Void dissolution initial

Apparently, the formation of the microporous structure within the PVdF—HFP copolymer was of critical importance to the success of Bellcore technology, and the ion conductivity was proportional to the uptake of the liquid electrolyte. To achieve the desired porosity of PVdF film, Bellcore researchers prepared the initial polymer blend of PVdF with a plasticizer dibutylphthalate (DBP), which was then extracted by low boiling solvents after film formation. Thus, a pore-memory would be left by the voids that were previously occupied by DBP. However, due to the incomplete dissolution of such high-melting DBP during the extraction process, the pore-memory could never be restored at 100% efficiency. Beside the total volume of pores thus created by the plasticizer. 

Figure 6.6 shows the effect of the processing cycle on the void diameter for pure water and air-water voids of 0.1 cm initial diameter under the specified cycle conditions. It was assumed that the air—water void initially consists of pure air, even though there is likely to be a small but finite water partial pressure. This plot can be divided into the various stages of void growth and dissolution and interpreted as follows. 

It is also noteworthy that after the initial period of growth, the higher density of the air-water vapor mixture produces a void that is slightly smaller than the pure water vapor void produced under identical conditions. The air-water void, however, cannot completely dissolve during the cure cycle, whereas the water void is capable of complete dissolution. 

From such microbubble-dissolution measurements, Bemd (ref. 16,17) outlined a physical model to explain much of the dynamic behavior of film-stabilized microbubbles.- One problematic aspect of this dynamic behavior involved the question of how a gas nucleus can be surrounded by a relatively impermeable film and yet subsequently act to produce cavitation when a gas/water interface is needed to initiate cavitation. Bernd (ref. 16) explains that if the stabilized gas microbubble enters a low-pressure area, the gas within the microbubble will attempt to expand. The surfactant film may also elastically attempt to expand. The surfactant film will then be expanded until essentially the surface tension of the water alone acts to contract the microbubble, since the protective shell no longer acts. The film has either been ruptured upon expansion, or it has expanded until it is ineffectual. Thus the microbubble (i.e., gas nucleus) should be capable of expanding to form a cavitation void or acquire additional gas in the form of water vapor or from surrounding dissolved gas. In addition, Bernd points out that it is reasonable to expect a gas microbubble to acquire such an effective... 

Positronium (Ps) annihilation probability in the nanovoids of the samples in initial state is found to be 11.13 %, whereas the mean nano void radii for the crystalline and liquid-crystalline samples are 0.33 and 0.28 nm, respectively. After dissolution of C6o fullerenes probability of Ps annihilation in nanovoids is decreased by the factor of 2.7. The general spectrum of lanthanum laurate initial pattern is presented in the Fig. 1. The calculated parameters of the investigated patterns are resulted in the Table 1. 

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