Evolutionary characteristics of coal based graphene structure in West Guizhou and Hanpo’ao,Hunan

As a strategic emerging material in the 21st century,graphene has attracted extensive attention due to its excellent performance. The research shows that coal can be used as the carbon source of graphene,and the properties of coal also affect the structural characteristics of graphene. Combined with the characteristics of complex coal meta- morphic origin and diverse types of coal metamorphism in China,this paper aims to study the impact characteristics of different metamorphic backgrounds on the graphene structure. Six coal samples from the deep superimposed hydro- thermal metamorphism in Western Guizhou and four coal samples from the magmatic thermal metamorphism in the Hanpo’ao area were collected, and all of them were treated with HCl-HF-HNO3 acid washing method to obtain the demineralized coal samples to eliminate the influence of minerals. After that,the coal-based graphite sample was obtained after the demineralized coal sample was treated at 2 800 °C in a medium frequency induction graphitiza- tion furnace. At last,the improved Hummers redox method was used to oxidize,ultrasonic peel and reduce the coal- based graphite to obtain graphene samples. The X-ray diffraction (XRD) used to test the microcrystalline size,spa- tial morphology and other information of the sample was used to characterize the demineralized coal-based graphite and graphene and obtain relevant structural parameters. The Raman spectrum used to test the defect and integrity of the sample was used to characterize the demineralized, coal-based graphite and graphene samples and obtain relevant parameters. The transmission electron microscope (TEM) used to observe the micro surface morphology of the samples was used to characterize the graphene samples and obtain images. The results of experiment and characteriza- tion are as follows:the images obtained by transmission electron microscopy (TEM) show that 3-5 layers of graphene sheets can be prepared from two types of metamorphic coals. The relevant parameters obtained by the X-ray diffraction (XRD) and Raman spectroscopy (Raman) show that the higher the metamorphic degree of coal, the higher the graphitization degree of corresponding coal-based graphite sample,and the larger the microcrystalline structure lamella of corresponding graphene sample,with fewer defects. Based on the testing parameters of the X- ray diffraction (XRD) and Raman spectroscopy (Raman),relative to magmatic thermal metamorphism,the changes of Lc ,d002 ,G-D,ID / IG of graphene samples in the metamorphic background of deep superimposed hydrothermal fluids vary greatly with Ro,max. Compared with the hydrothermal metamorphism,the variations of La and La /Lc of graphene samples in the magmatic thermal metamorphic background vary greatly with Ro,max . It shows that under the background of hydrothermal metamorphism, the higher the metamorphic degree of coal is, the easier it is to obtain graphene samples with good stacking property,strong directional arrangement and few defects. Under the condition of magmat- ic thermal metamorphism,the higher the metamorphic degree of coal is,the easier it is to obtain graphene samples with large transverse size and “flat round” spatial morphology. There is a need for further research on the work carried out today. What are the different effects of magma and non-magma on the structure of coal based graphene, or how temperature and pressure affect the structure coal-based graphene? These issues need further research for promo- ting the scientific development in the field of coal-based graphene.