CHE 450G: Practical Inorganic Chemistry

U of KY Dept of Chemistry

Using the Pneumatic Pellet Press

This handout describes how to use the pneumatic pellet press in used in the solid state synthesis of YBa2Cu3O7.

Instructions

  1. Prepare your sample. Grind your material into a fine powder using a mortar and pestle.

  2. The die pieces that you will use are shown below. Start from the left. Put part B into part A with the raised surface facing up. Now put the die body C into A. Finally, put the lower die D into A with the smoothest side facing up. Make sure that part D slides all the way to the bottom of the hole.

    the pieces

  3. Pour your powder into the die. You will want to make pellets that are no more than 10 mm thick. A typical preparation of synthesis of YBa2Cu3O7 will give you 2 pellets of approximately equal size.

  4. Put the die piston E into the die body with the smoothest face down. Be careful not to blow your powder out. Push the piston down until it stops.

  5. Place the assembled apparatus into the pellet press. If the platform is too high, loosen the knob (i.e. turn it counterclockwise) located on the front of the press. Do not loosen this all the way or it will fall out and spill a quart of hydraulic oil on the bench. CAUTION Align the apparatus in the exact middle of the press, with the top of the dies centered under the metal knob that projects downward from the top plate of the press.

    pressing the pellet

  6. Double check that the die assembly is centered and that the knob on the front of the press is firmly closed (do not overtighten). Pump the handle to raise the lower platform. There is a movable black line on the pressure dial -- this is a high pressure cutout. Pump the press until you have 20,000 psi of pressure and let your pellet sit at that pressure for a minute or two. Use extreme caution when pressing pellets. If the die is misaligned, it could shoot across the room with enough force to injure someone.

  7. When you are done, loosen the front knob to release the pressure and lower the platform. If it doesn't move on its own then press down on the platform gently. Retighten the knob.

  8. Remove the die containing your pellet and the piston. Turn it upside down. Find the cylindrical aluminum piece and place this on top. Put the whole assembly back into the press and pump the handle to force the pellet out (this should not generate appreciable pressure on the dial). Be sure to hold onto the body of the die as you do this or your pellet could fall out unexpectedly.

    removing the pellet

  9. Your pellet should be now be free from the die. Enjoy!

  10. CLEAN EVERYTHING THOROUGHLY WHEN YOU ARE FINISHED. Use cotton-tipped applicators and/or KimWipes to clean all residue from the die components. Do not use acid. Avoid scraping and scratching which could damage the die walls or faces.
FYI: A new, bare-bones pellet press starts at approximately $1,300 and better models cost around $3,000. A new set of evacuable metal dies like the ones you are using cost approximately $350, so don't abuse them (alas, someone did last semester...that's $350 less we could spend on other needed items)! Dies and presses are available commercially from Graseby-Specac, International Crystal Laboratories and other vendors.

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