Research On Ceramic Injection Molding And Rheological Behaviour

The objective of this study was to evaluate the effects of the dependence of the rheological behaviour on the solid loading for ceramic injection moulding . The average particle size and distribution decide on the solid loading. For the requirement of injection molding , the calcining and milling were done in order to increase the tape density of powder and improve particle shape and size distribution. The mode of Maron-Pierce was used to evaluate the processing of powder treatment. The suitable calining temperature and milling time had been given. Moreover, the thermal decompose of binder was studied, according to requirement of the feedstocks viscosity and the processing of thermal debinder .The ideal binder systems was achieved for ceramic injection moulding. The statistic principle and the rheology characteristic of feedstock was introduced to estimate the uniformity of foodstocks. The rheological behavior of feedstock is very key to injection moulding . Ceramic injection moulding was fitted with the power law model .The power law index "n"expresses the degree of shear sensitivity,n<1 . The viscosity is the most important rheological parameter for powder injection moulding . In this paper, the viscosity was measured by the capillary rheometer . According to the rheology date , the activation engery was calculated by Arrhenius type equation and the yield stress can be obtained by Casson model. Furthermore, for the necessity of injection molding, the ideal binder system and solid loading had been given. For near-net-shape molding , the molding machine needs to be controlled accurately. Molding process of the feedstock was investigated. The results show that molding temperature and injection and hold pressure ,temperature of mould ,time of keeping pressure and cooling are key processing parameters . In order to value the injection parameters , the density of green part was measured. According to Newton liquid experimental formula , the screw shear thinning to feedstock was calculated. The thermal decomposition behaviors of binder was studied. It was shown that the binder's decomposed behavior was not simply added by its components'thermal behavior because of the intersolubility of single component. The defect and the reason were analysed. By experiment once again and again , optimal debinding process of the green part was gave in this dissertation. The sintering process has been studied. The results show that high sintering temperature is of advantage to improve linear shrinkage rate and relative density of ceramic parts . But it is difficult to get stable t-ZrO2 under so high sintering temperature that the grain size has increased over the critical size. The ways of how to control the properties of the ceramic injection molding parts have been analyzed and discussed. The results show that to control the properties of parts is to strictly control the solids loading of powder, the process defects and the temperature of sintering. Through controlling the above three factors, the ceramic parts with desired mechanics and electrics performance are obtained. Presently, small-scale producing of lots of complicated ceramic parts have been made successfully.