Deng Yao, Chen Yu, Liu Hanxu, Yan Xin
School of Mechanical Engineering and Automation, Beihang University, Beijing 100191, China.
Advanced Manufacturing Center, Ningbo Institute of Technology, Beihang University, Ningbo 315100, China.
Nanomaterials (Basel). 2022 Feb 26;12(5):798. doi: 10.3390/nano12050798.
Two-dimensional transition metal carbides and nitrides (MXenes) are widely applied in the fields of electrochemistry, energy storage, electromagnetism, etc., due to their extremely excellent properties, including mechanical performance, thermal stability, photothermal conversion and abundant surface properties. Usually, the surfaces of the MXenes are terminated by -OH, -F, -O or other functional groups and these functional groups of MXenes are related surface properties and reported to affect the mechanical properties of MXenes. Thus, understanding the effects of surface terminal groups on the properties of MXenes is crucial for device fabrication as well as composite synthesis using MXenes. In this paper, using molecular dynamics (MD) simulation, we study the adhesion and friction properties of TiC and TiCO, including the indentation strength, adhesion energy and dynamics of friction. Our indentation fracture simulation reveals that there are many unbroken bonds and large residual stresses due to the oxidation of oxygen atoms on the surface of TiCO. By contrast, the cracks of TiC keep clean at all temperatures. In addition, we calculate the elastic constants of TiC and TiCO by the fitting force-displacement curves with elastic plate theory and demonstrate that the elastic module of TiCO is higher. Although the temperature had a significant effect on the indentation fracture process, it hardly influences maximum adhesion. The adhesion energies of TiC and TiCO were calculated to be 0.3 J/m and 0.5 J/m according to Maugis-Dugdale theory. In the friction simulation, the stick-slip atomic scale phenomenon is clearly observed. The friction force and roughness () of TiC and TiCO at different temperatures are analyzed. Our study provides a comprehensive insight into the mechanical behavior of nanoindentation and the surface properties of oxygen functionalized MXenes, and the results are beneficial for the further design of nanodevices and composites.
二维过渡金属碳化物和氮化物（MXenes）由于其极其优异的性能，包括机械性能、热稳定性、光热转换和丰富的表面性质，而被广泛应用于电化学、能量存储、电磁学等领域。通常，MXenes的表面由-OH、-F、-O或其他官能团终止，并且MXenes的这些官能团与表面性质相关，并据报道会影响MXenes的机械性能。因此，了解表面端基对MXenes性能的影响对于器件制造以及使用MXenes的复合材料合成至关重要。在本文中，我们使用分子动力学（MD）模拟研究了TiC和TiCO的粘附和摩擦性能，包括压痕强度、粘附能和摩擦动力学。我们的压痕断裂模拟表明，由于TiCO表面氧原子的氧化，存在许多未断裂的键和较大的残余应力。相比之下，TiC的裂纹在所有温度下都保持干净。此外，我们通过用弹性板理论拟合力-位移曲线来计算TiC和TiCO的弹性常数，并证明TiCO的弹性模量更高。尽管温度对压痕断裂过程有显著影响，但它几乎不影响最大粘附力。根据Maugis-Dugdale理论，计算出TiC和TiCO的粘附能分别为0.3 J/m和0.5 J/m。在摩擦模拟中，清晰地观察到了粘滑原子尺度现象。分析了TiC和TiCO在不同温度下的摩擦力和粗糙度（）。我们的研究全面深入地了解了纳米压痕的力学行为和氧官能化MXenes的表面性质，其结果有利于纳米器件和复合材料的进一步设计。
