Reaction of tributyl phosphate with oxidized iron: surface chemistry and tribological significance

Abstract

The chemistry of tributyl phosphate on Fe 3 O 4 was studied in ultrahigh vacuum using temperature-programmed desorption (TPD) and Auger spectroscopy. A portion of the tributyl phosphate desorbs intact with an activation energy of $120 kJ/mol. The remainder decomposes either by PAO bond scission to deposit surface butoxy species or appears to dehydrogenate desorbing C 2 or C 3 compounds and depositing hydrogen and carbon on the surface. The resulting hydrogen reacts either with the oxide to desorb water or with butoxy species yielding 1-butanol. The remaining butoxy species are stable up to $600 K where they decompose to desorb butanal via hydride elimination where again the hydrogen reacts with butoxy species to form 1-butanol or with the oxide to form water. The carbon deposited onto the surface further reduces the oxide to desorb as CO above $750 K, although a small amount of carbon is detected on the surface using Auger spectroscopy. Substantially larger amounts of carbon are deposited onto the surface when Fe 3 O 4 is exposed to tributyl phosphate at 300 K, where an Auger depth profile reveals that the carbon is located at the surface while the PO x species formed by tributyl phosphate decomposition diffuse rapidly into the oxide layer, leading to a film structure in which graphitic carbon is deposited onto a phosphorus-containing oxide layer.

Reactivity of Triphenyl Phosphorothionate in Lubricant Oil Solution

“…The reaction between TBT and iron was proposed to occur via an initial P=S bond scission to give tributyl phosphite. In accordance with [3,8,11,[17][18][19], this compound successively produced butoxy groups through P-O bond cleavage.…”

“…metal-free) additives, such as organosulfur compounds [6], phosphates [6][7][8][9][10][11][12][13][14][15][16], amine phosphates [12], phosphites [11,[17][18][19], phosphorothionates [12][13][14][20][21][22][23][24][25][26], and dithiophosphates [12,21,22,24].…”

Lubricating Properties of Organic Phosphate Ester Aqueous Solutions

“…Lubricants that incorporate phosphorus-containing molecules are used both as extreme-pressure and anti-wear additives [11,12]. We prepared an organic phosphate ester (DPZ), which is a surfactant.…”

Surface and Tribological Chemistry of Water and Carbon Dioxide on Copper Surfaces

“…For example, sulfur-containing additives react to form a sulfide, and those containing chlorine form low-friction ferrous chloride layers on iron [1][2][3][4][5][6][7][8][9], and more complex additives such as zinc dialkyl dithiophosphate have correspondingly more complex surface chemistry, ultimately resulting in the formation of a glassy anti-wear film [10][11][12][13][14][15]. Such film-forming surface reactions can be thought of as occurring in two steps, the first being the adsorption of the additive onto the surface, followed by a chemical reaction to form the surface film.…”

“…Since the wear rate increases with increasing load, and higher normal loads lead to higher interfacial temperatures due to Joule (frictional) heating, lubricant additives should ideally react more rapidly with increasing temperature, and this is generally found to be the case [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]17]. That is, the film growth kinetics of the additive respond to the severity of the tribological conditions.…”