Silica surface free energy data

Two methods can be used for the assessment of y and its components contact angle measurements and inverse gas chromatography (IGC) [31]. Chibowski and Perea-Carpio [32] reviewed the problems encountered when attempting to determine the surface free energy of powered solids, like silica particles, using the contact angle technique. Wu reviewed the different techniques that can be employed to measure the surface tension of polymer melts [30]. These techniques are based on the pendant and sessile drop techniques that require density data or contact angle measurements. 

Clay minerals are present in almost all surface-water and ground-water systems, and in many instances may be controlling the concentration of aluminum, silica, iron, magnesium, or other cations in solution. The thermodynamic data necessary to evaluate the state of reaction (saturation) are not available for some clay minerals, and for those minerals with published values, the data are in disagreement by as much as 10 kilocalories per mole for the same clay mineral. A critical review of the available data for kaolinite and sepiolite, incorporating both the most recent thermodynamic data for the components in the reaction schemes and a more complete computation for the solubility data, yields the values of -907.7 +1.3 and 1105.6 +0.4 kilocalories per mole for the free energy of formation of kaolinite and sepiolite, respectively. 

In order to determine how the surface of silica affects the value of the cell-aqueous medium free surface energy, one can compare the data, presented in Table 7.3, with the corresponding dependence for binary cellular suspension, mentioned in Turov and Barvinchenko (1997) (Figure 7.25a). The differences in the Ys values under fixed concentration of cellular mass in the suspension determine the changes in free energy in the result of the cell-surface interaction (Figure 7.25b). The mentioned... 

Data in Table 7.3 show that fumed silica also has affinity to the second component - crosslinked PEA. Free energies of mixing of PEA with AI2O3 and dispersed PEA are positive. Thus, the calculations have shown that only one filler has thermodynamic affinity to both network pol3miers (fumed silica), whereas AI2O3 only has affinity to PU, and PEA has no affinity to both networks. It was shown that the change in the thermodynamic functions by reinforcement depends on the filler amounts (possibly due to the already-mentioned factor relative to surface available for interaction.)... 

Tn a previous paper (14) a study of the yields of free radicals formed by y-irradiating n-hexane adsorbed on silica gel at 77 °K. showed that a transfer of energy occurred from the silica gel to the adsorbed hydrocarbon phase. This transfer was particularly pronounced at very low coverages. A saturation effect was observed the yields of radicals increased rapidly with the amount of hydrocarbon up to the electron fraction of 0.02, then a leveling off occurred. A decrease in the g = 2.0080 signal from the silica gel was observed at the same time, and at the electron fraction of 0.02 this signal had completely disappeared. From the saturation data the number of active sites on the silica gel surface... 

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