润滑介质对单晶硅相变与脆塑行为的影响

Phase Transformation and Brittle-ductile Behavior of Single Crystal Silicon under Lubrication

研究了分别在十五烷、无水乙醇和蒸馏水润滑下单晶硅的摩擦磨损行为及其相变和脆塑行为.结果表明:在十五烷润滑下单晶硅的摩擦系数和磨损体积损失最低,而在蒸馏水润滑下的摩擦系数和磨损体积损失最大;单晶硅在非极性溶剂十五烷润滑下发生明显的S i-I→a-S i相变,磨损表面光滑并呈现明显的金属塑性特征;单晶硅在无水乙醇润滑下发生轻度S i-I→a-S i相变,磨损表面特征为微弱的塑性变形和微断裂共存;在蒸馏水润滑下,单晶硅发生轻度的S i-I→S i-III相变,磨损表面变得粗糙并伴有大量微断裂;润滑介质的极性是影响单晶硅磨损表面相变和脆塑行为的主要因素之一.

Friction and wear, phase transformation and brittle-ductile behavior of single crystal silicon against Si3N4 under lubrication at low contact stress were studied. Friction and wear tests were performed on a UMT-2MT test rig under linear velocity of 3 mm/s and load of I N under boundary lubrication. Pentadecane, anhydrous ethanol and distilled water were used as lubricants during the tests. Single crystal silicon showed the lowest friction coefficient （0.136） and wear volume under lubrication of pentadecane. The morphologies and phase compositions of the worn surface were analyzed by means of scanning electron microscopy and Raman micro-spectroscopy. It was found that the worn surface of single crystal silicon lubricated by pentadecanc was characterized by ductile regime. Raman micro-spectrum analysis indicated that phase transformation of Si-Ⅰ to a-Si was involved on the worn surface. Under lubrication of anhydrous ethanol, the phase transformation of Si-Ⅰ to a-Si on the worn surface could be identified although a-Si is much less than that under lubrication of pentadecane. Coexistence of brittle and ductile characteristic could be found on the worn surface. A sight transformation of Si-Ⅰ to Si-Ⅲ on the worn surface of single crystal silicon lubricated by distilled water was, detected by Raman micro-spectrum. In addition, the worn surface became rough and a large number of micro-fracture was found. Polarity of the lubricants might be one of the main factors for phase transformation as well as brittle and ductile behavior of single crystal silicon.