Re: [EXTERNAL] Mounting Sample on High Temperature XRD Ribbon Heater

2019-07-26 Thread Payzant, Andrew 
We always used to spot weld the T/C to the bottom of the strip.

A big challenge is to avoid pickup of voltage from the strip (which is 
resistively heated) by the T/C – this can lead to false temperature 
indications, sometimes huge! I strongly recommend verification of the 
temperature by some other means, either by running an internal or external 
standard powder, by optical pyrometry, or something like that. If you run your 
heater using A/C rather than D/C power that will help reduce this effect.

Andrew

---
Dr. E. Andrew Payzant
Materials Engineering Group Leader
Neutron Scattering Division

Mailing Address:
Oak Ridge National Laboratory
P.O. Box 2008
Building 8600, MS 6475
Oak Ridge, TN, 37831

Cell: (865) 235-4981
Email: payza...@ornl.gov
https://www.ornl.gov/staff-profile/e-andrew-payzant




From: "Mibeck, Blaise" 
Date: Thursday, July 25, 2019 at 4:23 PM
To: Julian Richard Tolchard , "Payzant, 
Andrew" 
Cc: Rietveld list 
Subject: Re: [EXTERNAL] Mounting Sample on High Temperature XRD Ribbon Heater

Been a long day. I did have a new platinum ribbon heater and it working well!
I would like to know this: how is the thermocouple attached to these ribbon 
heaters? (From Edmond- Buehler)
Thanks for any more advice. I really appreciate the help!
Get Outlook for Android


From: Julian Richard Tolchard 
Sent: Thursday, July 25, 2019 10:40:26 AM
To: Payzant, Andrew ; Mibeck, Blaise 
Cc: rietveld_l@ill.fr 
Subject: RE: [EXTERNAL] Mounting Sample on High Temperature XRD Ribbon Heater

Andrew,

I agree completely. Pt does definitely have its problems, but it's hard to get 
radiant heaters that go so high in temperature.

My feeling is that if you want to pursue HT-XRD in any serious fashion you need 
to accept the idea that Pt / Ta strips and thermocouples etc are "consumables" 
and live with the associated cost. I know this is difficult for a lot of 
university labs, but once you adopt that mindset you can do much more 
interesting experiments.


Jools


From: Payzant, Andrew 
Sent: torsdag 25. juli 2019 17.08
To: Julian Richard Tolchard ; Mibeck, Blaise 

Cc: rietveld_l@ill.fr
Subject: Re: [EXTERNAL] Mounting Sample on High Temperature XRD Ribbon Heater

Jools,

You are right. “Lab grade” bottled N2 may have enough residual oxygen to cause 
problems, plus it is hard to purge the chamber properly to get the pO2 low 
enough to avoid issues.  But an H2/N2 mix might not be suitable, especially if 
it destabilizes his sample. Here are some other ideas:


  1.  I used to flow high purity N2 through a gettering furnace in series with 
the HTXRD chamber, and that, coupled with multiple purges of the chamber prior 
to starting the experiment, worked pretty well.
  2.  I have in the past used a Bühler HT furnace that had a secondary 
“surround heater” option. I had some success putting a gettering wire across 
these leads and running it at a higher temperature than the heater strip in 
order to remove traces of oxygen from the chamber. This has the advantage that 
as you heat up the walls of the chamber and release adsorbed oxygen it goes to 
the getter rather than the strip. It can be a bit tricky ensuring that the 
getter is hotter than the strip across the range of temperatures that you run.

However, I fully agree with you that a platinum foil is probably a better 
option for Blaise’s experiment. If he has one handy.

There are some caveats regarding platinum though. It is generally more 
expensive. It is readily attacked by silicon, iron, and other elements. You can 
get recrystallization and/or rapid grain growth at high temperatures, which 
dramatically changes the diffraction pattern from the strip during a HTXRD 
experiment. The relatively high CTE means that the strip height will change as 
the temperature increases, which will cause large peak shifts unless you are 
using parallel beam optics and even then will cause intensity variations at the 
lower 2thetas. If you work at a US government lab, platinum is a precious metal 
and there is some paperwork required every time you change heater strips. Also, 
if your sample melts or sinters, you may have some “fun” getting the platinum 
clean.

Andrew

*

Dr. E. Andrew Payzant
Materials Engineering Group Leader
Neutron Scattering Division
Neutron Sciences Directorate

Mailing address:
Oak Ridge National Laboratory
Dr. E. Andrew Payzant
P.O. Box 2008
Bldg. 8600, MS 6475
Oak Ridge, TN 37831

cell: (865) 235-4981
email: payza...@ornl.gov
https://www.ornl.gov/staff-profile/e-andrew-payzant

**



From: Julian Richard Tolchard 
mailto:julianrichard.tolch...@sintef.no>>
Date: Thursday, July 25, 2019 at 10:47 AM
To: "Mibeck, Blaise" mailto:bmib...@undeerc.org>>, Andrew 
Payzant

Re: [EXTERNAL] Mounting Sample on High Temperature XRD Ribbon Heater

2019-07-26 Thread Payzant, Andrew 
I agree with Tim. HT stages such as Anton Paar’s XRK900 provide excellent 
temperature control and stability across a range of atmospheres.
One advantage that strip heaters still have is in rapid heating and cooling.

