Preparation Of ZrO₂ Ceramic By Gel-casting

In this paper, ZrO₂ power dispersion mechanism in the water by the test means of sedimentation test,FTIR analysis and Zeta potential analysis was discussed. The main material is ZrO₂ power, and monomer, crosslinker, initiator and catalysis separately are acrylamide, N-N methlene acrylamide bouble, N-N-N'-N'tetramethyl-ethylenediamine and ammonium persulfate, the gel-casting forming process of ZrO₂ ceramic materials was studied, its mechanical properties were characterized by means of rotary viscometer agent, universal testing machine, scanning electron microscopy and X-ray diffraction, the influence of different types and different dosage of dispersant on the rheological property of zirconia slurry was investigated, and factors such as solid content and sintering temperature which influencing mechanical properities of zirconia ceramic was also investigated. The experimental results show that:After several attempts of three dispersants, we find that a dispersant named TH-241 was the best. Zeta potential analysis showed that adding dispersant TH-241 would enable the ZrO₂ powder potential absolute value to 47.5mV, its higher than pure ZrO₂ powder's, can reach at 16.9 mV, and the powder was more evenly dispersed and stable. FTIR analysis showed that: after ZrO₂ powders adsorbed dispersant TH-241, no new group was emerged, and this belonged to physical adsorption. By comprehensive analysis, we know that ZrO₂ powder dispersed in water belongs to the electrostatic stabilization mechanism.Conducted on the slurry rheology analysis we found that when the dispersant added up to 2.8 wt.%, pH = 9 10, ZrO₂ solid phase volume fraction of 38 vol.%, the slurry viscosity of the smallest, in order to 560 MPa·s, less gas hole content and easy gel- casting; by changing the content of catalyst, initiator, the gel time of slurry can be adjust, by adding 0.135 ml add 0.033 g of catalyst in 25 ml slurry the initiator can control the gel-point to 3 min after added agents and catalysts, the time of injection molding was better, and body strength can reach to 21.27 MPa.The results of the tests after different solid-phase content of green and sintered at different temperature strength and toughness of the specimen showed that the solid-phase content has little influence on the body strength, material shrinkage rate lower with the solid-phase content increase, and higher with the sintering temperature rise; the relationship between bending strength, relative density and solid phase content was the curve "M" shape, it is caused by two pairs of related factors-porosity and solid phase content. When solid-phase content of 38 vol.% and the sintering temperature of 1600℃, ZrO₂ ceramic materials contraction rate was 27.27 %, and the relative density, flexural strength and fracture toughness values was the largest, respectively as 98.36 %, 921.34MPa and 11.49 MPa·m1/2.SEM fracture surface analysis shows that the source of the specimen fracture ZrO₂ ceramics began in the internal pores and defects, when the relative density was high, fracture surface was relatively rough, corresponding to a higher strength and toughness; when the relative density was low, fracture surface was smooth, corresponding to the lower strength and toughness; XRD test results show that when the specimen was loaded, the t→m phase transformation was happened at ZrO₂ ceramic materials crystalline form, and the ZrO₂ ceramic materials improve strength and toughness.