在过去几十年的研究中，科学家和产业界试图采用先进的陶瓷胶态成型技术，来降低制造成本和提高部件的可靠性，解决大尺寸复杂形状的结构陶瓷部件的难题。然而，事实证明仅仅控制成型是远远不够的，还必须控制陶瓷烧结的收缩率。随着陶瓷收缩率的降低，力学性能会大幅下降。本文以低收缩、高性能的氧化铝陶瓷的制备工艺为研究主线，通过添加蓝晶石的相转变法、添加氧化铝预烧粉控制原料烧结活性这两种降低烧结收缩的方法制备低收缩氧化铝陶瓷，同时系统研究了Isobam自发凝固成型的成型机理和改善凝胶体系性能的方法，提出了聚合物-陶瓷颗粒双重网络的成型思路，发明了基于可交联的聚合物电解质分散剂的胶态成型方法和基于戊二醛和酒石酸的室温胶态成型方法，取得的主要创新结论如下：（1）采用环氧树脂的凝胶注模成型方法结合蓝晶石的相转变法，成功制备低收缩莫来石-氧化铝陶瓷，所制备的莫来石-氧化铝陶瓷的烧结收缩率为5%，抗弯强度为232.5±12.0 MPa。（2）Isobam凝胶体系适合于高性能低收缩陶瓷的成型，但是具有浆料粘度高、湿坯强度低的缺点。为了克服这些缺点并将其用于低收缩氧化铝陶瓷的制备中，研究了氧化铝-Isobam体系的浆料流变特性和凝胶过程，提出了Isobam的桥联絮凝的凝胶机制。同时还提出了二元羧酸辅助分散的Isobam凝胶体系，可以显著降低体系粘度，对坯体强度影响较小。（3）提出通过预烧粉的颗粒级配效应和预烧粉对细小氧化铝晶粒致密化过程的阻碍作用，可以大幅度减少片状孔，显著提高低收缩陶瓷的致密度和性能。在氧化铝中添加60% 1600°C氧化铝预烧粉，采用二元羧酸辅助分散的Isobam凝胶体系，成功制备了高性能的低收缩氧化铝陶瓷，线收缩率为7.79%，抗弯强度为294.6±33.0 MPa，致密度为91.5%。（4）设计并合成了一种可交联的聚合物电解质分散剂BTT。发现BTT在氧化铝浆料中有很强的静电稳定作用，同时凝胶湿坯中存在聚合物-陶瓷颗粒的双重网络，显著改善湿坯强度。（5）发明了基于戊二醛和酒石酸的室温胶态成型新方法，通过对戊二醛改性以调控凝胶速度，制得的坯体在较低的有机物含量下，到达了高凝胶强度。将此凝胶体系结合氧化铝预烧粉法，成功制备了具有较大尺寸、复杂形状的低收缩氧化铝陶瓷。
In the past few decades, scientists and industry have tried to use advanced ceramic colloidal forming techniques to reduce manufacturing costs and improve the reliability of ceramic components in order to overcome the difficulties in fabrication of structural ceramic components of large sizes and complex shapes. However, it turns out that it is not enough to just control the forming process, and the sintering shrinkage of ceramic must also be taken into consideration. As the sintering shrinkage of ceramics decreases, the mechanical properties will drop significantly. The main outline of this paper is the preparation of low-shrinkage alumina ceramics with high strength. Two methods of reducing sintering shrinkage adopted were phase transition with volume expansion of kyanite and addition of pre-sintered alumina powder to control the sintering activity of raw materials. Meanwhile, the mechanism of spontaneous gelation of Isobam with alumina and the improvement of the performance of the Isobam gelation system were systematically studied. A concept of gelcasting with formation of polymer-particle double network was proposed. A gelcasting method with a crosslinkable polyelectrolyte dispersant and a room-temperature gelcasting method of alumina with tartaric acid and glutaraldehyde were invented. The main innovative conclusions obtained are as follows:(1) Low-shrinkage mullite-alumina ceramics were successfully prepared utilizing gelcasting with epoxy resin and thermal decomposition of kyanite with volume expansion. The mullite-alumina ceramics fabricated have a sintering shrinkage of 5% and a bending strength of 232.5±12.0 MPa.(2) Isobam gelcasting system is suitable for forming of low-shrinkage ceramics of high performance, but it shows the disadvantages of high viscosity of slurries and low strength of wet green bodies. In order to overcome the shortcomings and apply the Isobam gelcasting system to the fabrication of low-shrinkage alumina ceramics, the rheological properties and gelation properties of the alumina-Isobam system were investigated, and a bridging mechanism of Isobam gelation was proposed. Moreover, an Isobam gelcasting system assisted by dicarboxylic acids was also proposed, which can significantly reduce the viscosity of the alumina slurry and has less effect on gelation strength.(3) It was proposed that via effects of particle grading and the reduced sintering activity of pre-sintered powder, the number of disk-like pores in low-shrinkage alumina ceramics can be reduced, leading to significant improvement of density and mechanical properties of low-shrinkage ceramics. With addition of 60% 1600°C pre-sintered alumina powder and the Isobam gelcasting system assisted by dicarboxylic acids, high-performance low-shrinkage alumina ceramics with a sintering shrinkage of 7.79% and a bending strength of 294.6±33.0 MPa were prepared.(4) A crosslinkable polyelectrolyte dispersant named BTT was designed and synthesized. It was found that BTT produces a strong electrostatic stabilization effect in alumina suspensions, and polymer-particle double network is supposed to form during gelation, leading to the high strength of ceramic wet green bodies.(5) A room-temperature gelcasting method of alumina with tartaric acid and glutaraldehyde was invented, and the modification of glutaraldehyde to control the gelation speed was studied. This gelcasting method shows high gelation strength with a low content of organic additives. By combining this gelcasting system with pre-sintered alumina powder, low-shrinkage alumina ceramics with large sizes and complex shapes were successfully fabricated.
