Theoretical And Experimental Research On The Preparation Of Carbon Nitride By Plasma CVD Method

Carbon nitride is a new kind of superhard material and have not been found in nature. So far, theoretical researches generally believe that the body elastic modulus of α、β、cubic、quasi-cubic carbon nitride phasecan be comparable to or even more than diamond. In addition,nice chemical inertness and wear-resisting properties also make carbon nitride materials be expected to have outstanding performances in terms of cutting tool coating.In this paper, the theoretical and experimental research of carbon nitride films by Plasma CVD method was carried out, and the main work is as follows:(1) Chemical adsorption calculations are carried out by Material Studio software. The results show that N2 molecule is not adsorbed by diamond transition layer and the carbide surface; while N atom is adsorbed by them. Combining with the fact that N2 molecule is difficult to be decomposed, the conclusion above provide the reason for using DC Arc Plasma Jet equipment for experiments and increasing N2 concentration to produce more N atoms to participate the reaction process. Then, the adsorption energies of N atom on diamond transition layer and on the carbide surface are compared, showing that the adsorption energy of N atom on carbide surface is bigger. From this perspective, carbon nitride is more easily prepared on carbide than that on diamond transition.(2) Mechanism research of carbon nitride by Plasma CVD method is carried out and the "chemical pump" model applied in carbon nitride preparation process is proposed, which derive but is different from "chemical pump" modelapplied in diamond preparation proposed by Wang Jitao.Then, a few factors as concentration of carbon source, deposition pressure, substrate temperature are discussed. For substrate temperature, the model of "diamond etched and carbon nitride deposition simultaneously " when the carbon nitride is prepared on the diamond transition layer is proposed. For concentration of carbon source, the rationality of the large proportion(100:1~10:1)of nitrogen source/carbon source is discussed and concluded. And the multiple change of the carbon source concentration(which is small flow) can affects largely on the carbon nitride films prepared. For deposition pressure, analysis showed that the effects by deposition pressure is related with the effects by carbon source concentration, affecting together largely on the carbon nitride films prepared.(3) Using the of DC Arc Plasma Jetequipment, firstly, carbon nitride films are prepared on the diamond transition layer under different substrate temperatures. Then, SEM and XRD tests are used to explore the effects of substrate temperature on carbon nitride deposition on diamond transition layer. Secondly, carbon nitride films are prepared on the carbide substrate. Then, SEM and XRD test are used to study the effects of concentration of carbon source on the deposition result. And relatively well-formed crystals of carbon nitride are got when the carbon resource flow is 15 sccm,and substrate temperature is 1000℃. Finally the experiments` results show good consistencies with chemical adsorption calculations and mechanism analysis.