Kinetic Studies Of The Attack of Refractory Materials By Fluorine Atoms

摘要

The true kinetics of the attack of molybdenum and tungsten surfaces by both atomic and diatomic fluorine were studied using microwave charge--fast flow vacuum system techniques coupled with electrical resistance heating of the reacting specimens. Experimental results are reported herein covering the surface temperature range from 700K to their respective thresholds. Exploratory kinetic data is also included for the fluorination of titanium, graphic and boron. It is shown that despite the wel known reactivity of molecular fluorine, dissociation produces a striking enhancement in the Mo- or W-atom removal probability at surface temperatures corresponding to appreciable steady state adatom populations. Interestingly enough, multiple local maxima appear in the Arrhenius diagram for the F-atom attack of Mo(s) and W(s)--these maxima presumably being attributable to the formation/desorption of distinct metal fluorides of widely discrepant stoichiometry and thermodynamic stability. (Author)