Standard Thoria Plots

One of the advantages that thoria presents is that it is very stable with respect to high temperatures. Once a thoria produced powder is high fired to 1600°C, it is virtually physically stable. The surface chemistry is also stable with no change in stoichiometry. It is therefore an ideal powder with which to perform basic research. 

Even the water adsorption isotherm reveals a good fit to the x plot. The plot in Fig. 63 is for water adsorption at 15°C on a powder that had been previously exposed to water seven times but had been out-gassed at 25°C for an extended period of time between exposures. For each exposure there was some additional irreversible adsorption. This would be the indication that the high energy planes and micropores were being masked for subsequent adsorption cycles. The lit to the linear x plot in Fig. 63 is quite good. 

In Table 22 the statistics for the three thoria adsorption isotherms are given. 

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For another example, the adsorption of N2 and Ar on the 25 C outgassed thoria are presented in Table 27. The advantages for these data are presented under the Standard Thoria Plots in Chapter 5, which are the stability and uniformity of this powder with this treatment, but in addition to these, the advantage is that the measurements could be performed in a very accurate and controlled gravimetric system and many data points were collected. There is still, however, the question of range selection. The fewer the data points selected for the BET and DP fit, the better the statistics should be. (After all, if one were to select two data points one would obtain a perfect fit.) A best... 

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