氧化物陶瓷闪烧机理及其应用研究进展

闪烧是近些年广受关注的一种电场辅助烧结技术。本文介绍了闪烧的起源与发展, 并对闪烧的基本特征进行了分析。在闪烧孕育与引发过程的研究方面, 发现了孕育阶段的非线性电导特征和电化学黑化现象, 提出了氧空位主导的缺陷机制; 在闪烧阶段的快速致密化研究方面, 提出了电场作用导致的缺陷产生和运动会在粉体颗粒间产生库仑力, 有利于烧结前期的致密化过程, 同时发现闪烧致密化过程中还伴随着金属阳离子的快速运动; 在闪烧阶段的晶粒生长和微结构演变方面, 发现了试样温度沿电流方向呈非对称分布, 试样中间位置的晶界迁移率明显提高, 提出电化学缺陷对微观结构有重大影响。基于上述研究成果, 本团队利用电场作用下出现的低温快速传质现象, 发展了陶瓷闪焊技术, 实现了同种陶瓷/陶瓷、陶瓷/金属, 甚至异种陶瓷/陶瓷之间的快速连接; 发展了陶瓷闪烧合成技术, 不仅实现了典型氧化物陶瓷的快速合成, 而且实现了高熵陶瓷和具有共晶形貌的氧化物陶瓷的快速合成; 发展了氧化物陶瓷的电塑性成形技术, 初步实现了氧化锆陶瓷低温低应力下的快速拉伸和弯曲变形。本文最后总结了闪烧机理研究面临的挑战, 并从焦耳热效应和非焦耳热效应两方面展望了闪烧的发展方向, 期望对闪烧技术在国内的发展有所裨益。

Research Progress on the Flash Sintering Mechanism of Oxide Ceramics and Its Application

Flash sintering is an electric field assisted sintering technology which has attracted much attention in recent years. This review introduces its origin, development, and basic characteristics. In the study of flash incubation and initiation process, the nonlinear conductivity characteristics and electrochemical blackening phenomenon are narrated, and the defect mechanism dominated by oxygen vacancy is recounted. As for rapid densification during flash sintering, it is proposed that the generation and movement of defects caused by electric field produce Coulomb force between powder particles, which is conducive to density in the early stage of flash sintering. Meanwhile, the densification process is accompanied by the rapid movement of metal cations. In terms of grain growth and microstructure evolution during the flash sintering, the sample temperature is asymmetrically distributed along the current direction, and the internal grain boundary mobility in the sample is significantly improved. During this stage, electrochemical defects exert a significant impact on the microstructure. Based on the above researches, we developed ceramic flash joining technology by using phenomenon of low-temperature rapid mass transfer under electric field, and realized rapid joining between similar kind of ceramics/ceramics, ceramics/metals, and even dissimilar ceramics/ceramics. A new ultrafast ceramic synthesis technology by flash sintering was developed, which not only realized the rapid synthesis of typical oxide ceramics, but also realized the rapid synthesis of high entropy ceramics and oxide ceramics with eutectic morphology. An electroplastic forming technology of oxide ceramics was developed, and a rapid tensile and bending deformation of zirconia ceramics at low temperature and low stress was preliminarily realized. Finally, this review summarizes the challenges in the field of flash sintering mechanism, and looks forward to the development direction of flash sintering from two aspects of Joule heating effect and nonthermal effect, aiming to be beneficial to the development of flash sintering technology in China.