Progress in industrialization of large-scale high-purity alumina parts prepared by spontaneous solidification

Recently, the research team led by Wang Shiwei, a researcher at the Shanghai Institute of Ceramics, Chinese Academy of Sciences, has cooperated with enterprises to build a spontaneous gelation system based on a multifunctional copolymer of isobutylene and maleic anhydride copolymer (PIBM) with independent intellectual property rights. Break through the key bottleneck problems such as deformation and cracking of large-sized ceramic wet blanks during the drying process, and successfully prepare large-size high-purity alumina ceramic grinding discs with diameters of 360mm to 600mm.

Large-sized structural ceramic components have a wide range of applications in semiconductor manufacturing equipment and other fields, but the molding of large-sized ceramic components is extremely challenging. Compared with the classic cold isostatic pressing and grouting molding, gelcasting (gelcasting, or gel injection molding) has outstanding advantages: the green microstructure is uniform, fundamentally ensuring the reliability of ceramic components; The billet has high strength and density, is convenient to handle, and can effectively reduce the risk of sintering shrinkage and cracking; near-net-shape molding can greatly reduce the machining cost. In addition, the injection molding process equipment is simple, which can effectively reduce the cost of production input, and has huge application potential in the preparation of large-sized ceramic components. However, the gel system based on free radical polymerization has the problems of monomer toxicity, oxygen inhibition and many types of additives and large amounts of additions. In addition, the drying mechanism of ceramic gels has not been clearly explained, which seriously hinders the injection technology Widely used in the preparation and industrialization of large-scale structural ceramic components.

Wang Shiwei's team has been exploring new gel curing systems since 2003. First, a water-soluble epoxy resin-polyamine gel system based on nucleophilic addition polymerization was developed (J. Am. Ceram. Soc., 2008), which was successfully applied to dense Al2O3, AlN and SiC, translucent Al2O3 Forming of advanced ceramics such as transparent Y2O3, YAG and AlON, and foam Al2O3. In 2011, the team discovered spontaneous solidification in the study of preparing Al2O3 ceramic slurry using PIBM (J. Mater. Res., 2013). Subsequently, the work focused on the universality of the PIBM spontaneous solidification system, the drying mechanism of the ceramic gel, the in-situ stress of the green body during the calcination process, and the development of large-scale ceramic component preparation technology.

Compared with other gel systems, the PIBM spontaneous coagulation system has obvious advantages such as fewer types of additives, less added amount, and simple operation. Under normal temperature atmospheric environment, only one organic copolymer can be used to spontaneously solidify Al2O3. The prepared Al2O3 ceramic wet blank has good flexibility. At the same time, the solidification system has wide universality and has been successfully applied to the preparation of porous, dense and transparent ceramics in various oxide and non-oxide systems. By comparing the drying process of the epoxy-polyamine gel system and the PIBM spontaneous coagulation system, the team found that the density of the organic network significantly affects the drying behavior of the ceramic wet blank. The organic network formed by the PIBM spontaneous solidification system is conducive to moisture transport, and the drying stress is easier to release, and the green body does not deform after drying; while the organic network formed by the epoxy resin-polyamine gel system hinders moisture transport, and the drying stress is large, The green body is easy to dry and deform.

In the past five years, the research team has published more than 20 research papers on PIBM spontaneous solidification and molding in international journals of materials and ceramics, and its core technology has been granted 6 Chinese invention patents. Since the report, PIBM's spontaneous solidification molding system has attracted extensive attention from domestic and foreign counterparts. At the same time, the research team has been committed to the promotion and application of new molding technology. In July 2017, with the new PIBM spontaneous solidification system as the technical core, Shanghai Silicate Institute and Jiangxi Pingxiang Enterprise jointly established Jiangxi Zhongkete Porcelain New Material Co., Ltd. to carry out the industrialization of large-scale high-purity alumina ceramic components . At present, the company has built a pilot production line, mastered the key technologies such as drying, debonding and high-temperature sintering of large-scale alumina grinding discs for spontaneous solidification molding, and prepared high-purity alumina grinding discs with various specifications from 360mm to 600mm in diameter. It has laid a solid foundation for large-scale production.

PIBM spontaneous solidification molding technology is applied to the preparation of large-scale advanced ceramic materials. It has significant originality and advancedness, and will provide a new low-cost manufacturing method for large-scale ceramic components required for the localization of China's semiconductor manufacturing equipment. The research was supported by the Pinghu New Materials Center Project of the Chinese Academy of Sciences, the Shanghai Excellent Technology Leader Project, the National Natural Science Foundation General Project, and the Ministry of Science and Technology's key R & D plan.