振荡压力对高性能氮化硅陶瓷烧结致密化的影响

Effect of Oscillatory Pressure on Sintering Densification of High Quality Silicon Nitride Ceramics

采用新型振荡压力烧结技术制备高性能氮化硅陶瓷,并对比热压烧结技术,研究了不同工艺下氮化硅陶瓷的致密度、物相、晶粒尺寸、微观形貌及力学性能变化规律,分析了振荡压力对氮化硅陶瓷的致密化作用.结果表明:振荡压力烧结工艺下氮化硅陶瓷实现了α相到β相的物相完全转变,相对密度达到了99.82%;对比热压烧结工艺,振荡压力作用下氮化硅陶瓷的晶粒尺寸明显增加,晶粒平均长径比由3.79增加到4.86,弯曲强度、硬度及断裂韧性分别提高到1333 MPa、16.2 GPa、12.1 MPa·m^(1/2),断裂表面能也明显提高.OPS试样晶粒表面观察到了明显的形变条纹和位错运动区域.振荡压力的引入提高了致密化速率和晶粒的生长驱动力,且能够促进氮化硅在致密化过程中塑性形变的产生,有效加快了烧结致密化进程.

Oscillatory pressure sintering(OPS)technique was used to prepare silicon nitride ceramics with high quality.In comparison with hot pressure(HP)sintering process,the density,phase,grain size,aspect ratio and microstructure of silicon nitride ceramics by two methods were further investigated.The densification effect of oscillatory pressure on silicon nitride ceramics were studied.The results indicate that the silicon nitride ceramic has reached a complete phase transition from a phase to p phase under OPS process and its relative density has reached 99.82%.The grain sizes of OPS specimen are significantly increased compared with the specimen prepared by HP process.The average aspect ratio of the grains has increased from 3.79 to 4.86 when the fabricated process changed from HP to OPS.Bending strength,hardness and fracture toughness reached 1333 MPa,16.2 GPa,12.1 MPa-m^(1/2),respectively.Fracture surface energy also increased with the introduction of oscillatory pressure.In addition,obvious deformation streaks and dislocation movement areas are observed through TEM analysis.Obviously,the application of oscillatory pressure improves the densification rate and the growth driving force of grains.The plastic deformation of silicon nitride during the densification process were also found.Thereby,the sintering densification process was accelerated.