高致密度高强度结构陶瓷的动态压力烧结研究

Densification sintering is a critical scientific technology in the preparation of ceramic materials. Due to limitations in the existing sintering technologies, it is difficult to obtain structural ceramic materials with submicron or nano-scale crystals, full density (nearly pore-free) and ultra-high strength simultaneously. In the previous studies, we found that the introducing of dynamic pressure could effectively eliminate pores, inhibit grain growth and enhance both density and strength at high temperature. Based on this novel idea on sintering, an oscillatory pressure sintering technology was applied to the densification sintering of structural ceramics. By a systematic study on the role of oscillatory pressure value and frequency on the rearrangement and packing of ceramic particles, especially on the grain movement, grain boundary migration and pores removal, it is prospective to prepare ceramics with full or nearly full density and ultra-high density, so as to cross the barriers on density and strength with the existing sintering technologies. Besides, the oscillatory pressure sintering technique presents remarkable features in the kinetics of sintering, the density mechanism under controllable grain growth. In consideration of such significant differences between oscillatory pressure sintering and the other traditional pressure-less sintering and statical pressure sintering technologies, a detain description is available, which shows important theoretical and practical significance for preparing the ceramics with high performances.

结构陶瓷的致密化烧结是陶瓷材料制备关键科学技术问题之一，而现有的烧结技术尚难以获得高致密度（几乎无气孔）超高强度的亚微米或纳米晶尺度的结构陶瓷材料。最近我们的初步研究发现，陶瓷粉末烧结过程中引入动态压力可显著消除陶瓷内气孔等缺陷且细化晶粒，致密度和抗弯强度均大幅提高。基于这一新的烧结思路，本项目将动态振荡压力烧结新技术应用于结构陶瓷的致密化烧结，一方面通过系统深入研究振荡压力和频率对陶瓷粉末颗粒的重排与密堆、特别是在致密化过程中晶粒移动与晶界的迁移、以及封闭气孔的排除的作用机制，可望突破现有结构陶瓷材料致密度和强度的局限性，制备出完全致密（接近理论密度）和超高强度的结构陶瓷材料；另一方面，由于动态振荡压力烧结过程与致密化机理不完全同于现有常压烧结和静态压力烧结，弄清其烧结动力学过程及晶粒生长可控的致密化机理对于制备高性能陶瓷具有重要的科学意义和应用价值。

结构陶瓷的致密化烧结是陶瓷材料制备关键科学技术问题之一，而现有的烧结技术尚难以获得高致密度（几乎无气孔）超高强度的亚微米或纳米晶尺度的结构陶瓷材料。针对这一技术瓶颈，本项目提出采用振荡压力烧结技术制备氧化锆陶瓷、氧化铝陶瓷、ATZ陶瓷、氮化硅陶瓷、氮化硼陶瓷等多种典型的结构陶瓷，并结合致密度、晶粒尺寸、微观结构、断裂形貌及可靠性等因素，深入讨论了振荡压力对陶瓷材料致密化进程和后续性能的影响规律，并与传统的常压烧结和热压烧结工艺进行了对比，初步揭示了振荡压力烧结工艺在陶瓷中的烧结和断裂机理。振荡压力烧结技术增加了陶瓷材料烧结的驱动力，强化了烧结过程中的颗粒重排，促进塑性流动和扩散蠕变的快速发生，降低烧结温度并可制备出近乎理论密度、低缺陷、超细晶的超强结构陶瓷材料。通过烧结过程中振荡压力和频率的实施优化，实现结构陶瓷的显微结构和力学性能的协同调控，其中振荡压力技术制备出的单相氧化锆陶瓷的抗弯强度超过1800MPa，ATZ陶瓷的抗弯强度超过2100MPa，氮化硅陶瓷强度接近1500MPa。上述性能达到了国际先进水平，同时陶瓷材料的断裂可靠性得到大幅提高。深入研究振荡压力烧结机理发现，该技术有助于在材料结构中形成共轭晶界，大幅提高晶界强度，从而使材料的断裂模式由沿晶断裂转变为穿晶断裂。