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9114 Furnace Fixed Point Cell Installation, Gradient Test, and Freezing Plateau Procedures

Cell Installation:

1. Put on clean cotton or powder free rubber gloves to avoid oil contamination of the cell.

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2. Remove the Fixed-Point Cell from carrying crate and plastic sleeve.
3. Place in a vertical support system.

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4. Clean the quartz or metal cell with Reagent Alcohol 95% purity or higher to remove any dust or oils that may be on the cell.
5. Put it back in the vertical holding stand.

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6. Peel off a piece of insulation that is about 0.25” thick from and place it in the re entrant well to provide cushion when the probes are inserted and prevent from damaging the cell and probe.

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7. Using a quartz rod move the insulation to the bottom of the well.

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8. Clean the cell basket with Reagent Alcohol 95% purity or higher.

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9. Place 1” thick piece of insulation at the bottom of the cell basket.

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10. Use the quartz rod to verify the insulation is at the bottom of the basket and sitting flat.

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11. Cut an 8.5 x 11” (21.5 x 28 cms) piece of paper in half across the width of the paper and roll the paper
lengthwise to place it in the basket.

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12. Hold the basket horizontally and slide the cell into the basket, and push with your finger until cell reaches the bottom of the basket.
13. Gently remove paper and return cell and basket to stand position.

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14. Place ½” (1.3 cm) thick piece of insulation on top of the cell. Ensure the hole in the center of the insulation piece is centered over the cell and an SPRT or glass rod can easily be inserted through it.
Important note: The thickness of the bottom and top insulation pieces are approximate and may need to be adjusted to work with different cell models to ensure the basket lid will fit.

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15. Place the basket top PN# 2810041 on top of the basket and using the hex key lock it into place by turning the set screw (one on each side) counterclockwise until it is almost at the same level as the pin.

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16. Screw the cell basket removal tool into the basket top, and then hold with one hand the basket and the cell basket removal tool with the other hand gently proceed to place the basket into the 9114’s well.

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17. Place 1” (2.54 cm) thick piece of insulation on top of the basket. Finally place the heat reflector on top of the insulation. Ensure the heat reflector sits on top of the furnace. Adjust insulation thickness if needed. Insert a glass rod or thermometer probe through the assembly to check alignment of the insulation pieces. The rod should be easy to insert and remove without catching or binding up.

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Gradient Test Procedure:

With the cell installed in the furnace, ramp the furnace up to about 5.0 below the melting point of the cell with a scan rate of about 2.0℃/min . For example, Aluminum melts at 660.323 so set the furnace to 655°C.

1. Move the SPRT from the preheat well to the cell. Then using a Lab Stand and with the SPRT fully inserted into the cell, place the lab stand clamp around the SPRT so that the handle of the SPRT is resting upon the clamp. Do not tighten the clamp onto the SPRT or handle . The SPRT should be able to move freely in the clamp. Mark the top of the lab stand arm.

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2. Using a ruler and marker, mark the lab stand at 2 cm intervals for 1 0 cms.

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3. Using a weight to hold the lab stand steady and having the SPRT sitting at the bottom of the fixed point cell to start measurement from the bottom of the cell.

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4. For the first measurement, allow SPRT to equilibrate approximately 30 minutes and take 20 samples and record the average of the readings.
5. After taking the reading, carefully raise the SPRT to the next line on the stand. Wait for about 10 minutes until the SPRT equilibrates at the new position and record the reading.

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6. Repeat the steps until the SPRT reaches the top mark position.
7. Repeat the testing downwards from the top mark position by dropping the SPRT every 2.0 cm until it reaches the bottom of the cell. Each time after changing the position of the SPRT, should wait at least 10 minutes till the SPRT equilibrates in the cell.
8. Calculate the average value of temperature at each testing point by averaging the two readings from the two directions testing (upwards testing from the bottom of the cell to the top and the downwards testing from the top to the bottom of the cell). 9. If the difference between the maximum reading and the minimum reading is in excess of 100 mK (recommended) the furnace control zones ( top or bottom heater ) must be adjusted. Adjust the temperature to one zone at a time, this will allow to see the effects of the adjustment and allow for a more accurate zone temperature adjustment. Adjusting can be repeated if needed.

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10. After adjusting the furnace top or bottom heater, wait for at least 2 hours till the furnace reaches equilibrium with the new parameters before taking new adjustment. Adjustments of the controller parameters are different for different furnace at different temperature points. A few times of trail may be
needed in order to get a good vertical temperature gradient.
11. The temperature at the bottom of the cell should be lower than that at the top to avoid breakage of the fixed point cells because the top of the cell should melt first than the bottom to allow expansion of the melted metal. We recommend the temperature of the bottom to be 30-100 mK colder than the top.

