Passage II

Oxyfluorocarbons (OFCs) are oils composed of only carbon (C), fluorine (F), and oxygen (O). They are useful as lubricants in exposed mechanical systems on spacecraft. However, OFCs tend to decompose upon exposure to heated metal surfaces, which usually have a metal oxide (MO) outer layer (see Figure 1).

When an oil decomposes, the mechanical systems stop working, crippling the spacecraft.

Chemists studied the de composition of 2 OFCs (OFC1 and OFC2).

Experiment 1

In a chamber at 100°C and 0.01 atmospheres (atm) pressure, 1.5 g of OFC1 was mixed with 50 mg of powdered iron(III)oxide (Fe₂O₃),an MO. The gases produced by the decomposition of the OFC caused the pressure to increase. The induction period (the time for the pressure to increase to 0.20 atm) was measured. Shorter induction periods indicate more rapid decomposition. The procedure was repeated at different temperatures, and for OFC2 (see Table 1).

Experiment 2

The induction periods of OFC1 with various powdered Fe compounds were measured as in Experiment 1 at 180°C (see Table2 ). Some of these compounds are hypoth­esized to exist on heated metal surfaces, or to form as minor by-products of the reaction shown in Figure 1.