Densification of porous Al2O3-Al4B2O9 ceramic composites fabricated by SLS process

Alumina-aluminum borate (2Al2O3 · B2O3) composites were fabricated by firing at 900° for 6 h of green selective laser sintering (SLS) parts obtained from alumina-25 wt% boron oxide powder blends. The resulting composites were partially densified by using the infiltration technique. Between the two infiltrants selected, the performance of colloidal silica as an infiltrant was found to be better by the evaluation in terms of density and bend strength of the composites. This was due to the formation of mullite (3Al2O3 · 2SiO2). The maximum density of the composite after infiltration with colloidal silica and firing was about 75% of theoretical density and the maximum bend strength was increased from 8 MPa to around 33 MPa. The infiltration with chromic acid into this composite yielded a solid solution of Al2O3-Cr2O3 whose density was about 80% of the theoretical density and the bend strength was around 15 MPa.