A

---
Dr. E. Andrew Payzant
Materials Engineering Group Leader
Neutron Scattering Division

Mailing Address:
Oak Ridge National Laboratory
P.O. Box 2008
Building 8600, MS 6475
Oak Ridge, TN, 37831

Cell: (865) 235-4981
Email: payza...@ornl.gov
https://www.ornl.gov/staff-profile/e-andrew-payzant




From: Timothy Hyde 
Date: Friday, July 26, 2019 at 6:07 AM
To: "Mibeck, Blaise" , Julian Richard Tolchard 
, "Payzant, Andrew" 
Cc: Rietveld list 
Subject: RE: [EXTERNAL] Mounting Sample on High Temperature XRD Ribbon Heater

Blaise,

Andrew, below correctly summarises the issues with strip heaters, and as Julian 
mentions, even if you can get them working satisfactorily they are essentially 
rather expensive consumables.

While for you not an immediate solution, for the reasons outlined by Andrew and 
Julian, we moved to alternative in situ heating technologies. Should you or 
anyone be considering replacing  a ribbon beater, please look into such 
alternatives from commercial suppliers such as Anton Paar, which have generally 
eliminated many of the issues that we are discussing below.

Tim

From: rietveld_l-requ...@ill.fr  On Behalf Of 
Mibeck, Blaise
Sent: 25 July 2019 21:23
To: Julian Richard Tolchard ; Payzant, Andrew 

Cc: rietveld_l@ill.fr
Subject: Re: [EXTERNAL] Mounting Sample on High Temperature XRD Ribbon Heater

Been a long day. I did have a new platinum ribbon heater and it working well!
I would like to know this: how is the thermocouple attached to these ribbon 
heaters? (From Edmond- Buehler)
Thanks for any more advice. I really appreciate the help!
Get Outlook for Android


From: Julian Richard Tolchard 
mailto:julianrichard.tolch...@sintef.no>>
Sent: Thursday, July 25, 2019 10:40:26 AM
To: Payzant, Andrew mailto:payza...@ornl.gov>>; Mibeck, 
Blaise mailto:bmib...@undeerc.org>>
Cc: rietveld_l@ill.fr 
mailto:rietveld_l@ill.fr>>
Subject: RE: [EXTERNAL] Mounting Sample on High Temperature XRD Ribbon Heater

Andrew,

I agree completely. Pt does definitely have its problems, but it's hard to get 
radiant heaters that go so high in temperature.

My feeling is that if you want to pursue HT-XRD in any serious fashion you need 
to accept the idea that Pt / Ta strips and thermocouples etc are "consumables" 
and live with the associated cost. I know this is difficult for a lot of 
university labs, but once you adopt that mindset you can do much more 
interesting experiments.


Jools


From: Payzant, Andrew mailto:payza...@ornl.gov>>
Sent: torsdag 25. juli 2019 17.08
To: Julian Richard Tolchard 
mailto:julianrichard.tolch...@sintef.no>>; 
Mibeck, Blaise mailto:bmib...@undeerc.org>>
Cc: rietveld_l@ill.fr
Subject: Re: [EXTERNAL] Mounting Sample on High Temperature XRD Ribbon Heater

Jools,

You are right. “Lab grade” bottled N2 may have enough residual oxygen to cause 
problems, plus it is hard to purge the chamber properly to get the pO2 low 
enough to avoid issues.  But an H2/N2 mix might not be suitable, especially if 
it destabilizes his sample. Here are some other ideas:


  1.  I used to flow high purity N2 through a gettering furnace in series with 
the HTXRD chamber, and that, coupled with multiple purges of the chamber prior 
to starting the experiment, worked pretty well.
  2.  I have in the past used a Bühler HT furnace that had a secondary 
“surround heater” option. I had some success putting a gettering wire across 
these leads and running it at a higher temperature than the heater strip in 
order to remove traces of oxygen from the chamber. This has the advantage that 
as you heat up the walls of the chamber and release adsorbed oxygen it goes to 
the getter rather than the strip. It can be a bit tricky ensuring that the 
getter is hotter than the strip across the range of temperatures that you run.

However, I fully agree with you that a platinum foil is probably a better 
option for Blaise’s experiment. If he has one handy.

There are some caveats regarding platinum though. It is generally more 
expensive. It is readily attacked by silicon, iron, and other elements. You can 
get recrystallization and/or rapid grain growth at high temperatures, which 
dramatically changes the diffraction pattern from the strip during a HTXRD 
experiment. The relatively high CTE means that the strip height will change as 
the temperature increases, which will cause large peak shifts unless you are 
using parallel beam optics and even then will cause intensity variations at the 
lower 2thetas. If you work at a US government lab, platinum is a precious metal 
and there is some paperwork required every

RE: [EXTERNAL] Mounting Sample on High Temperature XRD Ribbon Heater

2019-07-26 Thread Timothy Hyde 
Blaise,

Andrew, below correctly summarises the issues with strip heaters, and as Julian 
mentions, even if you can get them working satisfactorily they are essentially 
rather expensive consumables.

