Dual gradient direct ink writing for formation of kaolinite ceramic functionally graded materials

Abstract

Direct ink writing (DIW) technique has emerged as a powerful tool to create specific functionally graded materials (FGMs) products with macroscopic and microscopic porous architectures and mechanical properties. In order to explore the DIW process control method of ceramic composite FGMs, several additives (e.g., polysorbate, liquid paraffin and water) were mixed with kaolinite and barite powders to print the gradient materials with difference in both material compositions and structures. A stable ceramic slurry with a viscosity of 2.66–3.66 GP s at 5 MPa atmospheric pressure has been formulated by uniformly mixing 2 μm and 10 μm particles. Besides, the optimized flow rate of 150 mml/s and thickness of 0.5 mm were well proved to obtain good stacking of the slurry, whereas, the change of velocity shows little effect on the forming quality. The meso/macro pores of the gradient component can be achieved by adjusting the printing and sintering processes. The dual-extrusion DIW method presented here is versatile to be adapted to a wide range of biomimetic ceramic materials for the fabrication of FGMs objects with unprecedented properties.