多官能团共聚物一元凝胶体系的固化机理及干燥微观水输运和结构演化

There is an increasing appeal for advanced ceramics with large size and/or complicated shape. However, its application is prohibited by reliability and cost of advanced ceramics. Gelcasting possesses advantages of near-net forming, green body with homogeneous microstructure and so on, which is a promising approach to low-costly prepare reliable parts with large size and/or complicated shape. Unfortunately, former gelling system shows shortcomings of lots of organic additives and oxygen inhibition. Also, macro-deformation/crack of ceramic gel with large size during drying is still unsolved. We invent a gelling system only involving a copolymer with multi-functional groups, which has advantages of low addition, working well in air, low deformation during drying and no crack during pre-sintering. However, the gelling mechanism of the co-polymer is not clarified and cracking also occurs for the ceramic gel with large size during drying, which is a general phenomenon of gelcasting with large size. For this gelling system, we intend to research the adsorption mechanism of the copolymer on the particle surface and the interactions among particles, copolymer molecules and functional groups to clarify gelling mechanism. On the other hand, we will systematically investigate factors to disclose water transport and microstructure evolution of the gel during drying from microcosmic perspective. Correlation will be established between water transport, microstructure evolution and macro-shrinkage of ceramic gel with large size. The results achieved in this project will strengthen understanding of this gelling system and provide theoretical guidance for solving the problems of deformation and/or crack in ceramic gel with large size during drying.

大尺寸和复杂形状陶瓷部件需求日益迫切，但其应用受阻于部件可靠性和加工成本。注凝成型技术具有素坯微结构均匀和近净尺寸的优势，是低成本制备高可靠性、大尺寸和复杂形状陶瓷部件的优选方案。然而，现有凝胶体系存在有机物添加量大、氧阻聚和毒性以及大尺寸样品干燥变形和开裂等问题。项目申请人开发的多官能团共聚物一元凝胶体系具有添加量少、适于空气操作且无毒等特点，在预防干燥变形和预烧开裂等方面具有明显优势。但是，该体系的固化机理尚不明确，且大尺寸样品的干燥依然开裂（注凝大尺寸样品的共性问题）。本项目立足于该一元凝胶体系，研究共聚物在陶瓷颗粒表面的吸附机制以及颗粒、共聚物分子和官能团之间的相互作用，探明凝胶固化机理。在干燥方面，从微观角度研究干燥影响因素，揭示大尺寸陶瓷凝胶的微观水分输运和结构演变及宏观收缩的关联性。研究成果将完善一元凝胶体系的基础理论，为解决大尺寸陶瓷凝胶干燥变形和开裂等问题提供理论指导。

2011年，项目申请团队发明了多官能团共聚物一元凝胶体系，实现了先进陶瓷浆料的原位固化成型。该体系具有有机物添加量少、适于空气操作且无毒等特点，在预防干燥变形和预烧开裂等方面具有明显优势，引起了国内外二十多家研究单位的跟踪报道。但是，该体系的固化机理尚不明确，且大尺寸陶瓷凝胶的干燥依然开裂。对此，项目团队于2017年申请开展该体系的固化机理及干燥微观水输运和结构演化研究，并获资助，项目执行期由2018年1月至2021年12月。在此期间，项目团队（1）开展了共聚物溶液特性、共聚物的官能团种类、分子量、溶解时间、粉体杂质离子、环境温度等因素对浆料流变性的影响、固化过程共聚物分子结构和颗粒粒度的变化、浆料再固化和共聚物疏水修饰等研究，阐明了多官能团共聚物一元凝胶体系的固化机理，即陶瓷颗粒参与凝胶网络形成，吸附于相邻颗粒上的共聚物分子链之间通过疏水缔合和氢键等分子间作用力发生聚合，从而原位固化颗粒形成湿坯。（2）系统研究了陶瓷凝胶脱水收缩和湿坯干燥的内在和外界影响因素，揭示了陶瓷凝胶的微观水分输运和结构演变及宏观收缩的关联性，创新提出了脱水收缩浆料再流动提高颗粒堆积和压滤辅助湿坯脱水的方法。（3）基于凝胶机理和干燥的基础研究，开展了高强氧化铝泡沫陶瓷制备、高透过率类单晶氧化铝透明陶瓷制备和大尺寸高纯氧化铝陶瓷圆盘瓶颈技术基础研究。发表论文9篇，其中SCI论文6篇，EI论文2篇，中文核心1篇。申请发明专利4项，其中2项已获授权。培养博士和硕士研究生共5人，其中4人已毕业。上述研究成果不仅拓展了浆料原位固化成型的研究领域，包括新型自发凝固体系、脱水收缩新现象、凝胶再流动成型新方法等，而且解决了自发凝固成型技术在工程化过程中的瓶颈难题，参股企业能批量制备晶圆研磨载盘，并攻克了1010 mm超大尺寸高纯氧化铝陶瓷圆盘的关键制备技术，实现了良好的社会经济效益。