低维纳米材料的物性研究与结构预测
发布时间：2018-12-17 06:13
【摘要】：低维纳米材料具有独特的形貌特征和优异的物理化学性能,在物理学、光电子学、化学催化和材料制备等领域都具有广泛的实际应用价值。低维纳米材料的研究对象主要包括零维、一维和二维纳米材料。低维纳米材料具有独特的光学,电学和磁学性能使其成为纳米光电子器件的重要组成单元并被广泛应用于光电子、纳米微电子等领域。随着现代科技的飞速发展和实际应用的迫切需求,在实验上成功制备纳米材料变得尤为重要。实际上许多材料的实验研究受到了实验设备及实验条件的限制使得许多材料的物理性能并不能通过实验手段进行可靠测量,因而采用计算模拟技术研究纳米材料物理性能显得尤为必要。本文采用经典分子动力学方法,模拟研究低维纳米材料的机械和热力学稳定性能。本文以一维Cd Se纳米线、Cu纳米线,零维Ni纳米团簇为研究对象,建立了相应的初始结构模型,研究讨论了不同条件参数对了三种纳米材料的物理性能的影响并预测了可能发生的结构变化。本文的研究成果为低维纳米材料的实验合成与性能研究提供了重要的理论依据。主要研究内容如下:(一)采用分子动力学方法模拟研究了闪锌矿、纤锌矿结构CdSe纳米线的机械性能和纤锌矿结构Cd Se纳米线的热力学稳定性。研究结果表明:(1)两种结构的Cd Se纳米线的杨氏模量和最大拉伸强度都会随着温度和纳米线尺寸的增大而减小;同时在纤锌矿结构Cd Se纳米线的拉伸过程中,纳米线发生了明显的结构相变,且首次观测到新的TAR-4结构Cd Se纳米线。(2)纤锌矿结构CdSe纳米线的熔点与纳米线的尺寸和生长方向有很强的依赖关系:熔点会随着尺寸的增大而增大且[0001]方向的纳米线具有最高的熔化温度;通过观察纳米线的熔解行为,可以发现[0001]和[10-10]方向的纳米线存在表面预熔现象,而[2-1-10]方向的纳米线观测到内部预熔解行为。(二)采用恒压分子动力学方法模拟研究了不同大小的Ni纳米团簇在加压条件下的熔解性质及行为。研究结果表明Ni纳米团簇的熔点会随着压强和尺寸的增大而增大,且存在表面预熔现象。(三)通过在空心铜纳米线的外层包裹以及内部嵌入碳管,运用分子动力学的研究方法模拟研究了功能化碳纳米管增强空心铜纳米线的扭转过程。分析了空心铜纳米线的扭转临界角与温度,扭转率以及尺寸的变化关系,并观察了加入碳纳米管后空心铜纳米线的扭转屈曲行为。研究结果表明在碳管的支撑与保护下,临界扭转角在高温和低扭转率的条件下不会发生明显变化,然而由于纳米线存在的表面效应,空心铜纳米线的临界扭转角会随着纳米线尺寸的增加而减小。
[Abstract]:Low-dimensional nanomaterials with unique morphology and excellent physical and chemical properties have been widely used in physics, optoelectronics, chemical catalysis and material preparation. The research objects of low-dimensional nanomaterials include zero-dimensional, one-dimensional and two-dimensional nanomaterials. Low dimensional nanomaterials have unique optical, electrical and magnetic properties, which make them become important components of nano-optoelectronic devices and are widely used in photoelectron, nano-microelectronics and other fields. With the rapid development of modern science and technology and the urgent need of practical application, the successful preparation of nanomaterials has become particularly important. In fact, the physical properties of many materials can not be measured reliably by means of experiments because of the limitation of experimental equipment and experimental conditions. Therefore, it is necessary to study the physical properties of nanomaterials by computer simulation. In this paper, the mechanical and thermodynamic stability of low dimensional nanomaterials is simulated by classical molecular dynamics method. In this paper, the initial structure model of one-dimensional Cd Se nanowires, Cu nanowires and zero-dimensional Ni nanoclusters is established. The effects of different parameters on the physical properties of three kinds of nanomaterials were studied and the possible structural changes were predicted. The results of this paper provide an important theoretical basis for the experimental synthesis and performance study of low dimensional nanomaterials. The main research contents are as follows: (1) the mechanical properties of sphalerite and wurtzite CdSe nanowires and the thermodynamic stability of wurtzite Cd Se nanowires are studied by molecular dynamics simulation. The results show that: (1) the Young's modulus and maximum tensile strength of Cd Se nanowires of two structures decrease with the increase of temperature and size of nanowires; At the same time, during the stretching process of wurtzite Cd Se nanowires, the phase transition of the nanowires takes place obviously. New Cd Se nanowires with TAR-4 structure have been observed for the first time. (2) the melting point of wurtzite CdSe nanowires depends strongly on the size and growth direction of nanowires: the melting point increases with the increase of size. The nanowires in the direction of 0001 have the highest melting temperature. By observing the melting behavior of nanowires, it can be found that the surface premelting occurs in [0001] and [10-10] directions, while the internal premelting behavior is observed in [2-1-10] directions. (2) the melting properties and behavior of Ni nanoclusters with different sizes under pressure were studied by using constant pressure molecular dynamics method. The results show that the melting point of Ni nanoclusters increases with the increase of pressure and size, and there is a phenomenon of surface premelting. (3) the torsional process of functionalized carbon nanotubes reinforced hollow copper nanowires was simulated by molecular dynamics method by wrapping them in the outer layer of hollow copper nanowires and embedding carbon tubes inside them. The relationship between the critical torsion angle of hollow copper nanowires and temperature, torsion rate and size was analyzed, and the torsional buckling behavior of hollow copper nanowires with carbon nanotubes was observed. The results show that under the support and protection of carbon tubes, the critical torsion angle does not change significantly at high temperature and low torsion rate. However, due to the surface effect of nanowires, The critical torsion angle of hollow copper nanowires decreases with increasing the size of nanowires.
