Abstract The c-axis thermal conductivity (kc) of graphene paper (GP) is measured from 295 K to 12.3 K and extrapolation is used to identify the residual thermal reffusivity at the 0 K limit. To uncover the structural domain size based on the residual thermal reffusivity, we develop an anisotropic specific heat model to identify the phonons that sustain the heat conduction along the c-axis. This model predicts a c-mean free path (MFP) of 165 nm for graphite at room temperature (RT), very close to the value of 146 nm by molecular dynamics (MD) modeling. For widely studied normal graphite materials, this model predicts a structure domain size of 375 nm, close to the 404 nm grain size uncovered by transmission electron microscopy. Using our model, the c-MFP induced by defect in the GP is evaluated at 234 nm based on the low-momentum phonon scattering. This structural domain size significantly exceeds the graphene flake thickness (1.68–2.01 nm) in our GP, uncovering excellent c-direction atomic structure order. By subtracting the residual thermal reffusivity, the defect-free kc and c-MFP of GP are obtained. At RT, the defect-free kc is 9.67 Wm−1K−1, close to 11.6 Wm−1K−1 of graphite from the recent MD simulations.

中文翻译：

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低动量声子散射发现石墨烯纸的亚微米 c 轴结构域尺寸

摘要 石墨烯纸 (GP) 的 c 轴热导率 (kc) 在 295 K 至 12.3 K 范围内测量，并使用外推法确定 0 K 极限处的残余热扩散率。为了揭示基于残余热扩散率的结构域大小，我们开发了一个各向异性比热模型来识别沿 c 轴维持热传导的声子。该模型预测石墨在室温 (RT) 下的 c 平均自由程 (MFP) 为 165 nm，非常接近分子动力学 (MD) 建模得出的 146 nm 值。对于广泛研究的普通石墨材料，该模型预测结构域尺寸为 375 nm，接近透射电子显微镜发现的 404 nm 晶粒尺寸。使用我们的模型，基于低动量声子散射在 234 nm 处评估由 GP 中的缺陷引起的 c-MFP。这种结构域尺寸显着超过了我们 GP 中石墨烯薄片的厚度（1.68-2.01 nm），揭示了出色的 c 方向原子结构顺序。通过减去残余热扩散系数，得到GP的无缺陷kc和c-MFP。在 RT，无缺陷 kc 为 9.67 Wm-1K-1，接近最近 MD 模拟的石墨的 11.6 Wm-1K-1。