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MoS2/类金刚石碳多层结构摩擦学行为与机理

TRIBOLOGICAL BEHAVIOR AND MECHANISM OF MOS2/DIAMOND-LIKE CARBON MULTILAYER STRUCTURES

  • 摘要: 在汽车制动系统中, 摩擦材料的性能直接影响制动安全性与可靠性. 二硫化钼(MoS2)与类金刚石碳(Diamond Like Carbon, DLC)组成的复合材料因兼具优异自润滑性与高硬度、低摩擦特性而成为研究热点. 本研究采用分子动力学模拟方法, 系统研究了MoS2/DLC多层结构复合材料在纳米尺度下的摩擦行为与局部变形机制. 为满足汽车制动材料对高温稳定性与耐磨性的苛刻要求, 构建了MoS2薄膜及MoS2/DLC多层复合结构的摩擦模型, 重点分析了载荷、速度、温度、DLC层深度与层数对材料摩擦学性能的影响. 研究结果表明: 相同载荷下, 复合结构的摩擦系数较高, 但磨损原子数总体较少, 表明引入DLC层能够减少材料损伤, 同时改变切向阻力. 剪切应变与形貌分析显示, DLC层通过改变磨粒与MoS2的直接接触关系, 并以局部下陷、褶皱等方式参与接触区变形. 滑动速度由20 m/s增至160 m/s时, 复合结构的摩擦系数由0.2512增至0.5484; 温度由300 K升至800 K时, 摩擦系数由0.3724小幅降至0.3590. 改变DLC层位置可调节直接接触材料及局部剪切应变分布, 不同位置结构的摩擦力演化趋势相近. 固定DLC子层厚度, 其层数由双层增至五层, 平均摩擦系数呈上升趋势, 高剪切应变区域的空间分布随之改变, 该变化为层数与DLC总量的综合结构效应. 本研究揭示了DLC层的引入与空间配置能够共同调节摩擦阻力和局部变形行为, 可通过优化DLC的埋置深度和层数协调摩擦阻力与抗损伤能力之间的调控.

     

    Abstract: The performance of friction materials directly affects the safety and reliability of automotive braking systems. Composites comprising molybdenum disulfide (MoS2) and diamond-like carbon (DLC) have attracted considerable research interest because they combine excellent self-lubricating properties with high hardness and low friction. In this study, molecular dynamics simulations were performed to systematically investigate the nanoscale frictional behavior and local deformation mechanisms of MoS2/DLC multilayer composites. To address the stringent requirements for high-temperature stability and wear resistance in automotive brake materials, sliding friction models of MoS2 films and MoS2/DLC multilayer composites were constructed. The effects of normal load, sliding velocity, temperature, DLC layer depth, and number of DLC layers on tribological performance were examined. Under the same normal load, the composites exhibited higher friction coefficients but generally fewer atoms removed by wear than the MoS2 films, indicating that incorporating DLC layers reduced material damage while modifying tangential resistance. Analyses of shear strain and morphology revealed that the DLC layers altered direct contact between the abrasive particle and MoS2 and accommodated deformation within the contact region through local subsidence and wrinkling. As the sliding velocity increased from 20 to 160 m/s, the friction coefficient of the composite increased from 0.2512 to 0.5484. In contrast, increasing the temperature from 300 to 800 K slightly decreased the friction coefficient from 0.3724 to 0.3590. Varying the DLC layer position changed the material in direct contact with the abrasive particle and the local shear strain distribution, while the friction force exhibited similar evolution trends across structures with different layer positions. At a fixed individual DLC layer thickness, increasing the number of DLC layers from two to five produced an upward trend in the average friction coefficient and altered the spatial distribution of high-shear-strain regions. These changes reflected the combined effects of layer number and total DLC content. These findings demonstrate that the incorporation and spatial arrangement of DLC layers jointly regulate frictional resistance and local deformation, suggesting that optimizing DLC layer depth and number can help balance frictional resistance and damage resistance.

     

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