基于中子衍射的闪烧SiCw/ZrO2异质界面应力演变及致密化机理研究

成型烧结是制备陶瓷构件的典型工艺途径，但在烧结多相异质复合陶瓷时由于各组分的烧结速率不同，会在异质界面产生应力，形成烧结约束，造成异质陶瓷体系致密化缓慢或无法致密化。研究发现临界电场辅助闪烧新技术可突破异质复合陶瓷的烧结约束，实现低温无压快速致密化，但烧结机制尚不清楚。本项目以SiC晶须增韧ZrO2陶瓷体系为例，通过中子衍射技术原位测试闪烧各阶段体系异质界面应力，表征电场辅助下烧结约束力的演变过程，结合闪烧不同阶段体系电导特性、缺陷结构、晶须-陶瓷界面显微结构的表征，解决临界电场对烧结过程中约束应力的作用机制和闪烧传质机制等关键科学问题，揭示临界电场下陶瓷粉体克服晶须约束、实现快速致密化的烧结机理。本项目通过中子衍射技术实现闪烧过程应力在线测试，在研究手段上有特色和创新；发展了异质复合陶瓷低温无压快速致密化的新方法，在陶瓷烧结理论和烧结工艺方面有创新。

Forming and sintering is a typical technique for the production of ceramic bodies. During the sintering of ceramic composites consisting of different components, internal stresses can arise at the interface of the components from different sintering rates. This forms the so-called constrained sintering. These stresses lead to much lower densification rate or even incapacity to densification. Previous research revealed that flash sintering, a new sintering technology, could densify ceramic composites at low temperature and ambient pressure in very short term under the assistance of a critical electric field. However, the sintering mechanism is unclear. This project will take SiC whisker reinforced ZrO2 ceramics (SiCw/ZrO2) as an example to study the mechanisms of flash sintering of ceramic composites. The internal stress in SiCw/ZrO2 at different flash sintering stages will be in-situ measured through neutron diffraction technique and the stress variation versus electric field will be characterized. The electrical conductivity behaviors, the microstructure defects, and the whisker-ceramic interface microstructure of the SiCw/ZrO2 composites will be characterized at different flash sintering stages. The aim of this project is to solve the scientific topics including the effect of electric field on the internal stress and the enhanced mass transport mechanism during flash sintering, and to reveal the reason why the sintering constraint of whiskers disappears under critical electric field. This project developed an in-situ internal stress measurement technique through neutron diffraction and possess a new feature in research technique. This project develops a new sintering technique for ceramic composites under ambient pressure and low temperature with rapid densification rate. It will generate innovations in both ceramic sintering theories and sintering techniques.