Effect of powders on aluminum nitride components fabricated by PIM

Powder selection is essential to the success of powder injection molding (PIM). In this study, aluminum nitride (AlN) powder synthesized through carbon-thermal (C-R) reduction and direct nitridation (DN) were used as the raw material. These two kinds of powder were mixed with wax-based binder and the rheological properties of AlN feedstocks were examined. Then the green parts were fabricated by powder injection molding and sintered after solvent and thermal debinding. Finally, the appearance, microstructure and thermal conductivity of sintered AlN were inspected. It was found that the C-R powder has higher critical solid loading (60 vol%) than DN powder (58 vol%). Feedstocks viscosity decreased when the shear rate increased, indicating the presence of non-Newtonian pseudoplastic flow. The C-R powder also has better rheology properties with lower viscosity, higher melt flow rate, higher shear thinning, and higher activation energy. As for the performance after short-time sintering, the thermal conductivity of C-R AlN is 183 W·m−1·k−1 while the value of DN AlN is 130 W·m−1·k−1, and the bending strength of C-R AlN is 363 MPa while that of DN AlN is only 320 MPa.