The Effects of Environmental Water and Oxygen on the Temperature-Dependent Friction of Sputtered Molybdenum Disulfide
The Effects of Environmental Water and Oxygen on the Temperature-Dependent Friction of Sputtered Molybdenum Disulfide
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DOI：
10.1007/s11249-013-0233-8
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发表时间：
2013-12-01
影响因子：
3.2
通讯作者：
Burris, D. L.
中科院分区：
文献类型：
--
作者：
Khare, H. S.;Burris, D. L.
二硫化钼（MoS2）因其在惰性和高真空环境中的优异摩擦和磨损性能而闻名。然而，这些摩擦学性能在潮湿和高温环境中会降低，原因尚不完全清楚。一个流行的假设表明，水分和热能促进氧化，这增加了滑动界面的剪切强度。本研究的目的是阐明的贡献，水，氧气，和温度的摩擦学降解的二硫化钼。一般来说，我们发现在我们定义为转变温度的温度下出现最小摩擦系数。该转变温度范围为100至250摄氏度，并且是二硫化钼制备和热滑动历史的强函数。在转变温度以下，摩擦随着水的增加而增加，但对氧不敏感。在过渡区以上，摩擦随着氧气的增加而增加，但随着水的增加而在有限程度上降低。这些结果与先前的结果基本一致，但澄清了文献讨论中的一些不一致之处。与流行的假设相反，结果表明，水不会促进室温附近的氧化，但通过物理键合直接干扰片层剪切。升高的温度赶走水，从而减少摩擦，直到转变温度。结果表明，随着温度的升高，氧化会导致摩擦增加，高于转变温度。数据还表明，水通过置换环境氧或通过优先吸附到表面来帮助减轻高温氧化。
Molybdenum disulfide (MoS2) is well known for exceptional friction and wear properties in inert and high vacuum environments. However, these tribological properties degrade in humid and high temperature environments for reasons that are not fully understood. A prevailing hypothesis suggests that moisture and thermal energy facilitate oxidation, which increases the shear strength of the sliding interface. The purpose of this study is to elucidate the contributions of water, oxygen, and temperature to the tribological degradation of MoS2. Generally speaking, we found a minimum friction coefficient that occurred at a temperature we defined as the transition temperature. This transition temperature ranged from 100 to 250 A degrees C and was a strong function of the MoS2 preparation and thermal sliding history. Below the transition temperature, friction increased with increased water, but was insensitive to oxygen. Above the transition, friction increased with increased oxygen, but decreased to a limited extent with increased water. These results are generally consistent with prior results, but clarify some inconsistencies in the literature discussions. Contrary to the prevailing hypothesis, the results suggest that water does not promote oxidation near room temperature, but directly interferes with lamellar shear through physical bonding. Increased temperatures drive off water and thereby reduce friction up to the transition temperature. The results suggest that oxidation causes increased friction with increased temperature above the transition temperature. The data also suggest that water helps mitigate high temperature oxidation by displacing the environmental oxygen or by preferentially adsorbing to the surface.