Danayat Swapneel, Mona Zarin Tasnim, Nayal Avinash Singh, Annam Roshan Sameer, Garg Jivtesh
School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK, USA.
Nanoscale. 2024 Jul 25;16(29):13755-13783. doi: 10.1039/d4nr01352b.
Recent research has shed light on the importance of four-phonon scattering processes in the thermal conductivity () of 2D materials. The inclusion of 4 phonon scattering processes from first-principles has been shown to lead to a thermal conductivity of ∼1290 W m K in graphene at 300 K, significantly lower than the values predicted to be in excess of 4000 W m K based only on 3 phonon scattering processes. Four phonon processes are shown to be most significant for flexural ZA phonon modes, where the reflection symmetry selection rule (RSSR) is less restrictive for 4-phonon than 3-phonon scattering processes. This combined with the low frequencies of ZA phonon modes, leading to high populations, leads to higher 4-phonon than 3-phonon scattering of low frequency ZA phonon modes in graphene at 300 K. In this review, the role of parameters such as atomic structure, phonon dispersion and temperature on 4-phonon scattering processes in a wide range of 2D materials is reviewed. Materials such as graphene nanoplatelets (GnPs) have been extensively investigated for enhancement of the thermal conductivity of polymer composites. However, such enhancement is limited by the poor interfacial thermal conductance between the polymer and filler material. Interconnected filler networks overcome this issue through highly efficient continuous percolative heat transfer paths throughout the composite. Such 3D networks have been shown to enable ultra-high polymer thermal conductivities, approaching ∼100 W m K, and even exceeding those of several metals. In this review, different techniques used to achieve such interconnected 3D filler networks, namely, aerogels, foams, ice-templating, expanded graphite, hot pressing of filler coated polymer particles, the synergistic effect between multiple fillers, and the stitching of filler sheets, are discussed and their impact on thermal conductivity enhancement are presented.
最近的研究揭示了四声子散射过程在二维材料热导率（）中的重要性。从第一性原理出发考虑四声子散射过程，已证明在300K时石墨烯的热导率约为1290W·m⁻¹·K⁻¹，这显著低于仅基于三声子散射过程预测的超过4000W·m⁻¹·K⁻¹的值。结果表明，四声子过程对弯曲ZA声子模式最为显著，其中反射对称选择规则（RSSR）对四声子散射过程的限制比对三声子散射过程的限制要小。这与ZA声子模式的低频相结合，导致高占据数，使得在300K时石墨烯中低频ZA声子模式的四声子散射高于三声子散射。在这篇综述中，回顾了原子结构、声子色散和温度等参数在多种二维材料的四声子散射过程中的作用。诸如石墨烯纳米片（GnPs）等材料已被广泛研究用于提高聚合物复合材料的热导率。然而，这种提高受到聚合物与填充材料之间不良界面热导率的限制。相互连接的填充网络通过复合材料中高效的连续渗流热传递路径克服了这个问题。这种三维网络已被证明能够实现超高的聚合物热导率，接近~100W·m⁻¹·K⁻¹，甚至超过几种金属的热导率。在这篇综述中，讨论了用于实现这种相互连接的三维填充网络的不同技术，即气凝胶、泡沫、冰模板法、膨胀石墨、填充涂层聚合物颗粒的热压、多种填料之间的协同效应以及填充片的缝合，并介绍了它们对热导率提高的影响。
