Indentation hardness of biomorphic SiC

Vickers hardness (HV) measurements have been performed in SiC samples fabricated from various wood precursors (pine, beech, and eucalyptus): bioSiC. It was found that hardness was highly dependent on starting wood structure. The arrangement of wood cells determined the final microstructure of the bioSiC (pores distribution and SiC/Si ratio). Two well-differentiated regions could be observed in all samples; a fully dense area corresponding to the wood growth rings and another that was mostly porous (porosity volume fraction between 30% and 50%). Indents in dense regions revealed that hardness increased with decreasing SiC/Si ratio. Hardness values were compared with those of commercial reaction-bonded SiC and hot-pressed SiC. HV values in the porous region could be well described using a Ryskevitch-type equation.