The methods of synthesis ZrO2-Al2O3 composite beads are:
Step 1: Preparing solution
Weighing zirconium oxychloride, aluminum chloride, and yttrium chloride by certain proportion, the proportions of zirconium oxychloride and aluminum chloride component are decided by the final products needed to be prepared; the proportion of yttrium oxide in the composite material is 5.5%. Then mixing them with deionized water and stirring the mixture to fully dissolve.
Step 2: Adding ammonia
Adding ammonia into the solution prepared in step 1, the concentration of ammonia used in this step should be 5–7%, and it must be added slowly. The final PH value of the solution should be up to 8.5-9, then waiting 30 minutes for the solution subsiding.
Step 3: Removing chlorine
Handling the sediment prepared in step 2 with filter-press method, after then mixing it with deionized water and well stirring. To fully remove the chlorine, this step needs to be repeated 3–4 times.
Step 4: Sediment dissolution
Preparing the zirconium oxychloride solution, heating to 80 ℃, then placing the sediment (prepared in step 3) into solution, stirring until fully dissolve. The weight of zirconium oxychloride used in this step should be about half of the step 1’s.
Step 5: Adding organic solvent
Adding some binder and defoamer into the solution (prepared in step 4), stirring the mixture to fully combine. The weight of binder used in this step should be about 1/50, and the defoamer should be about 1/100 of the dissolution.
Step 6: Titration
Placing the solution (prepared in step 5) into titration equipment, dropping it into ammonia (The concentration of ammonia used here should be about 10%). Before dropping, we need to pour some oil (n-Alkanes) into the ammonia, about 2 mm on the surface of ammonia. The diameter of the ZrO2-Al2O3 composite beads can be controlled by adjusting the port size of titration equipment.
Step 7: Cleaning beads
Placing the beads into teflon grinding can, adding some ammonia in it. Then placing the can into planetary mill and rotating. The concentration of ammonia used in this step should be about 10%, and the rotating speed of planetary mill should be 100–150 RPM. This step needs to be repeated 3–4 times.
Step 8: Baking beads
Placing the beads (prepared in step 7) into oven and baking. The temperature of the oven should be 120 ℃.
Step 9: Discharging organic compound
Placing the beads (prepared in step 8) into debinding furnace and discharging. The rising time-temperature curve of debinding furnace should be: 2 hours to 160 ℃, keeping 1 hour, 25 hours to 600 ℃, and keeping 2 hours.
Step 10: Sintering
Placing the beads (prepared in step 9) into sintering furnace. The rising time-temperature curve of sintering furnace should be: 11 hours to 1250 ℃, and coolling naturally to room temperature.