Monitoring the Gas-Phase Products of a Shear-Induced Reactions in Ultra-high Vacuum

HEATHER ADAMS; MICHAEL GARVEY; OCTAVIO JAVIER FURLONG; WILFRED T. TYSOE

San Jose

Congreso; AVS 62nd International Symposium & Exhibition; 2015

Although tribochemical reactions are common in manufacturing, analysis of the mechanism and products is severely limited by the difficulty of probing a solid-solid interface that changes on small time scales. A method to analyze the gas-phase products of a tribochemical reaction in ultra-high vacuum has been developed to allow insight to be obtained into the decomposition pathways of short-chain alkylthiols on copper foils. A UHV tribometer is used to probe the alkylthiol-covered copper foil by using a mass spectrometer to measure the products evolved from the surface.Alkylthiols have been chosen due to their thermal stability on a copper surface, and their ability to form a tribofilm. Previous studies have found that sulfur moves into the sub-surface layer with rubbing, and the carbon is removed from the surface.The shear-induced decomposition of methyl thiolate produces gas-phase methane and measuring the amount of methane produced during each sliding cycle allows the shear-induced reaction rate to be measured. The results are analyzed to give insight into how sheer stress lowers the energy barrier for the decomposition reaction.