【摘要】：石墨烯是單原子層厚度的新型二維納米碳材料,被譽(yù)為新一代戰(zhàn)略材料,自從2004年被發(fā)現(xiàn)就一直是研究人員眼中炙手可熱的研究對象。目前,人們已經(jīng)可以應(yīng)用化學(xué)氣相沉積等方法生產(chǎn)制備大面積、高質(zhì)量的石墨烯。對于完美石墨烯的各種研究已趨于成熟,包括它卓越的力學(xué),熱學(xué),磁學(xué),以及電學(xué)性能等,這使它有望在高性能納米電子器件,復(fù)合材料,能量儲(chǔ)存等領(lǐng)域都獲得廣泛應(yīng)用。另外,對于石墨烯結(jié)合塊體金屬、環(huán)氧樹脂等的石墨烯復(fù)合材料的研究也已取得明顯進(jìn)展。值得注意的是,含缺陷石墨烯的性能研究剛剛起步就得到了廣泛關(guān)注,例如基于古老剪折工藝的石墨烯剪紙能改善石墨烯極限應(yīng)變偏小的局限,加強(qiáng)它的延展性;多孔石墨烯優(yōu)異的使用性能將石墨烯的應(yīng)用拓展到了DNA分子檢測等微觀過濾的領(lǐng)域。分子動(dòng)力學(xué)是一種成熟的數(shù)值模擬方法,它可以對微納材料進(jìn)行基本真實(shí)的機(jī)械模擬從而得到材料的多種機(jī)械性能,現(xiàn)已廣泛應(yīng)用于細(xì)觀材料的性能研究,并獲得了廣泛的認(rèn)同。本文主要以單/雙層石墨烯剪紙和多孔石墨烯為研究對象,使用分子動(dòng)力學(xué)工具LAMMPS對結(jié)構(gòu)施加單軸拉伸荷載直至結(jié)構(gòu)破壞,輔以成像軟件VMD,觀察了結(jié)構(gòu)的破壞過程,并繪制了不同結(jié)構(gòu)的拉伸應(yīng)力應(yīng)變曲線,得到了兩種石墨烯的拉伸變形及破壞機(jī)制。最后,對兩種石墨烯分別定義三個(gè)不同含義的無量綱幾何參數(shù)來建立不同的結(jié)構(gòu),通過模擬得到結(jié)構(gòu)的拉伸力學(xué)參數(shù)隨幾何參數(shù)的變化規(guī)律。通過比較,我們證實(shí)剪紙工藝確實(shí)能有效提高石墨烯的拉伸極限應(yīng)變3到6倍,即有效地提高了石墨烯的延展性。另外,我們通過對力學(xué)參數(shù)變化趨勢的研究,得到了有效調(diào)控石墨烯剪紙極限應(yīng)變大小的方法,即實(shí)現(xiàn)力學(xué)性能參數(shù)的可控性。這將為石墨烯在柔性器件中的使用奠定理論基礎(chǔ)。對雙層石墨烯剪紙結(jié)構(gòu)的研究證明剪紙工藝也能增大雙層石墨烯的極限應(yīng)變,且雙層石墨烯剪紙的變形規(guī)律和單層石墨烯剪紙的基本類似。對多孔石墨烯的研究表明,雖然多孔石墨烯中的納米孔的存在降低了石墨烯的強(qiáng)度,但是合理減小孔的密度仍然可以保持石墨烯高強(qiáng)度的優(yōu)勢,且通過合理改變幾何參數(shù)的大小可以人為地調(diào)控結(jié)構(gòu)力學(xué)參數(shù)的大小。多孔石墨烯的極限應(yīng)變,極限應(yīng)力和楊氏模量均隨著垂直于拉伸方向上孔的密度的增大而減小。另外,結(jié)構(gòu)的剛度嚴(yán)格隨孔密度的增大而減小。這將為石墨烯在過濾等高強(qiáng)度要求的應(yīng)用領(lǐng)域的設(shè)計(jì)提供參考。
[Abstract]:Graphene is a new two-dimensional nano-carbon material with the thickness of single atomic layer. It is praised as a new generation of strategic materials. It has been a hot research object in the eyes of researchers since it was discovered in 2004. At present, large area and high quality graphene can be produced by chemical vapor deposition. All kinds of research on perfect graphene have become mature, including its excellent mechanical, thermal, magnetic and electrical properties. It is expected to be widely used in high performance nanoelectronic devices, composite materials, energy storage and other fields. In addition, the research of graphene bonded bulk metal, epoxy resin and other graphene composites has also made remarkable progress. It is worth noting that the study on the properties of graphene containing defects has been paid more and more attention at the beginning. For example, the paper-cut of graphene based on the ancient shear folding process can improve the limit of the limit strain of graphene and strengthen its ductility. The excellent performance of porous graphene extends the application of graphene to microfiltration such as DNA molecular detection. Molecular dynamics is a mature numerical simulation method. It can be used to simulate the mechanical properties of micro and nano materials and obtain a variety of mechanical properties. It has been widely used in the study of properties of meso-materials. And has been widely recognized. In this paper, single / double layer graphene paper-cut and porous graphene were used to apply uniaxial tensile load to the structure and the imaging software VMD was used to observe the damage process of the structure. The tensile stress-strain curves of different structures were plotted and the tensile deformation and failure mechanisms of two graphene were obtained. Finally, three dimensionless geometric parameters with different meanings are defined for the two graphene to establish different structures, and the variation of tensile mechanical parameters with geometric parameters is obtained by simulation. By comparison, it is proved that paper-cut process can effectively increase the tensile limit strain of graphene by 3 to 6 times, that is, the ductility of graphene can be improved effectively. In addition, through the study of the changing trend of mechanical parameters, we have obtained an effective method to control the limit strain of graphene paper-cut, that is, to realize the controllability of mechanical properties. This will lay a theoretical foundation for the use of graphene in flexible devices. The study on the paper-cut structure of bilayer graphene proves that the paper-cutting process can also increase the limit strain of bilayer graphene, and the deformation law of double-layer graphene paper-cut is similar to that of monolayer graphene paper-cut. The study of porous graphene shows that the strength of graphene can be reduced by the existence of nano-pore in porous graphene, but the advantage of high strength of graphene can be maintained by reasonably decreasing the density of pore. The size of structural mechanics parameters can be adjusted artificially by changing the geometric parameters reasonably. The ultimate strain, ultimate stress and Young's modulus of porous graphene decrease with the increase of pore density perpendicular to the tensile direction. In addition, the stiffness of the structure decreases strictly with the increase of the hole density. This will provide reference for the design of graphene in high strength applications such as filtration.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O613.71

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本文編號：2145348