Acidic Attack of Perfluorinated Alkyl Ether Lubricant Molecules by Metal Oxide Surfaces

Abstract

N a t i o n a l A e r o n a u t i c s and Space A d m i n i s t r a t i o nLewis Research Center C l e v e l a n d , O h i o 44135 SUMMARYThe r e a c t i o n s o f l i n e a r p e r f l u o r o p o l y a l k y l e t h e r (PFAE) l u b r i c a n t s w i t h a-FezO3 and Fe203-based s o l i d s u p e r a c i d s were s t u d i e d . a-Fe2O3 proceeds i n two s t a g e s . The first s t a g e i s an i n i t i a l slow c a t a l y t i c d e c o m p o s i t i o n o f t h e f l u i d . T h i s r e a c t i o n r e l e a s e s r e a c t i v e gaseous p r o d u c t s which a t t a c k t h e m e t a l o x i d e and c o n v e r t i t t o FeF3. more r a p i d d e c o m p o s i t i o n o f t h e f l u i d , e f f e c t e d b y t h e s u r f a c e FeF3. A s t u d y of t h e i n i t i a l breakdown s t e p was p e r f o r m e d u s i n g a-Fe203, a-FezO3 p r e c o n v e r t e dt h e breakdown r e a c t i o n i n v o l v e s a c i d i c a t t a c k a t f l u o r i n e atoms on a c e t a l carbons i n t h e l i n e a r PFAE. P o s s i b l e approaches t o combat t h e p r o b l e m a r e o u t 1 i ned .The r e a c t i o n w i t hThe second s t a g e i s a

Study of the Thermal Decomposition of PFPEs Lubricants on a Thin DLC Film Using Finitely Extensible Nonlinear Elastic Potential Based Molecular Dynamics Simulation

“…It is well known that, in the presence of metal and metal oxide, the rapid degradation of PFPEs takes place at temperatures below their decomposition temperatures [21,22]. So, far, two different mechanisms have been reported: one is the decomposition caused by Lewis acid sites, [23,24] the other is the decomposition caused by nonLewis acid sites [25,26]. Suzuki and Kennedy [27] found that the flash temperature generated at the head/disk interface for an Al 2 O 3 -TiC slider on a rigid thin film magnetic disk is about 150 ∘ C under 1 N impact load.…”

A review of the effect of metals on the thermo-oxidative stability of perfluoropolyalkylether lubricants

“…A two-step fluid decomposition process has been proposed [6,8,15]: conversion of the metal surface to a metal fluoride which functions as a Lewis acid site; and catalytic decomposition of the fluid by interaction with these Lewis acid sites. A critical step that precedes this two-step process is the degradation of the PFPAE fluid due to either (i) the metal reactivity with the PFPAE fluid at high temperatures in a static environment or (ii) in a tribological environment at asperity contacts where the localized temperature and shear stresses are at a maximum.…”

“…Comparing hydrocarbon chemistry in oxidative environments, hydrocarbons have the tendency to form water and OH radicals via a free radical process. This situation does not apply to perfluorinated compounds due to the resistance of the C-F bond to the attack by free radicals and the thermodynamic instability of OF 2 and OF species [6,7]. This renders PFPAEs JOURNAL OF SYNTHETIC LUBRICATION…”

United States Air Force Summer Research Program 1991. Graduate Student Research Program (GSRP) Reports. Volume 9. Wright Laboratory

“…The iat r=0 is -Itlen as -v (19) The velocities Uc and U,, gre gc!ud~ hle rate of cooling and heating at the condenser and evaoraive sion. gr6 h te schermtic of a simple mode!…”

“…19,7]. We chose to use one of these chaotic time series for comparability with prior works and availability of data.…”