Preparation of unidirectional porous AlN ceramics via the combination of freeze casting and combustion synthesis

Unidirectional porous AlN ceramics(UP-AlNs)have attracted great attention for their wide applications in catalyst supports,filters and composite reinforcements.However,traditional fabrication processes usually require high temperature and long production cycle.Herein,UP-AlNs were successfully fabricated via the combination of tertiary butyl alcohol(TBA)-based freeze casting and combustion synthesis route using Al and AlN powders as raw materials.The microstructure,open porosity,thermal conductivity and compressive strength of UP-AlNs can be manipulated by synergistically regulating the AlN diluent content and Al/AlN solid loading of the freezing slurries.The optimal UP-AlNs exhibited controllable structure wavelength(λ)and open porosity in a wide range of 21.1-47.1μm and 54.2%-86.0%,respectively.In addition,the corresponding products also possessed anisotropic thermal conductivity and compressive strength.This novel route for the fabrication of UP-AlNs has the advantages of low cost,energy-saving and high efficiency,which shows significant promise for industrial applications.