While for you not an immediate solution, for the reasons outlined by Andrew and 
Julian, we moved to alternative in situ heating technologies. Should you or 
anyone be considering replacing  a ribbon beater, please look into such 
alternatives from commercial suppliers such as Anton Paar, which have generally 
eliminated many of the issues that we are discussing below.

Tim

From: rietveld_l-requ...@ill.fr  On Behalf Of 
Mibeck, Blaise
Sent: 25 July 2019 21:23
To: Julian Richard Tolchard ; Payzant, Andrew 

Cc: rietveld_l@ill.fr
Subject: Re: [EXTERNAL] Mounting Sample on High Temperature XRD Ribbon Heater

Been a long day. I did have a new platinum ribbon heater and it working well!
I would like to know this: how is the thermocouple attached to these ribbon 
heaters? (From Edmond- Buehler)
Thanks for any more advice. I really appreciate the help!
Get Outlook for Android


From: Julian Richard Tolchard 
mailto:julianrichard.tolch...@sintef.no>>
Sent: Thursday, July 25, 2019 10:40:26 AM
To: Payzant, Andrew mailto:payza...@ornl.gov>>; Mibeck, 
Blaise mailto:bmib...@undeerc.org>>
Cc: rietveld_l@ill.fr 
mailto:rietveld_l@ill.fr>>
Subject: RE: [EXTERNAL] Mounting Sample on High Temperature XRD Ribbon Heater

Andrew,

I agree completely. Pt does definitely have its problems, but it's hard to get 
radiant heaters that go so high in temperature.

My feeling is that if you want to pursue HT-XRD in any serious fashion you need 
to accept the idea that Pt / Ta strips and thermocouples etc are "consumables" 
and live with the associated cost. I know this is difficult for a lot of 
university labs, but once you adopt that mindset you can do much more 
interesting experiments.


Jools


From: Payzant, Andrew mailto:payza...@ornl.gov>>
Sent: torsdag 25. juli 2019 17.08
To: Julian Richard Tolchard 
mailto:julianrichard.tolch...@sintef.no>>; 
Mibeck, Blaise mailto:bmib...@undeerc.org>>
Cc: rietveld_l@ill.fr
Subject: Re: [EXTERNAL] Mounting Sample on High Temperature XRD Ribbon Heater

Jools,

You are right. “Lab grade” bottled N2 may have enough residual oxygen to cause 
problems, plus it is hard to purge the chamber properly to get the pO2 low 
enough to avoid issues.  But an H2/N2 mix might not be suitable, especially if 
it destabilizes his sample. Here are some other ideas:


  1.  I used to flow high purity N2 through a gettering furnace in series with 
the HTXRD chamber, and that, coupled with multiple purges of the chamber prior 
to starting the experiment, worked pretty well.
  2.  I have in the past used a Bühler HT furnace that had a secondary 
“surround heater” option. I had some success putting a gettering wire across 
these leads and running it at a higher temperature than the heater strip in 
order to remove traces of oxygen from the chamber. This has the advantage that 
as you heat up the walls of the chamber and release adsorbed oxygen it goes to 
the getter rather than the strip. It can be a bit tricky ensuring that the 
getter is hotter than the strip across the range of temperatures that you run.

However, I fully agree with you that a platinum foil is probably a better 
option for Blaise’s experiment. If he has one handy.

There are some caveats regarding platinum though. It is generally more 
expensive. It is readily attacked by silicon, iron, and other elements. You can 
get recrystallization and/or rapid grain growth at high temperatures, which 
dramatically changes the diffraction pattern from the strip during a HTXRD 
experiment. The relatively high CTE means that the strip height will change as 
the temperature increases, which will cause large peak shifts unless you are 
using parallel beam optics and even then will cause intensity variations at the 
lower 2thetas. If you work at a US government lab, platinum is a precious metal 
and there is some paperwork required every time you change heater strips. Also, 
if your sample melts or sinters, you may have some “fun” getting the platinum 
clean.

Andrew

*

Dr. E. Andrew Payzant
Materials Engineering Group Leader
Neutron Scattering Division
Neutron Sciences Directorate

Mailing address:
Oak Ridge National Laboratory
Dr. E. Andrew Payzant
P.O. Box 2008
Bldg. 8600, MS 6475
Oak Ridge, TN 37831

cell: (865) 235-4981
email: payza...@ornl.gov
https://www.ornl.gov/staff-profile/e-andrew-payzant

**



From: Julian Richard Tolchard 
mailto:julianrichard.tolch...@sintef.no>>
Date: Thursday, July 25, 2019 at 10:47 AM
To: "Mibeck, Blaise" mailto:bmib...@undeerc.org>>, Andrew 
Payzant mailto:payza...@ornl.gov>>
Cc: Rietveld list