Effect of Al₂O₃ addition on texturing in a rotating strong magnetic field and densification of B₄C

The properties of ceramics can be improved by controlling the microstructure through texturing ceramics in a strong magnetic field. Fabricating dense boron carbide (B₄C) requires high temperature sintering, therefore sintering additives are often used in order to densify B₄C ceramics at lower temperatures. However, combined effect of texturing and sintering additives on densification of B₄C has not been made clear yet. Here we report the effect of alumina (Al₂O₃) sintering additive on texturing in a strong magnetic field and densification of B₄C. Texturing was performed by rotating superconducting magnet at 12 T during slip casting process. Electron backscatter diffraction (EBSD) was used to observed the texturing projection. {0001} plane is clearly oriented in the plane parallel to rotating magnetic field. In addition, Lotgering factor was also calculated as quantitatively evaluation of texturing degree. Results on densification showed that addition of Al₂O₃ successfully increased density of B₄C sintered by spark plasma sintering (SPS) at 1800^oC to 97.8%. Formation of aluminum borate (Al₅BO₉) as secondary phase was detected by X-Ray diffraction (XRD). It is considered that the generation of Al₅BO₉ assisted finer densification of B₄C ceramic. Textured B₄C sintered at 1700^oC by SPS without alumina addition exhibited the highest orientation of c-axis. Addition of alumina caused decrease in degree of orientation of c-axis.