Property ratio method, heat

Surface Area Determination The surface-to-volume ratio is an important powder property since it governs the rate at which a powder interacts with its surroundings. Surface area may be determined from size-distribution data or measured directly by flow through a powder bed or the adsorption of gas molecules on the powder surface. Other methods such as gas diffusion, dye adsorption from solution, and heats of adsorption have also been used. It is emphasized that a powder does not have a unique surface, unless the surface is considered to be absolutely smooth, and the magnitude of the measured surface depends upon the level of scrutiny (e.g., the smaller the gas molecules used for gas adsorption measurement the larger the measured surface). 

Cook (Ref 17, p 36) designates the available energy as A, and states that this property, as well as the heat of explosion Q, and the ratio A/Q are the important quantities determining the total blast or "avaiable work potential or "available energy . The theory is presented in Chapter 11 of Ref 17, pp 265ff and is considered more reliable than experimental procedures, at least for CHNO expls. The experimental procedures referred to by Cook for determination of (A) include Trauzl Block Test and Ballistic Mortar Test. New methods have been proposed, such as determination of peak pressure or/and total energy ... 

The first successful application of this method was reported by Mullen and coworkers [18]. The removal of their solubilizing group occurs thermally at temperatures as low as 180 °C, yielding pentacene and a volatile tetrahalobenzene. The tetrachloro compound 4 (Fig. 3.3) formed good-quality films from spin-cast solution, and heating the film of the soluble precursor at 200 °C for 5 s yielded the desired acene film. FET properties for devices made from solution-cast films were quite good - measured mobilities were as high as 0.2 cm2 V-1 s-1 with on/off current ratios of 106. 

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