Study On Synthesis Of Carbon Materials By Microwave And Its Properties

Carbon element is existing in the nature and most closely related to human,one of the most important elements,it has the SP,SP2,SP3 hybridization of various electron orbital characteristics.Carbon nanomaterials include fullerenes,carbon nanotubes, graphene and so on. Carbon nanomaterials have advantages such as stable structure,good conductivity,strong electronic transmission ability.It is getting more and more attention of the researchers.Carbon materials can be used in catalysis,lithium ion battery electrode materials,super capacitor,oxygen reduction reaction,toxic pollutant adsorption,etc.Traditional synthesis methods of carbon nanomaterials include chemical vapor deposition method,high temperature pyrolysis method,laser ablation method,electrochemical method,hydrothermal method,and so on.These methods are energy consuming or time consuming,not good for energy saving.Microwave synthesis method is as a new type method of preparing materials,has the advantages of short reaction time,selective heating,low energy consumption etc.Microwave method is widely used in the synthesis of materials in recent years.This paper adopts the method of microwave for the fast synthesis of carbon nanomaterials within 30 minutes at low temperature.The paper mainly studied the influence of reaction time and reaction temperature on the reaction.This thesis mainly carried out the work of the following three parts:1. Microwave liquid low-temperature one step fast synthesis of carbon spheres and their adsorption ability testsThis method adopts carbon tetrachloride as the carbon source,metallic sodium as the reducing agent,the reaction is for 20 min to get the product,the reaction temperature is setting as 160 ℃,180 ℃,or200 ℃.In the conditions of three temperarures the products all are globular,the main body weight loss of products occur after 550 ℃ in the thermogravimetric analysis.You can see that the carbon balls have obvious fingerprint structure in the high-resolution TEM,the selective area diffraction has obvious diffraction ring,both of them show the high degree of graphitization of the carbon balls,corresponding to the thermogravimetric analysis.Raman analysis shows that the D peak is higher than the G peak,indicating high degree of product defects.Toluene and carbon dioxide adsorption are tested on the product,and the effects are good,the adsorption amount of toluene can reach 59.94mg/g,the adsorption amount of carbon dioxide can reach 1.13mmol/g.2. Microwave liquid low-temperature one step fast synthesis of carbon nanotubes and their application in oxygen reduction reactionThis method adopts microwave as the heat source,metallic sodium and alcohol as the reactants,cobalt chloride as the catalyst.The synthesis of carbon nanotubes is finished within 30 minutes,the reaction temperature is 180 ℃.The carbon nanotubes have mullti-walled structure,after washing and centrifugation the catalyst composition is excluded,the BET of the products is 100 m~2 / g- 200 m~2 / g.The method is quick and easy.Its energy consumption is low.The reactants are easy to get.The reaction have large amounts of product.Microwave heating is quick and selective,so the shortest reaction time is one minute to get the product.Raman test show that the surface defects level is high.Transmission electron microscopy(tem) shows that the diameters of the tubes are within 100 nm,lengths can reach micron grade.The low-cost method for producing CNT can be used for the oxygen reduction reaction,super capacitor,lithium ion batteries,toxic pollutants absorbtion,and other fields.In this paper,the CNT is used for oxygen reduction reaction,the influences of microwave reaction time and catalyst dosage are considered.3. Microwave liquid low-temperature one step fast synthesis of N-doped carbon nanotubes and their application in oxygen reduction reactionIt adopts microwave liquid method,the metal sodium,acetonitrile and alcohol as the reactants,acetonitrile as the nitrogen source as well,cobalt chloride as the catalyst.The nitrogen-doped carbon nanotubes are produced within 30 minutes at 180 ℃.The carbon nanotubes have mullti-walled structure,after washing and centrifugation the catalyst composition is excluded,the BET of the products is 100 m~2 / g- 200 m~2 / g.The method is quick and easy.Its energy consumption is low.The reactants are easy to get.The reaction have large amounts of product.Raman test show that the surface defects level is high.Transmission electron microscopy(tem) shows that the diameters of the tubes are within 100 nm,lengths can reach micron grade. In this paper,the N-doped CNT is used for oxygen reduction reaction,the influence of nitrogen content is considered,the ORR performace is improving as the nitrogen amount is increasing.