Characterisation of Mixing Uniformity and Rheological Properties of Alumina-Zirconia Powder for Ceramic Injection Moulding

The mixing uniformity and rheological properties of feedstock are crucial to the success of the ceramic injection moulding process. The suitability of developed feedstock may reduce the problems that arise during injection moulding, debinding and sintering. Therefore, this study is focused on identifying the optimum powder loading based on the mixing uniformity and rheological properties of materials. Uniformity characterisation of the mixture is determined based on the low torque value and at the steady state. Rheological studies were carried out using a capillary rheometer machine. The test was carried out at temperatures between 150 and 170 degrees C with the applied loads between 20 and 90 kgf. The feedstock used was a combination of alumina-zirconia powder with a binder that consisted of high density polyethylene, paraffin wax and stearic acid. The feedstocks are found to be pseudoplastic with uniform mixing achieved in less than 30 min. The powder loading of 57% by volume is found to be optimum for the ceramic injection moulding process based on the low values of viscosity, power law index and flow activation energy.