黄绿荧光碳化硅包覆石墨材料的制备与表征

Preparation and characterization of yellow-green fluorescence emitting SiC-encapsulated graphite

以膨胀石墨与硅溶胶为原料制备出一种碳化硅包覆石墨材料。利用电子显微镜、X射线衍射技术、热重分析和荧光光谱技术对样品的形貌、结构、组成以及光致发光性能进行表征。结果表明,与碳化硅材料相比,碳化硅包覆石墨材料的发光频带发生红移,即由原来的蓝光红移至黄绿光,拓展了碳化硅的光致发光光谱。其原因是由于位于材料内部的石墨与外部的碳化硅之间形成的内电场阻碍了电子回归基态,从而使得光电子恢复到基态所释放的能量低于纯碳化硅释放的能量。

SiC-encapsulated graphite was prepared by carbonization of a mixture of expanded graphite and silica sol at 1 300 ℃for 6 h, heat treatment in air at 700 ℃ for 4 h to remove unreacted surface carbon and HCl-HF etching to remove silica. XRD, TGA, TEM and SEM were used to characterize the samples. Results indicated that the fluorescence emission of the SiC-encapsulated graphite shifts from blue to yellow-green light compared to pure SiC. This might be caused by a built-in potential near the junction between graphite and SiC, which makes the energy of the photogenerated electron released while returning to ground state lower than that of pure SiC.