Fabrication of textured B4C ceramics with oriented tubal pores by strong magnetic field-assisted colloidal processing

Abstract

Highly structure-controlled B4C ceramics were prepared via strong magnetic field-assisted slip casting of a slurry, containing B4C base particles and pore-forming agents with a fiber shape. To achieve gas release at a lower porosity for maintaining its mechanical strength, these B4C ceramics had a structure in which a large number of oriented tubal pores were dispersed in a crystallographically-aligned and dense B4C matrix phase. The B4C microstructure, such as structuration and orientation degree distributions of the B4C grains and tubal pores, was characterized by SEM observation, EBSD analysis, and X-ray CT. Among the investigations, it was found that the oxidic impurities, as an inhibitor of sintering, which existed on the B4C surface, can be removed by ethylation and azeotropy due to an ethanol treatment followed by vacuum drying. Thus, an ethanol treatment of a green compact before sintering was significantly effective for the fabrication of the B4C ceramics, including the microstructure that coexisted with a dense matrix phase with tubal pores. The resultant ceramic specimens showed the remarkable three-point bending strength of 459−554 MPa, which is two times higher when compared to conventional B4C pellets with a similar porosity.