Effect of pretreatment process of B₄C powder on the surface properties and freeze-cast porous ceramics

The boron oxide and impurities existing on the surface of B₄C powder are detrimental to the sintering of the green body, greatly limiting its application. Here, we utilize three powder pretreatment methods, including washing powder in acid solution, alkali solution and ethanol solution, to solve this problem. Furthermore, the produced freeze-cast porous B₄C ceramics with unidirectionally aligned pore channels are studied in terms of the sinterability, pore morphology, microstructure and mechanical properties. The powder pretreatments contribute to the remove of boron oxide and impurities as well as the acceleration of densification process of the porous ceramics. The decreased porosity, wavelength and lamellar thickness, and high pore connectivity are the main reasons for the enhanced mechanical properties especially in the direction perpendicular to the freezing. By comparison, the purification with acid solution is established as the optimal technique for powder pretreatment. The research confirms that the pretreatment of B₄C powder is essential for the removal of boron oxide and impurities to improve performance, thereby widening the application scopes of materials.