Preparation Of Graphite Carbon Nitride Nanomaterials And Study On Its Field Emission Properties

Field electron emission,also known as cold cathode electron emission,has no time delay,can be started instantaneously,low power consumption,does not need to be heated,and can work at room temperature,greatly simplifying the structure of the cathode.In the display field,it not only inherits the advantages of CRT such as wide perspective,high brightness and high resolution,but also overcomes the disadvantages of CRT such as large size and high power consumption.In the field of vacuum electronic devices,it has the characteristics of instantaneous start-up,large current density,high frequency,and can reduce the volume,response time and low cost.It is a very ideal new electronic device.In this paper,g-C₃N₄ was grown on carbon fibers and graphite substrates using urea as precursor by thermal polycondensation.The samples were prepared by orthogonal experiment,and the structure,morphology and field emission properties of the samples were tested.The test results were analyzed by range analysis method,and the order of influencing factors was analyzed,then the optimized process parameters were determined.?1?g-C₃N₄ was grown on carbon fibers and graphite substrates by thermal polycondensation in dry urea powder environment by dry powder coating process.Three factors and four levels of orthogonal experiment were used to prepare the samples,and then the structure,morphology and field emission properties of the samples were tested.The test results were analyzed by range analysis method.The results show that the higher the temperature,the better the crystallinity of the sample,the smaller the size of the peeled particles,and the more uniform and dense the distribution,which is more conducive to the field emission performance.In the range analysis of the field emission test results,it is also shown that temperature is the most important factor affecting the electric field and current density of field emission.The optimized process parameters are:temperature 600?,heating rate 1?/min,holding time 240min.Under the optimized process conditions,the field emission opening electric field of carbon fiber substrate is 0.56 V/?m,the current density is 539?A/cm² at 2.0 V/?m,the field emission opening electric field of graphite substrate is 5.35 V/?m,and the current density is 218?A/cm²at 11 V/?m.?2?g-C₃N₄ was grown on carbon fibers and graphite substrates by thermal polycondensation in aqueous urea solution by wet urea solution growth process.Four factors and four levels of orthogonal experiment were used to prepare the samples,and then the structure,morphology and field emission properties of the samples were tested.The test results were analyzed by range analysis method.The results show that the higher the temperature is,the better the crystallinity of the sample is,and the smaller the irregular thin sheet is,which is more conducive to the field emission performance.In the range analysis of the field emission test results,it is also shown that temperature has the greatest influence on the field emission open electric field and current density,and the optimized process parameters are:temperature550?,heating rate 5?/min,holding time 120 min.Under the optimized process conditions,the field emission opening electric field of carbon fibers is 0.49 V/?m,and the current density is 558?A/cm² when the electric field reaches 2.0 V/?m.The field emission opening electric field of graphite substrate is 5.25 V/?m,while the current density is 273?A/cm² when the electric field is 11 V/?m.?3?ZnO/g-C₃N₄/carbon fiber composites were prepared by sol-gel method after g-C₃N₄was grown on carbon fibers through an optimized wet process.The effects of different zinc concentration and coating times on the structure and morphology of ZnO/g-C₃N₄/carbon fiber composites were investigated.The results show that the higher the concentration of Zn²⁺in the sol,the easier it is to form aggregated white ZnO particles on the surface;the more the times of plating,the more ZnO is contained in the composites;from the field emission characteristics analysis,it is found that the field emission characteristics of ZnO/g-C₃N₄/carbon fiber composites are better than that of g-C₃N₄/carbon fiber composites.