Adsorption and reactions of HFC-134a gas on the nascent surface of alumina

The adsorption and tribochemical reactions of HFC-134a (CF3CH2F) gas on the nascent surface of alumina (Al2O3) couple were investigated using an adsorption test apparatus in high vacuum at room temperature. The adsorption of HFC-134a and the desorption of the product gas of trifluoroethylene (CF2CHF) were detected during the rubbing processes with a quadrupole mass spectrometer. The adsorption rate of HFC-134a molecules was estimated to be (0.5–2.2)×1013 molecules/s in this experiment, and it increased with increasing pressure of the source gas and the sliding velocity. It was found that the desorption rate of CF2CHF was proportional to the adsorption rate of HFC-134a. XPS analysis revealed that AlF3, AlFxOy and fluorine-containing polymers were formed on the worn surface. Reaction mechanism of HFC-134a molecules on the nascent surface of Al2O3 was also proposed.