Polymer Derived Ceramics: Process

This page describes the process of converting a polymer structure into a ceramic structure by replication.

Safety[edit | edit source]

• All the chemical procedures must be done in chemical hood for primary engineering control.
• Disposable nitrile (neoprene + nitrile) gloves should be worn at all times while handling the chemicals.
• Lab coat (optionally with disposable sleeves) should be used.
• Unnecessary equipment and chemicals should be removed from them the chemical hood for better efficiency of the hood.
• The hood sash should be as low as possible while allowing yourself to perform the experiments, especially while weighing the powder, since the hood might be needed to be turned off to get rid of the vibrations)
• All the chemicals need to be stored in closed containers and designated storage spaces marked with appropriate labels.
• The solvents should only be dispensed inside the fume hood.

Chemical Waste[edit | edit source]

• The waste should be collected appropriate sized container.
• Use hazardous waste label for the waste containers.
• Spell out the solvent names in the container.
• Use EPA codes D001, F003, and D022.
• Throw in the 3D printed samples that might be wasted.
• "Request Waste Pick Up" when the container is full and/or project is done.

Chemicals required[edit | edit source]

Polymer structure to replicate (Polyurethane foam, 3D printed structure in our case)
Preceramic polymers

1. Durazane 1800 [Polysilazane] (yeilds SiCN)
2. Polyramic SPR - 036 [Polysiloxane] (Yields SiOC)
3. MK SILRES powder

Solvents

1. Acetone
2. 2-Propanol
3. Hexane
4. Toluene
5. Dimethyl Formamide (DMF)

Catalysts

1. Karstedt's catalyst Pt ~2% (diluted to 0.1% with p-xylene, depending on the requirement) for Durazane 1800 and SPR-036.

Storage[edit | edit source]

• Karstedt's Catalyst - Room temperature, cool and dry place.
• MK SILRES powder - Room temperature (max 34 degrees celcius), cool and dry place
• Durazane 1800 - Refrigerated
• Polyramic SPR - 036 - In freezer
• Solvents - in appropriately labeled chemical storage
• Use Parafilm to seal the Preceramic Polymers
• Take the chemicals out of the refrigerator 2 hours before use to avoid condensation of air when opened

Impregnation[edit | edit source]

Procedure (for PU foam)[edit | edit source]

• Step 1: Take Preceramic polymer (1:1 weight ratio to the PU foam).
• Step 2: Add acetone solvent (1/5th of the volume of the foam).
• Step 3: Add Pt catalyst(diluted to 0.1%) (amount = 100 uL for each 1g of the preceramic polymer).
• Step 4: Dip PU foam in the solution, squish it and dip again to make sure it is fully wet.
• Step 5: Let the PU foam dry for 24 hours.

Procedure for Durazane 1800 and SPR-036 (for 3D printed structures)[edit | edit source]

• Step 1: Take acetone (ratio 1:1 by weight with the precursor). (the total volume of the solution should be such that the 3d Printed structure should be fully immersed in the solution).
• Step 2: Mix Pt catalyst (0.1% dilution) (amount = 100 uL for each 1g of the preceramic polymer).
• Step 3: Immerse the 3D printed structure for 30 mins.
• Step 4: Add the preceramic polymer to the solution.
• Step 5: Keep it for 30-45 mins.
• Step 6: Take out the structure and dry it on open cell ceramic foam for 24 hours

Procedure of SILRES MK powder (for 3D printed structures)[edit | edit source]

The SILRES MK powder being solid has a little bit different from the other two chemicals.

• Magnetic stirrer is required for the mixing of the solution.
• The list of solvents and solubility of SILRES MK powder in them is as below

Solvent	Approximate Solubility of SILRES MK powder in the solvent
Acetone	30%
Isopropyl Alcohol (2- Propanol)	30-33%
Chloroform	40%
Hexane	45-50%
Toluene	Not tested
Dimethyl Formamide (DMF)	Not tested

• Step 1: Weigh the solvent and pour it into a beakeraccording to the solubility/ concentration mixture you want.
• Step 2: Weight the SILRES MK powder.
• Step 3: Start stirring vigorously the solvent with the help of magnetic stirrer.
• Step 4: Add the SILRES MK powder in very small amounts so that it does not coagulate.
• Step 5: After the solution is prepared immerse the 3D printed samples in the solution.
• Step 6: Keep the the solution aside for 30-45 minutes.
• Step 7: Take out the samples and dry them of an open cell ceramic foam for 24 hours.

Pyrolysis[edit | edit source]

Furnace specifications[edit | edit source]

Tubular furnace
Diameter = 10 cm, Length = 140 cm (minimum)
Maximum temperature = 1200 celcius
Inert gas environment (N2 or AR)

Process (PU foam)[edit | edit source]

• Step 1: Purge the furnace at room temperature for 5 hours with inert gas.
• Step 2: Heat from room temperature to 600 degrees at the rate 5 degrees/min .
• Step 3: Keep at 600 degrees for 30 mins.
• Step 4: Heat from 600 to 1200 degrees at the rate 10 degrees/min.
• Step 5: Keep at 1200 degrees for 1 hour.
• Step 6: Cool
• Gas flow at 400cc/min

Process 3D printed structures[edit | edit source]

• Step 1: Purge the furnace at room temperature for 5 hours with inert gas.
• Step 2: Heat from room temperature to 600 degrees at the rate 5 degrees/min .
• Step 3: Keep at a temperature above decomposition temperature of the polymer used to fully decompose the polymer. (This step can also be skipped in case of 3D printed structures)
• Step 4: Heat from 600 to 1200 degrees at the rate 10 degrees/min.
• Step 5: Keep at 1200 degrees for 1 hour.
• Step 6: Cool
• Gas flow at 400cc/min

Precautions[edit | edit source]

• Always keep the precursor bottles tightly sealed. Use parafilm for sealing.
• Take the chemicals out of the refrigerator 2 hours before use to avoid condensation of air when opened.
• Use a thermocouple to check, confirm and adjust the temperature on the furnace.
• Use Proper protective equipment such as Gas Mask, chemical handling gloves.