Study On Properties And Preparation Of Porous Al₂O₃ Ceramics

Porous ceramics were prepared using low-temperature combustion synthesized powders as starting materials.Efirect of Zr0₂,MgO,starch fuel,ignition temperature,Al³⁺concentration in precursor solutions,sintering temperatures on microstructures,open porosity,Vickers hardness,pore size distribution of the porous ceramics were investigated.?1?Porous alumina ceramics were fabricated using powders as starting materials,which were synthesized using sol combustiono Effects of Zr0₂,MgO,starch fuel,ignition temperature on properties of the porous ceramics were studied.The experimental results showed that open porosity of the porous ceramics first increased and then decreased as the addition of Zr0₂?3 mol%YZO3?rose from 0 to 20 mol%.The sample with addition of 15 mol%Zr0₂?3 mol%Y2O3?had the larger open porosity,much smaller average size of Al2O3 grains and markedly thicker bonding neck than other specimens,which were believed to be mainly responsible for its higher Vickers hardness.Starch fuel could significantly affect open porosity of the porous ceramics.Open porosity of porous ceramics first increased and then decreased with starch?The addition was 0,15,25,35,45,55 wt.%,respectively?added to the fuels.The specimen with addition of 35 wt.%starch showed the larger open porosity.The porous ceramics with additional starch as fuel exhibited much smaller average size of Al2O3 grains and markedly thicker bonding neck,which were mainly responsible for its higher Vickers hardness.Addition of MgO?1,2,3mol%?had no marked influence on open porosity of the porous ceramics,but could markedly promote Vickers hardness owing to the as-resulted thicker bonding neck.?2?Porous alumina nano-ceramics was successfully prepared using the powders produced via low-temperature combustion synthesis,followed by oxidation by H₂O₂.The experimental results showed that as the Al³⁺ concentration?0.75,1.0,1.5,2.0 mol/L respectively?in precursor solutions increased,the sintered porous ceramics exhibited larger open porosity,wider pore size distribution,larger peak pore size in pore size distribution,and thus lower Vickers hardness.When the Al³⁺ concentration in precursor solutions was 2.0 mol/L,and as the sintering temperature increased from 800? to 1200 C,open porosity of the as-prepared porous ceramics decreased,while the average Al2O3 grain size increased and the inter-granular combination decreased,which resulted in lower Vickers hardness.?3?Filter paper was first imprinted in the precursor solutions(Concentration of Al³⁺is 1 mol/L),followed by ignition to combustion synthesize Al2O3-Zr0₂ powders.Then porous Al2O3-Zr0₂ ceramic was fabricated from the powders,which was pressed and then sintered at 1000?.As the ignition temperature rose from 300 ? to 600 ?,open porosity of the porous ceramics first decreased and then increased;while the Vickers hardness first increased and then decreased.When Ignited at 400 ?,the porous Al2O3-Zr0₂ exhibited lower open porosity,higher Vickers hardness than those samples ignited at 300,500 or 600 ?.