Abstract Diamond-like carbon (DLC) is a promising solid lubricant used as a protective coating to reduce friction against alumina. Friction properties of DLC/alumina are strongly affected by temperature. To improve the friction performance of DLC, we investigate the friction behaviors of DLC/alumina at various temperatures and reveal the mechanisms by using our tight-binding quantum chemical molecular dynamics method. We observe an interesting volcano-type temperature dependence of friction coefficients in our friction simulations. Friction coefficients of DLC/alumina are low and show little change at 300–600 K because no tribochemical reactions occur at the interface. However, as the temperature increases, friction coefficients increase at 600–800 K and subsequently decrease at 800–1000 K. At 600–800 K, interfacial C-O and C-Al bonds between two substrates are formed during friction, leading to a high friction coefficient. Interestingly, further increment of temperature to 800–1000 K induces the graphitization of DLC. The graphite-like surface suppresses the interfacial bond formation, reducing the friction coefficient. We reveal that the volcano-type temperature dependence of friction coefficients is due to the tribochemical reactions generating interfacial bonds at 600–800 K and the graphitization of DLC reducing the number of interfacial bonds at 800–1000 K.

中文翻译：

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类金刚石碳对氧化铝的摩擦化学反应和石墨化产生摩擦系数的火山型温度依赖性：紧束缚量子化学分子动力学模拟

摘要 类金刚石碳 (DLC) 是一种很有前途的固体润滑剂，用作保护涂层以减少与氧化铝的摩擦。DLC/氧化铝的摩擦特性受温度影响很大。为了提高 DLC 的摩擦性能，我们研究了 DLC/氧化铝在不同温度下的摩擦行为，并通过使用我们的紧束缚量子化学分子动力学方法揭示了机制。我们在摩擦模拟中观察到摩擦系数的有趣火山型温度依赖性。DLC/氧化铝的摩擦系数很低，并且在 300-600 K 时几乎没有变化，因为界面处没有发生摩擦化学反应。然而，随着温度升高，摩擦系数在 600-800 K 时增加，随后在 800-1000 K 时降低。在 600-800 K 时，摩擦过程中在两个基材之间形成界面 CO 和 C-Al 键，导致高摩擦系数。有趣的是，温度进一步升高到 800-1000 K 会引起 DLC 的石墨化。类石墨表面抑制了界面结合的形成，降低了摩擦系数。我们发现摩擦系数的火山型温度依赖性是由于摩擦化学反应在 600-800 K 时产生界面键，而 DLC 的石墨化在 800-1000 K 时减少了界面键的数量。