本文選題：雙壁碳納米管振蕩器 + 分子動(dòng)力學(xué)�。� 參考：《南昌航空大學(xué)》2017年碩士論文

【摘要】：碳納米管(CNTs)自發(fā)現(xiàn)以來(lái)就以其良好的力學(xué)和電學(xué)性能受到了廣泛的關(guān)注。研究者們利用雙壁碳納米管(DWCNTs)之間超潤(rùn)滑的特性,將其運(yùn)用在振蕩器上,制造頻率超過(guò)GHz的機(jī)械振蕩器。本文以DWCNTs為研究對(duì)象,使用分子動(dòng)力學(xué)(Molecular Dynamics,MD)方法研究缺陷及預(yù)應(yīng)變對(duì)DWCNTs振蕩器性能的影響。研究的內(nèi)容和主要結(jié)論如下:(1)首先,本文在DWCNTs模型上分別對(duì)其內(nèi)外管引入空位缺陷,分析了空位缺陷的數(shù)量、位置分布和排列方式對(duì)DWCNTs振蕩器性能的影響。研究結(jié)果表明:當(dāng)空位缺陷分布在DWCNTs的內(nèi)管上時(shí),隨著空位缺陷的增加,振幅衰減加快,品質(zhì)因子(Q-factor,Q值)減小,振蕩頻率升高,主要原因是空位缺陷改變了DWCNTs層間的范德華勢(shì)(VDW Potential)的分布以及振蕩過(guò)程中發(fā)生的偏心搖擺振蕩使得能量衰減加快;當(dāng)空位缺陷分布在DWCNTs的外管上時(shí),在一定的數(shù)量范圍內(nèi),空位缺陷對(duì)Q值的影響并不是特別大。(2)其次,在公度DWCNTs振蕩器振蕩前,預(yù)先對(duì)其內(nèi)管或外管施加預(yù)應(yīng)變,分析室溫下預(yù)應(yīng)變對(duì)其振蕩性能的影響。研究結(jié)果表明:在室溫下,當(dāng)公度DWCNTs振蕩器受到拉伸應(yīng)變時(shí),隨著拉伸應(yīng)變的增加,公度DWCNTs振蕩器的能量耗散會(huì)加快,從而導(dǎo)致振幅衰減越來(lái)越快,其性能越來(lái)越差;當(dāng)公度DWCNTs振蕩器受到壓縮預(yù)應(yīng)變時(shí),隨著壓縮應(yīng)變的增加,公度DWCNTs振蕩器的振幅衰減同樣也越來(lái)越快,其性能也越來(lái)越差,而在無(wú)預(yù)應(yīng)變的時(shí)候其振蕩性能最穩(wěn)定。因此,在室溫下生產(chǎn)組裝公度DWCNTs振蕩器時(shí),應(yīng)該盡可能消除預(yù)應(yīng)變,從而降低對(duì)其性能的影響。(3)最后,在非公度DWCNTs振蕩器振蕩前,預(yù)先對(duì)內(nèi)管或外管施加應(yīng)變,研究不同溫度下預(yù)應(yīng)變對(duì)非公度DWCNTs振蕩器性能的影響。研究結(jié)果表明:在低溫下,當(dāng)振蕩前對(duì)非公度DWCNTs振蕩器施加預(yù)應(yīng)變時(shí),在小應(yīng)變階段,預(yù)應(yīng)變能提高非公度DWCNTs振蕩器的Q值,改善振蕩器的穩(wěn)定性,隨著應(yīng)變的繼續(xù)增加,Q值又會(huì)逐漸下降。隨著溫度的升高,預(yù)應(yīng)變對(duì)非公度DWCNTs振蕩器的改善效果越來(lái)越來(lái)弱,直到破壞振蕩器的穩(wěn)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.
【學(xué)位授予單位】：南昌航空大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN752

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