A quartz crystal microbalance (QCM)/Parr bomb system with a headspace
oxygen sensor is used to measure oxidation and deposition during therm
al oxidative stressing of jet fuel. The advantages of the oxygen senso
r technique in monitoring fuel oxidation is demonstrated. Simultaneous
measurement of deposition using the QCM shows a strong correlation be
tween oxidation and deposition in jet fuels. Studies performed over th
e temperature range 140 to 180 degrees C show that surface deposition
peaks at an intermediate temperature, while bulk deposition increases
with temperature. In studies of jet fuel antioxidants, we find that ra
pid increases in oxidation rate occur upon consumption of the antioxid
ant. The antioxidant appears to be consumed by reaction with alkylpero
xy radicals. In studies of metal deactivator (MDA) additives, we find
that MDA is consumed during thermal stressing, and this consumption re
sults in large increases in the oxidation rate of metal containing fue
ls. Mechanisms of MDA consumption are hypothesized.