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(wěn)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(jié)構(gòu)導(dǎo)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(dǎo)熱復(fù)合材料，成功實(shí)現(xiàn)了在較低CPEG導(dǎo)熱填料用量下CPEG/PI導(dǎo)熱復(fù)合材料導(dǎo)熱性能的快速、高效提升。當(dāng)CPEG用量為10 wt%時(shí)，CPEG/PI導(dǎo)熱復(fù)合材料具有最佳的導(dǎo)熱系數(shù)（λ, 1.92 W/(m·K)），遠(yuǎn)高于純PI的λ（0.28 W/(m·K)）。CPEG/PI導(dǎo)熱復(fù)合材料的λ在25~100oC溫度范圍內(nèi)循環(huán)升降溫1000次后幾乎沒有變化，表現(xiàn)出優(yōu)異的導(dǎo)熱性能穩(wěn)定性和環(huán)境溫度耐受性。通過有限元法從微納尺度模擬熱流的傳導(dǎo)過程揭示了CPEG/PI導(dǎo)熱復(fù)合材料具有高導(dǎo)熱的根本原因。基于有效介質(zhì)理論和能量守恒定律建立的導(dǎo)熱模型&經(jīng)驗(yàn)方程具有較好的理論計(jì)算/實(shí)驗(yàn)測試結(jié)果的擬合度和匹配度，更能反應(yīng)CPEG/PI導(dǎo)熱復(fù)合材料的λ實(shí)際變化情況。將CPEG/PI導(dǎo)熱復(fù)合材料置于手機(jī)CPU上能顯著降低CPU工作溫度，表現(xiàn)出優(yōu)異的導(dǎo)/散熱功能和實(shí)際應(yīng)用價(jià)值。
論文創(chuàng)新點(diǎn)
i. 采用微波輔助法簡單、高效、穩(wěn)定制備出碳納米管垂直柱立于剝離石墨表面的3D結(jié)構(gòu)導(dǎo)熱填料；
ii. 通過有限元法從微納尺度模擬CPEG/PI導(dǎo)熱復(fù)合材料的熱傳導(dǎo)過程，揭示其高導(dǎo)熱的根本原因；
iii. 優(yōu)化現(xiàn)有導(dǎo)熱模型和經(jīng)驗(yàn)方程，使其和CPEG/PI導(dǎo)熱復(fù)合材料導(dǎo)熱系數(shù)實(shí)測值具有更好匹配性。