Study On Process And Properties Of BNNTs/B₄C Ceramic Composites By Aqueous Tape Casting

After BNNTs/B4C cast tapes were prepared by aqueous tape casting and hot pressed sintering, the BNNTs/B4C ceramic composites were achieved. The effect of the dispersibility of the B4C powers on dispersant and pH, the effect of the rheology of the slurry on binder, plasticizer and solid loading was studied. The optimum technology parameter for the kind and content of dispersant, the kind and content of binder, the ratio R of plasticizer and binder, ball-milling time, solids loading were defined by experiments. The BNNTS/B4C ceramic composites were achieved by hot pressed sintering. The effect of different sintering temperature on BNNTs/B4C ceramic composites microstructure and mechanical properties was studied.The dispersing performance of the B4C powers in the water was characterized by the viscosity of the slurry and the Zeta potential. The effect of the viscosity of the slurry on dispersant, solid loading and ball-milling time was studied. The effect of the Zeta potential on pH was researched. The result showed that the dispersibility of the slurry was best when use PEI as the dispersant and the content was 1.0wt%; the the viscosity of the slurry was increased with the solid loading increasing; when the ball-milling time was 10h, the the viscosity of the slurry was minimum and the dispersibility of the slurry was best.Based on the result above, tape casting slurry was prepared by different binders and the rheology was measured. The result showed that tape casting slurry of suit tape cast was achieved when the R was 1.0, PVA was used as binder and the content of PVA was 5.0wt%, the solid loading was 40wt%. Tape casting slurry of suit tape cast was achieve when the R was 0.6, DM767 was used as binder, the content of DM767 was 10wt% and the solid loading was 50wt%. Tape casting slurry suit tape cast was achieved when the R was 1.0, gelatin was used as binder, the content of gelatin was 7.0wt% and the solid loading was 45wt%.The cast films were achieved after the tape casting slurry went by removing bubble in vacuum environment and then tape casting. The cast film was characterized. Compared with DM767 and gelatin, PVA was a better kind of binder. BNNTs/B4C ceramic composites was achieved by the laminated and hot-pressed after the organics of cast films was removed. The effect of different sintering temperature on BNNTs/B4C ceramic composite microstructure and mechanical properties was studied. The result showed that the average grain size of samples was increased with the temperature rising. The relative density, the flexure strength, the breaking tenacity and the Vickers hardness was increased at first decreased then with the temperature rising. At 2000?.The relative density, the flexure strength, the breaking tenacity and the Vickers hardness was 98.6%, 506.8MPa.,6.43MPa·m1/2 and 39.1GPa respectively. This moment, the mechanical properties of BNNTs/B4C ceramic composites was best.