3D printing of Al₂O₃/Cu-O interpenetrating phase composite

Porous alumina preforms were fabricated by indirect 3D printing using a blend of alumina and dextrin as a precursor material. The bimodal granulate powder distribution with a bed density of 0.8 g/cm₃ was increased to 1.4 g/cm₃ by overprinting. The porosity of the sintered bodies was controlled by adjusting the printing liquid to precursor powder ratio in the range of 33-44 vol%. The green bodies exhibited bending strengths between 4 and 55 MPa. An isotropic linear shrinkage of ∼17% was obtained due to dextrin decomposition and Al₂O₃ sintering at 1600 °C. Post-pressureless infiltration of the sintered preforms with a Cu-O alloy at 1300 °C for 1.5 h led to the formation of a dense Al₂O ₃/Cu-O interpenetrating phase composite (IPC). X-ray analysis of the fabricated composites showed the presence of α-Al₂O ₃, Cu and Cu₂O. CuAl₂O₄ spinel was not observed at the grain boundaries during HRTEM examination. The Al ₂O₃/Cu-O interpenetrating phase composite revealed a fracture toughness of 5.5 ± 0.3 MPam_1/2 and a bending strength of 236 ± 32 MPa. In order to demonstrate technological capability of this approach, complex-shaped bodies were fabricated.