Alloying Elements On The Silicon Nitride Preparation And Research

With Si powders as raw materials, alloy elements as additives, silicon nitride was prepared through the direct nitridation of Si powders. Categories and content of the additives and nitriding process were researched. The Synthesis mechanism of silicon nitride and function mechanism of some additives in the reaction were primarily studied.It is found that Fe promotes the nitridation best in the four additives of Fe, Mg, Al, Ti. Then Mg is second, Ti, Al is not that obvious for the nitridation. But Al accelerates the growth of β -Si3N4 to a certain extent.Composite elements Fe+Al enhances the nitridation better than Fe. But in order to gain pure silicon nitride, the contents of Fe+AI and Fe should be contained within 1% and 1.5% respectively, otherwise the compound of Fe-Si will appear in the products.The nitriding process of this experiment selected a reaction time of 10 hours at 1350 C, together with Fe and Fe + Al elements as additives. Only this is benefit to the nitridation of silicon powders.The composition of nitrided products, microstructure and morphology of reaction samples were studied by X-ray Diffraction (XRD) and Scan. Electron Microscope (SEM) . The results show that Si3N4 with high a phase and some P phase can be prepared under the nitriding conditions of 1350 C/10h. The microstructure of nitrided products is characterized by α -Si3N4 grain shape. The average grain size is 3.3 m.