Study On Preparation And Pulse Discharge Treatment Of Carbon-Nitrogen Precursor

In this thesis, the development on theoretical calculation and experimental synthesis of carbon nitride compounds has been introduced briefly. The properties and characterizing method of carbon nitride have also been summarized. Using melamine (C3H6N6) as raw material, a kind of carbon nitride precursor with turbostratic structure has been prepared, then treated by pulse discharge. The effects of pulse current density, applied pressure and treatment time on compositions and structures of the products have been studied. The compositions, structures, bonding properties and thermal stabilities of the precursor and the treated products have been characterized by elemental analysis, EDX, XRD, SEM, TEM, SAED, FTIR, TG.The experimental results suggest that higher current density used in pulse discharge treatment can change the structure of the precursor, while the high-nitrogen content of the products is maintained effectively. When the current density is 23 A/mm2 and the pressure is 100 MPa, the hydrogen contents of the products decrease slightly with the rise of treatment time, while the C/N atomic ratio increases. When the experimental highest temperature is about 920 ℃, C/N atomic ratio of the products is 0.93, their nitrogen contents are still higher than that of carbon nitride precursor and their layer structures disorder obviously. However, FTIR results show that the bonding properties seem no differences between the products and the precursor. When the treatment time becomes longer, the graphitizing of precursor appears. When the experimental pressure is applied to 50 MPa, a distinct discharge phenomenon has been observed in the products.In the obtained product treated for 55 s, an orthorhombic CNx crystal embodied in turbostric matrix was observed. The fringe spacing of 0.32 nm observed by HRTEM is corresponded to (002) plane of the CNx crystal , and also overlapped with data from XRD. The average composition of the product characterized by elemental analysis is: 32.95 at% C, 47.48 at% N and 19.57 at% H, in which the C/N atomic ratio is 1:1.45, closed to the stoichiometry of C3N4。...