A comparison of ground-based and space flight data: Atomic oxygen reactions with boron nitride and silicon nitride

The effects of atomic oxygen on boron nitride (BN) and silicon nitride (Si{sub 3}N{sub 4}) have been studied in low Earth orbit (LEO) flight experiments and in a ground-based simulation facility at Los Alamos National Laboratory. Both the in-flight and ground-based experiments employed the materials coated over thin ({approx}250{Angstrom}) silver films whose electrical resistance was measured in situ to detect penetration of atomic oxygen through the BN and Si{sub 3}N{sub 4} materials. In the presence of atomic oxygen, silver oxidizes to form silver oxide, which has a much higher electrical resistance than pure silver. Permeation of atomic oxygen through BN, as indicated by an increase in the electrical resistance of the silver underneath, was observed in both the in-flight and ground-based experiments. In contrast, no permeation of atomic oxygen through Si{sub 3}N{sub 4} was observed in either the in-flight or ground-based experiments. The ground-based results show good qualitative correlation with the LEO flight results, thus validating the simulation fidelity of the ground-based facility in terms of reproducing LEO flight results. 9 refs., 3 figs.