【摘要】：隨著電子元器件的特征尺寸進入到納米尺度,器件中的能量密度不斷增高,散熱問題日趨嚴重。所以尋求新型納米材料代替?zhèn)鹘y(tǒng)材料和研究其在納米尺度下的傳熱性質(zhì)成為當(dāng)前的熱門課題。在這些材料中,六方氮化硼結(jié)構(gòu)與石墨烯結(jié)構(gòu)相似,擁有良好的熱學(xué)性能,在電子元器件的研發(fā)中具有廣泛的應(yīng)用前景。本文采用了非平衡態(tài)分子動力學(xué)模擬的方法研究了可以實現(xiàn)主動調(diào)控氮化硼的熱導(dǎo)率的因素,為在電子器件中使用氮化硼時達成更高效率的熱量控制和管理,提供了理論參考。以單層氮化硼為對象,研究了如何通過應(yīng)變和三角形缺陷調(diào)控其熱導(dǎo)率。在拉伸應(yīng)變的作用下,氮化硼表面變得平整,熱導(dǎo)率隨著應(yīng)變增大而急劇下降;在壓縮應(yīng)變作用下,氮化硼結(jié)構(gòu)產(chǎn)生彎曲,熱導(dǎo)率小幅度下降。三角形缺陷在氮化硼中導(dǎo)致溫度突變,隨著缺陷數(shù)目增多,熱導(dǎo)率逐漸下降。三角形缺陷位于氮化硼中間時,從左到右和從右到左兩個方向的熱導(dǎo)率基本相同;缺陷位于一側(cè)時,兩個方向的熱導(dǎo)率明顯不同,出現(xiàn)熱整流現(xiàn)象,并采用瞬態(tài)熱流模擬驗證了這一結(jié)果。通過增加氮化硼的層數(shù)和構(gòu)建雙層氮化硼中的層間共價鍵,研究兩種不同形式的層間作用力對其熱導(dǎo)率的調(diào)控作用。氮化硼的熱導(dǎo)率隨著層數(shù)的增加而下降,并且范德華作用力強度越大,下降趨勢越明顯。在雙層氮化硼中隨著層間共價鍵的密度的增大,其熱導(dǎo)率迅速下降,并且當(dāng)層間共價鍵垂直于熱流方向分布時比平行于熱流方向分布時,氮化硼熱導(dǎo)率下降的幅度更大。研究了以二氧化硅和石墨烯作為基底時氮化硼的熱導(dǎo)率的變化情況,并構(gòu)建了振動基底模型來進一步調(diào)控其熱導(dǎo)率。當(dāng)基底和氮化硼中同時有熱流通過時,二氧化硅基底使氮化硼的熱導(dǎo)率下降,石墨烯基底可以小幅度提高氮化硼的熱導(dǎo)率,并且基底相互作用強度越強改變效果越明顯。振動基底與溫度浴長度相同,當(dāng)基底在熱浴處振動時,氮化硼熱導(dǎo)率上升;在冷浴處于振動時,氮化硼熱導(dǎo)率下降,熱導(dǎo)率改變的幅度與基底的振動頻率和振動方向相關(guān)。
[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.
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O613.81

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