Glassman’s criterion

Table 9.1 and Fig. 9.11 also depict vaporization temperatures of the metals in each product composition and give a graphical representation of Glassman s criterion. When Vvo (or Td, as the case dictates) of the refractory compound formed is greater than the vaporization temperature, Tb, of the metal reactant, small metal particles will vaporize during combustion and bum in the vapor phase. When the contra condition holds, much slower surface reactions will... 

Boron does not meet Glassman s criterion for vapor-phase combustion of the metal. Thus, the boron surface remains coated with a vitreous B203 layer and boron consumption becomes extremely slow consequently, boron is not burned efficiently in propulsion devices. 

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