基于分子动力学模拟的氮化硼热导率主动调控方法的研究

发布时间：2018-10-21 17:23

【摘要】：随着电子元器件的特征尺寸进入到纳米尺度,器件中的能量密度不断增高,散热问题日趋严重。所以寻求新型纳米材料代替传统材料和研究其在纳米尺度下的传热性质成为当前的热门课题。在这些材料中,六方氮化硼结构与石墨烯结构相似,拥有良好的热学性能,在电子元器件的研发中具有广泛的应用前景。本文采用了非平衡态分子动力学模拟的方法研究了可以实现主动调控氮化硼的热导率的因素,为在电子器件中使用氮化硼时达成更高效率的热量控制和管理,提供了理论参考。以单层氮化硼为对象,研究了如何通过应变和三角形缺陷调控其热导率。在拉伸应变的作用下,氮化硼表面变得平整,热导率随着应变增大而急剧下降;在压缩应变作用下,氮化硼结构产生弯曲,热导率小幅度下降。三角形缺陷在氮化硼中导致温度突变,随着缺陷数目增多,热导率逐渐下降。三角形缺陷位于氮化硼中间时,从左到右和从右到左两个方向的热导率基本相同;缺陷位于一侧时,两个方向的热导率明显不同,出现热整流现象,并采用瞬态热流模拟验证了这一结果。通过增加氮化硼的层数和构建双层氮化硼中的层间共价键,研究两种不同形式的层间作用力对其热导率的调控作用。氮化硼的热导率随着层数的增加而下降,并且范德华作用力强度越大,下降趋势越明显。在双层氮化硼中随着层间共价键的密度的增大,其热导率迅速下降,并且当层间共价键垂直于热流方向分布时比平行于热流方向分布时,氮化硼热导率下降的幅度更大。研究了以二氧化硅和石墨烯作为基底时氮化硼的热导率的变化情况,并构建了振动基底模型来进一步调控其热导率。当基底和氮化硼中同时有热流通过时,二氧化硅基底使氮化硼的热导率下降,石墨烯基底可以小幅度提高氮化硼的热导率,并且基底相互作用强度越强改变效果越明显。振动基底与温度浴长度相同,当基底在热浴处振动时,氮化硼热导率上升;在冷浴处于振动时,氮化硼热导率下降,热导率改变的幅度与基底的振动频率和振动方向相关。
[Abstract]:With the characteristic size of electronic components entering nanometer scale, the energy density in the devices is increasing, and the heat dissipation problem is becoming more and more serious. Therefore, it has become a hot topic to seek new nano materials instead of traditional materials and to study their heat transfer properties at nanometer scale. The structure of hexagonal boron nitride is similar to that of graphene and has good thermal properties. It has a wide application prospect in the research and development of electronic components. In this paper, the non-equilibrium molecular dynamics simulation method is used to study the factors that can actively regulate the thermal conductivity of boron nitride, which provides a theoretical reference for achieving more efficient heat control and management when using boron nitride in electronic devices. The thermal conductivity of monolayer boron nitride was studied by means of strain and triangular defects. Under the action of tensile strain, the surface of boron nitride becomes flat, the thermal conductivity decreases sharply with the increase of strain, and the structure of boron nitride bends and the thermal conductivity decreases slightly under the action of compression strain. Triangular defects lead to temperature mutation in boron nitride, and the thermal conductivity decreases with the number of defects increasing. When the triangular defect is in the middle of boron nitride, the thermal conductivity from left to right and from right to left is basically the same. The transient heat flux simulation is used to verify this result. By increasing the number of layers of boron nitride and constructing interlaminar covalent bonds in bilayer boron nitride, the effects of two different interlaminar forces on the thermal conductivity of boron nitride were studied. The thermal conductivity of boron nitride decreases with the increase of the number of layers, and the stronger the van der Waals force is, the more obvious the decreasing trend is. The thermal conductivity of double boron nitride decreases rapidly with the increase of interlaminar covalent bond density, and the decrease of thermal conductivity of boron nitride is larger when the interlayer covalent bond is perpendicular to the heat flux direction than that parallel to the heat flux direction. The variation of thermal conductivity of boron nitride with silicon dioxide and graphene as the substrate was studied, and a vibrating substrate model was constructed to further regulate the thermal conductivity of boron nitride. The thermal conductivity of boron nitride can be decreased by silicon dioxide substrate when the heat flux in the substrate and boron nitride is passing simultaneously, and the thermal conductivity of boron nitride can be improved slightly by graphene substrate, and the stronger the intensity of the substrate interaction is, the more obvious the effect is. The thermal conductivity of boron nitride increases when the substrate vibrates in the hot bath, while the thermal conductivity of boron nitride decreases when the thermal bath is in the cold bath. The amplitude of the change of thermal conductivity is related to the vibration frequency and vibration direction of the substrate.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O613.81

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