镁铝尖晶石透明陶瓷的晶界强韧化研究

Transparent spinel ceramics can be used as transparent armors, IR windows and IR domes thanks to the advantages of high optical quality, high strength, and excellent resistance to sand and rain erosion. After study for more than 50 years, highly transparent spinel ceramics can be successfully fabricated with the development of raw powder, sintering technology and additives. But the poor mechanical properties have become the limiting factor for the application of transparent spinel ceramics. To solve this problem, this project intends to optimize the grain boundary structure by adjusting the ratio of Al2O3/MgO, sintering procedure and sintering additive, and finally realize the strengthening and toughening for the transparent spinel ceramics. Firstly, the effect of Al2O3/MgO ratio and sintering procedure on the grain boundary structure will be studied. The relationship between grain boundary characteristic distribution and mechanical property will be established to optimize the fabrication process. Then, the grain boundary will be further toughened by the reduction of grain boundary energy, which can be achieved by the solute segregation of rare earth oxide. Finally, the relationship of grain boundary treatment method - microstructure – properties will be determined, and it will provide foundation for the preparation of highly transparent and high strength transparent spinel ceramics.

镁铝尖晶石透明陶瓷具有透光范围广、强度高、耐砂蚀雨蚀性好等优点，是透明装甲、红外窗口和整流罩的理想材料。经过50多年的发展，其在光学性能提升方面取得了突破性进展，但较低的力学性能阻碍了材料的广泛应用。本项目拟在保证光学质量的前提下，通过调控基体铝镁比、烧结工艺和烧结助剂等条件对晶界结构进行优化，合理设计晶界网络，最终实现镁铝尖晶石透明陶瓷的强韧化。首先，系统研究基体铝镁比和烧结工艺对晶界结构的影响，建立晶界特征分布与宏观力学性能之间的联系，优选出最佳的铝镁比和烧结工艺。在此基础上，利用稀土氧化物溶质偏析对晶界能的降低作用进一步强化晶界。最终构建晶界处理方法-微观结构-透明陶瓷性能之间的关系，建立一种新的强韧化机制，为高强、高透镁铝尖晶石透明陶瓷的制备奠定理论基础。

本项目针对透明装甲、红外窗口等领域对高透光性、高强度透明材料的应用需求，开展镁铝尖晶石透明陶瓷的强韧化研究。以高纯氧化铝和氧化镁为原料，通过无压反应烧结和热等静压后处理制备镁铝尖晶石透明陶瓷。首先，系统研究了基体铝镁比对陶瓷致密化过程和微观结构的影响规律。结果表明，富铝成分（n≥1.1）可以降低晶界迁移速率，有利于细晶、微气孔预烧体的制备，为后续热等静压处理过程中气孔的充分排出和晶粒均匀生长奠定基础。在组分优化的基础上，通过添加镧基和钇基烧结助剂进一步提高材料的力学性能。稀土氧化物在晶界偏析可以降低晶界能，实现晶粒的细化。但样品的抗弯强度随着稀土氧化物添加量的增加先增加后下降，这主要是因为过量稀土氧化物在晶界处聚集会使晶界强度降低，同时使透明陶瓷的光学性能恶化。因此，为同时保证样品的光学性能和力学性能，稀土氧化物的添加量需要控制在500ppm以下。添加50-100ppm含量YAG时，制备的镁铝透明陶瓷性能最佳，在400mm处透过率高于84%，三点抗弯强度达到358MPa，通过进一步进行热处理，可以将抗弯强度提高至385MPa。本项目的开展为后续制备高强、大尺寸镁铝尖晶石透明陶瓷奠定了理论基础。本项目相关研究成果发表学术论文4篇，申请发明专利2项，培养毕业硕士研究生3名。