MgO含量与颗粒度对Si_3N_4-Y_2O_3-MgO陶瓷液相烧结行为及力学性能的影响

本文基于Si_3N_4-Y_2O_3-MgO液相烧结体系,系统研究了MgO含量和颗粒度对材料致密度、物相组成、显微结构以及力学性能的影响效果与作用机制。结果显示,MgO含量的增加,会使得液相组分增多,进而提高材料的致密度,同时促进β-Si_3N_4晶粒的粗化生长;当液相含量相同但MgO颗粒度增大时,材料致密度和β-Si_3N_4晶粒长径比会同时出现降低趋势。这表明,液相组分MgO的颗粒度会直接影响液相的形成与分布,进而对润湿、颗粒重排及传质过程产生作用。当MgO含量与颗粒度分别为4%和0. 1μm时,材料相对密度、断裂韧性和维氏硬度获得最佳值,分别为99. 5%±0. 2%,(6. 9±0. 6) MPa·m^1/2,(18. 7±0. 1) GPa。

Effect of Content and Particle Size of MgO on Liquid-phase Sintering Behavior and Mechanical Properties of Si3 N4-Y2 O3-MgO Ceramics

The effects of MgO content and particle size on the density, phase composition, microstructure and mechanical properties of Si 3N 4-Y 2O 3-MgO liquid phase sintering system were investigated systematically in the present work. Results show that the effect of liquid phase could be more important due to the increase of MgO content, thus resulting in enhancing the final density of material and promoting the coarsening growth of β-Si 3N 4 grains. When the liquid phase content was the same but MgO particle size increased, the final density and aspect ratio of β-Si 3N 4 grains simultaneously tended to diminish. It is found that the MgO particle size has significant influence on the formation and distribution of liquid phase, hence affects the wettability, particle rearrangement and mass transfer during liquid phase sintering process. The relative density, fracture toughness and Vickers hardness reached maximum values of 99.5%±0.2%,(6.9±0.6) MPa·m 1/2 and (18.7±0.1) GPa, respectively at a MgO adding level of 4wt% and a particle size of 0.1 μm.