基于激光选区烧结的SiC(w)/Si3N4蜂窝陶瓷的多孔结构与性能调控

Honeycomb ceramics are extensively used in vehicle exhaust emissions control. The structure and property of honeycomb ceramics can directly impact catalyst effect and filter efficacy of final product. Those honeycomb ceramics manufactured by existing technologies have a common problem of simple channel structure. Furthermore, honeycomb ceramics that made from widely used iolite and other materials can’t be used under high temperature because of strength-weakening. In this case, this project chooses Si3N4 ceramic, which has better high temperature performances as base material, and applies SiC whiskers as reinforcing phase. Based on optimized 3D model of channel structure of pore, the project uses Selective Laser Sintering (SLS) technology to prepare complicated channel structural SiC(w)/Si3N4 honeycomb ceramics. Under the formed complex porous environment, the project regulates and controls the macro- and micro-structures and properties of honeycomb ceramics. The project focuses on two key scientific issues: first, the interaction mechanisms of composite ceramic powder and laser, together with time and space distribution of thermal and stress fields in SLS forming process; second, the collaborated reinforcing and toughening mechanisms of SiC whiskers and β-Si3N4 under complex porous environment. Based on these studies, the project establishes the relations among SLS forming technology, macro- and micro-structures and comprehensive properties of product and finally, fabricates high-performance and structure-controllable SiC(w)/Si3N4 honeycomb ceramics. This project will provide ponderable theoretic instructions and technology references for preparing high-performance and structure-controllable porous ceramic components using SLS technology.

蜂窝陶瓷是汽车尾气处理等领域应用非常广泛的催化剂载体，其结构和性能直接影响最终器件的催化效果和过滤效率。针对现有工艺制备蜂窝陶瓷存在孔道结构单一，且常用的堇青石等蜂窝陶瓷在高温下强度无法满足应用要求等问题，本项目选择高温性能更好的Si3N4陶瓷作为基体，引入SiC晶须作为增强相，基于优化的三维孔道结构模型，将激光选区烧结(SLS)技术应用于制备复杂孔道结构的SiC(w)/Si3N4蜂窝陶瓷，在形成的复杂多孔环境中对其宏微观结构及性能进行调控。本项目重点研究复合陶瓷粉体与激光的交互作用机制及材料内部温度场和应力场的时空分布，并研究复杂多孔条件下SiC晶须和β-Si3N4柱状晶粒的协同强韧化机理，建立SLS成型工艺-宏微观组织结构-综合性能的关系，最终制备出结构可控的高性能SiC(w)/Si3N4蜂窝陶瓷。本项目将为今后采用SLS技术制备结构可控的高性能多孔陶瓷部件提供理论指导和工艺参考。

针对现有工艺制备蜂窝陶瓷存在孔道结构单一，且常用的堇青石等蜂窝陶瓷在高温下强度无法满足应用要求等问题，本项目选择Si3N4陶瓷作为基体并引入SiC晶须，采用激光选区烧结(SLS)技术制备高性能SiC(w)/Si3N4蜂窝陶瓷。本项目首先采用溶剂蒸发法、溶解沉淀法等方法制备出满足SLS成形要求的高分子-SiC(w)/Si3N4复合陶瓷粉体，在此基础上，研究了SLS成形过程中复合陶瓷粉体与激光的相互作用机制，得到了复合陶瓷粉体参数以及SLS工艺参数对成形SiC(w)/Si3N4蜂窝陶瓷坯体力学性能等的影响规律，获得了复合陶瓷粉体特征、SLS成形工艺、烧结制度等对SiC(w)/Si3N4蜂窝陶瓷的微观组织结构、气孔率等的影响规律，得到了最佳的SLS工艺参数。系统研究了SiC晶须和β-Si3N4柱状晶粒的协同强韧化机理，建立了SLS成型工艺-宏微观组织结构-综合性能的关系，最终制备出了结构可控的高性能SiC（w）/Si3N4蜂窝陶瓷。本项目的实施为后续采用SLS技术制备高性能多孔陶瓷提供了理论指导和工艺参考。