| Graphite interlayer separation is a method for changing the properties of graphite materials and preparing allotropes and graphite interlayer compounds（GICs）.Using physical or chemical means to increase the graphite interlayer spacing,the graphite interlayer separation effect is formed,and the obtained graphite interlayer separation products have better performance than graphite.The key to the separation of graphite flakes is to overcome the strong van der Waals force between the graphite layers.The van der Waals force between the graphite layers makes the separation between the graphite layers difficult.The current separation methods include liquid phase separation,mechanical separation,high temperature separation method,redox method,etc.,but there are problems that the separation product cannot be mass-produced,the preparation efficiency of the separation product is low,the operation is complicated,the separation product with large size and complete structure is still in the laboratory stage,and the solvent used in the preparation process is difficult to remove.The environment is not friendly,and it is difficult to realize industrial production and preparation.Therefore,it is of great significance to explore a simple,low-cost and environmentally friendly graphite interlayer separation method.In this paper,the agents containing ammonia molecules is introduced as the intercalation agents;ball milling is introduced in the intercalation stage to enhance the intercalation effect;combined with thermal excitation,the intercalation agents are thermally decomposed,thereby overcoming the van der Waals force between the graphite layers.The main contents and research results are as follows:First,ammonia（NH3·H2O）,ammonium carbonate（（NH4）2CO3）and ammonium bicarbonate（NH4HCO3）containing ammonia molecules were used as intercalation agents,and the intercalation agents were inserted between the graphite layers by stirring and ultrasonic respectively.The intercalation agent is decomposed by applying external thermal excitation,and the gas pressure generated by the decomposition overcomes the van der Waals force between the graphite layers,thus achieving the purpose of separating graphite layers.In this method,the"wedge-shaped structure"of ammonia molecules is used to pry the graphite sheets from the edge to realize the physical intercalation of the intercalation agent.The results show that the separation effect is the best when NH3·H2O is used as the intercalation agent.In addition,fourier transform infrared spectroscopy（FTIR）results showed that no C≡N or C=N bonds were formed,which indicated that the intercalation agent containing ammonia molecules does not chemically react with graphite,but is inserted between the graphite layers through physical intercalation.After high temperature heating treatment,the intercalation agents can be removed cleanly by thermal decomposition.Secondly,in the process of graphite interlayer separation,a ball milling process is introduced in the intercalation stage of the intercalation agent,and a muffle furnace with a stable thermal environment is used as the thermal excitation method.The mechanical force exerted by ball milling strengthens the intercalation effect,which makes the intercalation agent go deeper between the graphite layers.The effect of ball milling on the separation effect between the graphite layers is studied.The analysis results of Raman spectroscopy（Raman）and scanning electron microscope（SEM）show that the speed of the ball mill is not as fast as possible.The low-speed operation of the ball mill is conducive to the uniform mixing of materials,and the high-speed operation will destroy the structure of the intercalation products and increase the defect degree of the graphite interlayer separation products.The FTIR data show that the intercalation agents NH3·H2O,（NH4）2CO3 and NH4HCO3 inserted between the graphite layers are completely decomposed after being heated in a muffle furnace at 800～900℃,and the intercalation agent will not be left to cause damage to the structure of the separation products.Through X-ray diffraction（XRD）analysis results,the（002）diffraction peaks of the intercalation product after ball milling and the graphite interlayer separation products after heating in the muffle furnace are shifted to the left compared with single ultrasound,indicating that the interlayer spacing is large,ball milling enhances the intercalation effect.Finally,the graphite interlayer separation products were prepared by ball milling assisted by free arc and microwave thermal excitation,respectively.The mechanism of different thermal excitations to separate graphite sheets was studied,and the effect of different thermal excitation methods on the separation of graphite layers was investigated.The working electrode was used for electrochemical testing.Among them,due to the large output energy of the free arc to the graphite structure,the phenomenon of destroying the structure of the graphite interlayer separation products occurs.Compared with the muffle furnace and free arc thermal excitation method,the separation products prepared by ball milling assisted microwave has higher overall transparency and complete morphology,and the number of product layers is less.The high-resolution transmission electron microscope（HRTEM）measurement,occasionally it can be measured that the number of separation products layers does not exceed 10 layers.The SEM image shows that the separation effect of ball milling assisted microwave heating between graphite layers is significantly better than that of muffle furnace and free arc.Electrochemical tests show that at a scan rate of 10 m V/s,it exhibits the characteristics of electric double-layer capacitance. |
