Reaction Control by Mechanical Field and Its Application

利用球盘摩擦试验机在氟里昂气氛下研究了陶瓷与氟里昂的摩擦化学反应。在不接触空气的情况下，用微型XPS分析了摩擦表面的反应产物。研究发现，即使是陶瓷也能与氟里昂HFC-134a反应，尽管它们被认为是化学惰性材料。XPS分析表明，陶瓷与氟里昂HFC-134a发生摩擦化学反应，在摩擦轨迹上生成金属氟化物和含氟有机化合物。由于反应产物较软，摩擦系数和磨损率较低。金属氧化物、氮化物和碳化物被用作试件。反应产物取决于陶瓷的键合特性。离子陶瓷(氧化物、氮化物)和共价陶瓷(碳化物)的主要产物分别是金属氟化物和有机氟化物。金属氟化物比有机氟化物具有更好的减摩效果。摩擦条件、载荷、滑动速度和氟里昂压力对摩擦化学反应速率有影响，在恶劣条件下反应产物增多，起到润滑剂的作用。然而，在恶劣的条件下，当反应加速时，观察到化学磨损。反应还受氟里昂分子结构的影响。含有C-H键的氟里昂比CF4活性高得多。由此可见，在机械接触能的作用下，化学惰性陶瓷更容易与氟里昂发生反应。XPS分析揭示了摩擦轨迹上金属氟化物和有机氟化物的形成。研究结果可应用于陶瓷的气相润滑和化学机械抛光。

Tribochemical reactions of ceramics with Freons were carried out using a ball on disk friction tester under freon atmosphere. The reaction products at friction surfaces were analyzed by micro-XPS without exposure to air. It was found that even ceramics were reacted with freon HFC-134a, although they are known as a chemically inert material. XPS analyzes revealed the formation of metal fluorides and fluorine-containing organic compounds on the friction track by the tribochemical reaction of ceramics and freon HFC-134a. Since the reaction products are soft, friction coefficient and wear rate became low. Metal oxides, nitrides and carbides were used for test pieces. The reaction products were dependent on the bond character of ceramics. The main products on ionic ceramics (oxides, nitrides) and covalent ceramics (carbides) were metal fluorides and organic fluorides, respectively. Metal fluorides were more effective for low friction than organic fluoride. The tribochemical reaction rate was affected by friction conditions, load, sliding speed and pressure of freon.The amount of the reaction products increased at severe conditions, and the products act as a lubricant. However, chemical wear was observed when the reaction was accelerated at severe conditions. The reaction was also affected by the molecular structure of freon. The freon containing C-H bond was much more reactive than CF_4.It can be concluded from the results that chemically inert ceramics are easily react with freons under the effect of mechanical energy at mechanical contacts. XPS analyzes revealed the formation of metal fluorides and organic fluorides at friction track. The results can be applied to a gas - phase lubrication and a chemical-mechanical polishing for ceramics.