Specific surface area summarized calculations

Calculations of a from concentrations in the bulk solution indicate values of around 0.3% at the start of the induction period (B63,B56). These are likely to be minimum estimates, because they assume that no CH is formed in reality, small amounts may be, on account of concentration gradients, which will themselves introduce an error in the same direction. Reported values of a at the end of the induction period, summarized by Odier and Dorr (OlO), range from 0.1% to an improbable 8%. Their own estimate of 12% is supported by subsequent evidence from cross-polarization NMR (R16). Assuming a specific surface area of 300 m kg a value of 1% corresponds to a mean depth of attack of about 10 nm. 

For calculations dealing with the specific surface area the harmonic mean would best summarize the data. The harmonic mean is weighted towards the smaller particles because the reciprocal /di is larger for smaller diameters, which have a higher surface to mass ratio. Thus, if the properties of interest are affected by the surface area. e.g.. drug dissolution, then a more representative mean diameter would weight the smaller particles more heavily than the larger particles which have a much smaller specific surface area. 

For some samples, the APD method cannot be applied to calculate the specific surface area. Thermal CB, for example, has a lower graphitic order than the other CB discussed above. In the APD of thermal black, monolayer formation is only indicated by a shoulder (Fig. 18.7). Thus, the end of the monolayer formation cannot be determined with the required precision, making a mean-ingfiil determination of the surface area impossible. It can be summarized that as long as the carbon samples have a sufficient graphitic order, from the APD a reasonable estimate for the specific surface area can be obtained. 

C. Summarizing Statements Referring to Calculations of Specific Surface Area... 

In Section V, concrete examples have demonstrated that the calculation of specific surface area includes some new or modified ideas and based on these the calculation methods for as Irom different isotherm equations can be widened. These ideas are summarized as follows ... 

Furthermore, to clarify the reason for the decrease in ECSA, transmission electron microscopy analyses were carried out for the MEA samples (the same specification and operated under conditions similar to those for Fig. 2), and the results are summarized in Fig. 5. The tendency for the particle size of the cathode catalyst to increase agrees well with the tendency for the ECSA to decrease as shown in Fig. 4. The extent of the decrease in the surface area calculated from Rg. 5 is approximately 1/1.8 after 17,000h of operation. Considering that the operation conditions of the samples represented in Fig. 5 were not exactly the same as those for the samples represented in Fig. 4 in addition to experimental errors, it may be concluded that the decrease in the ECSA of the cathode is mainly due to the increase in the catalyst particle size of the cathode catalyst, i.e., sintering. 

In order to demonstrate the suitability of the DOC-model to infer solute localization from scattering and conductivity measurements, we have summarized in Table 9.2 the action of solutes which induce different effects on the three basic constraints. The values are calculated by solving simultaneously the volume, surface and curvature constraints, illustrating this on a sample with a chain length i = 12 A, a polar volume fraction 0 of 0.25 and a specific area E of 0.02 A /A. ... 

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