), trichloromethane (CHCl3) and tetrachloromethane (CCl4) into dry air, nitrogen and oxygen have been measured in the temperature range 318-453 K and at atmospheric pressure by the use of the Taylor dispersion method. For dichloromethane, trichloromethane and tetrachloromethane, the diffusion coefficients do not vary in practice on substituting pure nitrogen or oxygen for dry air. The diffusion coefficients decrease with increasing molecular weight and those for trichloromethane and tetrachloromethane are systematically smaller than those for dichloromethane by about 14 and 25%, respectively. The present results can be reproduced well by the functional form D = ATB, where D(cm2s-1) is the diffusion coefficient at 101.325 kPa (1 atm) and T(K) is the absolute temperature. The constants A and B are as follows: dichloromethane-(air, nitrogen, oxygen), A = 8.67×10-6, B = 1.66; trichloromethane-(air, nitrogen, oxygen), A = 7.90×10-6, B = 1.65; tetrachloromethane-(air, nitrogen, oxygen), A = 9.36×10-6, B = 1.60.
Direct methanol fuel cell (DMFC) using polymer electrolyte membrane (PEM) is gaining recognition as a power source of portable electronics. However certain methanol through the PEM (i.e. methanol crossover) is known to cause the degradation of efficiency and output. Since, it is significant to develop a measurement method of mass diffusion coefficient in PEM. Therefore, we have newly developed the Soret Forced Rayleigh Scattering method (SFRS) using CO2 laser for measuring mass diffusion coefficient in PEM. SFRS is a noncontact and high-speed ( ~100ms) measurement technique. In the present study, we present difficulties and resolutions using heterodyne detection etc. in applying SFRS to solutions in PEM, and report preliminary result of diffusion coefficient of 13 wt% methanol aqueous solutions in Nafion 117 by newly constructed apparatus.
In this study, the phase transitions of mono-disperse poly(ethylene oxide), PEOn, thin films with thickness less than 1 μm were investigated as a function of sample mass which was proportional to sample thickness. The solvent cast PEOn thin films consisted of the crystal lamella oriented to in-plane and out of plane directions showed several melting peaks on DSC heating curves. However PEOn thin films prepared by slow cooling from the molten state showed branch-like crystal lamella with homogenous thickness and a single melting peak on DSC heating curves. The crystallization process of PEOn on cooling was restricted strongly with the decrease of sample mass. The crystallization exothermic peak became broader and smaller with the decrease of sample mass, and was varnished for PEO thin film less than 200 nm thickness.