缺陷及预应变对双壁碳纳米管振荡器的影响

发布时间：2018-05-03 23:31

  本文选题：双壁碳纳米管振荡器 + 分子动力学　； 参考：《南昌航空大学》2017年硕士论文

【摘要】：碳纳米管(CNTs)自发现以来就以其良好的力学和电学性能受到了广泛的关注。研究者们利用双壁碳纳米管(DWCNTs)之间超润滑的特性,将其运用在振荡器上,制造频率超过GHz的机械振荡器。本文以DWCNTs为研究对象,使用分子动力学(Molecular Dynamics,MD)方法研究缺陷及预应变对DWCNTs振荡器性能的影响。研究的内容和主要结论如下:(1)首先,本文在DWCNTs模型上分别对其内外管引入空位缺陷,分析了空位缺陷的数量、位置分布和排列方式对DWCNTs振荡器性能的影响。研究结果表明:当空位缺陷分布在DWCNTs的内管上时,随着空位缺陷的增加,振幅衰减加快,品质因子(Q-factor,Q值)减小,振荡频率升高,主要原因是空位缺陷改变了DWCNTs层间的范德华势(VDW Potential)的分布以及振荡过程中发生的偏心摇摆振荡使得能量衰减加快;当空位缺陷分布在DWCNTs的外管上时,在一定的数量范围内,空位缺陷对Q值的影响并不是特别大。(2)其次,在公度DWCNTs振荡器振荡前,预先对其内管或外管施加预应变,分析室温下预应变对其振荡性能的影响。研究结果表明:在室温下,当公度DWCNTs振荡器受到拉伸应变时,随着拉伸应变的增加,公度DWCNTs振荡器的能量耗散会加快,从而导致振幅衰减越来越快,其性能越来越差;当公度DWCNTs振荡器受到压缩预应变时,随着压缩应变的增加,公度DWCNTs振荡器的振幅衰减同样也越来越快,其性能也越来越差,而在无预应变的时候其振荡性能最稳定。因此,在室温下生产组装公度DWCNTs振荡器时,应该尽可能消除预应变,从而降低对其性能的影响。(3)最后,在非公度DWCNTs振荡器振荡前,预先对内管或外管施加应变,研究不同温度下预应变对非公度DWCNTs振荡器性能的影响。研究结果表明:在低温下,当振荡前对非公度DWCNTs振荡器施加预应变时,在小应变阶段,预应变能提高非公度DWCNTs振荡器的Q值,改善振荡器的稳定性,随着应变的继续增加,Q值又会逐渐下降。随着温度的升高,预应变对非公度DWCNTs振荡器的改善效果越来越来弱,直到破坏振荡器的稳定性。
[Abstract]:Carbon nanotubes (CNTs) have attracted wide attention for their excellent mechanical and electrical properties since their discovery. The researchers used the superlubricating properties of double-walled carbon nanotubes (DWCNTs) to create mechanical oscillators with frequencies higher than GHz. In this paper, DWCNTs is used to study the effects of defects and prestrain on the performance of DWCNTs oscillators by molecular dynamics molecular dynamics (MD) method. The contents and main conclusions of the study are as follows: (1) first of all, the vacancy defects are introduced into the DWCNTs model for the internal and external tubes, and the effects of the number, position distribution and arrangement of the vacancy defects on the performance of the DWCNTs oscillator are analyzed. The results show that when the vacancy defect is distributed on the inner tube of DWCNTs, the amplitude attenuation increases with the increase of the vacancy defect, the quality factor Q-factor-Q value decreases, and the oscillation frequency increases. The main reason is that the vacancy defect changes the distribution of VDW potential between the DWCNTs layers and the eccentric swing oscillation in the oscillation process, which accelerates the energy decay. When the vacancy defect is distributed on the outer tube of DWCNTs, it is within a certain range. The effect of vacancy defect on Q value is not particularly large. Secondly, the pre-strain is applied to the inner or outer tube before the DWCNTs oscillator oscillates, and the effect of pre-strain on the oscillation performance at room temperature is analyzed. The results show that, at room temperature, the energy dissipation of the DWCNTs oscillator accelerates with the increase of tensile strain, which results in a faster amplitude attenuation and worse performance. With the increase of compression strain, the amplitude attenuation and performance of the DWCNTs oscillator become faster and worse, and the oscillation performance is the most stable without prestrain. Therefore, when producing the assembled DWCNTs oscillator at room temperature, the prestrain should be eliminated as far as possible to reduce the effect on its performance. Finally, before the incommensurate DWCNTs oscillator oscillates, the strain is applied to the inner or outer tube in advance. The effect of prestrain on the performance of incommensurate DWCNTs oscillator at different temperatures is studied. The results show that at low temperature, when pre-strain is applied to the incommensurate DWCNTs oscillator before oscillation, at the small strain stage, the pre-strain can increase the Q value of the incommensurate DWCNTs oscillator and improve the stability of the oscillator. As the strain continues to increase, the Q value will decrease gradually. With the increase of temperature, the improvement effect of prestrain on the incommensurate DWCNTs oscillator becomes weaker and weaker until the stability of the oscillator is destroyed.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN752

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