提交时间: 2017-05-02
摘要: Polyimide/reduced graphene oxide [PI/r-GO] core-shell structured microspheres were fabricated by in situ reduction of graphene oxide [GO], which was coated on the surface of PI microspheres via hydrogen bonding and pi-pi stacking interaction. The highly o
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Due to the growing needs of thermal management in modern electronics, polyimide-based (PI) composites are increasingly demanded in thermal interface materials (TIMs). Graphene woven fabrics (GWFs) with a mesh structure have been prepared by chemical vapor deposition and used as thermally conductive filler. With the incorporation of 10-layer GWFs laminates (approximate 12 wt%), the in-plane thermal conductivity of GWFs/PI composite films achieves 3.73 W/mK, with a thermal conductivity enhancement of 1418% compared to neat PI. However, the out-of-plane thermal conductivity of the composites is only 0.41 W/mK. The in-plane thermal conductivity exceeds its out-of plane counterpart by over 9 times, indicating a highly anisotropic thermal conduction of GWFs/PI composites. The thermal anisotropy and the enhanced in-plane thermal conductivity can be attributed to the layer-by-layer stacked GWFs network in PI matrix. Thus, the GWFs-reinforced polyimide films are promising for use as an efficient heat spreader for electronic cooling applications.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Polypropylene and calcium carbonate were prepared by melt extrusion in a twin screw extruder or cast- ing in a kneader extruder. The dispersion of CaCO3 particles in PP was analysed through the observation of impact-fracture surface, polished surface, cross-section surface and film using scanning electron microscopy (SEM), focused ion beam (FIB) and optical transmission microscopy (OTM). Only basic infor- mation on particle dispersion was obtained from the investigation of fracture surfaces by SEM and the FIB cross-sections by virtue of the ambiguous phase contrast and the limited area observed. However, the SEM images from polished-surfaces and the film images observed in OTM show the different particle dispersion in different samples. The derived Particle Size Distribution (PSD) curves from OTM images explain the difference of impact strength, demonstrating the relationship between particle dispersion and mechanical properties.