John Wong wrote:

Laura Lambert wrote: John Wong wrote: Laura Lambert wrote: John Wong wrote: Laura Lambert wrote:  Thursday, June 04, 2015, 9:07 Container was sprayed with TaC and let dry. Container has 3x Ta heat shields including center block. Container was loaded into EVAP2 yesterday and pumped down overnight. HS water valves were opened up this morning, no leaks detected. IGP1 = 4.6e-7 Torr. Tapped up manually to 40A. Waited ~25min, Vacuum stable. IGP1 = 5.0e-7 Torr. Initiating auto-ramp. TGHT will be ramped to reach 2000C  Friday, June 05, 2015, 10:01 IGP1 = 4.5e-7 Torr. TGHT = 313A, 4.47V OMEGA = 1444C Increasing ramping rate to 1.0A/min  Friday, June 05, 2015, 11:31 IGP1 = 1.2e-6 Torr. Increasing ramping rate to 2.0A/min    Friday, June 05, 2015, 12:01 TGHT reached to 465A/7.56V, temp is stable at 2000C. Current vac at 1.2e-6 Torr and coming down Cooling down process can be initiated after 4 hours.     Friday, June 05, 2015, 13:21 OMEGA = 1995C Increasing TGHT to 470A to achieve desired max temperature of 2000C Friday, June 05, 2015, 15:59 TGHT sat at max desired temperature of 2000C for ~4hrs. TGHT = 470A, 7.7V Initiating auto-cool at 1.0A/min.  Monday, June 08, 2015, 11:31 Vented in air and opened up this morning. Target container mostly sintered, two tiny patches near both ends not fully sintered. Will re-install and re-sinter next week as another container with priority needs to be sintered first.  Tuesday, June 09, 2015, 10:45 See attachements for 'not-fully-sintered' photos    Wednesday, June 10, 2015, 12:06 After inspecting the target container,  the inner tube surface has "dark" patches, which may not be evenly coated or the coating layer was too think.   See link for photos:  https://www.dropbox.com/sh/m94mjuuodwhz5jb/AADEBv_Kha_p_1An40eftWNHa?dl=0  Attempt to re-spray the container and re-sinter.        Friday, June 12, 2015, 14:58 re-sprayed with second layer of TaC spray this morning. re-loaded into evap2. HS water valves opened, no leaks detected. will ramp-up over weekend.  Friday, June 12, 2015, 16:07 Vacuum comes down to 6.1e-6 Torr. Initiated auto-ramping at 0.2A/min for 300A first.

Sunday, June 14, 2015, 09:37  

TGHT at 254.2A/3.5V3, DV = 1.614V Temp at 1177C. 

Vacuum is stable at 3.2e-7 Torr.  

Increase ramping rate at 2A/min until TGHT reached 300A. 

Sunday, June 14, 2015, 10:04  

TGHT reached 300A, temp 1368C.

Tapping up to ~1800C

Sunday, June 14, 2015, 11:26 

TGHT at 425A/6.84V, DV 3.59V, temp at 1814C, 

Vacuum coming down, currently at 7.5e-7 Torr. 

Will remain at that current for at least 4 hours before cooling down

Sunday, June 14, 2015, 17:15  

Target container has been sintered with TiC for over 6 hours at 1823C, with TGHT at 425A/6.84V, DV at 3.584V. 

Vac at 4.9e-7 Torr.  

Cooling initiated.  

Chamber can be vented tomorrow and target container can be taken out for inspection. 

 Monday, June 15, 2015, 11:38

Target container was taken out for inspection.  

It's observed that the coated/sintered TaC surface is improved.  The sintered temperature was only gone up just above 1800C, so there still some area near the ends that is still somewhat "brownish", fully sintered shows a

smooth .  (see attachment) 

Spraying into a cylinder tube can be challenging.  It was observed that the coating was dispersed out from the end cap to the centre tube.  For that reason, the container isn't has much protective layer;vthe Ta surface can

react with carbides and the container eventually breaks.  Take the endcap process for example,  the caps are evenly coated with TaC and can be sintered up to 2000C (see e-log Evap ID 202).

Suggestions:  

Using a spray ball nozzle or some sort so that the inner tube can be evenly coated. 

Under investigating...