Wang Yang, Collinson David W, Kwon Heungdong, Miller Robert D, Lionti Krystelle, Goodson Kenneth E, Dauskardt Reinhold H
Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA.
Department of Mechanical Engineering, Stanford University, Stanford, CA, USA.
Small. 2023 Jul;19(28):e2301383. doi: 10.1002/smll.202301383. Epub 2023 Mar 27.
Thermal transport in polymer nanocomposites becomes dependent on the interfacial thermal conductance due to the ultra-high density of the internal interfaces when the polymer and filler domains are intimately mixed at the nanoscale. However, there is a lack of experimental measurements that can link the thermal conductance across the interfaces to the chemistry and bonding between the polymer molecules and the glass surface. Characterizing the thermal properties of amorphous composites are a particular challenge as their low intrinsic thermal conductivity leads to poor measurement sensitivity of the interfacial thermal conductance. To address this issue here, polymers are confined in porous organosilicates with high interfacial densities, stable composite structure, and varying surface chemistries. The thermal conductivities and fracture energies of the composites are measured with frequency dependent time-domain thermoreflectance (TDTR) and thin-film fracture testing, respectively. Effective medium theory (EMT) along with finite element analysis (FEA) is then used to uniquely extract the thermal boundary conductance (TBC) from the measured thermal conductivity of the composites. Changes in TBC are then linked to the hydrogen bonding between the polymer and organosilicate as quantified by Fourier-transform infrared (FTIR) and X-ray photoelectron (XPS) spectroscopy. This platform for analysis is a new paradigm in the experimental investigation of heat flow across constituent domains.
当聚合物和填料域在纳米尺度上紧密混合时，由于内部界面的超高密度，聚合物纳米复合材料中的热传输变得依赖于界面热导率。然而，缺乏能够将界面间的热导率与聚合物分子和玻璃表面之间的化学性质及键合联系起来的实验测量方法。表征非晶态复合材料的热性能是一项特别具有挑战性的任务，因为其固有的低导热率导致界面热导率的测量灵敏度较差。为了解决这个问题，本文将聚合物限制在具有高界面密度、稳定复合结构和不同表面化学性质的多孔有机硅酸盐中。分别使用频率相关的时域热反射（TDTR）和薄膜断裂测试来测量复合材料的热导率和断裂能。然后利用有效介质理论（EMT）和有限元分析（FEA）从复合材料的测量热导率中唯一地提取热边界导率（TBC）。通过傅里叶变换红外（FTIR）和X射线光电子能谱（XPS）对聚合物与有机硅酸盐之间的氢键进行定量分析，进而将TBC的变化与之联系起来。这个分析平台是跨组成域热流实验研究中的一个新范例。
