After silica nanoparticles in solutions were filtered by a syringe filter with a much larger pore size than the particle diameter Dp, the filtrated effects on the rapid coagulation rate in 1 M KCl solution, the dynamic light scattering diameter, and the zeta potential at pH ∼ 6 were investigated by employing the particles of two different sizes: S particles (Dp ∼ 50 nm) of silica and latex and L particles (Dp ∼ 300 nm) of silica. It was found that the hydrodynamic diameters of silica particles became a little smaller and the absolute values of their zeta potentials decreased significantly by filtration, but that is not the case for latex particles. As for the rapid coagulation rate, the value of silica S particles increased more than 2 orders of magnitude by filtration, but no significant difference was found in the case of silica L and latex S particles. From these data, it was postulated that the gel-like layer was removed from the surface of silica S particles by filtration and the existence of the gel-like layer resulted into about 2 orders of magnitude reduction of the rapid coagulation rate. The extraordinary reduction of rapid coagulation of silica particles at Dp < 150 nm was successfully estimated by the revised Smoluchowski theory, which we call the Higashitani-Mori (HM) model. It was also found that the rapid coagulation rate of filtrated particles decreased slowly with a decreasing particle size at Dp < ca. 250 nm, which was also estimated properly by the HM model, neglecting the contribution of the redispersion of coagulated particles. Another finding in this study was that the gel-like layers were recovered with time even if they were removed by filtration, although the detailed mechanism of this recovering is not known at present and left as a future problem.
The liquid surfactant membrane has advantages superior to those of other types of liquid membranes, but its biggest bottleneck lies in the demulsification process for separating the stripping solution from the organic phase containing surfactant and carrier. This paper is concerned with the electrostatic coalescence of the W/O emulsion stabilized with surfactant in an a.c. high-voltage current applied between two insulated flat electrodes. Effects of the dispersed phase hold-up, the applied voltage and the frequency on the phase separation rate were studied.The separation rate was larger for lower initial hold-up of the dispersed phase. When the initial hold-up was less than 40%, the coagulation stage preceded the coalescence stage and the separation rate decreased. The separation rate increased approximately with the second order of the applied voltage. It also increased with frequency and tended to become constant at frequencies in the range of 1000 to 2000 Hz. The water content of the separated oil phase decreased with increase in frequency.
It is elucidated that electron diffusion rate in titania electrode in dye-sensitized solar cells should be very rapid, i.e., highly crystallized TiO2 one-dimensional materials are needed. Three kinds of TiO2 nanoscale materials (1,2) were synthesized, applied for dye-sensitized solar cells, and all cells made of these three materials showed high light-to-electricity conversion efficiency, around 9%. Electrochemical impedance spectroscopy is very useful to investigate electron transport processes in dye-sensitized solar cells (5). Strong distribution of electron density induced by distribution in irradiation light under steady state conditions must be taken into consideration to determine parameters participating electron transport processes accurately and to evaluate the quality of the cells correctly.
The particle size distribution of sub-micrometer and nanometer sized range is one of the most basic and important characters of powder. In this review, new size analysis techniques measured by the counting methods in suspension were introduced, and the advantage and considering points of those techniques were discussed.
Abstract It has been shown that a standard screw‐extruder with a little modification is very useful for the measurement of flow properities of various plastics melt over a wide range. Results obtained are very interesting and it is expected that they have applicability to polymer processing. A range of flow rates covering both extrusion and injection molding applications were considered.
