▎ 摘　　要

A new and efficient method to produce a large quantity of high-quality and non-oxidized graphene flakes from powdered natural graphite by using a high-intensity cavitation field in a pressurized ultrasonic reactor is demonstrated. TEM and selected-area electron diffraction (SAED) confirmed the ordered graphite crystal structure of graphene. Atomic force microscopy (AFM) was used to examine the thickness of the graphene sheets. The delamination (exfoliation) of natural graphite in the liquid phase depends on the physical effects of ultrasound, which break down the 3D graphite structure into a 2D graphene structure. The prepared graphene is of high purity and without defects because no strongly oxidizing chemicals are used and no toxic products result. TEM shows that graphene nanosheets were produced with sizes in the range of tens to hundreds of square nanometers; these nanosheets were smooth and without any ripples and corrugations. High-resolution TEM (HRTEM) and SAED analysis confirmed that the products were graphene nanosheets.