In tape casting molding, ceramic powder and dispersant are first added to the solvent, and the particles are agglomerated through ball milling or ultrasonic vibration, and the solvent wets the powder. Then the binder and plasticizer are added again, and a stable and uniform slurry is obtained through secondary ball milling; The slurry is molded on the tape casting machine again to obtain the blank; After that, moisture is carried out to evaporate the solvent, and the binder forms a network structure between the ceramic powders to obtain a blank film; Product categories: ceramic plunger, ceramic pump core, ceramic valve core, ceramic piston, ceramic shaft sleeve, ceramic suction cup, microporous ceramics, etc; Materials: alumina, zirconia, silicon nitride, silicon carbide. Then, the blank film is machined to obtain the required specific shape; Finally, the required finished products are obtained through glue discharge and sintering.
With the unremitting efforts of the materials discipline workers, on the basis of the original tape casting method, a new water-based tape casting method has been developed, such as gel tape casting process, isostatic pressure tape casting process and UV initiated polymerization process.
1. Gel tape casting process
The gel tape casting molding utilizes the principle of organic monomer polymerization to carry out tape casting molding. This method is to add ceramic powder, dispersant and plasticizer into the mixed solution of organic monomer and cross-linking agent to prepare a concentrated suspension with low viscosity and high solid volume fraction (more than 50%). Then, after the initiator and catalyst are added, the temperature is controlled and the monomer polymerization reaction is initiated, so that the viscosity of the suspension increases, and then the in-situ solidification molding occurs. Finally, the green body with certain strength and suitable for machining is prepared.
The gel tape casting process not only significantly reduces the amount of organics in the slurry, but also increases the solid volume fraction and product density and strength, which is more and more conducive to the construction of a resource-saving and environment-friendly society.
2. Isostatic pressure tape casting process
The solid phase volume fraction of tape casting slurry is quite high, and it is also accompanied by the evaporation of solvent in the wet process, leaving air holes in the green billet. Therefore, the green billet film obtained through tape casting is generally of structural texture, high density, and it is very easy to obtain a hard green billet indirectly through tape casting.
Although the cast film blank obtained by tape casting is hard enough and loose in structure, it has the ductility of hao. Therefore, the density of the blank can be improved by isostatic pressing secondary forming. However, the isostatic pressure tape casting equipment is relatively cheap, so it will make the process simpler and increase the cost.
3. UV initiated polymerization molding process
In view of the shortcomings of water-based tape casting process, researchers used the mechanism of UV initiation in situ polymerization to add UV photosensitive monomer and UV photopolymerization initiator into the slurry and initiate the UV in-situ polymerization reaction, so that the slurry can be cured in situ. Compared with the traditional tape casting process, the UV initiated tape casting process can be completed by adding an UV light source to a common tape casting machine, eliminating the most difficult wet process to cause material molding failure.