Process, Microstructures And Properties Of Novel Zirconia Ceramics For Surgical Knife Materials

The toughening effect due to stress induced tetragonal to monoclinic?t?m?transformation is the basis for the application of zirconia as structural ceramics.In order to enhance the toughening effect,rare earth oxide materialsare usually utilized to stabilize the tetragonal zirconia?t-ZrO₂?.Among them,3mol.%yttrium oxide stabilized zirconia ceramics?3Y-TZP?has attracted a lot of attentions due to its ideal strength and high toughness.However,the conventional preparation route of powders by co-precipitation is complicated and low efficiency.In addition,the spontaneous t?m phase transformation within 3Y-TZP is observed in hydrothermal or humid environment,resulting in weakening of mechanical properties,which is not conducive to its application in the field of medical cutting tools.The preparation of Ce⁴⁺and Y³⁺co-stabilized zirconia has been proved to be an effective way to restrain or even eliminate hydrothermal aging while taking into account with good mechanical properties.Therefore,it is of great academic value and practical significance to explore and optimize the powder preparation process and prepare Ce-Y co-stabilized zirconia ceramics with high performance.Taking rare earth nitrate and nano monoclinic zirconia powders as raw materials,3mol.%Y₂O₃ stabilized zirconia powders?3Y-ZrO₂?and 1.5mol.%Y₂O₃-5.5mol.%CeO₂co-stable zirconia powders?1.5Y5.5Ce-ZrO₂?were prepared respectively by a novel coating method.The powder preparation process was optimized,and the densification and grain growth during the sintering process were systematically discussed in combination with cold isostatic pressure and atmospheric pressure sintering processes.The densities and microstructures of 3Y and 1.5Y5.5Ce prepared at different sintering temperatures and holding time were analyzed,and the effects of Y³⁺and Ce⁴⁺co-doping on their mechanical properties,such as hardness and fracture toughness,were studied.On this basis,the sintering processing parameters of coating-zirconia were optimized,and Ce-Y co-stabilized ceramics with high performance were obtained.XRD results show that after calcination at 800?for 2h,the coated rare earth/zirconia powders mainly compose of monoclinic zirconia?m-ZrO₂?.With the temperature increasing from 1450?to 1600?,the content of m-ZrO₂ gradually reduces.The complete stabilizing temperatures for tetragonal in 3Y-ZrO₂ and 1.5Y5.5Ce-ZrO₂ are 1600?and 1550?,respectively.Binary Ce-Y co-doping shows a stronger stability effect than that of unitary Y³⁺doping.The content and distribution of rare earth have obvious influence on grain size,and the non-uniform distribution of rare earth ions results in a wide distribution range of grain size.The doping of Ce⁴⁺increases the average grain size and weakens the inhibition of the size effect on the phase transition from t?m.Therefore,1.5Y5.5Ce-ZrO₂ shows a relatively higher fracture toughness.With the optimized sintering process?sintering temperature 1550?and sintering time 2h?,the vickers hardness,fracture toughness and flexural strength reach9.41GPa,8.06 MPa·m^1/2,688.23MPa,respectively.The fracture toughness and flexural strength of 1.5Y5.5Ce-ZrO₂ are 26.33%and 72.38%respectively,which are higher than those of 3Y-ZrO₂.The vickers hardness of 1.5Y5.5Ce-ZrO₂is 6.27%lower than that of 3Y-ZrO₂.In order to improve the sintering properties of powders by Ce⁴⁺doping,0.5wt.%,1.0wt.%,1.5wt.%,and 2.0wt.%TiO₂ and MgO were added as sintering aid to further improve the sintering density.After adding 0.5wt.%of MgO,the density and vickers hardness of the composite ceramics increase by 3.43%and 22.95%compared with those of1.5Y5.5Ce-ZrO₂,but the fracture toughness decreases to less than 7MPa·m^1/2.Commercial3Y-TZP zirconia preforms and self-made 1.5Y5.5Ce-ZrO₂ zirconia preforms were prepared by the method of tape casting,and their hardness,fracture toughness and wear properties were compared,respectively.And the biocompatibility of self-made 1.5Y5.5Ce-ZrO₂ zirconia ceramics was tested.1.5Y5.5Ce-ZrO₂ was selected as the material for the preparation of surgical knives.