Freezing Plateau Procedure:

All freezing plateaus except Tin are realized in a similar way. After the gradient test the furnaces should still be sitting at 5℃ below the freezing point, and the monitor SPRT still inserted in the fixed point cell. Or, if the user is only going to perform the freezing plateau at this time the monitor SPRT should be inserted in the preheat well.
In order to obtain a good freezing plateau, the furnace’s display offset should be calibrated first. The
calibration procedure of the furnace controller display offset can be found in the 9114 user’s guide (Section 8: Furnace Calibration in the User’s Guide of 9114 furnace), and we recommend to only adjust the R0 if the furnace is going to be used at one temperature point only.
Indium, Zinc and Aluminum Freezing Plateau:
1. Set the temperature of the furnace about 3℃ higher than the freezing point at the scan rate of 0.3°C/min. Leave the cell in the furnace for overnight to fully melt the cell.
2. The next morning decrease the temperature of the furnace to 3°C below the plateau temperature at the
scan rate of 0.1°C/min.

3. Insert the monitor SPRT from the preheat well to the fixed point cell. Supercool occurs when the temperature of the metal decreases to less than the freezing point right before nucleation happens. The
amounts of supercool varies from metal to metal in fixed point cells. Watch the readout and wait till
recalescence* happens. After recalescence occurs, remove the monitor SPRT from the cell and insert it
in the preheat well, and immediately insert a room temperature quartz tubing or rod into the cell for induction of nucleation* for 2 minutes. Two minutes later, insert another room temperature quartz tubing or rod into the cell for induction for 2 minutes. Make sure to clean the quartz rods or tubing using reagent alcohol before inserting them in the cell. The length of recalescence can be between 0.1 and 2°C.

Recalescence*: A sudden temperature increase in supercooling molten metal because of burst of nucleation.
Nucleation*: Is the initial process to form crystals from the molten metal when the metal begins to solidify.

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4. After induction, set the maintenance temperature to 0.5°C below the plateau temperature with the scan rate of 0.1°C/min.
5. It is recommended to wait for 2 hours till the freezing plateau fully stabilizes before starting testing or calibration.
6. After waiting for 2 hours, the test SPRT (DUT*) can be inserted into the fixed point cell. Wait about 20 minutes till the DUT completely stabilizes in the cell and then start testing or calibration.
7. After the DUT probe is done, insert another DUT probe into the cell for testing or calibration.
8. The freezing plateau can last up to 10-15 hours. Multi DUT probes can be tested or calibrated in one freezing plateau.

DUT*: Device under test

9. After testing is done or the freezing plateau is over, proceed to freeze the cell. For the Al cell, set the furnace temperature to 450C with a scan rate of 1.5°C/min to avoid breakage of Al cell. When the furnace reaches 450C, the SPRT can be taken out of the furnace. For the Zinc and Indium cells, drop the furnace to 5C below the freezing point at the scan rate of 2.5°C/min.

Tin Freezing Plateau:
1. Set the furnace to 3 above the freezing point, and it will take 4-6 hours to completely melt the Tin metal. It is recommended to leave it overnight for fully melting the tin cell. It is also recommended to set the cutout of the furnace to 250°C. 
2. Next day set the furnace to 3°C below the Tin freezing point to initiate the freeze.
3. When the furnace temperature reaches the freezing point of tin, cool the cell in place with compressed air for a few minutes (normally 3-6 minutes) till recalescence occurs. A gas port is provided on the rear of the furnace, and the gas flow is adjusted to about 45 CFH (cubic feet per hour).
4. After recalescence occurs, insert a quartz tubing or rod from room temperature into the cell for 2 minutes for induction. Two minutes later, insert another room temperature quartz tubing or rod into the cell for induction for 2 minutes.

5. After induction, set the furnace temperature at 0.5°C below the plateau temperature with a scan rate of 0.1°C/min.
6. The test SPRTs (DUTs) should be placed into the preheat wells while the monitor SPRT is coming to equilibrium.
7. Watch the monitor SPRT till the plateau reaches fully equilibrium and stable. It is recommended to wait for 2 hours before starting testing or calibration.
8. The freezing plateau could last up to 20 hours if the steps described on this procedure is followed.
9. Move the first test SPRT (DUT) from the preheat well to the fixed point cell, and the DUT will reach equilibrium in about 20 minutes and then proceed to take measurements.
10. Continue to cycle each test SPRT (DUT) between the preheat well and fixed point
cell until all DUTs are measured.

11. After the last DUT is measured move the monitor SPRT from the preheat well to the fixed point cell, and the reading of the temperature should be within the desired level of agreement with the initial reading.
12. After the end of the freezing plateau proceed to freeze the cell: Drop the furnace to 5C below the freezing point at the scan rate of 2.5°C/min.

 

 

 

 

 

 

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