助烧剂对反应烧结Si_3N_4/SiC材料性能的影响

The Effect of Sintering Additives on the Performance of Si_3n_4/sic Materials by Reaction Sintering

采用反应烧结制备Si3N4/SiC材料。研究不同含量Al2O3、Y2O3及Fe2O3对烧结制品性能的影响,并分析三者在反应烧结中助烧机理的异同点。通过X射线衍射仪、扫描电子显微镜以及万能试验机分别表征材料的物相组成、微观结构和力学性能。实验结果表明:添加Al2O3和Y2O3难以提高试样的体积密度,能够适当提高试样的抗弯强度,促进生成Si2N2O相以及β-Si3N4,降低试样的氮化增重,液相冷却析出Si5AlON7和Y5Si3O12N;添加Fe2O3能够显著提高试样的抗弯强度和体积密度,促进生成β-Si3N4,有利于提高试样的氮化增重量、抗弯强度以及体积密度,Fe2O3最终会与Si形成稳定型的Fe3Si相;试样中同时添加Fe2O3及Al2O3/Y2O3时,可以更好地提高试样体积密度,但二者反应烧结时会相互抑制,不利于提高试样的抗弯强度。

Si3N/SiC refractory material was fabricated by reaction sintering. The effect of Al2O3, Y2O3 and Fe2O3 on the performance was researched, and the mechanisms of reaction sintering also were analyzed. The composition of phase and the microstructure of samples were characterized respectively by X-ray diffraction （XRD） and scanning electron microscopy （SEM）, and the bulk density and mechanical properties were characterized respectively by Archimedes method and universal test machine. The experimental results show that the adding of A1203 and Y203 was difficult to improve the bulk density of samples. It increased the bending strength of samples properly. The adding of AI203 and Y203 promoted tile generation of Si2N：O and fi-Si3N4, and reduced the increasing weight of the samples. The liquid phase precipitated SisA1ON7 and YsSi3OI2N finally. The bulk density and bending strength of samples were increased significantly by adding Fe203.The adding of Fe：O3 formed liquid phase with Si which promoted the generation of B-Si3N4 and precipitated FegSi finally. The bulk density was increased and the bending strength was reduced when the samples added Fe203, A1203 and Y2O3 at the same time.