中文摘要：

以天然鳞片石墨为原料，氧化插层制备可膨胀石墨，微波热解膨胀后，对膨胀石墨进行二次氧化插层并微波膨胀，采用超声剥离法制备出包含大量少层数碳原子的石墨烯纳米片。采用傅里叶红外光谱（FTIR）、X射线衍射（XRD）、扫描电镜（SEM）、原子力显微镜（AFM）和拉曼光谱（Raman）对其结构和形貌进行分析。结果表明，氧化插层增大了石墨层间距，膨胀石墨更易于进一步氧化插层引入含氧基团；在微波作用下，石墨内部含氧基团热分解放出气体，进一步增大石墨层间距，甚至部分剥离；对二次膨胀处理的石墨薄片进行超声剥离可得到石墨烯纳米片，大部分石墨烯层数低于5层。

英文摘要：

Graphene nanosheets with few-layer graphene have been prepared successfully by ultrasonic exfoliat- ion after the secondary expanded graphite. The expanded graphite was prepared from natural flake graphite by oxidation intercalation and microwave expansion. The structure and morphology were characterized by Fourier transform infrared spectroscopy （FT-IR）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, atomic force microscope （AFM） and Raman spectra （Raman）. The results show that the layer distance of graphite was increased by oxidation intercalation which was easier in the expanded graphite,compared with nat- ural graphite, and the oxygenic groups were grafted at the edge of or between the layers. The graphene nanosheets were finally fabricated by ultrasonic exfoliation after the secondary expanded graphite, which con- tained a large number of graphene which was less than 5 layers. It provides a simple and efficient method to produce graphene nanosheets.