Study On The Preparation Of Zirconia Ceramic Slurry For Additive Manufacturing

As a kind of metal oxide ceramic,zirconia has high hardness,toughness and good bio-compatibility,and is usually used in the biomedical industry.Traditional processing methods of zirconia have the characteristics of long cycle and high cost.The micro-flow extrusion forming in additive manufacturing can extrude the nano ceramic slurry from the micron channel into filaments.A three-dimensional part is printed by layer and layer stacking in this process,which has the characteristics of customization and rapid prototyping.The strength of extruded wire is too low in the process of forming,and the ceramic slurry is required to meet the requirements of high solid phase and low viscosity,and is capable of keeping stable in the process of extruding and printing.In this paper,the preparation of zirconia ceramic slurry for additive manufacturing was studied,and the zirconia ceramic slurry meeting the requirements of micro-flow extrusion forming was prepared for printing zirconia ceramic denture.The main contents were as follows:（1）The stable dispersion mechanisms involved in the preparation of slurry and the rheological properties of slurry were analyzed.It was put forward that the particles in slurry were mainly subject to van der Waals,electrostatic repulsion and spatial repulsion.The factors affecting these effects were explained by analyzing mathematical models,lading a foundation for the preparation of high solid phase and low viscosity slurry.The rheological analysis indicated that the sum of the three effects directly determined the viscosity of slurry,and the rheological mathematical model provided a theoretical basis for analyzing the rheology of the prepared ceramic slurry.（2）The factors influencing the dispersion and rheological properties of zirconia ceramic slurry during preparation were studied,the effect of ball milling on the preparation of high solid ceramic slurry was studied for the first time and the preparation process was determined experimentally.Results showed that high solid phase and low viscosity slurry can be obtained by adding dispersant sodium polyacrylate 5～6 wt%,adjusting the p H value to 8.5 and ball milling treatment ball grinding for 12 h at 600 r/min.The viscosity test found that the viscosity of the prepared ceramic slurry decreased with increasing shear rate and showed shear thinning behavior.（3）The micro-flow extrusion forming and printing process were analyzed,the optimal forming process parameters of zirconia ceramic paste were determined through experiments,and zirconia ceramic parts were printed.The main parameters involved in the printing process were extrusion speed,extrusion head diameter,printing speed,height and inner diameter of the barrel.Results showed that when the extrusion speed was 0.08 mm/s,the diameter of extrusion head was 0.8 mm/s,the printing speed was 15 mm/s,the height was0.7 mm,and the line width was 0.83 mm,the forming was the best.（4）Sintering densifying,performance testing and characterization were conducted for printed parts.The sintering process 1 500℃for 2 h was obtained by sintering the printed parts,and used to sinter and densify zirconia parts.A series of performance tests and characterization were conducted for the sintered and densified parts,as a result that shrinkage rate 58.9%,surface roughness 17.1 mm,hardness 1 370 HV,bending strength474±20 MPa,fracture toughness 3.8 MPa·m^0.5,relative density 98.4%.Based on the analysis of these tests and characterizations,it was concluded that the printed parts had excellent performances after sintering.