writer：Yongqiang Guo, Shuangshuang Wang, Kunpeng Ruan, Haitian Zhang and Junwei Gu*
keywords：thermally conductive
source：期刊
specific source：npj Flex Electron
Issue time：2021年

In this work, carbon nanotubes pillared grew on exfoliated graphite by microwave-assisted method is utilized as thermally conductive fillers (CPEG) in polyimide (PI) to fabricate CPEG/PI thermally conductive composites with the combining ways of “in-situ polymerization, electrospinning, lay-up & hot-pressing”. The prepared CPEG/PI composites realized the maximum thermal conductivity (λ, 1.92 W/(m·K)) at low CPEG amount (10 wt%), much higher than that of pure PI (0.28 W/(m·K)). The λ of CPEG/PI composites show almost no change after 1000 cycles of heating and cooling in the temperature of 25~100^oC. The finite element analysis simulates the nano/microscale heat transfer in CPEG/PI composites to reveal the internal reason of the λ enhancement. The improved thermal conductivity model & empirical equation could better reflect the actual λ change trend of CPEG/PI composites. Actual application test shows the CPEG/PI composites could significantly reduce the operating temperature of CPU in mobile phone.

本文通过微波辅助法高效、稳定地制备出剥离石墨（EG）表面垂直生长取向碳纳米管（CNT）的3D结构导热填料（CPEG），并借助“原位聚合-静电纺丝-层叠模压”法制备CPEG/PI导热复合材料，成功实现了在较低CPEG导热填料用量下CPEG/PI导热复合材料导热性能的快速、高效提升。当CPEG用量为10 wt%时，CPEG/PI导热复合材料具有最佳的导热系数（λ, 1.92 W/(m·K)），远高于纯PI的λ（0.28 W/(m·K)）。CPEG/PI导热复合材料的λ在25~100^oC温度范围内循环升降温1000次后几乎没有变化，表现出优异的导热性能稳定性和环境温度耐受性。通过有限元法从微纳尺度模拟热流的传导过程揭示了CPEG/PI导热复合材料具有高导热的根本原因。基于有效介质理论和能量守恒定律建立的导热模型&经验方程具有较好的理论计算/实验测试结果的拟合度和匹配度，更能反应CPEG/PI导热复合材料的λ实际变化情况。将CPEG/PI导热复合材料置于手机CPU上能显著降低CPU工作温度，表现出优异的导/散热功能和实际应用价值。