Mechanochemical reaction and relationship to tribological response of silicon nitride in n-alcohol

Milling tests and sliding tests were conducted to see how mechanochemical r eactions influenced the friction and wear characteristics of Si3N4 in norma l-chain, (n)-alcohols. Si3N4 powder was milled with n-alcohol to obtain mec hanochemical reaction products. Silicon alkoxide and long-chain hydrocarbon s might be produced in the mechanochemical reaction between Si3N4 and n-alc ohols. Silicon alkoxide were hydrolyzed to form silica gel to determine the yield by post-treatment. Silica gel was the main product in lower alcohol and hydrocarbons were the main products in higher alcohol. In the sliding t ests, Si3N4 was slid against the same material in CH3OH and in C9H19OH. Hyd rodynamic lubrication, where the friction coefficient was < 0.01, occurred in CH3OH for sliding speed exceeding 1600 mm/s. Friction coefficient of Si3 N4 in C9H19OH was 0.05-0.11. Wear of Si3N4 in CH3OH was much higher than th at in C9H19OH. Precursors of silica gel, reduced friction of Si3N4 in alcoh ol; hydrocarbons did not act as a lubricant, however. The specific wear rat e of Si3N4 ball in the sliding test correlated very well with the yield of silica gel produced in the milling test. Our results suggest that friction and wear of Si3N4 are influenced by the reactivity of the mechanochemical r eaction producing silicon alkoxide. (C) 1999 Elsevier Science S.A. All righ ts reserved.