Hello, I am preparing a germanate glass, which is being melted in a alumina crucible (1300ºC). However, after the cooling I am having problems to remove the glass from the crucible. Seems that both materials are bonded. Do you recommend some spray, or any kind of material that could be used as a layer, and so could make easier the removal of the glass from the crucible? Or any other choice to make the glass removable.
PS: I need the entire sheet of glass, not broken pieces.
Normally glasses will melt in the crucible and then cast into graphite molds. These graphite molds with glass are then annealed in the oven at 550-600 ° C and slowly cooled. Glass remains a piece and does not adhere to graphite.
Theoretically, you can glasses in graphite crucible melt under protective atmosphere and then slowly to cool with the furnace, but it does not work with all glasses.
Because of the high viscosity of this glass I couldn't cast in a mold, I guess even if I try to cast most of the sample will remain in the crucible. That is one of the reasons why I am cooling in the crucible.
I am thinking in try to cover the crucible with ceramic paper or shelf primer. Do you think it will work?
The budget is not enough for a platinum one. Are there other choices, not so expensive?
Use a sheet of expanded graphite (Grafoil from Ucar or Papyex from Mersen) that you can form to match the shape of your crucible. As such kind of sheet can be heated at very high temperature and is very flexible with zero permeability to liquids, it should work. However, be careful that such material needs to be protected from air, otherwise it will be oxidised above 400°C.
Alain
- Badges
- Science topic
- Similar topics
- Engineering
- Materials Engineering