采用超声辅助的水热法及后续热处理法,将硅溶胶、蔗糖、氧化石墨烯自组装制备出具有优异电化学性能的SiO_2@碳-石墨烯(SiO_2@C-G)杂化物。结果表明:SiO_2与蔗糖的质量比是影响SiO_2@C-G杂化物电化学性能的重要因素。15-SiO_2@C-G杂化物(SiO_2与蔗糖的质量比为0.15),表现出较好的可逆储锂性能。电流密度为100 m A·g^(-1) ,首次放电比容量为906 m Ah·g^(-1) ,循环216次后,该电极材料的放电比容量可保持在542 m Ah·g^(-1) 。优异的循环稳定性及可逆容量归因于杂化物良好的导电性,SiO_2颗粒较小的尺寸及均匀分布三者之间的协同效应。该文提出的方法有望为导电性差的金属氧化物基电极材料提供一种简单环保的制备策略。
In order to improve the thermal stability of condensed polynuclear aromatic(COPNA) resin synthesized from vacuum residue, 1,4-benzenedimethanol was added to cure COPNA resin. The curing mechanism was investigated by proton nuclear magnetic resonance spectrometry, solid carbon-13 nuclear magnetic resonance spectrometry and Fourier transform infrared spectroscopy. Microstructures of the uncured and the cured COPNA resins were studied by scanning electron microscopy and X-ray diffractometry. The thermal stability of COPNA resins before and after curing was tested by thermogravimetric analysis. The element composition of the cured COPNA resin heated at different temperatures was analyzed by an element analyzer. The results showed that the uncured COPNA resin reacted with the cross-linking agent during the curing process, and the curing mechanism was confirmed to be the electrophilic substitution reaction. Compared with the uncured COPNA resin, the cured COPNA resin had a smooth surface, well-ordered and streamlined sheet structure with more crystalline solids, better molecular arrangement and orientation. The weight loss process of the uncured and cured COPNA resins was divided into three stages. Carbon residue of the cured COPNA resin was 41.65% at 600 ℃, which was much higher than 25.02% of the uncured COPNA resin, which indicated that the cured COPNA resin had higher thermal stability.
Li ShibinSun QiqianWang YuweiWu MingboZhang Zailong
A bisphenol epoxy resin was used as modifier to increase the heat resistance of condensed poly-nuclear aromatic(COPNA) resin. The basic properties of COPNA resin and modified resin were characterized by Fourier transform infrared spectroscopy(FT-IR), nuclear magnetic resonance spectroscopy(1H-NMR), vapor pressure osmometry(VPO) and elemental analysis(EA). Average structural parameters of resins were calculated by the improved Brown-Ladner method, and heat resistance of resins was tested by thermogravimetric analysis(TGA). The chemical structure, mechanical properties and heat resistivity of the resin/graphite composites prepared with different resins were compared. The results show that the adhesive property and heat resistance of COPNA resin can be remarkably improved by addition of 5 wt.% epoxy resin. The reason is that the reactions between epoxy groups of epoxy resin and hydroxyl groups of COPNA resin improve the heat resistance and adhesive property of COPNA resin. Electric motor brushes with good mechanical properties and low electrical resistivity were successfully prepared by using the modified resin as binder.
