Abstract: The porosity and flexural strength of porous alumina ceramic fabricated by direct ink writing forming method is a pair of negatively correlated performance index. However, high porosity and high flexural strength are required in the fields of thermal insulation and filtration to meet their service demands. Orthogonal experiments are designed with four key process parameters: inner diameter of extrusion head, filling rate, extruded filament layer height/inner diameter of extrusion head and printing speed, then the influence mechanisms of different process parameters on the porosity and flexural strength are verified, and the correlation mathematical equation between the porosity and flexural strength is determined by the measurement and statistics of porosity and flexural strength of porous ceramics formed under different parameters. The experimental results show that the filling rate has the most significant effect on the porosity and flexural strength of porous alumina ceramics. And when the filling rate is small, the results of the span between adjacent extruded filaments is large, the formed macro-structure pore size and the porosity is large, however the flexural strength is small. When the inner diameter of the extrusion head is 0.41 mm, the filling rate is 50%, the extruded filament layer height/inner diameter of extrusion head is 60%, and the printing speed is 1 200 mm/min, the formed ceramic sample meets a high porosity of 66.32% ± 1.12% and a flexural strength of 10.54 MPa ± 0.32 MPa, and the correlation between porosity and flexural strength. Finally, the preparation of porous ceramic with high porosity and high flexural strength is achieved, and a certain reference for complex porous ceramic structures with high porosity and high strength fabricated by 3D printing technology can be provided by the results.

Key words: direct ink writing, porous alumina ceramic, porosity, flexural strength, correlation research