工艺参数对自蔓燃制备氮化硅粉体的影响

Effect of SHS Processing Parameters on Preparation of Silicon Nitride Powder

采用自蔓燃高温合成方法（self-propagating high-temperature synthesis,简称SHS）合成氮化硅粉体,分析了自蔓燃高温合成氮化硅过程中氮气、温度、稀释剂与孔隙率等方面的影响.采用XRD研究相的组成,用SEM观察粉末的显微结构.研究结果表明：只要控制反应中的工艺参数,就可以采用自蔓燃得到不同相含量的Si3N4粉体;考虑到燃烧温度（Tcom）,在氮化硅粉体的合成过程中,涉及到3个反应机制：低温机制,中温机制,高温机制;氮气压力下硅粉的自蔓燃合成反应,必须要引入Si3N4稀释剂,来控制反应温度和反应速度,获得不同相含量的粉体;NH4Cl在反应中分解,为反应提供了NH3,并与硅粉反应;压坯气孔率控制在30%～70%,否则反应不能进行.SHS法可以制备纯度很高的氮化硅粉体.此法较传统方法合成的氮化硅设备简单,成本低廉,纯度高,填充性好,烧结活性好.

Si3N4 powders were prepared by the self-propagating high-temperature synthesis （SHS） technique. The effects of nitrogen purity and pressure, combustion temperature, diluents content and the porosity were studied during the process. The phase constituent of SHS product was investigated by X-ray diffraction analysis, and the microstructure analysis was carried out by SEM. The results indicate that the different type of Si3N4 powder can be prepared by SHS as long as the parameters were controlled during the reaction. Considering the combustion temperature, the SHS Si3N4 process involves three mechanisms： low-temperature mechanism, moderate-temperature mechanism and high-temperature mechanism. During the process, Si3N4 powder must be introduced as starting raw material in order to control reaction temperature and obtain the desired α content of Si3N4 powder. During the process, NH4Cl decompose to NH3 which reacts with Si powders. The porosity of the body should be controlled at 30% - 70%, otherwise, SHS reaction will not carry on. The results indicate that SHS method can prepare Si3N4 powders with high purity. SHS technology has the advantage over traditional technology in simply equipments, low cost and high quality and excellent sintering activity.