I am looking for a suitable binder for binding my ferrite powders, preferably organic binder that would decompose while sintering at around 500 degree Celsius.
Previously I have used PVA as binder, however after molding and drying the sample at around 500 degree Celsius, the sample did not bind properly and while holding the sample, the powders usually stick to the hand and would break very easily even when pressed mildly with hand.
when preparing a binder like PVA , one has to make 10% solution in water and heat it slowly. few drops of PVA can be added to ferrite powder and grind until it is almost uniformly mixed. no need to add too much. once you think the amount of PVA is sufficient then press powder into pellet or toroid shape, apply enough pressure.
Then you will get pellet having good density and it will not break unless we don't handle it properly
You can also try to use PVA or polyvinyl butyral, believe the sinter temperature to be using is low, you should use a higher temperature. Could make an initial ramp up to 500 degrees to 5 degrees per minute and then a slower ramp 3 degrees per min up to a temperature of 800 degrees for 2 hours. I think that your sample will be with a good density.
Yes, I agree with Dr. Chaitanya Varma. You apply a pressure of about 5-7 tons/cm2 for 5 minutes, then pellet definitely not crack/break.
Donot use PVA directly. Add some water in PVA and make thin. Use layer by layer first powder, then PVA solution again powder and then press ( 5tons), go for high temperature (above 700 deg) calcination for two hrs and slowly cooled to room temperature. Try this
Most common binder is PVA.
Just dilute the PVA into water for few minutes, once you feel like gum, then add one or two drops into either ferrite or ferroelectric powder.
Yes. I definitely agree with Dr. Chaithnya Varma. The reason for cracks in the ceramic samples is not only the binder but excess application of pressure during pelletisation also leads to cracks. One more importanant condition is the heating rate of sintering and soaking rate. If these are properly maintained one would fairly good density. The usage of binders like PVA, PEG,
Considering wrought steels, a significant element in increasing strength is carbon, added as graphite. Copper is usually added for dimensional control purposes and to provide some solid solution strengthening. To enhance hardenability, the most commonly used additions have been nickel and molybdenum, as these elements do not form stable oxides at normal sintering temperatures.
Thank You all for your answers. I had tried most of the procedures that have been suggested. I used a 5% PVA solution and added dropwise to the ferrite while continuously grinding the same. After adding sufficient amount I pressed the powder in a die mold with a pressure of about 2.5 tons. And the pressed pellets were annealed at about 500 degree celsius. However the strength of the formed pellets were not too strong.
I require the pellets not only for characterization, but also for using it as an end product. Therefore I would like to get some suggestion regarding binders/hardeners that would provide me good strength and at the same time the added binders/hardeners should not affect my original composition(ferrite) properties.
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