本文選題：石墨烯 + 面熱膨脹系數(shù)��； 參考：《西南科技大學(xué)》2017年碩士論文

【摘要】：本文采用分子動(dòng)力學(xué)模擬的方法,對(duì)無(wú)缺陷和帶空位缺陷單層石墨烯的面熱膨脹系數(shù)進(jìn)行了研究。重點(diǎn)討論了溫度、模型尺寸及采樣區(qū)域面積等對(duì)單層石墨烯的面熱膨脹系數(shù)的影響。研究結(jié)果表明,無(wú)缺陷和帶空位缺陷單層石墨烯的面熱膨脹系數(shù)隨溫度的變化均呈非線性變化,并且在很大溫度范圍內(nèi)均為負(fù)值(熱收縮),當(dāng)溫度高于600 K 時(shí),面熱膨脹系數(shù)隨溫度的變化很小,幾乎處于無(wú)熱膨脹狀態(tài)。在無(wú)缺陷單層石墨烯的面熱膨脹系數(shù)的研究中,還發(fā)現(xiàn)石墨烯的模型尺寸和采樣區(qū)域面積對(duì)面熱膨脹系數(shù)的變化有著較大的影響。當(dāng)石墨烯的模型尺寸小于一定尺寸時(shí)(此尺寸稱(chēng)為臨界值),具有尺寸效應(yīng),隨著模型尺寸的增大石墨烯的面熱膨脹系數(shù)絕對(duì)值變小,且此時(shí),采樣區(qū)域面積大于模型尺寸的一定比例時(shí),才可得較穩(wěn)定的數(shù)據(jù)或易于收斂。當(dāng)石墨烯的模型尺寸大于臨界值時(shí),無(wú)尺寸效應(yīng),隨著模型尺寸的增大石墨烯的面熱膨脹系數(shù)無(wú)明顯變化,此時(shí),采樣區(qū)域面積大于一定尺寸即可得到較穩(wěn)定的數(shù)據(jù)或易于收斂,與模型尺寸無(wú)關(guān)。在本研究中根據(jù)實(shí)驗(yàn)數(shù)據(jù),提出了一個(gè)經(jīng)驗(yàn)公式,在指定溫度范圍內(nèi)可計(jì)算出無(wú)缺陷單層石墨烯的面熱膨脹系數(shù)。此外,本文對(duì)于帶有空位缺陷的單層石墨烯的面熱膨脹系數(shù)也進(jìn)行了研究。研究結(jié)果發(fā)現(xiàn),在較大的溫度范圍隨著缺陷比例的增加面熱膨脹系數(shù)的絕對(duì)值減小;帶集中空位缺陷的單層石墨烯,其面熱膨脹系數(shù)的絕對(duì)值相對(duì)小于帶分散空位缺陷的單層石墨烯的面熱膨脹系數(shù)的絕對(duì)值,特別是在缺陷比例較大時(shí)更為明顯。
[Abstract]:In this paper, the surface thermal expansion coefficients of graphene monolayers with and without defects were studied by molecular dynamics simulation. The effects of temperature, model size and sampling area on the surface thermal expansion coefficient of graphene monolayer were discussed. The results show that the surface thermal expansion coefficient of graphene monolayer without defects and with vacancy defects shows nonlinear variation with temperature, and is negative in a wide range of temperatures (thermal shrinkage, when the temperature is higher than 600K), The coefficient of surface thermal expansion varies little with temperature and is almost in the state of no thermal expansion. In the study of the surface thermal expansion coefficient of graphene monolayer without defects, it is also found that the model size of graphene and the change of the coefficient of thermal expansion across the sample area have a great influence on the surface thermal expansion coefficient of graphene monolayer. When the model size of graphene is less than a certain size (this size is called critical value, it has size effect, the surface thermal expansion coefficient of graphene becomes smaller with the increase of model size, and at this time, Only when the sampling area is larger than a certain proportion of the model size, can stable data be obtained or converged easily. When the model size of graphene is larger than the critical value, there is no size effect, and the surface thermal expansion coefficient of graphene does not change obviously with the increase of the model size. The sample area is larger than a certain size, and the data can be stable or convergent, independent of the model size. Based on the experimental data, an empirical formula is proposed to calculate the surface thermal expansion coefficient of graphene monolayer without defects within a specified temperature range. In addition, the surface thermal expansion coefficient of graphene monolayer with vacancy defects is also studied. The results show that the absolute value of thermal expansion coefficient decreases with the increase of defect ratio in a large temperature range. The absolute value of the surface thermal expansion coefficient is relatively smaller than that of the monolayer graphene with dispersed vacancy defects, especially when the defect ratio is large.
【學(xué)位授予單位】：西南科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TB383.1

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本文編號(hào)：1819744