The Influence of the Green Density on the Quality of ZTA Zirconia Toughened Alumina Plungers

Abstract

The purpose of this study is to investigate the effect of the green density (ρ<sub>g</sub>) on the sintered density (ρ<sub>s</sub>), shrinkage according height and diameter (HS, DS), relative density, porosity and hardness of ZTA ceramic plungers. Zirconia toughened alumina is characterized by excellent properties of hardness, toughness, thermal and chemical resistance, which make composite material interesting for multiple applications. Some of the significant applications of ZTA ceramics are in the production of biomedical implants, cutting tools, parts for pumps and others. The material is composed of high purity alumina 90% and 10% of zirconium oxide. This material successfully compensate fragility of the alumina and zirconium oxide price. After 24 hours of milling in a ball mill (Dorst, Germany) slurry with a specific surface 25 832 cm2/g was transferred into a mixer with addition of binders (PVA + soap based binder) through a vibrating sieve (British and Foreign Patents). Solid content (%) of the slurry in amount of 69.16 was confirmed by thermogravimetric and differential gravimetric analyzes. The 1000 kg of the powder dried by spray drying (Spray dryer Niro) contains 2.6% of binders and 0.2% of moisture. Three sets of plungers with outer diameter of 3.6 cm, inner diameter of 2.0 cm and height of 7.6 cm were produced by cold isostatic pressing (CIP) using different pressures. The first set marked as 'A' was pressed by pressure of 80 MPa, the second set marked as 'B' was pressed by pressure of 100 MPa, and third set marked as 'C', was pressed by pressure of 150 MPa. According to statistical data processing, comparison and analysis of the results it is concluded that the quality of the ZTA plungers, in specific presented case, significantly depends on the green density (ρ<sub>g</sub>).