Overall thickness, separators

To overcome the poor mechanical properties of polymer and gel polymer type electrolytes, microporous membranes impregnated with gel polymer electrolytes, such as PVdF. PVdF—HFP. and other gelling agents, have been developed as an electrolyte material for lithium batteries.Gel coated and/ or gel-filled separators have some characteristics that may be harder to achieve in the separator-free gel electrolytes. For example, they can offer much better protection against internal shorts when compared to gel electrolytes and can therefore help in reducing the overall thickness of the electrolyte layer. In addition the ability of some separators to shutdown... 

Early work relied on the use of packed columns, but all modern GC analyses are accomplished using capillary columns with their higher theoretical plate counts and resolution and improved sensitivity. Although a variety of analytical columns have been employed for the GC of triazine compounds, the columns most often used are fused-silica capillary columns coated with 5% phenyl-95% methylpolysiloxane. These nonpolar columns in conjunction with the appropriate temperature and pressure programming and pressure pulse spiking techniques provide excellent separation and sensitivity for the triazine compounds. Typically, columns of 30 m x 0.25-mm i.d. and 0.25-qm film thickness are used of which numerous versions are commercially available (e.g., DB-5, HP-5, SP-5, CP-Sil 8 CB, etc.). Of course, the column selected must be considered in conjunction with the overall design and goals of the particular study. 

The effect of reactant concentration can be divided into two separate influences. The simplest is obvious Lower overall concentrations result in a slower rate. This does not necessarily mean a thinner fihn, however—sometimes the opposite. The reason for this is clear if we return to our introductory discussion on the CD process—rapid precipitation. It is clear that if the reaction is too fast, it will terminate with most of the product precipitating homogeneously in solution rather than depositing on the substrate (which requires time to occur). This results in a very thin film, if any fihn at all. Similarly, for the less extreme case of a CD reaction that terminates, not within a second, but still in a short time, the final fihn thickness will be small. At the other extreme, if the reaction is extremely slow, a thick fihn can be built up, but it may take a very long time for this to occur (weeks, even months). It is therefore evident that there is an optimum rate for the reaction, which can be controlled by a combination of reactant concentrations, temperature, and pH. 

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