含有定向排列颗粒的氮化硅陶瓷各向异性研究

通过添加α—Si3N4晶须，利用流延成型和热压烧结技术制备舍有定向排列颗粒、各向异性的Si3N4陶瓷。研究α-Si3N4相在流延膜及烧结块体中的分布状态，并通过XRD、SEM和力学性能对流延膜和烧结块体的各向异性进行表征。结果表明，1550℃下烧结制备的块体T（与流延方向平行的平面）、N（与流延方向垂直的平面）、P（侧面）三个面的I（210）／I（102）值与等轴状α-Si3N4粉体的相应值比较，其中T面的值较大，N面和P面的值较小；在T面的显微结构中存在平行于流延方向排列的大颗粒；试样不同面的力学性能（断裂韧性和抗弯强度）中，T面最好，P面次之，N面最差；I（210）／I（102）值、显微结构、力学性能测试结果表明所制备的氮化硅陶瓷存在各向异性。

Anisotropy study of Si3N4 ceramic with aligned and elongated grains

Silicon nitride （Si3N4 ） ceramics with aligned and elongated grains were prepared by adding α-Si3N4 whiskers and using tape casting and hot-press sintering. The distribution of α-Si3N4 phase in the green tapes and sintering samples was studied, and the green tapes and sintering samples were charac- terized by XRD, SEM and mechanical properties. The results show that α-Si3N4 whiskers are aligned along the direction of tape casting in the green tapes. The I（210）/I（102） value of T plane （parallel to the tape casting direction） in the sample sintered at 1 550℃ is higher than that of α-Si3N4 powders, while that of N plane （normal to the tape casting direction） and P plane （the side plane） is less. There exist large grains aligning along the direction parallel to that of tape casting. The mechanical proper- ties in T plane are best, followed by P plane and N plane. The I（210）/I（102） value, microstructure and mechanical properties suggest that α-Si3N4 phase is aligned better in the substrate and silicon ni- tride ceramics is anisotropic.