Surface free energy, oxides used

Inequality (4), which conveys that the spreading of the oxide over the surface of the metal will occur if the interactions per unit interfacial area exceed twice the interfacial free energy of oxide-gas, is both simple and illuminating. Indeed, inequality (4) is satisfied if Ooxide-gas - -s sufficiently small and/or Ucs is sufficiently large. From the data available in the literature (20) on the surface free energies of oxides, those pertinent to the oxides used as catalytic substrates are summarized in Table I. 

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