Tuesday, May 02, 2023, 14:03

Two np-TiO2 spun fibrous pellets and 1 batch of fibre mats were wrapped with graphite foils and loaded into a target boat.

Sample will be heated to 1875C, similar to the previous process, see e-log ID#605 (TGHT: 440A/7.6V).

TGHT will be autoramped to 350 A and monitor the conditions before ramping up further.

Good vacuum: 3e-5 Torr

Bad vacuum: 5e-5 Torr

Omega slope: 1.08

In the previous process (ID#605), Ta-foil was inserted at both ends of the tubes to hold the sample together. However, it was observed that the out-gassing of the material reacted with the Ta-foil, causing issues. Therefore, it's decided not to cover the ends with Ta-foil, and the sensor is now looking at the graphite foil. It had previously determined the slope for SiC material set for its emissivity, but need to note any errors that may have arisen due to the change in the sample setup.

See attachment#1 for sample setup - note that Omega sensor is slightly looking at the edge of the Ta-boat tube. 

Initiate autoramp: 1 A/min

Chamber has been pumped down below 5.6e-6 Torr.

 Tuesday, May 02, 2023, 15:31

Vacuum spike TGHT at 75A, auto-ramping down kicked in.

 Wednesday, May 03, 2023, 12:18Thursday, May 04, 2023, 15:16

TGHT has been holding at 350A/5.7V (1995W) for almost 2hrs, temp is reading at 1368C - 232C lower than the previous process (ID#605) with TGHT = 348/5.8V (2018W).

Pressure started to come down around 344A/5.5V, temp 1331C - see attachment #2.

Current status overall view - see attachment #3

Continue to ramp up t0 440A at 1A/min and monitor.

 Wednesday, May 03, 2023, 14:47

TGHT reached 440A/7.5V, temp reading at 1672C.  Pressure is coming down, currently at 1.8e-6 Torr.  Will keep at this setting overnight and will check the Omega/emmissivity to confirm the temperature.

 Thursday, May 04, 2023, 10:54

Eractic vacuum spikes started just over 3 hrs ago.  Temp at 1681 C; TGHT has been stable at 440A/7.6V. Pressure ranging between 5.0e-7 to 1.5 e-6 and gradually decreasing, see attachment #4. 

Will perform the omega/emmissivity measurement.

 Thursday, May 04, 2023, 15:16

Temperature was checked with the digital and analogue pyrometers. 

With the analogue pyrometer on the Ta-container (left end, top surface), measured temp = 1360 C, with e=0.22, correction + 200 C => 1560 C

With the Omega pyrometer (right end), 1-color mode with e= 0.22, temp = 1585 C. 

Setting Omega pyrometer to 2-color mode with e= 0.99 temp = 1516 C --  this is in agreement with the measurements for Ta.  Note that the pyrometer is looking at some part of the Ta container which is not covered by the sample wrapped with the graphite foil (see attachment #5). 

From e-log#596, temp was reported at 1520 C (slope at 0.99) with a Ta-foil at the end of the tube, but from e-log#605, temp was reported at 1864 C (slope at 0.99) - possibly an error occurred during that time.

In conclusion, the temp should be at 1530 C +/- 10C with TGHT = 440A/7.7V (3388W).

 Thursday, May 04, 2023, 15:43

Vacuum spikes continue every 30 min lasting for 10 min. 

Tapped down TGHT to 430A/7.5V, temp reading at 1500 C.  Will monitor if any improvement with the vacuum.

 Friday, May 05, 2023, 09:34

Vacuum spikes continue to happen; see attachment #6 for the striptool overview.

Lower TGHT to 420A/7.3V, temp = 1480 C.

 Friday, May 05, 2023, 10:10

Vacuum spikes continue every 20-30 min lasting for 10 min. 

Lower TGHT to 410A/7.1V, temp = 1450 C

 Friday, May 05, 2023, 11:25

Vacuum spikes continue,

Lower TGHT to 400A/6.93V, temp = 1433 C

 Friday, May 05, 2023, 12:20

Vacuum spikes - lower TGHT to 390A/6.7V, temp at 1407C

Friday, May 05, 2023, 13:19

Vacuum spikes - lower TGHT to 380A/6.5V, temp at 1388C

Friday, May 05, 2023, 13:47

Vacuum spikes - lower TGHT to 370A/6.3V, temp at1373 C

Friday, May 05, 2023, 14:16

Vacuum spikes - lower TGHT 360A/6.1V, temp at 1348 C

Friday, May 05, 2023, 15:11

Vacuum spikes - lower TGHT 350A/5.9V, temp at 1308 C

Friday, May 05, 2023, 16:34

Vacuum spikes - lower TGHT 340A/5.7V, temp at 1371 C

Friday, May 05, 2023, 16:56

Vacuum spikes continue; container possibly broken.

Slow ramp down TGHT at -0.5A/min to see when the vacuum spikes would stop.

 Monday, May 08, 2023, 09:54

TGHT was ramped down over the weekend.  Chamber was kept under vacuum and vacuum continued to spike; suspecting problem with the gauge?! see attachment &7 for an over view.

Will take out the samples for exam.