Study On Preparation And Properties Of Graphitic Carbon Nitride Synthesized By Microwave Method

As a polymer semiconductor,graphitic carbon nitride?g-C₃N₄?,with good chemical stability and distinctive electronic structure,can be used as an ideal photocatalytic material.In addition,two-dimensional g-C₃N₄ nanosheets have a similar structure to graphene.Under the action of a high load force,relative slippage occurs between the layers,which makes g-C₃N₄have a lubricating effect and potential applications in the field of lubrication.In this subject,the g-C₃N₄ was synthesized via microwave heating with different carbon-and nitrogen-rich organic materials as precursors,and carbon fiber as microwave absorber,respectively.The visible light photocatalytic properties and lubricating properties of g-C₃N₄were investigated.The main conclusions are as follows:?1?Urea,thiourea,dicyandiamide,melamine or cyanuric chloride was used as raw materials respectively,and g-C₃N₄ with different morphologies were prepared by microwave heating.Results showed that g-C₃N₄ could be synthesized by microwave method with nither urea nor cyanuric chloride as precursors.With thiourea,dicyandiamide and melamine as precursors,the g-C₃N₄ with the morphologies of macroporous honeycomb structures,bulk structures and two-dimensional nanosheet structures were synthesized,separately.The photocatalytic degradation of rhodamine B?RhB?aqueous solution was used to evaluate the photocatalysitc activity of g-C₃N₄.Results showed that the two-dimensional nanostructure g-C₃N₄ exhibited the best photocatalytic performance,which could degrade 90.4%of RhB in 40minutes.The degradation rate of RhB for the macroporous honeycomb structures and bulk g-C₃N₄ was only 51.1%and 41.0%in 40 min.?2?The reduced graphene oxide?rGO?/graphitic carbon nitride composite?GCN?was rapidly synthesized by microwave irradiation using graphene oxide and melamine as raw materials,carbon fiber as microwave absorber,respectively.GCN was successfully constructed by the mixture of rGO and g-C₃N₄,and the existence of rGO did not disturb the lattice structure of g-C₃N₄,but it decreased the size of g-C₃N₄.The smaller size of g-C₃N₄ was probably due to the existence of GO and rGO in the formation process of g-C₃N₄,inhibiting the further growth of g-C₃N₄.With the increased of rGO content,the band gap of GCN decreased gradually.This could be ascribed to the formation of heterojunction between rGO and g-C₃N₄,and the charge transfered between the rGO and g-C₃N₄ lead to the change of Fermi level.The photocatalytic activities of samples were evaluated by the degradation of aqueous rhodamine B?RhB?.Results showed that the composition of rGO is beneficial to the improvement of the photocatalytic performance of g-C₃N₄.The efficiency of the photocatalysis of samples is increased with rGO content.?3?The modified g-C₃N₄ synthesized by the amidation reaction of oleic acid and g-C₃N₄in methylene chloride exhibited a good dispersion stability.The results of the four-ball friction method showed that the friction performance of the lubricant improved with the g-C₃N₄ as a lubricant additive.As the mass fraction of g-C₃N₄ was 0.02%,the lubricating oil exhibited the best friction performance,its wear spot diameter decreased by 7.8%.After modification by oleic acid,the dispersion stability of g-C₃N₄ was improved,and the corresponding anti-wear performance exhibited by the lubricating oil additive became better.The anti-oxidation T534was added to the base oil containing g-C₃N₄ as an additive for lubricating oil,and the friction performance of the lubricating oil was improved to a greater degree,because the presence of T534 could prevent the oil and g-C₃N₄ from being oxidized.