Aqueous tape casting of B4C ceramics

B4C green tapes are prepared by aqueous tape casting and a spark plasma sintering (SPS) process using polyethylenimine (PEI) as dispersant, hydroxypropyl methyl cellulose (HPMC) as binder and polyethylene glycol (PEG) as plasticiser. The influences of solid content, dispersant content, mass ratio of plasticiser to binder (R value) and milling time on the slurry viscosity are studied. The samples are characterised by means of hardness tester, universal testing machine and scanning electron microscopy. The results indicate that the solid content of B4C slurry achieves 47.5wt-% with milling time of 12h when the content of PEI, HPMC and PEG is 1.5, 5 and 5wt-%, respectively. The relative density of B4C ceramics subject to SPS at 1600 degrees C and 50MPa for 8min is up to 97.2%. The Vickers hardness, flexural strength and fracture toughness of B4C ceramics reach 36.5 +/- 0.7GPa, 510.3 +/- 19.4MPa and 5.04 +/- 0.29MPam(-1/2), respectively.