I want to add polyvinyl alcohol (PVA) to ZrO2 Y2O3 powder in order to make it more coherent.
How much PVA can I add to the powder and how can I mix them together? Can I use a ball milling machine for mixing them?
Also, how can I remove this binder before sintering?
Actually estimation of amount of PVA to mix with the Powder, become Little bit difficult some time , even if get excess , better to optimize. We use drop by drop addition, 2-3 drops to 10 gm powder should be sufficient, but for ZrO2 in large volume, I dont know. .So you can start with 1-2 drop/10gm and see the result.
As far as mixing is concerned, in our samples we just add the PVA and grind the mixure in Mortal pastle (just) before pelletization and sinter. usually sintering temperature remains more than 700 oC , Thus removal of binder is completed while sintering, itself.
About ball milling, we have not tried. If it is High energy ball milling, i doubt for mixing as internal pressure and energy is so high that even many time calcination is not require, how binder will be effectively remains for the purpose of binding. I logically can not digest.
Initially the PVA solution was prepared from amount of PVA powder was added to certain volume of distilled water. The mixture was heated at 100°C and stirred vigorously until the PVA was dissolved completely in the water. This took about one hour. Then the solution was cooled down to room temperature. The PVA solution was then added to the mixture of Al2O3-YSZ and mixed with an electric stirrer to form homogenous suspension. The slurry was stirred at 150 rpm for 1hr. Separately, (10-20) balls of zirconia were included to the slurry and it was then placed on a roller. The balls were 10-20 mm in diameter and the porcelain ball mill jar was 2-4 liter in volume. The slurry was milled and mixed for ~24hr. During the milling mixing, the materials were blended and the particle sizes of the ceramic composite powders would be reduced. For more information you can download my article as follows:
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only thing that i would suggest beside of above mentioned is the heating rate, especially if you want to sintering cubes/bars with "1-2 drop/10gm" , is better to heat till 100 or 150ºC with 3 ºc/min and then dwell around 1 hour then go up with any other rate that is suitable for you. by this you will avoid cracking the samples by giving time to the resulted CO2 leaving the samples.
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