【学位授予单位】：上海师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1
本文编号：2383788
[Abstract]:Low-dimensional nanomaterials with unique morphology and excellent physical and chemical properties have been widely used in physics, optoelectronics, chemical catalysis and material preparation. The research objects of low-dimensional nanomaterials include zero-dimensional, one-dimensional and two-dimensional nanomaterials. Low dimensional nanomaterials have unique optical, electrical and magnetic properties, which make them become important components of nano-optoelectronic devices and are widely used in photoelectron, nano-microelectronics and other fields. With the rapid development of modern science and technology and the urgent need of practical application, the successful preparation of nanomaterials has become particularly important. In fact, the physical properties of many materials can not be measured reliably by means of experiments because of the limitation of experimental equipment and experimental conditions. Therefore, it is necessary to study the physical properties of nanomaterials by computer simulation. In this paper, the mechanical and thermodynamic stability of low dimensional nanomaterials is simulated by classical molecular dynamics method. In this paper, the initial structure model of one-dimensional Cd Se nanowires, Cu nanowires and zero-dimensional Ni nanoclusters is established. The effects of different parameters on the physical properties of three kinds of nanomaterials were studied and the possible structural changes were predicted. The results of this paper provide an important theoretical basis for the experimental synthesis and performance study of low dimensional nanomaterials. The main research contents are as follows: (1) the mechanical properties of sphalerite and wurtzite CdSe nanowires and the thermodynamic stability of wurtzite Cd Se nanowires are studied by molecular dynamics simulation. The results show that: (1) the Young's modulus and maximum tensile strength of Cd Se nanowires of two structures decrease with the increase of temperature and size of nanowires; At the same time, during the stretching process of wurtzite Cd Se nanowires, the phase transition of the nanowires takes place obviously. New Cd Se nanowires with TAR-4 structure have been observed for the first time. (2) the melting point of wurtzite CdSe nanowires depends strongly on the size and growth direction of nanowires: the melting point increases with the increase of size. The nanowires in the direction of 0001 have the highest melting temperature. By observing the melting behavior of nanowires, it can be found that the surface premelting occurs in [0001] and [10-10] directions, while the internal premelting behavior is observed in [2-1-10] directions. (2) the melting properties and behavior of Ni nanoclusters with different sizes under pressure were studied by using constant pressure molecular dynamics method. The results show that the melting point of Ni nanoclusters increases with the increase of pressure and size, and there is a phenomenon of surface premelting. (3) the torsional process of functionalized carbon nanotubes reinforced hollow copper nanowires was simulated by molecular dynamics method by wrapping them in the outer layer of hollow copper nanowires and embedding carbon tubes inside them. The relationship between the critical torsion angle of hollow copper nanowires and temperature, torsion rate and size was analyzed, and the torsional buckling behavior of hollow copper nanowires with carbon nanotubes was observed. The results show that under the support and protection of carbon tubes, the critical torsion angle does not change significantly at high temperature and low torsion rate. However, due to the surface effect of nanowires, The critical torsion angle of hollow copper nanowires decreases with increasing the size of nanowires.
【学位授予单位】：上海师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1
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