Yongqiang Guo, Shuangshuang Wang, Kunpeng Ruan, Haitian Zhang and Junwei Gu*. Highly thermally conductive carbon nanotubes pillared exfoliated graphite/polyimide composites. npj Flexible Electronics, 2021, 5: 16. 2020IF=12.740.
（https://doi.org/10.1038/s41528-021-00113-z）
Abstract
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 25~100oC. 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.
本文通過微波輔助法高效、穩定地制備出剝離石墨（EG）表面垂直生長取向碳納米管（CNT）的3D結構導熱填料（CPEG），并借助“原位聚合-靜電紡絲-層疊模壓”法制備CPEG/PI導熱復合材料，成功實現了在較低CPEG導熱填料用量下CPEG/PI導熱復合材料導熱性能的快速、高效提升。當CPEG用量為10 wt%時，CPEG/PI導熱復合材料具有最佳的導熱系數（λ, 1.92 W/(m·K)），遠高于純PI的λ（0.28 W/(m·K)）。CPEG/PI導熱復合材料的λ在25~100oC溫度范圍內循環升降溫1000次后幾乎沒有變化，表現出優異的導熱性能穩定性和環境溫度耐受性。通過有限元法從微納尺度模擬熱流的傳導過程揭示了CPEG/PI導熱復合材料具有高導熱的根本原因。基于有效介質理論和能量守恒定律建立的導熱模型&經驗方程具有較好的理論計算/實驗測試結果的擬合度和匹配度，更能反應CPEG/PI導熱復合材料的λ實際變化情況。將CPEG/PI導熱復合材料置于手機CPU上能顯著降低CPU工作溫度，表現出優異的導/散熱功能和實際應用價值。
論文創新點
i. 采用微波輔助法簡單、高效、穩定制備出碳納米管垂直柱立于剝離石墨表面的3D結構導熱填料；
ii. 通過有限元法從微納尺度模擬CPEG/PI導熱復合材料的熱傳導過程，揭示其高導熱的根本原因；
iii. 優化現有導熱模型和經驗方程，使其和CPEG/PI導熱復合材料導熱系數實測值具有更好匹配性。