Direct ink writing of dense alumina ceramics prepared by rapid sintering

Direct ink writing, as one kind of 3D printing technology, can produce alumina ceramics with complex shapes that are difficult to be obtained by conventional technology. However, how to quickly and efficiently produce dense and high-strength alumina ceramics by directing ink writing remains a challenge. In this work, a simple formulation of alumina inks containing trace amounts of organic additives (including 0.54 wt% dispersants and 0.9 wt% binders) was applied to prepare dense ceramics with various complex structures. The dispersants activate alumina particles through electrostatic repulsion and spatial site resistance effects, which can help alumina inks with a high mass fraction show the excellent printability. In addition, sintering aids significantly promote densification of alumina ceramics and reduce sintering temperature by introducing lattice defects and forming liquid phases. Due to the trace organics in the green bodies and low sintering temperature, a rapid temperature rise and organic burnout can be adopted to shorten debinding and sintering time and improve productivity. This work provides a new additive manufacturing idea for simple and efficient preparation of dense alumina ceramics with high mechanical properties and complex structures.