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

Abstract

The properties of ceramics can be improved by controlling the microstructure through texturing ceramics in a strong magnetic field. Fabricating dense boron carbide (B 4 C) requires high temperature sintering, therefore sintering additives are often used in order to densify B 4 C ceramics at lower temperatures. However, combined effect of texturing and sintering additives on densification of B 4 C has not been made clear yet. Here we report the effect of alumina (Al 2 O 3 ) sintering additive on texturing in a strong magnetic field and densification of B 4 C. 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 Al 2 O 3 successfully increased density of B 4 C sintered by spark plasma sintering (SPS) at 1800 o C to 97.8%. Formation of aluminum borate (Al 5 BO 9 ) as secondary phase was detected by X-Ray diffraction (XRD). It is considered that the generation of Al 5 BO 9 assisted finer densification of B 4 C ceramic. Textured B 4 C sintered at 1700 o C by SPS without alumina addition exhibited the highest orientation of c-axis. Addition of alumina caused decrease in degree of orientation of c-axis.