Production method of zirconia ceramic rod extrusion molding process

Production method of zirconia ceramic rod extrusion molding process

Zirconia ceramic rod extrusion molding is the process of placing ceramic slurry with a plastic belly into an extruder, and applying extrusion pressure to the slurry to obtain the formed body through a machine nozzle with a certain shape. By changing the nozzle, various shapes of billets can be extruded. Extrusion forming belongs to the plastic method of forming, which is significantly different from injection molding.

Injection molding is the process of filling a mold with a certain shape and strength by utilizing the fluidity characteristics of the slurry. Plastic forming is the process of utilizing the plasticity of the slurry and undergoing certain processing techniques, such as extrusion, to make the slurry into a green body with a certain shape and strength.

The preparation of extrusion slurry requires high requirements for slurry during extrusion molding. The basic performance requirements for slurry that can be used for extrusion molding include:

① The particle size requirement of the powder is relatively fine, and the particle shape is smooth. It is better to use powder milled with small grinding balls for a long time;

② The dosage of solvents, plasticizers, and binders should be appropriate;

③ The slurry should be highly uniform, otherwise the quality of the billet formed by extrusion is not good.

The key to preparing extrusion slurry is the plasticization of the slurry. Plasticizing is the process of using Plasticizer to make the original non plastic slurry plastic. Many raw materials for advanced ceramics do not have plasticity, so plasticization is necessary when using extrusion molding. Organic Plasticizer usually consists of Adhesive, plasticizer and solvent.

Wax based binder in thermoplastic systems is a commonly used binder in ceramic slurry extrusion processes. Its advantages include low viscosity, high solid content of the slurry, and low cost, but it has shortcomings such as easy phase separation, unstable slurry performance, and poor shape retention. In addition to organic binders, inorganic binders are also affected by the sintering process; Burn loss; It is valued for its low carbon residue and low carbon content.

AlOOH, which has received widespread attention in the preparation of zirconia ceramics by extrusion, can be used as a bonding agent for extrusion molding and as a sintering aid to directly convert it into a zirconia matrix during the sintering process, thereby avoiding contamination of the matrix.

Water-based adhesives are easy to remove, have a fast degreasing speed, and have little environmental pollution, making them a promising adhesive. Due to the interaction between binders and various additives with the powder, it can affect the rheological behavior of the slurry and the colloidal properties of the powder surface, ultimately affecting the physical properties of sintered products. This is particularly important to pay attention to when preparing water-based slurries. Especially, water-based slurry is prone to solid-liquid phase separation, leading to continuous increase in extrusion pressure and blockage of the extruder. It is necessary to improve the stability of the slurry to improve this situation.

Disadvantages of extrusion molding

Extrusion molding has the advantages of low pollution, easy automation, continuous production, and high efficiency, but the structure of the extrusion nozzle is complex and requires high processing accuracy. In addition, due to the abundance of solvents and adhesives in the slurry, the shrinkage of the green body during drying and firing is significant, which affects its performance.

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