Due to their low vapor pressures, low melting points, high boiling points, high radiation resistance and high thermal stability, room temperature ionic liquids (RTILs) appear to be suitable candidates as new aerospace lubricants for the upcoming return to the Moon and eventual Mars missions and for air and rotorcraft applications, hi this study, three ionic liquids having the same cation, l-butyl-3-methylimidazolium, but different sulfate anions were tested using an ultra-high vacuum Spiral Orbit Tribometer (SOT) and a thermal gravimetric analysis (TGA) unit. Specifically, l-butyl-3- methylimidazoluim methyl sulfate, ethyl sulfate, and octyl sulfate were tested. The SOT experiments revealed that the lifetimes of the three ionic liquids decreased with increasing alkyl substituent length on the sulfate anion. Infrared and Raman spectra were taken to detect unused ionic liquids and graphitic degradation products respectively. The infrared spectra showed some slightly degraded, but still usable, ionic liquid is shed in all runs, indicating that the lifetimes are shorter than they would be if all lubricant had been used. Raman spectra indicated that various amounts of amorphous graphitic material were produced as the final degradation product of all three ionic liquids. SOT testing indicated that these three ionic liquids have normalized lifetimes greater than those of two commonly used space lubricants and coefficients of friction less than those of the same two lubricants. TGA analysis showed that the methyl sulfate ionic liquid had the highest thermal stability in air.
Evaluation of an alkyl sulfate series of 1-butyl-3methylimidazolium based room temperature ionic liquids for use as aerospace lubricants
Bewertung einer Alkylsulfatreihe der auf 1-Butyl-3Methylimidazolium basierenden RT-ionischen Flüssigkeiten für die Eignung als Raumfahrtschmierstoffe
2009
17 Seiten, 14 Bilder, 1 Tabelle, 5 Quellen
Aufsatz (Konferenz)
Englisch
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